7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Official reprint from UpToDate www.uptodate.com 2023 UpToDate, Inc. and/or its affiliates. All Rights Reserved. Permanent cardiac pacing: Overview of devices and indications : Mark S Link, MD : N A Mark Estes, III, MD : Susan B Yeon, MD, JD, FACC All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through: Jun 2023. This topic last updated: Jun 27, 2023. INTRODUCTION Cardiac pacemakers are effective treatments for a variety of bradyarrhythmias. By providing an appropriate heart rate and heart rate response, cardiac pacing can reestablish effective circulation and normalize hemodynamics that are compromised by a slow heart rate. This topic will present a broad review of the role of cardiac pacing in a variety of settings. The management of the specific disorders is discussed separately as is a description of the different types of pacemakers and pacing modes. (See "Sinus node dysfunction: Treatment" and "Third- degree (complete) atrioventricular block" and "Second-degree atrioventricular block: Mobitz type II" and "Modes of cardiac pacing: Nomenclature and selection".) GENERAL CONSIDERATIONS Despite the myriad of clinical situations in which permanent pacing is considered, most management decisions regarding permanent pacemaker implantation are driven by the following clinical factors: The association of symptoms with a bradyarrhythmia The location of the conduction abnormality The absence of a reversible cause https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 1/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Symptoms Patients are often evaluated for permanent cardiac pacemaker placement because of symptoms that may be due to bradyarrhythmias (eg, dizziness, lightheadedness, syncope, fatigue, and poor exercise tolerance). These patients will often have evidence of persistent or intermittent sinus node dysfunction or atrioventricular (AV) conduction abnormalities. Establishing a direct correlation between symptoms and bradyarrhythmias, typically by taking a careful history and documenting the cardiac rhythm with either an electrocardiogram or ambulatory monitoring (external or insertable cardiac monitor [also sometimes referred to as an implantable cardiac monitor or an implantable loop recorder]), is essential for choosing the optimal candidates for pacemaker insertion [1,2]. A direct correlation between symptoms and bradyarrhythmias will increase the likelihood of pacemaker therapy resulting in clinical improvement. Conversely, failure to document such a correlation, or the presence of an alternative explanation for symptoms, decreases the likelihood of benefit from pacemaker insertion. Location of conduction abnormality The location of an AV conduction abnormality (ie, within the AV node or below the AV node in the His-Purkinje system) is an important determinant of both the probability and the likely pace of progression of conduction system disease ( figure 1). (See "Second-degree atrioventricular block: Mobitz type I (Wenckebach block)" and "Second-degree atrioventricular block: Mobitz type II".) Disease within the AV node is suggested by the following: First-degree AV block with significant PR prolongation (see "First-degree atrioventricular block") Second-degree AV block, Mobitz type I (Wenckebach) (see "Second-degree atrioventricular block: Mobitz type I (Wenckebach block)") Normal QRS complex Disease below the AV node, in the His-Purkinje system, is suggested by: Normal or minimally prolonged PR interval Second-degree AV block, Mobitz type II (see "Second-degree atrioventricular block: Mobitz type II") Third-degree (complete) AV block (see "Third-degree (complete) atrioventricular block") A wide QRS complex (bundle branch block and/or fascicular block) Disease in the His-Purkinje system is generally considered to be more concerning because it can progress quickly and lead to complete heart block. As a result, permanent pacemaker placement https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 2/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate is likely to be recommended, as it is more likely to provide significant clinical benefit in such patients. Reversible causes In addition to intrinsic conduction system disease, there are a number of extrinsic causes of bradyarrhythmias which are reversible. While patients who have a reversible bradyarrhythmia may require temporary pacemaker support, in most circumstances permanent cardiac pacing is not indicated or required. Some of the more common reversible causes of bradyarrhythmia include: Medications (eg, beta blockers, nondihydropyridine calcium channel blockers, antiarrhythmic medications [eg, sotalol, amiodarone]). (See "Etiology of atrioventricular block", section on 'Medications'.) Toxic, metabolic, and electrolyte disturbances (eg, hyperkalemia, digoxin toxicity). Acute myocardial ischemia or infarction. (See 'Post-myocardial infarction' below and "Conduction abnormalities after myocardial infarction", section on 'Management of patients with AV block'.) Cardiac trauma (eg, postoperative, blunt chest trauma, indwelling pulmonary artery catheters). Lyme disease. Cardiac surgery, especially valve disorder surgery. Transcatheter aortic valve implantation. Reversible causes of bradyarrhythmias and the management of reversible causes with temporary cardiac pacing are discussed in detail separately. (See "Temporary cardiac pacing", section on 'Reversible conditions'.) Concurrent ICD Some patients with an indication for a permanent pacemaker require an upgrade to an implantable cardioverter-defibrillator (ICD) or may require cardiac resynchronization therapy. ICDs (with the exception of the subcutaneous ICD) have antitachycardia and antibradycardia pacing therapeutic capabilities. In patients who have a permanent pacemaker and require an ICD or cardiac resynchronization therapy, the pacemaker should be upgraded to the appropriate device so that all functions can be served by one pulse generator. (See "Subcutaneous implantable cardioverter defibrillators".) TYPES OF PERMANENT PACEMAKER SYSTEMS https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 3/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Cardiac pacemakers generally consist of two components: a pulse generator ( picture 1), which provides the electrical impulse for myocardial stimulation; and one or more electrodes (commonly referred to as leads), which deliver the electrical impulse from the pulse generator to the myocardium. A "leadless" pacemaker is now also available ( picture 2). Transvenous leads have potential long-term complications (eg, venous thrombosis, infection, lead malfunction, etc). Leadless cardiac pacing systems offer the promise of long-term pacing capability without lead- associated complications. Pulse generators Pulse generators are the "battery" component of the pacemaker ( picture 1), generating the electrical impulse which is transmitted to the myocardium, resulting in the heart beat. Pulse generators are currently implanted most commonly in the infraclavicular region of the anterior chest wall. The majority are placed in a pre-pectoral position, but in some cases a sub-pectoral position is advantageous. The pulse generator transmits the electrical impulse to the myocardium via transvenous leads. Epicardial systems are still available and may be necessary as a result of anatomical limitations to placing a transvenous lead(s). But these epicardial leads typically do not last as long. For the leadless systems, the pulse generator and the electrode are one self-contained unit, which is positioned via the femoral vein into the right ventricle (RV). (See 'Leadless systems' below.) Transvenous systems The vast majority of contemporary cardiac pacing systems utilize transvenous electrodes (leads) for transmission of the pacing impulses from the pulse generator to the myocardium. Transvenous leads, however, are associated with a nontrivial rate of long- term complications, including: Infection Venous thrombosis and resultant subclavian vein occlusion Lead malfunction Tricuspid valve injury (resulting in tricuspid regurgitation) The approach to the management of long-term transvenous lead complications is discussed separately. (See "Cardiac implantable electronic devices: Periprocedural complications" and "Cardiac implantable electronic devices: Long-term complications" and "Cardiac implantable electronic device lead removal".) His bundle pacing His bundle pacing has been developed to prevent the harmful effects of RV pacing. In this modality, the RV lead is actively fixed in the area of the His bundle with subsequent ventricular activation via the His-Purkinje system. Theoretically, this will reduce the https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 4/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate odds that dyssynchrony will occur. His bundle pacing may be beneficial in those with an anticipated high percent of RV pacing and possibly even those who have an indication for cardiac resynchronization therapy (CRT) such as a left bundle branch block. Clinical trials are ongoing [3,4]. While clinical trials are ongoing, registry data on His bundle pacing indicate a high rate of intervention for lead dislodgement. High capture thresholds result in more rapid battery depletion of the pacemaker pulse generator. This form of conduction system pacing is less commonly used than pacing in the region of the left bundle, as described below. (See 'Left bundle pacing' below.) Left bundle pacing Left bundle pacing has emerged as a competitor to His bundle pacing. While His bundle pacing typically occurs with the lead placed at the junction of the AV node and His bundle, left bundle pacing occurs with placement of the lead in the septum of the RV. Observational data show lower capture thresholds and dislodgement rates with left bundle area pacing compared with His bundle pacing. However, there are no large-scale randomized controlled trials. Epicardial systems Epicardial cardiac pacemaker systems utilize a pulse generator with leads that are surgically attached directly to the epicardial surface of the heart. These systems have largely been replaced by transvenous systems for patients requiring long-term cardiac pacing, although there is still a role for the occasional patient with vascular access problems (eg, venous thrombosis, congenital anatomical variations, prosthetic tricuspid valve). The major role for epicardial pacing systems in current practice is for temporary pacing following cardiac surgery; such systems, however, are designed as temporary systems that must be removed within the first days to weeks following cardiac surgery. Leadless systems In response to the limitations of both transvenous and epicardial pacing systems, efforts have been made to develop leadless cardiac pacing systems [5-12]. Leadless ventricular pacing Contemporary leadless systems include the pulse generator and the electrode within a single unit that is placed into the RV via a transvenous approach [13]. Multiple prospective, nonrandomized, multicenter trials with single-chamber RV leadless pacemakers followed for up to 12 months have demonstrated safety and efficacy [6,9,11,14-17]. In the SELECT-LV study, a prospective, nonrandomized study of safety and efficacy of leadless pacing for CRT among patients who "failed" conventional CRT, the leadless device was successfully implanted in 34 of 35 patients [12]. The primary efficacy endpoint (biventricular pacing on ECG at one month) was achieved in 33 of 34 patients; however, significant procedure https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 5/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate and device-related complication occurred in three patients (9 percent) at the time of implant and in eight patients (23 percent) within the first month postimplant. Leadless cardiac pacing systems have been approved for use in Europe since 2013, and, in April 2016, the first leadless cardiac pacing system was approved for use in the United States [18]. As of December 2016, two leadless pacemaker systems are approved by the US Food and Drug Administration (FDA) and commercially available, with slightly different sizes and implantation requirements [19]: Micra measures 2.6 x 0.7 cm, requires a 23-French introducer sheath, and was approved by the US FDA in 2016. Nanostim measures 4.2 x 0.6 cm and requires an 18-French sheath. However, the Nanostim was pulled from the market in 2017 because of early battery depletion issues. In 2022, the Aveir (a modification of the Nanostim device) was approved by the US FDA. In general, leadless pacemakers have been placed via the transfemoral approach, but in select patients the leadless pacemaker has been successfully implanted via a transjugular approach [20]. Following device approval and introduction into general clinical practice, patients have been prospectively enrolled in a registry to allow for postmarketing "real world" evaluation of safety and efficacy [6,7,9,21-29]. Among a cohort of 1817 patients from the postapproval registry, 1801 (99.1 percent) had successful implantation of the Micra leadless pacemaker at 179 centers [21]. A total of 41 major complications were reported at 30-day follow-up (2.3 percent), comparable to the major complication rate in the pre-approval investigational trial. Among 16 patients from three leadless pacemaker trials [6,7,9] who subsequently required device removal, the device was successfully extracted in 15 of 16 patients (94 percent), including all five patients in whom the device was in place for <6 weeks [22]. In a subsequent report on the extraction experience among 1423 worldwide recipients of the Nanostim device, among whom 73 patients underwent attempted device retrieval (implant duration ranging from one day to four years), 66 devices (90 percent) were successfully retrieved [23]. Of the 73 attempted retrievals, 53 were done in response to the clinical alert about potential battery malfunction, with the other 20 patients (1.4 percent) having another clinical indication for device retrieval. This rate of necessary revision is similar to the reported experience with the Micra device, in which an actuarial revision rate of 1.4 percent has also been reported [24]. https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 6/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate A report has been published describing the successful removal of the Nanostim device up to nearly three years postimplant [25]. Leadless pacemakers have been successfully implanted, with good short-term results, in patients at high risk of device infection, including hemodialysis patients (197 of 201 patients successfully implanted with no infections over mean 6.2 month follow-up) [26] and patients with a prior cardiac implantable electronic device (CIED) infection (105 patients implanted 30 days from prior infected CIED explant with no infections over mean 8.5 month follow-up) [27]. Among a small cohort of 43 patients who had the device implanted while on anticoagulant therapy, only one patient experienced a bleeding complication [28]. While implantation appears safe in patients treated with warfarin or another oral anticoagulant, additional data are required to guide the optimal approach to implantation in this setting. Leadless cardiac pacing holds promise as a long-term permanent cardiac pacing option for patients requiring single ventricle (RV only) pacing and appears both safe and efficacious in the short term. Leadless AV sequential pacing While initial leadless pacemakers could only sense and pace the RV, contemporary devices have the capacity to maintain AV synchrony: The US FDA-approved Micra AV uses an accelerometer-based algorithm to sense atrial activity and pace the ventricle and thus provide VDD pacing [30]. The device is used to treat patients with normal sinus function and complete AV block. The investigational leadless pacing system (Aveir DR) is composed of one device implanted in the right atrium and one device implanted in the RV. A prospective multicenter study of this system enrolled 190 patients with sinus node dysfunction and 100 with AV block [31]. The implantation procedure was successful in 98.3 percent of patients. The primary safety endpoint of freedom from complications at 90 days was met in 90.3 percent of patients. The first primary performance endpoint of adequate atrial capture threshold and sensing amplitude was met in 90.2 percent of patients. The second primary performance endpoint of at least 70 percent AV synchrony at three months while sitting was met in 97.3 percent of patients. COMMON INDICATIONS https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 7/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Permanent pacemaker implantation is most commonly indicated for sinus node dysfunction or high-grade/symptomatic AV block. Guidelines for implantation of cardiac pacemakers have been published jointly by the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society (ACC/AHA/HRS) [1]. Although there are occasional cases that cannot be categorized according to these guidelines, they are, for the most part, comprehensive and have been widely endorsed. Similar guidelines have been established by the European Society of Cardiology [2]. Some indications for permanent pacing are relatively certain or unambiguous, while others require considerable expertise and judgment. It is helpful to divide the indications for pacemaker implantation into three specific categories, or classes, as defined by the ACC/AHA/HRS guidelines [1]: Class I Conditions in which permanent pacing is definitely beneficial, useful, and effective. In such conditions, implantation of a cardiac pacemaker is considered acceptable and necessary, provided that the condition is not due to a transient cause. Class II Conditions in which permanent pacing may be indicated but there is conflicting evidence and/or divergence of opinion; class IIA refers to conditions in which the weight of evidence/opinion is in favor of usefulness/efficacy, while class IIb refers to conditions in which the usefulness/efficacy is less well established by evidence/opinion. Class III Conditions in which permanent pacing is not useful/effective and in some cases may be harmful. Sinus node dysfunction The need for permanent pacing in patients with sinus node dysfunction is based largely upon the correlation of bradycardia with symptoms ( table 1) [1,2]. While patients with a heart rate of less than 40 beats per minute or pauses of greater than four seconds are more likely to develop symptoms, there is no definitive threshold for heart rate (or pause length) that determines the absolute need for a permanent pacemaker. This is especially true if the bradycardia occurs during sleep. Class I The following conditions are considered class I indications for pacemaker placement [1,2]: Sinus bradycardia in which symptoms are clearly related to the bradycardia (usually in patients with a heart rate below 40 beats per minute or frequent sinus pauses). Symptomatic chronotropic incompetence (an impaired heart rate response to exercise, generally defined as failure to achieve 85 percent of the age-predicted maximum heart rate during a formal or informal stress test or the inability to mount an age-appropriate heart https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 8/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate rate during activities of daily living, [ie, as documented by ambulatory monitoring]). (See "Prognostic features of stress testing in patients with known or suspected coronary disease", section on 'Heart rate response to exercise'.) Symptomatic sinus bradycardia due to the effects of clinically necessary evidence-based therapy (eg, antianginal or antiarrhythmic medications) with no effective alternative. Class II The following are considered to be class II indications for pacemaker placement in patients with sinus node dysfunction: Sinus bradycardia (heart rate <40 beats per minute) in a patient with symptoms suggestive of bradycardia, but without a clearly demonstrated association between bradycardia and symptoms. Sinus node dysfunction in a patient with unexplained syncope. Chronic heart rates <40 beats per minute while awake in a minimally symptomatic patient. Patients with sinus bradycardia of lesser severity (heart rate >40 beats per minute) who complain of dizziness or other symptoms that correlate with the slower rates are also potential candidates for pacemaker therapy. Acquired AV block Acquired AV block is the second most common indication for permanent pacemaker placement. Many disorders can cause acquired AV block, and these are discussed in detail separately. (See "Etiology of atrioventricular block" and "Third-degree (complete) atrioventricular block" and "Second-degree atrioventricular block: Mobitz type II" and "Second- degree atrioventricular block: Mobitz type I (Wenckebach block)".) Class I The following conditions represent severe conduction disease and are generally considered to be class I indications for pacing when not attributable to reversible causes: Complete (third-degree) AV block with or without symptoms Advanced second-degree AV block (block of two or more consecutive P waves) Second-degree AV block, Mobitz type II (with or without symptoms) Symptomatic second-degree AV block, Mobitz type I (Wenckebach) Exercise-induced second- or third-degree AV block (in the absence of myocardial ischemia) Some controversy exists concerning asymptomatic patients with congenital complete heart block (eg, complete heart block and a structurally normal heart). The ACC/AHA/HRS guidelines recommend permanent pacemaker implantation in patients with congenital complete heart block and any high-risk feature (symptoms attributed to bradycardia, wide QRS rhythm, mean https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 9/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate daytime heart rate <50 beats per minute, complex ventricular ectopy, or ventricular dysfunction), while noting that permanent pacing is reasonable in individuals with congenital complete heart block without these risk factors [1]. Similar recommendations are included in the European guidelines [2]. (See "Congenital third-degree (complete) atrioventricular block", section on 'Treatment'.) Class II Patients with varying degrees of acquired AV block may still benefit from pacemaker placement. In such patients, determinations are often based upon correlation of bradycardia with symptoms, exclusion of other causes of symptoms, and in rare instances based on results of electrophysiology (EP) testing. Conditions in which pacemaker placement can be considered include the following: First-degree AV block when there is hemodynamic compromise because of effective AV dissociation secondary to a very long PR interval. (See "First-degree atrioventricular block", section on 'Management'.) Bifascicular or trifascicular block associated with syncope that can be attributed to transient complete heart block, based upon the exclusion of other plausible causes of syncope ( table 2). Alternating bundle-branch block would also fulfill this criterion. (See "Chronic bifascicular blocks".) AV block in some patients may be due to the effects of medications (eg, antianginal or antiarrhythmic medications), a potentially reversible cause. However, if the pertinent medications cannot be discontinued (ie, alternative therapies are unavailable), permanent pacemaker insertion may be performed to allow for ongoing therapy with the drugs causing AV block [1,32]. Post-myocardial infarction The indications for permanent pacing, including those related to patients after an MI, are presented in detail separately. In general, our approach is in agreement with published professional society guidelines for implantation of a permanent cardiac pacemaker [1,33]. (See "Conduction abnormalities after myocardial infarction".) Neurally-mediated syncope Evaluation of the patient with syncope can be clinically challenging. Once a diagnosis of neurocardiogenic syncope is established or suspected, effective treatment can be similarly challenging. The use of pacemakers in this disorder is limited to very selected patients whose syncopal events are clearly associated with a marked cardioinhibitory or bradycardic event. Pacemaker treatment is effective only in patients with a marked isolated cardioinhibitory or bradycardic cause of syncope. However, since many patients have both bradycardic and vasodepressor https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 10/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate components, some patients with an indication for pacemaker placement may not have a significant improvement in symptoms with pacing. In fact, pacing is rarely necessary in neutrally- mediated syncope. (See "Reflex syncope in adults and adolescents: Treatment".) OTHER INDICATIONS Congenital complete heart block Congenital complete heart block has a variety of causes but most commonly is due to maternal neonatal lupus. Congenital complete heart block can present in utero, as a neonate, or later in childhood, with management directed by the time of presentation (ie, prenatal or postnatal) as well as the severity of symptoms. This topic is discussed separately. (See "Congenital third-degree (complete) atrioventricular block".) Neuromuscular diseases A number of neuromuscular diseases are associated with AV block, including myotonic muscular dystrophy, Kearns-Sayre syndrome, Erb dystrophy (limb-girdle), and peroneal muscular atrophy. Patients with these disorders have a class I indication for pacemaker placement once any evidence of second- or third-degree block develops. This is true even if the patient is asymptomatic, because there may be unpredictably rapid progression of AV conduction disease. (See "Inherited syndromes associated with cardiac disease".) Due to this potential for rapid progression, patients with these disorders are considered to have a class IIb indication for pacemaker placement even with first-degree AV block, regardless of symptoms [1,34]. Some of these patients may also require an implantable cardioverter- defibrillator or cardiac resynchronization therapy (CRT) [35]. (See "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF".) Long QT syndrome High-risk patients with congenital long QT syndrome have been treated with pacemakers to prevent ventricular arrhythmias, generally with a dual chamber pacemaker. However, most of these patients are now treated with an implantable cardioverter-defibrillator, which has pacing capability as well. (See "Congenital long QT syndrome: Treatment".) Bradycardia-induced ventricular arrhythmias Bradycardia and/or prolonged pauses can precipitate ventricular arrhythmias. Although this phenomenon is most commonly associated with QT prolongation, it can occur in patients with a normal QT interval. Patients with pause- dependent ventricular arrhythmias, with or without QT prolongation, have an indication for pacemaker implantation. As noted above, however, many of these patients will be treated with an implantable cardioverter-defibrillator, which also has pacing capability. (See 'Long QT syndrome' above.) https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 11/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Hypertrophic cardiomyopathy Pacing for medically refractory, symptomatic hypertrophic cardiomyopathy with significant resting or provoked left ventricular outflow obstruction is not generally recommended, particularly in patients who are candidates for septal reduction therapy [36]. The role of pacing in patients with HCM, along with the utilization of implantable cardioverter-defibrillators, is discussed in detail separately. (See "Hypertrophic cardiomyopathy: Management of patients with outflow tract obstruction", section on 'Therapies of limited benefit'.) Heart failure Neither single-chamber RV pacing nor dual-chamber right heart pacing (RA and RV) are indicated for the treatment of heart failure symptoms in patients with heart failure. However, CRT, also referred to as biventricular pacing, is used to improve symptoms and survival in patients with medically refractory advanced heart failure, nonischemic or ischemic cardiomyopathy, and left bundle branch block. The use of CRT is discussed in detail separately, including the potential use of CRT in patients who have reduced left ventricular systolic function and an indication for permanent pacing in whom pacing will be frequent (ie, >40 percent cumulative pacing). (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system".) CLASS III: PACING NOT INDICATED These are conditions that do not reliably improve with cardiac pacing, or are considered to lack adequate evidence of benefit from permanent pacing. Most of these conditions are bradyarrhythmias that are asymptomatic or due to reversible causes. Syncope of undetermined etiology. This may require extensive investigation, including ambulatory monitoring, neurologic evaluation, electrophysiologic testing, and perhaps tilt- table testing. Cardiac pacing may be considered if no other etiology of syncope is uncovered, and the history strongly suggests a cardiogenic origin. In such cases, the patient must understand that permanent pacing may not alleviate the symptoms, since no correlation between symptoms and rhythm has been documented. In addition, if a pacemaker is implanted because of a strong clinical suspicion that the patient's symptoms are due to a bradyarrhythmia, in the absence of any objective evidence of conduction system disease, reimbursement may be disallowed. Sinus bradycardia without significant symptoms. Sinoatrial block or sinus arrest without significant symptoms. https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 12/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Asymptomatic prolonged RR intervals with atrial fibrillation or other causes of transient ventricular pause. Asymptomatic bradycardia during sleep. Asymptomatic second-degree Mobitz I (Wenckebach) AV block. A hyperactive cardioinhibitory response to carotid sinus stimulation in the absence of symptoms or in the presence of vague symptoms such as dizziness, lightheadedness, or both. Right bundle branch block with left axis deviation without syncope or other symptoms compatible with intermittent AV block. Reversible AV block, such as those associated with electrolyte abnormalities, Lyme disease, sleep apnea, enhanced vagal tone, and some cases that occur postoperatively. AV block associated with drugs such as beta blockers, diltiazem, or verapamil is not always reversible and can be associated with underlying conduction system disease [32]. (See "Etiology of atrioventricular block", section on 'Medications'.) Long QT syndrome or torsades de pointes due to reversible causes. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Arrhythmias in adults" and "Society guideline links: Cardiac implantable electronic devices".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 13/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topic (see "Patient education: Pacemakers (The Basics)" and "Patient education: Bradycardia (The Basics)") Beyond the Basics topic (see "Patient education: Pacemakers (Beyond the Basics)") SUMMARY AND RECOMMENDATIONS General considerations Two general factors guide the vast majority of decisions regarding permanent pacemaker insertion: the association of symptoms with an arrhythmia and the potential for progression of the rhythm disturbance, which is largely dependent on the anatomical location of the conduction abnormality. (See 'General considerations' above.) Association of symptoms with arrhythmia Patients frequently present for consideration of pacemaker placement because of symptoms that may be due to bradyarrhythmias (eg, dizziness, lightheadedness, syncope, fatigue, and poor exercise tolerance). It is critical to attempt to establish a direct correlation between symptoms and bradyarrhythmias, which will increase the likelihood of recommending pacemaker placement. (See 'Symptoms' above.) Risk of progression The location of an atrioventricular (AV) conduction abnormality (ie, within the AV node or below the AV node in the His-Purkinje system) is an important determinant of both the probability and the likely pace of progression of conduction system disease. Disease below the AV node, in the His-Purkinje system, is generally considered to be less stable; as a result, permanent pacemaker placement is more likely to be recommended. (See 'Location of conduction abnormality' above.) Types of pacemaker systems Pacemakers ( picture 1) are most commonly placed in a thoracic pre-pectoral position and connected to one or two transvenous leads, which are positioned endocardially. Epicardial lead placement is still a viable option for patients with limited transvenous access. Leadless pacing systems are now available and hold significant promise for the future. (See 'Types of permanent pacemaker systems' above.) Indications for pacemaker implantation The most common indications for pacemaker implantation are sinus node dysfunction followed by AV block. All other indications are https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 14/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate much less common and include neurocardiogenic syncope and iatrogenic causes (eg, post- AV node ablation). While patients with a heart rate of less than 40 beats per minute, or pauses of greater than four seconds, are more likely to develop symptoms, there is no definitive threshold for heart rate (or pause length) which determines the absolute need for a permanent pacemaker. (See 'Common indications' above.) When to consider CRT or ICD With the advent of cardiac resynchronization therapy (CRT), it is important to also take into consideration the patient's left ventricular function at the time a pacemaker is considered. If the patient has left ventricular dysfunction and requires frequent pacing, it would be appropriate to consider CRT and/or an implantable cardioverter-defibrillator. Whether His bundle or left bundle pacing will provide benefits similar to CRT is yet to be determined. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system".) Pacing not indicated Conditions with a lack of adequate evidence of benefit from permanent pacing, in which permanent pacing is generally non indicated, include, among others, syncope of undetermined etiology, asymptomatic sinus bradycardia, asymptomatic first-degree and second-degree Mobitz I (Wenckebach) AV block, reversible AV block, and long QT syndrome or torsades de pointes due to a reversible cause. (See 'Class III: Pacing not indicated' above.) ACKNOWLEDGMENT The UpToDate editorial staff acknowledges David L Hayes, MD, who contributed to earlier versions of this topic review. Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2019; 74:e51. 2. Glikson M, Nielsen JC, Kronborg MB, et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Eur Heart J 2021; 42:3427. https://www.uptodate.com/contents/permanent-cardiac-pacing-overview-of-devices-and-indications/print 15/24 7/6/23, 3:09 PM Permanent cardiac pacing: Overview of devices and indications - UpToDate 3. Upadhyay GA, Vijayaraman P, Nayak HM, et al. On-treatment comparison between corrective His bundle pacing and biventricular pacing for cardiac resynchronization: A secondary analysis of the His-SYNC Pilot Trial. Heart Rhythm 2019; 16:1797. 4. Upadhyay GA, Vijayaraman P, Nayak HM, et al. His Corrective Pacing or Biventricular Pacing for Cardiac Resynchronization in Heart Failure. J Am Coll Cardiol 2019; 74:157. 5. Auricchio A, Delnoy PP, Butter C, et al. Feasibility, safety, and short-term outcome of leadless ultrasound-based endocardial left ventricular resynchronization in heart failure patients: results of the wireless stimulation endocardially for CRT (WiSE-CRT) study. Europace 2014; 16:681. 6. Reddy VY, Knops RE, Sperzel J, et al. Permanent leadless cardiac pacing: results of the LEADLESS trial. Circulation 2014; 129:1466. 7. Knops RE, Tjong FV, Neuzil P, et al. Chronic performance of a leadless cardiac pacemaker: 1-