View source for Pacemaker

{{Short description|Medical device for artificially stimulating heart contractions}}
{{otheruses}}
{{Infobox medical intervention
| name         = Pacemaker
| image        = St Jude Medical pacemaker with ruler.jpg|
| caption      = [[St. Jude Medical#Products|St. Jude single-lead pacemaker]] with ruler in cm (released in 2005<ref>{{Cite web |title=Devices@FDA |url=https://www.accessdata.fda.gov/scrIpts/cdrh/devicesatfda/index.cfm?db=pma&id=334237 |access-date=2022-04-27 |website=www.accessdata.fda.gov}}</ref><ref>{{Cite report |publisher=St. Jude Medical |date=October 2008 |title=Product Performance Report – Cardiac Rhythm Management |url=https://www.cardiovascular.abbott/content/dam/bss/divisionalsites/cv/pdf/reports/1.3.7.3/Oct_2008_PPR_060711.pdf |access-date=2022-04-27 |archive-date=2022-08-19 |archive-url=https://web.archive.org/web/20220819090738/https://www.cardiovascular.abbott/content/dam/bss/divisionalsites/cv/pdf/reports/1.3.7.3/Oct_2008_PPR_060711.pdf }}</ref>)
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|specialty=[[Cardiology]], [[electrophysiology]]}}

A '''pacemaker''', also known as an '''artificial cardiac pacemaker''', is an [[Implant (medicine)|implanted]]  [[medical device]] that generates [[Pulse (signal processing)|electrical pulses]] delivered by [[electrode]]s to one or more of the [[Heart chamber|chambers of the heart]]. Each pulse causes the targeted chamber(s) to [[muscle contraction|contract]] and pump blood,<ref>{{Cite web |title=UpToDate |url=https://www.uptodate.com/contents/pacemakers-beyond-the-basics/print#:~:text=The%20conduction%20system%20stimulates%20precise,sinus%20node%20(figure%201). |access-date=2022-08-02 |website=www.uptodate.com}}</ref> thus regulating the function of the [[electrical conduction system of the heart]].

The primary purpose of a pacemaker is to maintain an even [[heart rate]], either because the heart's natural [[cardiac pacemaker]] provides an inadequate or irregular heartbeat, or because there is a [[heart block|block]] in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow a cardiologist to select the optimal pacing modes for individual patients. Most pacemakers are on demand, in which the stimulation of the heart is based on the dynamic demand of the [[circulatory system]]. Others send out a fixed rate of impulses.<ref name="bhf">{{cite web |title=Pacemakers |url=https://www.bhf.org.uk/informationsupport/treatments/pacemakers |access-date=28 July 2022}}</ref>

A specific type of pacemaker, called an [[implantable cardioverter-defibrillator]], combines pacemaker and [[defibrillator]] functions in a single [[Implant (medicine)|implantable device]].<ref>{{Cite web |title=Overview of Pacemakers and Implantable Cardioverter Defibrillators (ICDs) – Health Encyclopedia – University of Rochester Medical Center |url=https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=85&contentid=p00234 |access-date=2022-08-02 |website=www.urmc.rochester.edu}}</ref> Others, called [[Cardiac resynchronization therapy|biventricular pacemakers]], have multiple electrodes stimulating different positions within the ventricles (the lower heart chambers) to improve their synchronization.<ref>{{Cite web |title=Biventricular Pacemaker |url=https://my.clevelandclinic.org/health/treatments/16784-biventricular-pacemaker |access-date=2022-08-02 |website=Cleveland Clinic}}</ref>
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== Methods of cardiac pacing ==
[[File:AtrialPacemakerECG.JPG|thumb|An [[ECG]] in a person with a single-chamber pacemaker to the [[atrium (heart)|atrium]]. Note the circle around one of the sharp electrical spikes in the position where the P wave would be expected.]]
[[File:Duelchamber.JPG|thumb|An ECG of a person with a dual-chamber pacemaker]]

=== Percussive pacing ===
Percussive pacing, also known as transthoracic mechanical pacing, is the use of the closed fist, usually on the left lower edge of the [[human sternum|sternum]] over the [[right ventricle]] in the [[venae cavae|''vena cava'']], striking from a distance of 20–30&nbsp;cm to induce a ventricular beat (the ''British Journal of Anaesthesia'' suggests this must be done to raise the ventricular pressure to 10–15&nbsp;mmHg to induce electrical activity). This is an old procedure used only as a life-saving means until an electrical pacemaker is brought to the patient.<ref>{{cite journal |vauthors=Eich C, Bleckmann A, Paul T | title = Percussion pacing in a three-year-old girl with complete heart block during cardiac catheterization | journal = Br J Anaesth | volume = 95 | issue = 4 | pages = 465–67 | date = October 2005 | pmid = 16051649 | doi = 10.1093/bja/aei209 | doi-access = free }}</ref>

=== Transcutaneous pacing ===
{{Main|Transcutaneous pacing}}
Transcutaneous pacing (TCP), also called external pacing, is recommended for the initial stabilization of hemodynamically significant [[bradycardia]]s of all types. The procedure is performed by placing two pacing pads on the patient's chest, either in the anterior/lateral position or the anterior/posterior position. The rescuer selects the pacing rate, and gradually increases the pacing current (measured in mA) until electrical capture (characterized by a wide [[QRS complex]] with a tall, broad [[T wave]] on the [[electrocardiogram|ECG]]) is achieved, with a corresponding pulse. Pacing artifact on the ECG and severe muscle twitching may make this determination difficult. External pacing should not be relied upon for an extended period of time. It is an emergency procedure that acts as a bridge until transvenous pacing or other therapies can be applied.<ref>{{Cite book |last1=Shah |first1=Maully |url=https://books.google.com/books?id=7hGdDgAAQBAJ&dq=External+pacing+should+not+be+relied+upon+for+an+extended+period+of+time.&pg=PA196 |title=Cardiac Pacing and Defibrillation in Pediatric and Congenital Heart Disease |last2=Rhodes |first2=Larry |last3=Kaltman |first3=Jonathan |year=2017 |publisher=John Wiley & Sons |isbn=978-0-470-67109-2 |language=en}}</ref>

=== Epicardial pacing ===
{{Main|Epicardial}}
[[File:Pacemaker dependent asystole.jpg|thumb|ECG rhythm strip of a threshold determination in a patient with a temporary (epicardial) ventricular pacemaker. The epicardial pacemaker leads were placed after the patient collapsed during [[aortic valve]] surgery. In the first half of the tracing, pacemaker stimuli at 60 beats per minute result in a wide QRS complex with a [[right bundle branch block]] pattern. Progressively weaker pacing stimuli are administered, which results in [[asystole]] in the second half of the tracing. At the end of the tracing, distortion results from muscle contractions due to a (short) hypoxic [[seizure]]. Because decreased pacemaker stimuli do not result in a ventricular [[escape rhythm]], the patient can be said to be pacemaker-dependent and needs a definitive pacemaker.]]

Temporary epicardial pacing is used during open heart surgery should the surgical procedure create atrio-ventricular block. The electrodes are placed in contact with the outer wall of the ventricle (epicardium) to maintain satisfactory cardiac output until a temporary transvenous electrode has been inserted.<ref>{{cite book |last1=Valchanov |first1=Kamen |last2=Jones |first2=Nicola |last3=Hogue |first3=Charles W. |title=Core Topics in Cardiothoracic Critical Care |date=2018 |publisher=Cambridge University Press |isbn=978-1-108-66567-4 }}{{pn|date=August 2024}}</ref>

Permanent epicardial pacing leads can be implanted surgically and tunneled to the pulse generator pocket. These leads are either passively touching the heart and sewn in place, or have a screw mechanism to actively fix to the heart.

=== Transvenous pacing (temporary) ===
{{Main|Transvenous pacing}}
Transvenous pacing, when used for temporary pacing, is an alternative to transcutaneous pacing. A pacemaker wire is placed into a vein, under sterile conditions, and then passed into either the right atrium or right ventricle. The pacing wire is then connected to an external pacemaker outside the body. Transvenous pacing is often used as a bridge to permanent pacemaker placement. It can be kept in place until a permanent pacemaker is implanted or until there is no longer a need for a pacemaker and then it is removed.

[[File:Fluoroscopy pacemaker leads right atrium ventricle.png|thumb|Right atrial and right ventricular leads as visualized under x-ray during a pacemaker implant procedure. The atrial lead is the curved one making a U shape in the upper left part of the figure.]]

=== Permanent transvenous pacing ===
Permanent pacing with an implantable pacemaker involves transvenous placement of one or more pacing electrodes within a chamber, or chambers, of the heart, while the pacemaker is implanted under the skin below the clavicle. The procedure is performed by incision of a suitable vein into which the electrode [[Lead (electronics)|lead]] is inserted and passed along the vein, through the valve of the heart, until positioned in the chamber. The procedure is facilitated by [[fluoroscopy]] which enables the physician to view the passage of the electrode lead. After satisfactory lodgement of the electrode is confirmed, the opposite end of the electrode lead is connected to the pacemaker generator.

There are three basic types of permanent pacemakers, classified according to the number of [[Heart chamber|chambers]] involved and their basic operating mechanism:<ref name="url_Heart_Rhythm_Society">{{cite web |url=http://www.hrspatients.org/patients/treatments/pacemakers.asp |title=Pacemakers, Patient and Public Information Center: Heart Rhythm Society |archive-url=https://web.archive.org/web/20100619152432/http://hrspatients.org/patients/treatments/pacemakers.asp |archive-date=2010-06-19 }}</ref>
* ''Single-chamber pacemaker''. In this type, only one pacing lead is placed into a chamber of the heart, either the [[Atrium (heart)|atrium]] or the [[Ventricle (heart)|ventricle]].<ref name="url_Heart_Rhythm_Society" />
* ''Dual-chamber pacemaker''. Here, wires are placed in two chambers of the heart. One lead paces the atrium and one paces the ventricle. This type more closely resembles the natural pacing of the heart by assisting the heart in coordinating the function between the atria and ventricles.<ref name="url_Heart_Rhythm_Society" />
*''Biventricular pacemaker''. This pacemaker has three wires placed in three chambers of the heart. One in the atrium and two in either ventricle. It is more complicated to implant.<ref name="url_Heart_Rhythm_Society" />
* ''Rate-responsive pacemaker''. This pacemaker has sensors that detect changes in the patient's physical activity and automatically adjust the pacing rate to fulfill the body's metabolic needs.<ref name="url_Heart_Rhythm_Society" />

The pacemaker generator is a [[hermetically sealed]] device containing a power source, usually a [[Lithium metal battery|lithium-iodide battery]], a sensing amplifier which processes the electrical manifestation of naturally occurring heart beats as sensed by the heart electrodes, the [[computer]] logic for the pacemaker and the output circuitry which delivers the pacing impulse to the electrodes.

Most commonly, the generator is placed below the subcutaneous fat of the chest wall, above the muscles and bones of the chest. However, the placement may vary on a case-by-case basis.

The outer casing of pacemakers is so designed that it will rarely be rejected by the body's [[immune system]]. It is usually made of [[titanium]], which is inert in the body.

=== Leadless pacing ===
Leadless pacemakers are devices that are as small as a capsule and are small enough to allow the generator to be placed within the heart, therefore avoiding the need for pacing leads.<ref name=":0">{{Cite web|url=http://www.hospitalhealthcare.com/cardiology/leadless-pacemaker-new-era-cardiac-pacing|title=The leadless pacemaker: A new era in cardiac pacing|website=Hospital Healthcare Europe|language=en|access-date=2019-02-01|archive-url=https://web.archive.org/web/20190202041642/http://www.hospitalhealthcare.com/cardiology/leadless-pacemaker-new-era-cardiac-pacing|archive-date=2019-02-02}}</ref>    As pacemaker leads can fail over time, a pacing system that avoids these components offers theoretical advantages.  Leadless pacemakers can be implanted into the heart using a steerable catheter fed into the [[femoral vein]] via an incision in the groin.<ref name=":0" />

== Basic function ==


=== Pacing modes ===
Modern pacemakers usually have multiple functions. The most basic form monitors the heart's native electrical rhythm. When the pacemaker wire or "lead" does not detect heart electrical activity in the chamber – atrium or ventricle – within a normal beat-to-beat time period – most commonly one second – it will stimulate either the atrium or the ventricle with a short low voltage pulse. If it does sense electrical activity, it will hold off stimulating. This sensing and stimulating activity continues on a beat by beat basis and is called "demand pacing". In the case of a dual-chamber device, when the upper chambers have a spontaneous or stimulated activation, the device starts a countdown to ensure that in an acceptable – and programmable – interval, there is an activation of the ventricle, otherwise again an impulse will be delivered.

The more complex forms include the ability to sense and/or stimulate both the atrial and ventricular chambers.

{| class="wikitable" style="margin: 1em auto 1em auto"
|+ {{anchor|mode}}The revised NASPE/BPEG generic code for antibradycardia pacing<ref>{{cite journal |vauthors=Bernstein AD, Daubert JC, Fletcher RD, Hayes DL, Lüderitz B, Reynolds DW, Schoenfeld MH, Sutton R | s2cid = 12887364 | title = The revised NASPE/BPEG generic code for antibradycardia, adaptive-rate, and multisite pacing. North American Society of Pacing and Electrophysiology/British Pacing and Electrophysiology Group | journal = Pacing Clin Electrophysiol | volume = 25 | issue = 2 | pages = 260–64 | year = 2002 | pmid = 11916002 | doi = 10.1046/j.1460-9592.2002.00260.x }}</ref>
! I || II || III || IV || V
|-
| Chamber(s) paced || Chamber(s) sensed || Response to sensing || Rate modulation || Multisite pacing
|-
| O = None || O = None || O = None || O = None || O = None
|-
| A = Atrium || A = Atrium || T = Triggered || R = Rate modulation || A = Atrium
|-
| V = Ventricle || V = Ventricle || I = Inhibited || || V = Ventricle
|-
| D = Dual (A+V) || D = Dual (A+V) || D = Dual (T+I) || || D = Dual (A+V)
|}

From this the basic ventricular "on demand" pacing mode is VVI or with automatic rate adjustment for exercise VVIR – this mode is suitable when no synchronization with the atrial beat is required, as in atrial fibrillation. The equivalent atrial pacing mode is AAI or AAIR which is the mode of choice when atrioventricular conduction is intact but the [[sinoatrial node]] of the natural pacemaker is unreliable – sinus node disease (SND) or [[sick sinus syndrome]]. Where the problem is [[atrioventricular block]] (AVB) the pacemaker is required to detect (sense) the atrial beat and after a normal delay (0.1–0.2 seconds) trigger a ventricular beat, unless it has already happened – this is VDD mode and can be achieved with a single pacing lead with electrodes in the right atrium (to sense) and ventricle (to sense and pace). These modes AAIR and VDD are unusual in the US but widely used in Latin America and Europe.<ref>{{cite journal |vauthors=Böhm A, Pintér A, Székely A, Préda I | title = Clinical Observations with Long-term Atrial Pacing | journal = Pacing Clin Electrophysiol | volume = 21 | issue = 1 | pages = 246–49 | year = 1998 | pmid = 9474681 | doi = 10.1111/j.1540-8159.1998.tb01097.x | s2cid = 23277568 }}</ref><ref>{{cite journal | author = Crick JC | title = European Multicenter Prospective Follow-Up Study of 1,002 Implants of a Single Lead VDD Pacing System | journal = Pacing Clin Electrophysiol | volume = 14 | issue = 11 | pages = 1742–44 | year = 1991 | pmid = 1749727 | doi = 10.1111/j.1540-8159.1991.tb02757.x | s2cid = 698053 }}</ref> The DDDR mode is most commonly used as it covers all the options though the pacemakers require separate atrial and ventricular leads and are more complex, requiring careful programming of their functions for optimal results.

Automatic pacemakers are designed to be over-ridden by the heart's natural rate at any moment that it gets back to a non-pathologic [[Sinus rhythm|normal sinus rhythm]] and can reinitiate influencing the electric activity in the heart when the pathologic event happens again.<ref>{{Cite book|url=https://books.google.com/books?id=EWVo9DT2-A4C&q=%22Demand+pacemaker%22&pg=PA322|title=Rapid Interpretation of EKG's: An Interactive Course|last=Dubin|first=Dale|date=2000|publisher=Cover Publishing Company|isbn=978-0-912912-06-6|language=en}}</ref> A "[[ventricle (heart)|ventricular]]-demand pacemaker" produces a narrow vertical spike on the [[ECG]], just before a wide [[QRS]]. The spike of an "[[atrial]]-demand pacemaker" appears just before the [[P wave]].<ref>{{Cite web|url=https://www.uptodate.com/contents/ecg-tutorial-pacemakers|title=UpToDate|website=www.uptodate.com|access-date=2018-09-10}}</ref>

Comparably, a '''Triggered Pacemaker''' is activated immediately after an electrical activity is commenced in the heart tissue by itself. A "ventricular triggered pacemaker" produces the impulse just after a pulse is created in the ventricular tissue and it appears as a simultaneous spike with QRS. An "atrial triggered pacemaker" is the mode in which an impulse is produced immediately after an electrical event in the atrium. It appears as a [[Electric discharge|discharge]] following the p wave but prior to the QRS which is commonly widened.<ref>{{Cite book | url=https://books.google.com/books?id=GXOQbDsCyLoC&q=%22Triggered+pacemaker%22&pg=PA421 |title = Basic and Bedside Electrocardiography|isbn = 978-1-4511-4791-9|last1 = Baltazar|first1 = Romulo F.|year = 2012| publisher=Lippincott Williams & Wilkins }}</ref>

=== Threshold ===
The heart is composed of an excitable tissue and an electrical pulse of a certain voltage is needed to "capture" the myocardium to make the heart function. The minimum voltage to achieve this is called the threshold. As this is a probabilistic property, the actual voltage used is higher than the threshold (usually by a 50–100% margin). Additionally, the electrical pulse has a time component and proper description of a threshold is a voltage and pulse width.

All electrical circuits require a complete connection between the cathode and the anode. For some pacing leads, both connections to the heart are provided in a single lead ("bipolar") and some only provide a single connection ("unipolar"). In unipolar, the second connection is internally from the heart to the generator through the body (blood, tissue, etc).

Also important is the [[electrical impedance|impedance]]. The lower the impedance, the more current is needed to achieve the threshold voltage and lowers the battery life. The impedance is affected by the integrity of the pacing lead and the electrode-tissue interface of the lead with the heart.

=== Sensing and sensitivity ===
An important aspect of pacemaker function is sensing the intrinsic heart activity. This is called sensing. Larger sensed voltages are desired and it is expected that the ventricle produces larger voltages than the atria.

The minimum voltage to sense an event is called the sensitivity. The higher the sensitivity, the less that is sensed, and vice-versa. Too low of a sensitivity can cause troubles with sensing P waves, T waves, and noise; sensing these things is called "over sensing". A sensitivity too high may result in missed sensing of P waves in the atria and QRS in the ventricles, and is called "under sensing."

== Biventricular pacing ==
{{center|
[[File:Cardiac resynchronisation therapy.png|thumb|Three leads can be seen in this example of a cardiac resynchronization device: a right atrial lead (solid black arrow), a right ventricular lead (dashed black arrow), and a coronary sinus lead (red arrow). The coronary sinus lead wraps around the outside of the left ventricle, enabling pacing of the left ventricle. Note that the right ventricular lead in this case has two thickened aspects that represent conduction coils and that the generator is larger than typical pacemaker generators, demonstrating that this device is both a pacemaker and a cardioverter-defibrillator, capable of delivering electrical shocks for dangerously fast abnormal ventricular rhythms.]]
}}
{{Main|Cardiac resynchronization therapy}}

Cardiac resynchronization therapy (CRT) is used for people with [[heart failure]] in whom the left and right ventricles do not contract simultaneously ([[ventricular dyssynchrony]]), which occurs in approximately 25–50% of heart failure patients. To achieve CRT, a biventricular pacemaker (BVP) is used, which can pace both the [[Interventricular septum|septal]] and lateral walls of the [[left ventricle]]. By pacing both sides of the left ventricle, the pacemaker can resynchronize the ventricular contractions.

CRT devices have at least two leads, one passing through the ''vena cava'' and the [[right atrium]] into the [[right ventricle]] to stimulate the [[Interventricular septum|septum]], and another passing through the ''vena cava'' and the right atrium and inserted through the [[coronary sinus]] to pace the epicardial wall of the left ventricle. Often, for patients in normal sinus rhythm, there is also a lead in the right atrium to facilitate synchrony with the atrial contraction. Thus, the timing between the atrial and ventricular contractions, as well as between the septal and lateral walls of the left ventricle can be adjusted to achieve optimal cardiac function.

CRT devices have been shown to reduce mortality and improve quality of life in patients with heart failure symptoms; a LV ejection fraction less than or equal to 35% and QRS duration on EKG of 120&nbsp;ms or greater.<ref>{{cite journal |vauthors=Cleland JG, Daubert JC, Erdmann E, Freemantle N, Gras D, Kappenberger L, Tavazzi L | title = The effect of cardiac resynchronization on morbidity and mortality in heart failure | journal = N. Engl. J. Med. | volume = 352 | issue = 15 | pages = 1539–49 | year = 2005 | pmid = 15753115 | doi = 10.1056/NEJMoa050496 | s2cid = 13938919 | url = http://eprints.gla.ac.uk/128401/1/128401.pdf }}</ref><ref>{{cite journal |vauthors=Bardy GH, Lee KL, Mark DB, Poole JE, Packer DL, Boineau R, Domanski M, Troutman C, Anderson J, Johnson G, McNulty SE, Clapp-Channing N, Davidson-Ray LD, Fraulo ES, Fishbein DP, Luceri RM, Ip JH | s2cid = 19118406 | title = Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure | journal = N. Engl. J. Med. | volume = 352 | issue = 3 | pages = 225–37 | year = 2005 | pmid = 15659722 | doi = 10.1056/NEJMoa043399 | doi-access = free }}</ref>

Biventricular pacing alone is referred to as CRT-P (for pacing). For selected patients at risk of arrhythmias, CRT can be combined with an [[implantable cardioverter-defibrillator]] (ICD): such devices, known as CRT-D (for defibrillation), also provide effective protection against life-threatening arrhythmias.<ref name=Texas2011>{{cite journal |vauthors=Ganjehei L, Razavi M, Massumi A | title = Cardiac resynchronization therapy: a decade of experience and the dilemma of nonresponders | journal = Texas Heart Institute Journal | volume = 38 | issue = 4 | pages = 358–60 | year = 2011 | pmid = 21841860 | pmc = 3147217 }}</ref>

== Conduction System Pacing ==
Conventional placement of ventricular leads in or around the tip or ''apex'' of the right ventricle, or RV apical pacing, can have negative effects on heart function. It has been associated with increased risk of [[atrial fibrillation]], [[heart failure]], weakening of the heart muscle and potentially shorter life expectancy. [[bundle of his|His bundle pacing]] (HBP) and left bundle branch area pacing (LBBAP) leads to a more natural or perfectly natural ventricular activation and has generated strong research and clinical interest. By stimulating the [[Purkinje fibers|His–Purkinje]] fiber network directly with a special lead and placement technique, HBP causes a synchronized and therefore more effective ventricular activation and avoids long-term heart muscle disease. HBP in some cases can also correct [[bundle branch block]] patterns.<ref>{{cite journal |last1=Sharma |first1=Parikshit S. |last2=Vijayaraman |first2=Pugazhendhi |last3=Ellenbogen |first3=Kenneth A. |title=Permanent His bundle pacing: shaping the future of physiological ventricular pacing |journal=Nature Reviews Cardiology |volume=17 |issue=1 |pages=22–36 |doi=10.1038/s41569-019-0224-z |pmid=31249403 |year=2020 |s2cid=195698761 }}</ref><ref>{{cite journal |title=Focus on Electrophysiology: His Bundle Pacing: A More Physiologic Alternative For Pacing |journal=American College of Cardiology |date=April 26, 2019 |url=https://www.acc.org/latest-in-cardiology/articles/2019/04/14/12/42/focus-on-ep-his-bundle-pacing-a-more-physiologic-alternative-for-pacing }}</ref>

== Advancements in function ==
[[File:X-ray of pacemaker with right atrial and ventricular lead.jpg|thumb|350px|Posteroanterior and lateral [[chest radiograph]]s of a pacemaker with normally located leads in the right atrium (white arrow) and right ventricle (black arrowhead), respectively]]
A major step forward in pacemaker function has been to attempt to mimic nature by utilizing various inputs to produce a rate-responsive pacemaker using parameters such as the [[QT interval]], pO<sub>2</sub> – pCO<sub>2</sub> (dissolved [[oxygen]] or [[carbon dioxide]] levels) in the arterial-venous system, physical activity as determined by an [[accelerometer]], [[body temperature]], [[Adenosine triphosphate|ATP]] levels, [[adrenaline]], etc.
Instead of producing a static, predetermined heart rate, or intermittent control, such a pacemaker, a 'Dynamic Pacemaker', could compensate for both actual respiratory loading and potentially anticipated respiratory loading. The first dynamic pacemaker was invented by Anthony Rickards of the [[The Heart Hospital|National Heart Hospital]], London, UK, in 1982.<ref>{{cite journal | title=Anthony Francis Rickards | journal = Heart | pmc = 1768450 | year = 2004 | volume = 90 | pages=981–82 | doi = 10.1136/hrt.2004.045674 | issue=9}}</ref>

Dynamic pacemaking technology could also be applied to future [[artificial heart]]s. Advances in transitional tissue welding would support this and other artificial organ/joint/tissue replacement efforts. Stem cells may be of interest in transitional tissue welding.{{Citation needed|date=April 2013}}

Many advancements have been made to improve the control of the pacemaker once implanted. Many of these have been made possible by the transition to [[microprocessor]] controlled pacemakers. Pacemakers that control not only the ventricles but the [[Atrium (heart)|atria]] as well have become common. Pacemakers that control both the atria and ventricles are called dual-chamber pacemakers. Although these dual-chamber models are usually more expensive, timing the contractions of the atria to precede that of the ventricles improves the pumping efficiency of the heart and can be useful in congestive heart failure.

Rate responsive pacing allows the device to sense the physical activity of the patient and respond appropriately by increasing or decreasing the base pacing rate via rate response algorithms.

The DAVID trials<ref>{{cite journal |vauthors=Wilkoff BL, Cook JR, Epstein AE, Greene HL, Hallstrom AP, Hsia H, Kutalek SP, Sharma A | title = Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial | journal = JAMA | volume = 288 | issue = 24 | pages = 3115–23 | date = December 2002 | pmid = 12495391 | doi = 10.1001/jama.288.24.3115 | doi-access = free }}</ref> have shown that unnecessary pacing of the right ventricle can exacerbate [[heart failure]] and increases the incidence of atrial fibrillation. The newer dual-chamber devices can keep the amount of right ventricle pacing to a minimum and thus prevent worsening of the heart disease.

== Considerations ==

=== Insertion ===
A pacemaker may be implanted whilst a person is awake using [[local anesthetic]] to numb the skin with or without [[sedation]], or asleep using a [[general anesthetic]].<ref name=":1">{{Cite book|last=Ramsdale, David R.|title=Cardiac pacing and device therapy|date=2012|publisher=Springer|others=Rao, Archana.|isbn=978-1-4471-2939-4|location=London|oclc=822576869}}</ref> An antibiotic is usually given to reduce the risk of infection.<ref name=":1" />  Pacemakers are generally implanted in the front of the chest in the region of the left or right shoulder.  The skin is prepared by clipping or shaving any hair over the implant site before cleaning the skin with a disinfectant such as [[chlorhexidine]].  An incision is made below the collar bone and a space or pocket is created under the skin to house the pacemaker generator.  This pocket is usually created just above the [[pectoralis major]] muscle (prepectoral), but in some cases the device may be inserted beneath the muscle (submuscular).<ref>{{cite journal |last1=Pena |first1=Rafael E. |last2=Shepard |first2=Richard K. |last3=Ellenbogen |first3=Kenneth A. |title=How to Make a Submuscular Pocket |journal=Journal of Cardiovascular Electrophysiology |date=December 2006 |volume=17 |issue=12 |pages=1381–83 |doi=10.1111/j.1540-8167.2006.00665.x |pmid=17081202 |s2cid=38032736 |doi-access=free }}</ref> The [[Lead (electronics)|lead or leads]] are fed into the heart through a large vein guided by X-ray imaging ([[fluoroscope|fluoroscopy]]). The tips of the leads may be positioned within the [[Ventricle (heart)|right ventricle]], the [[Atrium (heart)|right atrium]], or the coronary sinus, depending on the type of pacemaker required.<ref name=":1" /> Surgery is typically completed within 30 to 90 minutes.  Following implantation, the surgical wound should be kept clean and dry until it has healed.  Some movements of the shoulder within a few weeks of insertion carry a risk of dislodging the pacemaker leads.<ref name=":1" />

The batteries within a pacemaker generator typically last 5 to 10 years. When the batteries are nearing the end of life, the generator is replaced in a procedure that is usually simpler than a new implant. Replacement involves making an incision to remove the existing device, disconnecting the leads from the old device and reconnecting them to a new generator, reinserting the new device and closing the skin.<ref name=":1" />

==== Periodic pacemaker checkups ====
[[File:PaceMakerRemoteMonitoringDevicesTwoKinds.jpg|thumb|Two types of remote monitoring devices used by pacemaker patients]]
Once the pacemaker is implanted, it is periodically checked to ensure the device is operational and performing appropriately; the device can be checked as often as is deemed necessary. Routine pacemaker checks are typically done in-office every six months, though will vary depending upon patient/device status and remote monitoring availability. Newer pacemaker models can also be interrogated remotely, with the patient transmitting their pacemaker data using a transmitter at home connected to a cellular telephone network.

During in-office follow-up, diagnostic tests may include:
* Sensing: the ability of the device to "see" intrinsic cardiac activity (atrial and ventricular depolarization).
* Impedance: A test to measure lead integrity. Large and/or sudden increases in impedance can indicate a lead fracture, while large and/or sudden decreases in impedance can be caused by insulation failure.
* Threshold amplitude: The minimum voltage (generally in hundredths of volts) required in order to pace the atrium or ventricle connected to the lead.
* Threshold duration: The time that the device requires at the preset amplitude to reliably pace the atrium or ventricle connected to the lead.
* Percentage of pacing: The percentage of time that the pacemaker has been actively pacing since the previous device interrogation, which shows how dependent the patient is on the device.
* Estimated battery life at current rate: As modern pacemakers are "on-demand" and only pace when necessary, battery lifespan is affected by how much the pacemaker is utilized. Other factors affecting battery life include programmed output and algorithms (features) that use battery power.
* Any events that were stored since the last follow-up, in particular [[arrhythmias]] such as [[atrial fibrillation]]. These are typically stored based on specific criteria set by the physician and specific to the patient. Some devices have the availability to display intracardiac electrograms showing the onset of an event as well as the event itself, which helps to diagnose its cause or origin.

=== Magnetic fields, MRIs, and other lifestyle issues ===
A patient's lifestyle is usually not modified to any great degree after the insertion of a pacemaker. There are a few activities that are unwise, such as full-contact sports and exposure of the pacemaker to intense magnetic fields.

The pacemaker patient may find that some types of everyday actions need to be modified. For instance, the shoulder harness of a vehicle [[seatbelt]] may be uncomfortable if it falls across the pacemaker insertion site. Women will not be able to wear bras for a while after the operation, and later might have to wear bras with wide shoulder straps.

For some sports and physical activities, special pacemaker protection can be worn to prevent possible injuries, or damage to the pacemaker leads.

Pacemakers may be affected by [[Magnetic field|magnetic]] or [[electromagnetic field]]s, and [[Ionising radiation|ionising]] and [[acoustic radiation]]. However, a 2013 study found that "The overall risk of clinically significant adverse events related to EMI (electromagnetic interference) in recipients of CIEDs (cardiovascular implantable electronic devices) is very low. Therefore, no special precautions are needed when household appliances are used. Environmental and industrial sources of EMI are relatively safe when the exposure time is limited and distance from the CIEDs is maximized. The risk of EMI-induced events is highest within the hospital environment."<ref name=beinart>{{cite journal| last1=Beinart|first1=R|last2=Nazarian|first2=S| title=Effects of external electrical and magnetic fields on pacemakers and defibrillators: from engineering principles to clinical practice| journal=Circulation |date=24 December 2013 | volume= 128 | issue= 25 | pages= 2799–809 | pmid=24366589 | doi=10.1161/CIRCULATIONAHA.113.005697|doi-access=free| pmc=3908865}}</ref> The study lists and tabulates many sources of interference, and many different potential effects: damage to circuitry, asynchronous pacing, etc. Some sources of hazard in older devices have been eliminated in newer ones.

Activities involving strong [[magnetic field]]s should be avoided. This includes activities such as [[arc welding]] with certain types of equipment,<ref>{{cite journal |vauthors=Marco D, Eisinger G, Hayes DL | title = Testing of work environments for electromagnetic interference| journal = Pacing Clin Electrophysiol | volume = 15 | issue = 11 Pt 2 | pages = 2016–22 | date = November 1992 | pmid = 1279591 | doi = 10.1111/j.1540-8159.1992.tb03013.x | s2cid = 24234010}}</ref> and maintaining heavy equipment that may generate strong magnetic fields. Some medical procedures, particularly [[magnetic resonance imaging]] (MRI), involve very strong magnetic fields or other conditions that may damage pacemakers.

However, many modern pacemakers are specified to be [[Safety_of_magnetic_resonance_imaging#Implants|MR conditional or MRI conditional]], safe to use during MRI subject to certain conditions.<ref name=maass>{{cite journal |last1=Maass |first1=A. H. |last2=Hemels |first2=M. E. W. |last3=Allaart |first3=C. P. |title=Magnetic resonance imaging in patients with cardiac implantable electronic devices |journal=Netherlands Heart Journal |date=December 2018 |volume=26 |issue=12 |pages=584–90 |doi=10.1007/s12471-018-1192-3 |pmid=30406601 |pmc=6288036 }}</ref> The first to be so specified was the [[Medtronic]] Revo MRI SureScan, approved by the US FDA in February 2011,<ref>{{cite web | title=Revo MRI SureScan Pacing System – P090013|publisher=U.S. Food and Drug Administration - Medical Device Approvals and Clearances | date=24 February 2011 | url=http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DeviceApprovalsandClearances/Recently-ApprovedDevices/ucm244469.htm | archive-url=https://web.archive.org/web/20121020065907/http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DeviceApprovalsandClearances/Recently-ApprovedDevices/ucm244469.htm | archive-date=20 October 2012 }}</ref> which was the first to be specified as MR conditional.<ref>{{cite web| title=Terminology |publisher=Magnetic Resonance Safety Testing Services | url=http://www.magneticresonancesafetytesting.com/Terminology.php|url-status=live| access-date=13 February 2023|archive-url=https://web.archive.org/web/20131011031738/http://magneticresonancesafetytesting.com/genpg.asp?pgname=Terminology|archive-date=11 October 2013}}</ref><ref>Husten, Larry. [https://www.forbes.com/sites/larryhusten/2013/02/13/fda-approves-second-generation-mri-friendly-pacemaker-system-from-medtronic/ "FDA Approves Second Generation MRI-Friendly Pacemaker System From Medtronic"]. ''Forbes'', 2013-02-13.</ref> There are several conditions to use of MR Conditional pacemakers, including certain patients' qualifications and scan settings. An MRI conditional device has to have MRI settings enabled before a scan, and disabled afterwards.<ref>{{Cite report|chapter-url=https://www.cardiovascular.abbott/content/dam/bss/divisionalsites/cv/pdf/guides/2b323673-151a-480a-9f93-06c2433ca230.pdf|title=MRI-Ready Systems Manual - MRI Procedure Information for the MR Conditional System|publisher=St. Jude Medical|year=2016|chapter=For physicians: V: Select and save MRI settings; VII: Disable MRI settings}}</ref>

{{As of|2014}} the five most commonly used cardiac pacing device manufacturers (covering more than 99% of the US market) made FDA-approved MR-conditional pacemakers.<ref>{{cite journal |last1=Ferreira |first1=António M |last2=Costa |first2=Francisco |last3=Tralhão |first3=António |last4=Marques |first4=Hugo |last5=Cardim |first5=Nuno |last6=Adragão |first6=Pedro |title=MRI-conditional pacemakers: current perspectives |journal= Medical Devices: Evidence and Research|date=7 May 2014 |volume=7 |pages=115–24 |doi=10.2147/MDER.S44063 |pmid=24851058 |pmc=4019608 |doi-access=free }}</ref> The use of MRI may be ruled out by the patient having an older, non-MRI Conditional pacemaker, or by having old pacing wires inside the heart, no longer connected to a pacemaker.

A 2008 US study found<ref>{{cite web
|url=http://www.bidmc.org/News/InResearch/2008/November/MP3PlayerStudy.aspx
|title=MP3 Headphones Interfere With Implantable Defibrillators, Pacemakers – Beth Israel Deaconess Medical Center
|publisher=www.bidmc.org
|access-date=2008-11-10
|archive-date=2010-09-27
|archive-url=https://web.archive.org/web/20100927014850/http://www.bidmc.org/News/InResearch/2008/November/MP3PlayerStudy.aspx
}}</ref> that the magnetic field created by some headphones used with portable music players or cellphones may cause interference if placed very close to some pacemakers.

In addition, according to the [[American Heart Association]], some home devices have the potential to occasionally inhibit a single beat. Cellphones do not seem to damage pulse generators or affect how the pacemaker works.<ref>{{cite web|title=What is a pacemaker?|url=http://hrmreview.net/what-is-pacemaker/|publisher=HRMReview|access-date=22 May 2014|archive-url=https://web.archive.org/web/20140522160829/http://hrmreview.net/what-is-pacemaker/|archive-date=22 May 2014}}</ref> It is recommended that objects containing magnets, or generating a significant magnetic field, should not be in close proximity to a pacemaker. Induction cooktops, in particular, can pose a risk.<ref>{{cite journal |last1=Irnich |first1=Werner |last2=Bernstein |first2=Alan D. |title=Do induction cooktops interfere with cardiac pacemakers? |journal=EP Europace |date=May 2006 |volume=8 |issue=5 |pages=377–84 |doi=10.1093/europace/eul014 |pmid=16635999 }}</ref>

Before medical procedures, the patient should inform all medical personnel that they have a pacemaker. Having a pacemaker does not imply that a patient requires the use of [[antibiotic]]s to be administered before procedures such as dental work.<ref>{{cite journal |last1=Baddour |first1=Larry M. |last2=Epstein |first2=Andrew E. |last3=Erickson |first3=Christopher C. |last4=Knight |first4=Bradley P. |last5=Levison |first5=Matthew E. |last6=Lockhart |first6=Peter B. |last7=Masoudi |first7=Frederick A. |last8=Okum |first8=Eric J. |last9=Wilson |first9=Walter R. |last10=Beerman |first10=Lee B. |last11=Bolger |first11=Ann F. |last12=Estes |first12=N.A. Mark |last13=Gewitz |first13=Michael |last14=Newburger |first14=Jane W. |last15=Schron |first15=Eleanor B. |last16=Taubert |first16=Kathryn A. |title=Update on Cardiovascular Implantable Electronic Device Infections and Their Management |journal=Circulation |date=26 January 2010 |volume=121 |issue=3 |pages=458–77 |doi=10.1161/circulationaha.109.192665 |pmid=20048212 |doi-access=free }}</ref>

=== End-of-life care and pacemaker deactivation ===
A panel of the [[Heart Rhythm Society]], a US specialist organization based in Washington, DC, deemed that it was legal and ethical to honor requests by patients, or by those with legal authority to make decisions for patients, to deactivate implanted cardiac devices. Lawyers say that the legal situation is similar to removing a feeding tube, though {{As of|2010|lc=y}} there was no legal precedent involving pacemakers in the United States. A patient in many jurisdictions (including the US) is deemed to have a right to refuse or discontinue treatment, including a pacemaker that keeps them alive. Physicians have a right to refuse to turn it off, but are advised by the HRS panel that they should refer the patient to a physician who will.<ref>{{cite web |title=Heart devices can be turned off near end of life |url=https://amednews.com/article/20100531/profession/305319943/4/ |website=amednews.com |date=May 31, 2010 |archive-url=https://web.archive.org/web/20171024071522/https://amednews.com/article/20100531/profession/305319943/4/ |archive-date= Oct 24, 2017 }}</ref><ref>{{Cite web|url=https://www.hrsonline.org/documents/end-life-and-heart-rhythm-devices/download|title=End of Life and Heart Rhythm Devices|publisher=Heart Rhythm Society|year=2014 |url-status=live |archive-url=https://web.archive.org/web/20231023164918/https://www.hrsonline.org/documents/end-life-and-heart-rhythm-devices/download |archive-date= Oct 23, 2023 }}</ref> Some patients consider that hopeless, debilitating conditions, such as severe strokes or late-stage dementia, can cause so much suffering that they would prefer not to prolong their lives with supportive measures.<ref>{{cite news |last1=Butler |first1=Katy |title=What Broke My Father's Heart |url=https://www.nytimes.com/2010/06/20/magazine/20pacemaker-t.html |work=The New York Times |date=18 June 2010 |url-access=subscription |url-status=live |archive-url=https://web.archive.org/web/20240402125756/https://www.nytimes.com/2010/06/20/magazine/20pacemaker-t.html |archive-date= Apr 2, 2024 }}</ref>

=== Privacy and security ===
Security and privacy concerns have been raised with pacemakers that allow wireless communication. Unauthorized third parties may be able to read patient records contained in the pacemaker, or reprogram the devices, as has been demonstrated by a team of researchers.<ref name="ICD-Radio">{{cite conference | date = May 2008 | first = Daniel |  last = Halperin | author2 = Thomas S. Heydt-Benjamin | author3 = Benjamin Ransford|author4=Shane S. Clark|author5=Benessa Defend|author6=Will Morgan|author7=Kevin Fu|author8=Tadayoshi Kohno|author9=William H. Maisel|
url=http://www.secure-medicine.org/icd-study/icd-study.pdf |via=Archimedes Center for Medical Device Security |title=Pacemakers and Implantable Cardiac Defibrillators: Software Radio Attacks and Zero-Power Defenses |conference=IEEE Symposium on Security and Privacy |
access-date = 2008-08-10}}</ref> The demonstration worked at short range; they did not attempt to develop a long range antenna. The proof of concept exploit helps demonstrate the need for better security and patient alerting measures in remotely accessible medical implants.<ref name="ICD-Radio" /> In response to this threat, Purdue University and Princeton University researchers have developed a prototype firewall device, called MedMon, which is designed to protect wireless medical devices such as pacemakers and insulin pumps from attackers.<ref>{{cite web | url=http://www.esecurityplanet.com/network-security/researchers-develop-personal-firewall-solution-for-pacemakers-insulin-pumps.html | title=Researchers Develop Personal Firewall Solution for Pacemakers, Insulin Pumps | publisher=eSecurity Planet |first1=Jeff |last1=Goldman | access-date=2012-04-20 | date=2012-04-20 |archive-url= https://web.archive.org/web/20120423170749/http://www.esecurityplanet.com/network-security/researchers-develop-personal-firewall-solution-for-pacemakers-insulin-pumps.html |archive-date= Apr 23, 2012 }}</ref>

=== Complications ===
[[File:UOTW 15 - Ultrasound of the Week 1.webm|thumb|[[Ultrasound]] showing non capture of a pacemaker<ref>{{cite web|title=UOTW #15 |first1=Ben |last1=Smith |url=https://www.ultrasoundoftheweek.com/uotw-15/|website=Ultrasound of the Week|access-date=27 May 2017|date=26 August 2014 |url-status=unfit |archive-url=https://web.archive.org/web/20181106201010/https://www.ultrasoundoftheweek.com/uotw-15/ |archive-date= Nov 6, 2018 }}</ref>

]]
Complications from having [[surgery]] to implant a [[Pacemaker failure|pacemaker]] are uncommon (each 1–3% approximately), but could include: infection where the pacemaker is implanted or in the bloodstream; [[allergy|allergic reaction]] to the dye or [[anesthesia]] used during the procedure; swelling, bruising or bleeding at the generator site, or around the heart, especially if the patient is taking [[blood thinners]], elderly, of thin frame or otherwise on chronic [[steroid]] use.<ref>{{Cite web|url=http://www.mayoclinic.org/tests-procedures/pacemaker/details/risks/cmc-20198664|title=Risks – Pacemaker |website=Mayo Clinic |access-date=2016-12-01 |url-status=live |archive-url=https://web.archive.org/web/20170218212112/http://www.mayoclinic.org/tests-procedures/pacemaker/details/risks/cmc-20198664 |archive-date= Feb 18, 2017 }}</ref>

A possible complication of dual-chamber artificial pacemakers is 'pacemaker-mediated tachycardia' (PMT), a form of reentrant tachycardia. In PMT, the artificial pacemaker forms the anterograde (atrium to ventricle) limb of the circuit and the atrioventricular (AV) node forms the retrograde limb (ventricle to atrium) of the circuit.<ref name=Olshansky>{{EMedicine|article|159645|Pacemaker-Mediated Tachycardia}}</ref> Treatment of PMT typically involves reprogramming the pacemaker.<ref name="Olshansky" />

Another possible complication is "pacemaker-tracked tachycardia," where a [[supraventricular tachycardia]] such as [[atrial fibrillation]] or [[atrial flutter]] is tracked by the pacemaker and produces beats from a ventricular lead.<ref>{{cite book |doi=10.1016/B978-1-4377-1616-0.00029-1 |chapter=Pacemaker Troubleshooting and Follow-up |title=Clinical Cardiac Pacing, Defibrillation and Resynchronization Therapy |date=2011 |last1=Love |first1=Charles J. |pages=844–888 |isbn=978-1-4377-1616-0 }}</ref> This is becoming exceedingly rare as newer devices are often programmed to recognize supraventricular tachycardias and switch to non-tracking modes.<ref>{{cite journal |last1=Kamalvand |first1=Kayvan |last2=Tan |first2=Kim |last3=Kotsakis |first3=Athanasios |last4=Bucknall |first4=Cliff |last5=Sulke |first5=Neil |title=Is Mode Switching Beneficial? A Randomized Study in Patients With Paroxysmal Atrial Tachyarrhythmias |journal=Journal of the American College of Cardiology |date=August 1997 |volume=30 |issue=2 |pages=496–504 |doi=10.1016/S0735-1097(97)00162-9 |pmid=9247524 |s2cid=23092273 }}</ref>

It is important to consider leads as a potential nidus for [[Thrombosis|thromboembolic]] events. The leads are small-diameter wires from the pacemaker to the implantation site in the heart muscle, and are usually placed intravenously through the [[subclavian vein]] in order to access the right atrium. Placing a foreign object within the venous system in such a manner may disrupt blood-flow and allow for thrombus formation. Therefore, patients with pacemakers may need to be placed on  anti-coagulation therapy to avoid potential life-threatening thrombosis or embolus.<ref>{{cite journal |last1=Noheria |first1=Amit |last2=DeSimone |first2=Christopher V. |last3=Asirvatham |first3=Samuel J. |title=Cardiac Implantable Electronic Device Lead Thrombus as a Nidus for Pulmonary and Systemic Embolization |journal=JACC: Clinical Electrophysiology |date=November 2018 |volume=4 |issue=11 |pages=1437–39 |doi=10.1016/j.jacep.2018.08.019 |doi-access=free |pmid=30466849 }}</ref><ref>{{cite book |doi=10.1007/978-88-470-2139-6_66 |chapter=Pacemaker/ICD Patients: To Anticoagulate or Not to Anticoagulate? |title=Cardiac Arrhythmias 1999 - Vol.1 |date=2000 |last1=Santomauro |first1=M. |last2=Costanzo |first2=A. |last3=Ottaviano |first3=L. |last4=Cresta |first4=R. |last5=Minichiello |first5=S. |last6=Prastaro |first6=M. |last7=Chiariello |first7=M. |pages=494–500 |isbn=978-88-470-0071-1 }}</ref>

These leads may also damage the [[Tricuspid valve|tricuspid valve leaflets]], either during placement or through wear and tear over time. This can lead to [[tricuspid regurgitation]] and [[right-sided heart failure]], which may require [[Valve replacement|tricuspid valve replacement]].<ref>{{cite journal |last1=Lin |first1=Grace |last2=Nishimura |first2=Rick A. |last3=Connolly |first3=Heidi M. |last4=Dearani |first4=Joseph A. |last5=Sundt |first5=Thoralf M. |last6=Hayes |first6=David L. |title=Severe Symptomatic Tricuspid Valve Regurgitation Due to Permanent Pacemaker or Implantable Cardioverter-Defibrillator Leads |journal=Journal of the American College of Cardiology |date=May 2005 |volume=45 |issue=10 |pages=1672–75 |doi=10.1016/j.jacc.2005.02.037 |doi-access=free |pmid=15893186 }}</ref>

Sometimes leads will need to be removed. The most common reason for lead removal is infection; however, over time, leads can degrade due to a number of reasons such as lead flexing.<ref name="Wilkoff">{{cite journal |last1=Wilkoff |first1=Bruce L. |last2=Love |first2=Charles J. |last3=Byrd |first3=Charles L. |last4=Bongiorni |first4=Maria Grazia |last5=Carrillo |first5=Roger G. |last6=Crossley |first6=George H. |last7=Epstein |first7=Laurence M. |last8=Friedman |first8=Richard A. |last9=Kennergren |first9=Charles E.H. |last10=Mitkowski |first10=Przemyslaw |last11=Schaerf |first11=Raymond H.M. |last12=Wazni |first12=Oussama M. |title=Transvenous Lead Extraction: Heart Rhythm Society Expert Consensus on Facilities, Training, Indications, and Patient Management |journal=Heart Rhythm |date=July 2009 |volume=6 |issue=7 |pages=1085–1104 |doi=10.1016/j.hrthm.2009.05.020 |pmid=19560098 }}</ref> Changes to the programming of the pacemaker may overcome lead degradation to some extent. However, a patient who has several pacemaker replacements over a decade or two in which the leads were reused may require lead replacement surgery.

Lead replacement may be done in one of two ways. Insert a new set of leads without removing the current leads (not recommended as it provides additional obstruction to blood flow and heart valve function) or remove the current leads and then insert replacements. The lead removal technique will vary depending on the surgeon's estimation of the probability that simple traction will suffice to more complex procedures. Leads can normally be disconnected from the pacemaker easily, which is why device replacement usually entails simple surgery to access the device and replace it by simply unhooking the leads from the device to replace and hooking the leads to the new device. The possible complications, such as perforation of the heart wall, come from removing the lead{s} from the patient's body.

The free end of a pacemaker lead is actually implanted into the heart muscle with a miniature screw or anchored with small plastic hooks called tines. The longer the leads have been implanted (starting from a year or two), the more likely that they will have additional attachments to the patient's body at various places in the pathway from device to heart muscle, since the body tends to incorporate foreign devices into tissue. In some cases, for a lead that has been inserted for a short amount of time, removal may involve simple traction to pull the lead from the body. Removal in other cases is typically done with a laser or cutting device which threads like a cannula with a cutting edge over the lead and is moved down the lead to remove any organic attachments with tiny cutting lasers or similar device.<ref>{{Cite web |title=What is Laser-Assisted Lead Extraction? {{!}} DFW |url=https://www.heartplace.com/services-laser-lead-extraction |access-date=2022-09-16 |website=HeartPlace |language=en |archive-date=2022-09-20 |archive-url=https://web.archive.org/web/20220920165250/https://www.heartplace.com/services-laser-lead-extraction }}</ref><ref>{{cite journal |last1=Gaca |first1=Jeffrey G. |last2=Lima |first2=Brian |last3=Milano |first3=Carmelo A. |last4=Lin |first4=Shu S. |last5=Davis |first5=R. Duane |last6=Lowe |first6=James E. |last7=Smith |first7=Peter K. |title=Laser-Assisted Extraction of Pacemaker and Defibrillator Leads: The Role of the Cardiac Surgeon |journal=The Annals of Thoracic Surgery |date=May 2009 |volume=87 |issue=5 |pages=1446–51 |doi=10.1016/j.athoracsur.2009.02.015 |pmid=19379883 }}</ref>

Pacemaker lead malposition in various locations has been described in the literature. Treatment varies, depending on the location of the pacer lead and symptoms.<ref>{{cite journal |last1=Kalavakunta |first1=Jagadeesh Kumar |last2=Gupta |first2=Vishal |last3=Paulus |first3=Basil |last4=Lapenna |first4=William |title=An Unusual Cause of Transient Ischemic Attack in a Patient with Pacemaker |journal=Case Reports in Cardiology |date=2014 |volume=2014 |article-number=265759 |doi=10.1155/2014/265759 |pmid=24826308 |pmc=4008350 |doi-access=free }}</ref>

Another possible complication called [[twiddler's syndrome]] occurs when a patient manipulates the pacemaker and causes the leads to be removed from their intended location and causes possible stimulation of other nerves.

Overall life expectancy with pacemakers is excellent, and mostly depends upon underlying diseases, presence of atrial fibrillation, age and sex at the time of first implantation.<ref>{{cite journal |last1=Brunner |first1=M |title=Long-term survival after pacemaker implantation Prognostic importance of gender and baseline patient characteristics |journal=European Heart Journal |date=January 2004 |volume=25 |issue=1 |pages=88–95 |doi=10.1016/j.ehj.2003.10.022|pmid=14683747 |doi-access=free }}</ref>

== Other devices ==
Sometimes devices resembling pacemakers, called [[implantable cardioverter-defibrillator]]s (ICDs) are implanted. These devices are often used in the treatment of patients at risk from sudden cardiac death. An ICD has the ability to treat many types of heart rhythm disturbances by means of pacing, [[cardioversion]], or [[defibrillation]]. Some ICD devices can distinguish between ventricular fibrillation and [[ventricular tachycardia]] (VT), and may try to pace the heart faster than its intrinsic rate in the case of VT, to try to break the tachycardia before it progresses to ventricular fibrillation. This is known as ''fast-pacing'', ''overdrive pacing'', or ''anti-tachycardia pacing'' (ATP). ATP is only effective if the underlying rhythm is ventricular tachycardia, and is never effective if the rhythm is ventricular fibrillation.

{| class="wikitable" style="margin: 1em auto 1em auto"
|+ NASPE / BPEG Defibrillator (NBD) code – 1993<ref name=NASPE_defib_code>{{cite journal |last1=Bernstein |first1=Alan D. |last2=Camm |first2=A. John |last3=Fisher |first3=John D. |last4=Fletcher |first4=Ross D. |last5=Mead |first5=R. Hardwin |last6=Nathan |first6=Anthony W. |last7=Parsonnet |first7=Victor |last8=Rickards |first8=Anthony F. |last9=Smyth |first9=Nicholas P.D. |last10=Sutton |first10=Richard |last11=Tarjan |first11=Peter P. |title=The NASPE */BPEG ** Defibrillator Code |journal=Pacing and Clinical Electrophysiology |date=September 1993 |volume=16 |issue=9 |pages=1776–80 |doi=10.1111/j.1540-8159.1993.tb01809.x |pmid=7692407 }}</ref>
! I || II || III || IV
|-
| Shock chamber || Antitachycardia pacing chamber || Tachycardia detection || Antibradycardia pacing chamber
|-
| O = None || O = None || E = Electrogram || O = None
|-
| A = Atrium || A = Atrium || H = Hemodynamic || A = Atrium
|-
| V = Ventricle || V = Ventricle || || V = Ventricle
|-
| D = Dual (A+V) || D = Dual (A+V) || || D = Dual (A+V)
|}

{| class="wikitable" style="margin: 1em auto 1em auto"
|+ Short form of the NASPE/BPEG Defibrillator (NBD) code<ref name="NASPE_defib_code" />
| ICD-S || ICD with shock capability only
|-
| ICD-B || ICD with bradycardia pacing as well as shock
|-
| ICD-T || ICD with tachycardia (and bradycardia) pacing as well as shock
|}

== History ==
[[File:Arne Larsson.jpg|thumb|In 1958, [[Arne Larsson (patient)|Arne Larsson]] (1915–2001) became the first person to receive an implantable pacemaker. He had 26 devices during his life and campaigned for other patients needing pacemakers.]]

=== Origin ===
In 1889, [[John Alexander MacWilliam]] reported in the ''[[BMJ|British Medical Journal]]'' (BMJ) of his experiments in which application of an electrical impulse to the human heart in [[asystole]] caused a [[Ventricle (heart)|ventricular]] contraction and that a heart rhythm of 60–70 beats per minute could be evoked by impulses applied at spacings equal to 60–70/minute.<ref>{{cite journal |author=McWilliam JA |year=1889 |title=Electrical stimulation of the heart in man |journal=Br Med J |volume=1 |issue= 1468|pages=348–50 |doi=10.1136/bmj.1.1468.348 |pmc=2154721 |pmid=20752595 }}</ref>

In 1926, [[Dr Mark Cowley Lidwill|Mark C Lidwill]] of the [[Royal Prince Alfred Hospital]] of Sydney, supported by physicist Edgar H. Booth of the [[University of Sydney]], devised a portable apparatus which "plugged into a lighting point" and in which "One pole was applied to a skin pad soaked in strong salt solution" while the other pole "consisted of a needle insulated except at its point, and was plunged into the appropriate cardiac chamber". "The pacemaker rate was variable from about 80 to 120 pulses per minute, and likewise the voltage variable from 1.5 to 120 volts".<ref>{{cite book |doi=10.1002/9781119333050.ch1 |chapter=History of cardiac pacing and defibrillation in the young |title=Cardiac Pacing and Defibrillation in Pediatric and Congenital Heart Disease |date=2017 |last1=Rhodes |first1=Larry |last2=Campbell |first2=Robert |pages=1–11 |isbn=978-0-470-67109-2 }}</ref> In 1928, the apparatus was used to revive a [[Stillbirth|stillborn]] infant at [[Crown Street Women's Hospital]] in Sydney, whose heart continued "to beat on its own accord", "at the end of 10 minutes" of stimulation.<ref>Lidwell M C, "Cardiac Disease in Relation to Anaesthesia" in ''Transactions of the Third Session'', Australasian Medical Congress, Sydney, Australia, Sept. 2–7, 1929, p. 160.</ref><ref name="Mond_1982">{{cite journal |vauthors=Mond HG, Sloman JG, Edwards RH | title = The first pacemaker | journal = Pacing and Clinical Electrophysiology | volume = 5 | issue = 2 | pages = 278–82 | year = 1982 | pmid = 6176970 | doi = 10.1111/j.1540-8159.1982.tb02226.x | s2cid = 22049678 }}</ref>

In 1932, American physiologist [[Albert Hyman]], with the help of his brother, described an electro-mechanical instrument of his own, powered by a spring-wound hand-cranked motor. Hyman himself referred to his invention as an "artificial pacemaker", the term continuing in use to this day.<ref>{{cite journal |last1=Aquilina |first1=O |title=A brief history of cardiac pacing |journal=Images in Paediatric Cardiology |date=2006 |volume=8 |issue=2 |pages=17–81 |pmc=3232561 |pmid=22368662 }}</ref><ref>{{cite journal | vauthors = Furman S, Szarka G, Layvand D | title = Reconstruction of Hyman's second pacemaker | journal = Pacing Clin Electrophysiol | volume = 28 | issue = 5 | pages = 446–53 | year = 2005 | pmid = 15869680 | doi = 10.1111/j.1540-8159.2005.09542.x | s2cid = 29138993 }}</ref>

An apparent [[Wikt:hiatus|hiatus]] in the publication of research conducted between the early 1930s and [[World War II]] may be attributed to the public perception of interfering with nature by "reviving the dead".<ref>{{Cite book |last1=Kidder |first1=David S. |url=https://books.google.com/books?id=Z5gfbaYTWlkC&dq=%22reviving+the+dead%22+pacemaker&pg=PA308 |title=The Intellectual Devotional: Health: Revive Your Mind, Complete Your Education, and Digest a Daily Dose of Wellness Wisdom |last2=Oppenheim |first2=Noah D. |last3=Young |first3=Bruce K. |year=2009 |publisher=Harmony/Rodale |isbn=978-1-60529-330-1 |language=en}}</ref> For example, "Hyman did not publish data on the use of his pacemaker in humans because of adverse publicity, both among his fellow physicians, and due to newspaper reporting at the time. Lidwell may have been aware of this and did not proceed with his experiments in humans".<ref name="Mond_1982" />

=== Transcutaneous ===
In 1950, Canadian electrical engineer [[John Alexander Hopps|John Hopps]] designed and built the first external pacemaker based upon observations by cardio-thoracic surgeons [[Wilfred Gordon Bigelow]] and [[John Callaghan (physician)|John Callaghan]] at [[Toronto General Hospital]].<ref>{{Cite web|url=http://collectionscanada.gc.ca/pam_archives/index.php?fuseaction=genitem.displayItem&lang=eng&rec_nbr=104318&rec_nbr_list=104318,3588818,815761,4385271,4385234,4385226,4385302,4385311,4385420,4385246|archive-url=https://web.archive.org/web/20200728125042/https://collectionscanada.gc.ca/pam_archives/index.php?fuseaction=genitem.displayItem&lang=eng&rec_nbr=104318&rec_nbr_list=104318,3588818,815761,4385271,4385234,4385226,4385302,4385311,4385420,4385246|archive-date=2020-07-28|title=John Alexander Hopps fonds|date=2008-03-19|website=Archival description|publisher=[[Library and Archives Canada]]|access-date=16 Sep 2016}}</ref> The device was first tested on a dog at the [[University of Toronto]]'s [[Banting Institute]].<ref>{{cite web|url=http://www.ieee.ca/history/milestones/pacemaker.html|title=IEEE Milestone in Electrical Engineering and Computing|access-date=September 5, 2009|archive-date=February 25, 2021|archive-url=https://web.archive.org/web/20210225103835/http://www.ieee.ca/history/milestones/pacemaker.html}}</ref> A substantial external device using [[vacuum tube]] technology to provide [[transcutaneous pacing]], it was somewhat crude and painful to the patient in use and, being powered from an AC wall socket, carried a potential hazard of [[electric shock|electrocution]] of the patient and inducing [[ventricular fibrillation]].<ref>{{Cite book |last=Silva |first=Regis A. de |url=https://books.google.com/books?id=NI0LtnwdBg0C&dq=John+Hopps+external+pacemaker+vacuum+tube&pg=PA14 |title=Heart Disease |year=2013 |publisher=ABC-CLIO |isbn=978-0-313-37607-8 |language=en}}</ref>

A number of innovators, including [[Paul Zoll]], made smaller but still bulky transcutaneous pacing devices from 1952 using a large rechargeable battery as the power supply.<ref>{{cite web |title=Paul Maurice Zoll |url=https://news.harvard.edu/gazette/story/2001/04/harvard-gazette-paul-maurice-zoll/ |website=Harvard Gazette |date=19 April 2001 }}</ref>

In 1957, William L. Weirich published the results of research performed at the [[University of Minnesota]]. These studies demonstrated the restoration of heart rate, cardiac output and mean aortic pressures in animal subjects with complete [[heart block]] through the use of a [[myocardial]] electrode.<ref>{{cite journal |vauthors=Weirich WL, Gott VL, Lillehei CW | title = The treatment of complete heart block by the combined use of a myocardial electrode and an artificial pacemaker | journal = Surg Forum | volume = 8 | pages = 360–63 | year = 1957 | pmid = 13529629 }}</ref>

In 1958 Colombian doctor Alberto Vejarano Laverde and Colombian electrical engineer [[Jorge Reynolds Pombo]] constructed an external pacemaker, similar to those of Hopps and Zoll, weighing 45&nbsp;kg and powered by a 12 volt car [[lead–acid battery]], but connected to electrodes attached to the heart. This apparatus was successfully used to sustain a 70-year-old priest, Gerardo Florez.<ref>{{cite journal |last1=Reynolds |first1=Jorge |title=The Early History of Cardiac Pacing in Colombia |journal=Pacing and Clinical Electrophysiology |date=March 1988 |volume=11 |issue=3 |pages=355–61 |doi=10.1111/j.1540-8159.1988.tb05018.x |pmid=2452427 |s2cid=20374411 }}</ref>

The development of the [[silicon]] [[transistor]] and its first commercial availability in 1956 was the pivotal event that led to the rapid development of practical cardiac pacemaking.<ref>{{Cite journal |first2=Victor |last2=Parsonnet |first1=Kirk |last1=Jeffrey |date=19 May 1998 |title=Cardiac Pacing, 1960–1985 |journal=Circulation |volume=97 |issue=19|pages=1978–91 |doi=10.1161/01.CIR.97.19.1978 |pmid=9609092 |doi-access=free }}</ref>

=== Wearable ===
In 1958, engineer [[Earl Bakken]] of Minneapolis, Minnesota, produced the first wearable external pacemaker for a patient of [[C. Walton Lillehei]]. This transistorized pacemaker, housed in a small plastic box, had controls to permit adjustment of pacing heart rate and output voltage and was connected to electrode [[Lead (electronics)|leads]] which passed through the skin of the patient to terminate in electrodes attached to the surface of the [[myocardium]] of the heart.

In the UK in the 1960s, Lucas Engineering in [[Birmingham]] was asked by Mr Abrams of The [[Queen Elizabeth Hospital Birmingham|Queen Elizabeth Hospital]] to produce a prototype for a transistorised replacement for the electro-mechanical product. The team was headed by Roger Nolan, an engineer with the Lucas Group Research Centre. Nolan designed and created the first blocking oscillator and transistor-powered pacemaker. This pacemaker was worn on a belt and powered by a rechargeable sealed battery, enabling users to live a more-normal life.

One of the earliest patients to receive this Lucas pacemaker device was a woman in her early 30s. The operation was carried out in 1964 by South African cardiac surgeon Alf Gunning,<ref>{{cite web|url=http://livesonline.rcseng.ac.uk/biogs/E001783b.htm |title= Gunning, Alfred James – Biographical entry – Plarr's Lives of the Fellows Online |publisher=Livesonline.rcseng.ac.uk |access-date=2013-12-29}}</ref><ref>{{cite web |url=http://www.nds.ox.ac.uk/about-us/our-history |title=Our history |website = Nuffield Department of Surgical Sciences |publisher=University of Oxford |access-date=26 October 2020}}</ref> a student of [[Christiaan Barnard]]. This pioneering operation took place under the guidance of cardiac consultant [[Peter Sleight]] at the [[Radcliffe Infirmary]] in Oxford and his cardiac research team at St George's Hospital in London.<ref>{{cite web|url=http://www.bcs.com/pages/Cardiac_Pacemakers.asp |title=British Cardiovascular Society |publisher=Bcs.com |access-date=2013-12-29 |archive-url=https://web.archive.org/web/20131212164351/http://www.bcs.com/pages/Cardiac_Pacemakers.asp |archive-date=2013-12-12 }}</ref><ref>{{cite journal |last1=Record |first1=C O |last2=Sleight |first2=P |last3=Gunning |first3=A J |last4=Kenworthy-Browne |first4=J M |last5=Richings |first5=M |title=Treatment of chronic heart block with the Lucas induction coil pacemaker |journal=Heart |date=1 November 1971 |volume=33 |issue=6 |pages=938–42 |doi=10.1136/hrt.33.6.938 |pmid=5120241 |pmc=458452 }}</ref>

=== Implantable ===
[[File:PPM.png|thumb|350px|Illustration of implanted cardiac pacemaker showing locations of cardiac pacemaker leads]]
The first clinical implantation into a human of a fully implantable pacemaker was on October 8, 1958,<ref>{{cite book |last1=Tesler |first1=Ugo Filippo |title=A History of Cardiac Surgery: An Adventurous Voyage from Antiquity to the Artificial Heart |date=2020 |publisher=Cambridge Scholars Publishing |isbn=978-1-5275-4480-2 |page=151 }}</ref> at the [[Karolinska Institute]] in Solna, [[Sweden]], using a pacemaker designed by inventor [[Rune Elmqvist]] and surgeon [[Åke Senning]] (in collaboration with Elema-Schönander AB, later Siemens-Elema AB), connected to electrodes attached to the [[myocardium]] of the heart by [[thoracotomy]]. The device failed after three hours. A second device was then implanted which lasted for two days. The world's first implantable pacemaker patient, [[Arne Larsson (patient)|Arne Larsson]], went on to receive 26 different pacemakers during his lifetime. He died in 2001, at the age of 86, outliving the inventor and the surgeon.<ref>{{cite news|last=Altman| first=Lawrence| title=Arne H. W. Larsson, 86; Had First Internal Pacemaker| url=https://www.nytimes.com/2002/01/18/world/arne-h-w-larsson-86-had-first-internal-pacemaker.html|access-date=3 March 2014|newspaper=New York Times|date=18 Jan 2002}}</ref>

In 1959, temporary [[transvenous pacing]] was first demonstrated by Seymour Furman and John Schwedel, whereby the [[catheter]] electrode was inserted via the patient's [[basilic vein]].<ref>{{cite journal |vauthors=Furman S, Schwedel JB | title = An intracardiac pacemaker for Stokes-Adams seizures | journal = N. Engl. J. Med. | volume = 261 | issue = 5 | pages = 943–48 | year = 1959 | pmid = 13825713 | doi=10.1056/NEJM195911052611904}}</ref>

In February 1960, an improved version of the Swedish Elmqvist design was implanted by Doctors [[Orestes Fiandra]] and Roberto Rubio in the Casmu 1 Hospital of [[Montevideo]], Uruguay. This pacemaker, the first implanted in the Americas, lasted until the patient died of other ailments, nine months later. The early Swedish-designed devices used batteries recharged by an induction coil from the outside.

Implantable pacemakers constructed by engineer [[Wilson Greatbatch]] entered use in humans from April 1960 following extensive [[animal testing]]. The Greatbatch innovation varied from the earlier Swedish devices in using primary cells (a [[mercury battery]]) as the energy source. The first patient lived for a further 18 months.

The first use of [[transvenous pacing]] in conjunction with an implanted pacemaker was by [[Victor Parsonnet|Parsonnet]] in the United States,<ref name="pmid83641">{{cite journal | vauthors = Parsonnet V | title = Permanent transvenous pacing in 1962 | journal = Pacing Clin Electrophysiol | volume = 1 | issue = 2 | pages = 265–68 | year = 1978 | pmid = 83641 | doi = 10.1111/j.1540-8159.1978.tb03472.x| s2cid = 12263609 }}</ref><ref>{{cite journal | title = Preliminary Investigation of the Development of a Permanent Implantable Pacemaker Using an Intracardiac Dipolar Electrode |vauthors=Parsonnet V, Zucker IR, Asa MM | journal = Clin. Res. | volume = 10  | page = 391 | year = 1962}}</ref><ref name="pmid14484083">{{cite journal | vauthors = Parsonnet V, Zucker IR, Gilbert L, Asa M | title = An intracardiac bipolar electrode for interim treatment of complete heart block | journal = Am. J. Cardiol. | volume = 10 | issue = 2| pages = 261–65 | year = 1962 | pmid = 14484083 | doi =10.1016/0002-9149(62)90305-3 }}</ref> Lagergren in Sweden<ref>{{cite journal | author = Lagergren H | title = How it happened: my recollection of early pacing | journal = Pacing Clin Electrophysiol | volume = 1 | issue = 1 | pages = 140–43 | year = 1978 | pmid = 83610 | doi = 10.1111/j.1540-8159.1978.tb03451.x | s2cid = 9118036 }}</ref><ref>{{cite journal |vauthors=Lagergren H, Johansson L | title = Intracardiac stimulation for complete heart block | journal = Acta Chirurgica Scandinavica | volume = 125 | pages = 562–66 | year = 1963 | pmid = 13928055 }}</ref> and Jean-Jacques Welti in France<ref>Jean Jacques Welti:Biography, Heart Rhythm Foundation{{Full citation needed|date=October 2020}}</ref> in 1962–63.
The transvenous, or pervenous, procedure involved incision of a vein into which was inserted the [[catheter]] electrode lead under [[Fluoroscopy|fluoroscopic]] guidance, until it was lodged within the [[trabeculae]] of the right ventricle. This became the method of choice by the mid-1960s.

Cardiothoracic surgeon [[Leon Abrams]] and medical engineer [[Ray Lightwood]] developed and implanted the first patient-controlled variable-rate heart pacemaker in 1960 at [[the University of Birmingham]]. The first implant took place in March 1960, with two further implants the following month. These three patients made good recoveries and returned to a high quality of life. By 1966, 56 patients had undergone implantation with one surviving for over {{frac|5|1|2}} years.<ref>[http://www.birmingham.ac.uk/documents/culture/bookletfinalpdf.pdf Blue Plaque Guide]</ref><ref>{{cite web|url=http://bhamalumni.org/NetCommunity/Page.aspx?pid=1111&frcrld=1|archive-url=https://web.archive.org/web/20141006065509/http://bhamalumni.org/NetCommunity/Page.aspx?pid=1111&frcrld=1|archive-date=2014-10-06|title=University of Birmingham|work=bhamalumni.org}}</ref>

=== Lithium battery ===
[[File:Cardiac pacer with sold-state power source.jpg|thumb|350x350px|The first lithium-iodide cell-powered pacemaker. Invented by Anthony Adducci and Art Schwalm. [[Cardiac Pacemakers, Inc.|Cardiac Pacemakers Inc]]. 1972<ref name="Schwalm1974">{{Cite patent|country=US|number=3822707|title=Metal-enclosed cardiac pacer with solid-state power source|pubdate=1974-07-09|gdate=1972-04-17|inventor1-last=Adducci|inventor1-first=Anthony J.|inventor2-last=Schwalm|inventor2-first=Arthur W.|assign= Cardiac Pacemekers Inc.}}</ref>]]
The preceding implantable devices all suffered from the unreliability and short lifetime of the available primary cell technology, mainly the [[mercury battery]]. In the late 1960s, several companies, including [[ARCO]] in the US, developed [[Atomic battery|isotope-powered]] pacemakers, but this development was overtaken by the development in 1971 of the [[lithium iodide]] cell by [[Wilson Greatbatch]].<ref>{{Cite web |title=The History of Nuclear Powered Pacemakers |url=http://large.stanford.edu/courses/2015/ph241/degraw2/ |access-date=2023-04-18 |website=large.stanford.edu}}</ref> Lithium-iodide or lithium anode cells became the standard for pacemaker designs.

A further impediment to the reliability of the early devices was the diffusion of water vapor from body fluids through the [[epoxy]] resin encapsulation, affecting the electronic circuitry. This phenomenon was overcome by encasing the pacemaker generator in a hermetically sealed metal case, initially by [[Telectronics]] of Australia in 1969, followed by [[Cardiac Pacemakers, Inc.]] of [[St. Paul, Minnesota]] in 1972. This technology, using [[Titanium#Medical|titanium]] as the encasing metal, became the standard by the mid-1970s.

On July 9, 1974, [[Manny Villafaña|Manuel A. Villafaña]] and [[Anthony Adducci]], the founders of [[Cardiac Pacemakers, Inc.]] ([[Guidant]]), manufactured the world's first pacemaker with a lithium anode and a lithium-iodide electrolyte solid-state battery. Lithium-iodide or lithium anode cells increased the life of pacemakers from one year to as long as eleven years, and has become the standard for pacemaker designs. They began designing and testing their implantable cardiac pacemaker powered by a new longer-life lithium battery in 1971. The first patient to receive a CPI pacemaker emerged from surgery in June 1973.<ref name="Schwalm1974" /><ref>{{cite web|title=Pioneers of the Medical Device Industry| url=http://www.mnhs.org/collections/medTech/org_cardiac_pacemakers.php| publisher=Minnesota Historical Society}}</ref>

Liza Morton was fitted with an implantable pacemaker at 11 days old in 1978, at Glasgow's Yorkhill hospital, Scotland. She was the youngest baby to bear such an implant at the time.<ref>{{cite journal| title= Permanent cardiac pacemaker in infants and children | date= 1986| pmid= 2429390| last1= Dasmahapatra| first1= H. K.| last2= Jamieson| first2= M. P.| last3= Brewster| first3= G. M.| last4= Doig| first4= B.| last5= Pollock| first5= J. C.| journal= The Thoracic and Cardiovascular Surgeon| volume= 34| issue= 4| pages= 230–35| doi= 10.1055/s-2007-1020418}}</ref><ref>{{cite news| title= Doctors gave me a pacemaker when I was 11 days old | date= 17 January 2023| url= https://www.bbc.com/news/uk-scotland-tayside-central-64303138}}</ref>

=== Intra-cardial ===
In 2013, several firms announced devices that could be inserted via a leg catheter rather than invasive surgery. The devices are roughly the size and shape of a pill, much smaller than the size of a traditional pacemaker. Once implanted, the device's prongs contact the muscle and stabilize heartbeats. Development of this type of device was continuing.<ref>{{cite web| url=http://singularityhub.com/2013/12/27/medtronics-minimally-invasive-pacemaker-the-size-of-a-multivitamin/ |title=Medtronic's Minimally Invasive Pacemaker the Size of a Multivitamin |publisher=Singularity Hub |access-date=2013-12-29|date=2013-12-27 }}</ref> In November 2014, Bill Pike of [[Fairbanks, Alaska]], received a [[Medtronic]] Micra pacemaker in Providence St Vincent Hospital in [[Portland, Oregon]]. D. Randolph Jones was the EP doctor. Also in 2014, [[St. Jude Medical Inc.]] announced the first enrollments in the company's leadless Pacemaker Observational Study evaluating the Nanostim leadless pacing technology. The Nanostim pacemaker received European [[CE marking]] in 2013. Post-approval implant trials were carried out in Europe.<ref>{{cite web|url=http://www.dicardiology.com/article/european-post-approval-trial-nanostim-leadless-pacemaker-begins/ |title=European Post-Approval Trial for Nanostim |publisher=DAIC |date=2014-03-18 |access-date=2015-05-04}}</ref> The European study was stopped after reports of six perforations that led to two patient deaths. After investigations, St Jude Medical restarted the study.<ref>{{cite web| url=http://www.medscape.com/viewarticle/827034|publisher=Medscape|title=First-in-Human Data|access-date=2014-06-19}}</ref> In the United States, this therapy had not been approved by the FDA {{As of|2014|lc=y}}.<ref>{{cite web|title=Leadless Pacing from St. Jude Medical |url=http://www.sjm.com/leadlesspacing/intl/options/leadless-pacing |archive-url=https://web.archive.org/web/20141029105333/http://www.sjm.com/leadlesspacing/intl/options/leadless-pacing |archive-date=2014-10-29 }}</ref> While the St Jude Nanostim and the Medtronic Micra are single-chamber pacemakers, it was anticipated that leadless dual-chamber pacing for patients with atrioventricular block would become possible with further development.<ref>{{cite web | last=Stiles | first=Steve | title=New Data on Leadless Pacemaker Supports Efficacy, Safety | website=Medscape | date=24 March 2014 | url=https://www.medscape.com/viewarticle/822457}}</ref>

=== Reusable pacemakers ===

Worldwide each year, in a simple procedure to avoid explosions, thousands of pacemakers are removed from bodies to be cremated. Pacemakers with significant remaining battery life are potentially life-saving devices for people in low- and middle-income countries (LMICs).<ref>{{Cite news| url=https://www.bbc.com/news/health-24828244/ |title=British charity calls for re-use of pacemakers abroad |journal=BBC News |access-date=2018-07-31|date=2013-11-19 |last1=Mazumdar |first1=Tulip }}</ref> The [[National Academy of Medicine|Institute of Medicine]], a US [[non-governmental organization]], has reported that inadequate access to advanced cardiovascular technologies is a major contributor to cardiovascular disease morbidity and mortality in LMICs. Ever since the 1970s, multiple studies worldwide have reported on the safety and efficacy of pacemaker reuse. {{As of|2016}}, widely acceptable standards for safe pacemaker and ICD reuse had not been developed, and there continued to be legal and regulatory barriers to widespread adoption of medical device reuse.<ref>{{cite journal |last1=Crawford |first1=TC |last2=Eagle |first2=KA |title=Reuse of cardiac implantable electronic devices to improve and extend lives: a call to action. |journal=Heart Asia |date=2017 |volume=9 |issue=1 |pages=34–35 |doi=10.1136/heartasia-2016-010835 |pmid=28191825 |pmc=5278341}}</ref>

== In animals ==

Pacemakers have also been implanted in animals such as cats, dogs and horses.<ref>{{cite web |url=https://www.cbsnews.com/minnesota/news/meet-mousey-mns-1st-cat-with-a-pacemaker/ |title=Meet Mousey: MN's 1st Cat With A Pacemaker |website=CBS Minnesota |date=2012-02-13}}</ref><ref>{{cite web |url=https://edition.cnn.com/2019/05/10/health/georgia-pacemakers-donations-pets-trnd/index.html |title= A cardiac nurse couldn't afford a pacemaker for her dog, so she started a program to donate used ones to pets |author=Michelle Lou |website=CNN |date=2019-05-10}}</ref><ref>{{cite web |url=https://www.horseandhound.co.uk/news/horse-fitted-with-first-ever-pacemaker-40341 |title= Horse fitted with first ever pacemaker  |website=Horse & Hound |date=2001-02-06}}</ref>

== Manufacturers ==
Current and prior manufacturers of implantable pacemakers
* [[Biotronik]] (Germany)
* [[Boston Scientific]] (US)
* [[Cardiac Pacemakers, Inc.|Cardiac Pacemaker Inc.]]; [[Guidant]] (US) (now owned by Boston Scientific)
* [[Intermedics]] (US)
* [https://en.lepumedical.com/ Lepu Medical] (China)
* [https://www.medicoweb.com/main/en/pacemaker/ Medico] (Italy)
* [[Medtronic]] (US)
* [[Sorin Group]] (Italy) (merged with [[Cyberonics]] to form [[LivaNova]]; in 2018, LivaNova sold its cardiac rhythm management business unit to [[MicroPort]] for $190M<ref>{{cite web|url=https://www.massdevice.com/livanova-closes-190-crm-sale-to-microport/|title=LivaNova closes $190 CRM sale to MicroPort|website=Mass Device|date=30 April 2018}}</ref> )
* [[St. Jude Medical]] (US) (now owned by [[Abbott Laboratories]])
* [[Abbott Laboratories|Abbott]] (US)

{{Incomplete list|date=February 2021}}

== See also ==
* [[Biological pacemaker]]
* [[Button cell]]
* [[Electrical conduction system of the heart]]
* [[Implantable cardioverter-defibrillator]]
* [[Infective endocarditis]]
* [[Pacemaker syndrome]]

== References ==
{{reflist}}

== External links ==
* [http://www.analog.com/library/analogDialogue/archives/46-11/pacing_artifacts.pdf Detecting and Distinguishing Cardiac Pacing Artifacts] {{Webarchive|url=https://web.archive.org/web/20160304000405/http://www.analog.com/library/analogDialogue/archives/46-11/pacing_artifacts.pdf |date=2016-03-04 }}
* [https://www.nhlbi.nih.gov/health/defibrillators Implantable Cardioverter Defibrillator from National Heart, Lung and Blood Institute]
* [https://web.archive.org/web/20100925001511/http://escardio.org/communities/EHRA/education/webinars/Pages/welcome.aspx Current indications for CRT-P and CRT-D: Webinar from the European Heart Rhythm Association (EHRA)]

{{Cardiac surgery and other cardiovascular procedures}}

{{Authority control}}

{{DEFAULTSORT:Pacemaker (artificial)}}
[[Category:1959 introductions]]
[[Category:Cardiac electrophysiology]]
[[Category:Embedded systems]]
[[Category:Implants (medicine)]]
[[Category:Neuroprosthetics]]
[[Category:Prosthetics]]
[[Category:Cybernetics]]
[[Category:Biomedical engineering]]
[[Category:Medical devices]]
[[Category:Canadian inventions]]
[[Category:Australian inventions]]