7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate Official reprint from UpToDate www.uptodate.com 2023 UpToDate, Inc. and/or its affiliates. All Rights Reserved. Overview of pacemakers in heart failure : E Kevin Heist, MD, PhD : Frederick Masoudi, MD, MSPH, FACC, FAHA : Todd F Dardas, MD, MS 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: May 03, 2023. INTRODUCTION Cardiac implantable electronic devices (CIEDs), such as cardiac pacemakers and implantable cardioverter-defibrillators (ICDs), are increasingly used in patients with heart failure (HF) and at risk for HF. The impact of CIEDs on the incidence and progression of HF is complex and depends upon both the nature of the device (eg, ICD and/or single chamber, dual chamber, or biventricular pacemaker), and device programming. The role and effects of cardiac implantable electronic devices in patients with HF will be reviewed here. Indications for cardiac resynchronization therapy (CRT), ICD, permanent pacemakers, and the various modes of cardiac pacing are discussed separately. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system" and "Cardiac resynchronization therapy in atrial fibrillation" and "Cardiac resynchronization therapy in heart failure: System implantation and programming" and "Implantable cardioverter-defibrillators: Overview of indications, components, and functions" and "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF" and "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy" and "Permanent cardiac pacing: Overview of devices and indications" and "Modes of cardiac pacing: Nomenclature and selection".) Use of pacemakers and ICDs as continuous monitoring devices is discussed separately. (See "Ambulatory ECG monitoring", section on 'Permanent pacemakers and implantable cardioverter- defibrillators'.) https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 1/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate Secondary mitral regurgitation is common in patients with HF. The effects of atrioventricular (AV) optimization in patients with dual chamber pacemakers and CRT on mitral regurgitation are discussed separately. (See "Management and prognosis of chronic secondary mitral regurgitation".) ROLE OF PACING IN HEART FAILURE Approach to pacemaker or ICD use In patients with HF (or at risk for HF due to systolic dysfunction), pacing that may worsen HF is avoided while CIEDs likely to provide clinical benefit are prescribed. While right ventricular (RV) pacing can exacerbate or precipitate HF in patients with left ventricular (LV) systolic dysfunction, evidence-based device therapy (including cardiac resynchronization therapy [CRT] and ICDs) improves clinical outcomes in selected patients with HF and/or LV systolic dysfunction. (See 'Clinical effects of pacing' below.) Our approach is in general agreement with the 2022 American College of Cardiology/American Heart Association/Heart Failure Society of America (ACC/AHA/HFSA) guidelines on the management of HF [1], the 2021 European Society of Cardiology HF guidelines [2], and the 2018 ACC/AHA/Heart Rhythm Society guidelines on the evaluation and management of patients with bradycardia and cardiac conduction delay [3]. For patients with HF (or at risk for HF due to systolic dysfunction): Determine if an indication for a pacemaker, CRT, and/or ICD is present. Indications for pacing include symptomatic sinus node dysfunction or AV block, as presented separately. (See "Permanent cardiac pacing: Overview of devices and indications".) Indications for CRT with biventricular pacing for patients in sinus rhythm or with atrial fibrillation are presented separately. These devices are appropriate for selected HF patients with systolic dysfunction and ventricular dyssynchrony. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system" and "Cardiac resynchronization therapy in atrial fibrillation".) CRT is performed with a pacemaker that simultaneously paces the right and left ventricles (biventricular pacemaker). CRT can improve cardiac function, symptoms, and survival in selected patients with HF with LV systolic dysfunction (particularly those with LV ejection fraction [LVEF] 35 percent, very wide QRS, and left bundle branch block). In addition, CRT can improve outcomes in selected patients with LV systolic dysfunction https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 2/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate (LVEF 35 percent) who require a pacemaker with anticipated requirement for significant (>40 percent) ventricular pacing (thus avoiding the detrimental effects of isolated RV pacing). The role of cardiac contractility modulation in patients with HF is discussed separately. (See "Investigational therapies for management of heart failure", section on 'Cardiac contractility modulation'.) Indications for an ICD are presented separately. The impact of an ICD on HF outcomes is discussed below. (See 'Implantable cardioverter-defibrillators' below and "Implantable cardioverter-defibrillators: Overview of indications, components, and functions" and "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF" and "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy".) For patients who have an indication for a CIED that may include RV pacing, the adverse effects of isolated RV pacing can be minimized by appropriate device selection and programming. (See 'Device selection and programming' below and "Permanent cardiac pacing: Overview of devices and indications" and "Modes of cardiac pacing: Nomenclature and selection".) If a standard indication for CIED is not present, cardiac pacing does not play a role in treating or preventing HF. (See 'Clinical effects of pacing' below.) Device selection and programming For patients with HF and/or systolic dysfunction who require a pacemaker or an ICD, ventricular dyssynchrony should be minimized, either by utilizing CRT (with biventricular pacing or conduction system pacing) or by minimizing RV pacing. Determine if CRT is indicated, as discussed separately. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system" and "Cardiac resynchronization therapy in atrial fibrillation" and "Cardiac resynchronization therapy in heart failure: System implantation and programming".) Many candidates for ICD therapy also have indications for CRT and should receive a device with both functions (CRT-D). (See "Implantable cardioverter-defibrillators: Overview of indications, components, and functions" and "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF" and "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy".) Conduction system (His bundle or left bundle branch) pacing is another pacing option that can be used for resynchronization or to minimize the effects of isolated RV pacing. (See https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 3/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate "Cardiac resynchronization therapy in heart failure: Indications and choice of system", section on 'Conduction system pacing' and "Permanent cardiac pacing: Overview of devices and indications", section on 'His bundle pacing' and "Permanent cardiac pacing: Overview of devices and indications", section on 'Left bundle pacing'.) For patients who are not candidates for CRT (by biventricular pacing or conduction system pacing), the following methods may be used to minimize RV pacing (see 'Pacing modes to limit RV pacing' below): Managed ventricular pacing Devices with this capability allow native conduction to occur, even in the setting of substantial PR prolongation or second-degree AV block. If high-grade AV block develops, the device will switch modes to dual-chamber pacing. These devices are appropriate for patients with first- or second-degree AV block, for whom they can substantially reduce the frequency of ventricular pacing. (See "Modes of cardiac pacing: Nomenclature and selection", section on 'Modes to minimize ventricular pacing'.) Standard devices programmed to minimize RV pacing Many patients with HF and systolic dysfunction do not have a pacemaker or an ICD with a managed ventricular pacing (or comparable) programming option. However, in patients with intact AV conduction, the following device programming options can reduce the frequency of ventricular pacing (see "Modes of cardiac pacing: Nomenclature and selection") ( table 1): - - Prolonged programmed AV intervals Eliminating rate responsive AV delay DDI (dual-chamber sequential AV pacing with atrial sensing but not tracking) or DDIR (DDI rate-responsive) pacing AAI (atrial demand) pacing (see "Sinus node dysfunction: Treatment") However, these programming options also have limitations, and, in many patients with conduction system disease, it is difficult to effectively minimize ventricular pacing. CLINICAL EFFECTS OF PACING Data from both retrospective analyses and a randomized trial show that RV pacing can exacerbate HF, hypothesized to result from the following: https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 4/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate When the native conduction system is normal, the QRS duration is 120 ms, and ventricular contraction is synchronized. Synchronous ventricular contraction optimizes cardiac function. Standard RV pacing causes the RV to contract before the LV (interventricular dyssynchrony). In addition, RV pacing simulates the effect of left bundle branch block, causing the septum to contract before the lateral wall (intraventricular dyssynchrony). Ventricular dyssynchrony can reduce cardiac efficiency. Additionally, asynchronous ventricular pacing can impede cardiac pump function by inducing asynchrony in atrial and ventricular contraction. Although such alterations in cardiac pump function may be clinically imperceptible in patients without an underlying cardiomyopathy, it can be important in the setting of a failing ventricle, resulting in increased HF symptoms [4]. The relationships between ventricular dyssynchrony, HF, and resynchronization therapy are discussed in detail separately. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system", section on 'Rationale for CRT'.) Greater RV pacing worsens outcomes Although it had been proposed that dual-chamber (right atrial and RV) pacing might be beneficial in patients with HF, a randomized trial (DAVID) and observational studies found that DDD (dual-chamber paced and sensed) pacing can exacerbate HF, likely due to the detrimental effect of RV pacing. The hypothesis that dual-chamber pacing might improve cardiac function in patients with HF was based upon the following observations [5]. Pacing permits more aggressive beta blocker therapy for HF, which may be limited by symptomatic bradycardia. Dual-chamber pacing allows optimization of the AV interval, thereby improving coordination between atria and ventricles, optimizing valve closure, and minimizing mitral regurgitation. In addition, atrial pacing has been reported to reduce the frequency of atrial fibrillation in some studies (see "The role of pacemakers in the prevention of atrial fibrillation"). A potential benefit of dual-chamber pacing was suggested in an initial uncontrolled study of 17 patients with idiopathic dilated cardiomyopathy who had medically refractory HF and severe symptoms [6,7]. These findings provided the rationale for the DAVID trial, which did not confirm any benefit. The DAVID trial studied dual-chamber (right atrial and RV) pacing in patients with HF with LV systolic dysfunction [8]. The trial found that rate-responsive dual-chamber (DDDR) pacing increased HF admissions and mortality compared to ventricular demand pacing (VVI), likely due to the RV component of dual chamber pacing ( table 1) [9]. https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 5/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate The trial enrolled 506 patients with an LVEF 40 percent and an indication for ICD implantation but no indication for antibradycardia pacing [8]. The patients were randomly assigned to VVI pacing with a lower rate limit of 40 beats per minute (VVI-40) or to DDDR pacing with a lower rate limit of 70 beats per minute (DDDR-70). The frequency of RV pacing was substantially higher in the DDDR-70 compared to the VVI-40 group (60 versus 1 percent) due to a relatively short programmed AV interval (typically 180 ms) in the DDDR group. Thus, the trial effectively compared DDDR pacing with sinus rhythm. At one-year follow-up, there was a detrimental effect of DDDR-70 pacing. Survival free of the primary composite end point of death or hospitalization for HF was significantly lower in the DDDR-70 group (73 versus 84 percent in the VVI-40 group). There were nominally higher rates of both components of the primary end point in the DDDR-70 group: mortality (10.1 versus 6.4 percent) and HF hospitalization (22.6 versus 13.3 percent), but these differences were not statistically significant. In a post-hoc analysis, the detrimental effects of DDDR-70 pacing were more pronounced in patients with a baseline QRS 110 ms [10]. Patients with QRS prolongation were more likely than those with a normal QRS to have other markers of poor outcome (eg, worse systolic function and a history of HF). Thus, it is not clear if baseline conduction abnormalities themselves or associated cardiac abnormalities predisposed patients to the adverse consequences of RV pacing. A post-hoc analysis of data from the MOST trial of pacing modes in patients with sinus node dysfunction further supports the deleterious effects associated with RV pacing [11]. This analysis was restricted to the 1339 of 2010 participants with a normal QRS duration (120 ms). In this subgroup, 707 had been assigned to DDDR and 632 to VVIR pacing. Regardless of pacing mode, patients with a higher cumulative proportion of ventricular pacing had significantly higher rates of subsequent HF hospitalization and atrial fibrillation. Pacing modes to limit RV pacing Given the results of these studies, later randomized trials studied pacing modes selected to avoid or limit RV pacing. Settings that avoided or limited RV pacing led to similar outcomes to those with back-up ventricular pacing. The DAVID II trial found that atrial pacing and back-up ventricular pacing produced similar rates of event-free survival and quality of life [12]. The trial randomly assigned 600 patients with LVEF 40 percent and an indication for ICD implantation but no indication for antibradycardia pacing to AAI (atrial demand) pacing at 70 beats/min or VVI (ventricular demand) pacing at 40 beats/min. The primary combined end point of time to HF hospitalization or death was similar in the two treatment groups, with overall incidence of https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 6/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate 11.1, 16.9, and 24.6 percent at one, two, and three years, respectively. The incidence of atrial fibrillation, syncope, appropriate or inappropriate shocks, and quality-of-life measures were also similar. The INTRINSIC RV trial found that dual-chamber rate-responsive pacing with the AV Search Hysteresis algorithm to minimize ventricular pacing (DDDR AVSH at 60 to 130 beats per minute) produced similar outcomes as back-up ventricular (VVI at 40 beats per minute) pacing. Individualized programming with attention to the PR interval is important since very long programmed AV delay using the AV Search Hysteresis algorithm can result in significant bradycardia or pacemaker syndrome in the presence of more advanced or progressive AV block [13]. IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS ICDs are recommended for the primary and secondary prevention of sudden cardiac death (SCD) in selected patients with ischemic and nonischemic cardiomyopathy. By reducing the incidence of arrhythmic death, ICDs may result in more patients surviving to advanced stages of heart failure (HF). (See "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF" and "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy".) ICDs can influence the incidence and progression of HF by two mechanisms: Contemporary transvenous ICDs also function as cardiac pacemakers. As an example, the DAVID trial, discussed above, involved dual-chamber ICDs. Thus, the detrimental impact of RV pacing also applies to ICDs. Because many patients with an ICD do not have a standard indication for pacing, efforts to minimize ventricular pacing are particularly important in these patients. The programming and device selection options discussed above are also available in ICDs. (See 'Role of pacing in heart failure' above.) By aborting arrhythmic deaths, ICDs prolong survival in patients with substantial cardiac disease. Such patients may later progress to more advanced HF. This phenomenon was illustrated in a post-hoc analysis from the MADIT II trial [14]. In this trial, 1218 patients with a prior myocardial infarction and an LVEF 30 percent were randomly assigned to ICD implantation or conventional medical therapy. The patients assigned to ICD therapy had significantly lower risks of death. At a mean follow-up of 20 https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 7/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate months, patients assigned to ICD therapy were significantly more likely to be hospitalized for HF than those assigned to conventional therapy (23 versus 17 percent). Among patients assigned to ICD therapy, the incidence of HF was significantly greater after appropriate ICD therapy compared to before such therapy (23 versus 16 events per 100 person years). Both the incidence of initial HF admissions and the intensity of recurrent admissions increased after appropriate ICD therapies. In contrast, there was no difference in the incidence of HF after inappropriate device therapies. These data suggest that appropriate ICD therapies are more common in patients who have or will soon experience worsening HF. Thus, life-prolonging ICD therapies may transform SCD risk to subsequent HF risk, although short-term mortality is improved. 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: Heart failure 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. 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: Cardiac resynchronization therapy (The Basics)") SUMMARY AND RECOMMENDATIONS https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 8/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate The impact of cardiac implantable electronic devices (CIEDs) on the incidence and progression of heart failure (HF) depends upon the type of device and device programming. In patients with HF (or at risk for HF due to systolic dysfunction), right ventricular (RV) pacing can exacerbate or precipitate HF. In contrast, evidence-based device therapy (cardiac resynchronization therapy [CRT], conduction system pacing, and implantable cardioverter-defibrillator [ICD] use) improves clinical outcomes in selected patients with HF and/or systolic dysfunction. (See 'Approach to pacemaker or ICD use' above.) Patients with HF (or at risk for HF due to systolic dysfunction) are evaluated to determine if standard indications one or more of the following CIEDs are present, which are discussed separately (see 'Approach to pacemaker or ICD use' above): Permanent pacemaker therapy. (See "Permanent cardiac pacing: Overview of devices and indications" and "Modes of cardiac pacing: Nomenclature and selection".) CRT. Many candidates for ICD therapy also have indications for CRT and should receive a combined device (CRT-D), as discussed separately. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system" and "Cardiac resynchronization therapy in atrial fibrillation".) ICD. (See "Implantable cardioverter-defibrillators: Overview of indications, components, and functions" and "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF" and "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy".) If a standard indication for CIED is not present, cardiac pacing does not play a role in treating or preventing HF. (See 'Approach to pacemaker or ICD use' above and 'Clinical effects of pacing' above.) For patients with HF (or at risk for HF due to systolic dysfunction) who require a pacemaker or an ICD, ventricular dyssynchrony should be minimized, either by utilizing CRT (with biventricular pacing or conduction system pacing) or by minimizing RV pacing. (See 'Device selection and programming' above.) CRT with biventricular pacing is indicated for selected HF patients and for some patients with left ventricular systolic dysfunction at risk for developing HF. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system" and "Cardiac resynchronization therapy in atrial fibrillation".) https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 9/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate Conduction system (His bundle or left bundle branch) pacing is another pacing option that can be used for resynchronization or to minimize the effects of isolated RV pacing. (See "Cardiac resynchronization therapy in heart failure: Indications and choice of system", section on 'Conduction system pacing' and "Permanent cardiac pacing: Overview of devices and indications", section on 'His bundle pacing' and "Permanent cardiac pacing: Overview of devices and indications", section on 'Left bundle pacing'.) For patients who are not candidates for CRT (by biventricular pacing or conduction system pacing), RV pacing may be minimized using managed ventricular pacing or programming of standard devices. (See 'Pacing modes to limit RV pacing' above.) ACKNOWLEDGMENT The UpToDate editorial staff thank Michael Cao, MD, and Leslie A Saxon, MD, who contributed to earlier versions of this topic review. Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation 2022; 145:e895. 2. McDonagh TA, Metra M, Adamo M, et al. 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J 2021; 42:3599. 3. 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. 4. Saxon LA, Stevenson WG, Middlekauff HR, Stevenson LW. Increased risk of progressive hemodynamic deterioration in advanced heart failure patients requiring permanent pacemakers. Am Heart J 1993; 125:1306. 5. Auricchio A, Salo RW. Acute hemodynamic improvement by pacing in patients with severe congestive heart failure. Pacing Clin Electrophysiol 1997; 20:313. https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 10/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate 6. Hochleitner M, H rtnagl H, Ng CK, et al. Usefulness of physiologic dual-chamber pacing in drug-resistant idiopathic dilated cardiomyopathy. Am J Cardiol 1990; 66:198. 7. Hochleitner M, H rtnagl H, H rtnagl H, et al. Long-term efficacy of physiologic dual- chamber pacing in the treatment of end-stage idiopathic dilated cardiomyopathy. Am J Cardiol 1992; 70:1320. 8. Wilkoff BL, Cook JR, Epstein AE, et al. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA 2002; 288:3115. 9. Sweeney MO, Prinzen FW. A new paradigm for physiologic ventricular pacing. J Am Coll Cardiol 2006; 47:282. 10. Hayes JJ, Sharma AD, Love JC, et al. Abnormal conduction increases risk of adverse outcomes from right ventricular pacing. J Am Coll Cardiol 2006; 48:1628. 11. Sweeney MO, Hellkamp AS, Ellenbogen KA, et al. Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction. Circulation 2003; 107:2932. 12. Wilkoff BL, Kudenchuk PJ, Buxton AE, et al. The DAVID (Dual Chamber and VVI Implantable Defibrillator) II trial. J Am Coll Cardiol 2009; 53:872. 13. http://www.fac.org.ar/qcvc/llave/c121i/levinep.php (Accessed on December 08, 2014). 14. Goldenberg I, Moss AJ, Hall WJ, et al. Causes and consequences of heart failure after prophylactic implantation of a defibrillator in the multicenter automatic defibrillator implantation trial II. Circulation 2006; 113:2810. Topic 3493 Version 27.0 https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 11/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate GRAPHICS Revised NBG code for pacing nomenclature I II III IV V Position Chamber(s) Chamber(s) Response to Rate Multisite Category paced sensed sensing modulation 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 V = Ventricle I = Inhibited D = Dual D = Dual (A+V) (A+V) D = Dual (T+I) D = Dual (A+V) S = Single (A or V) S = Single (A or V) Manufacturer's designation only: Note: Positions I through III are used exclusively for antibradyarrythmia function. Adapted from Bernstein AD, Daubert JC, Fletcher RD, et al. Pacing Clin Electrophysiol 2002; 25:260. Graphic 68327 Version 3.0 https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 12/13 7/6/23, 10:57 AM Overview of pacemakers in heart failure - UpToDate Contributor Disclosures E Kevin Heist, MD, PhD Equity Ownership/Stock Options: Oracle Health [Device diagnostics]. Consultant/Advisory Boards: Biotronik [Cardiac resynchronization therapy and atrial fibrillation]; Boston Scientific [Cardiac resynchronization therapy and atrial fibrillation]. All of the relevant financial relationships listed have been mitigated. Frederick Masoudi, MD, MSPH, FACC, FAHA Consultant/Advisory Boards: Bristol Meyers Squibb [Hypertrophic cardiomyopathy]; Colorado Prevention Center [Diabetes trial steering committee, study sponsor, Better Therapeutics]; TurningPoint [Utilization policy review]. Other Financial Interest: American College of Cardiology [Cardiovascular disease]; Massachusetts Medical Society [Cardiovascular disease]. All of the relevant financial relationships listed have been mitigated. Todd F Dardas, MD, MS No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/overview-of-pacemakers-in-heart-failure/print 13/13