Editing Pacemaker (section)

== 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 |url-status=dead }}</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 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|url-status=dead}}</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" />