Increased risk of progressive hemodynamic deterioration in advanced heart failure patients requiring permanent pacemakers

The Story of Managed Ventricular Pacing

A significant milestone in cardiac pacing occurred approximately two decades ago, when the primary operating mode was reimagined to more closely mimic normal top-down cardiac activation. When introduced, Managed Ventricular Pacing (MVP™; Medtronic, Minneapolis, MN, USA) was an unprecedented dual-chamber mode as it preferentially paced the right atrium in the AAI/R mode and simultaneously protected against transient heart block, albeit only in the instance of dropped ventricular beats. At the time, dual-chamber DDD/R with atrial-based timing and programmable atrioventricular delay was state of the art. MVP™ “unlocked” conventional dual-chamber pacing by not consistently requiring a 1:1 atrioventricular relationship during its primary operating mode (ie, AAI/R+). Ultimately, MVP™ emerged as a primitive means to promote His–Purkinje activation, and it is not a coincidence that its roots can be traced back to first-in-man permanent His-bundle pacing.

Use and Outcomes of Dual Chamber or Cardiac Resynchronization Therapy Defibrillators Among Older Patients Requiring Ventricular Pacing in the National Cardiovascular Data Registry Implantable Cardioverter Defibrillator Registry

IMPORTANCE

Frequent right ventricular (RV) pacing can cause and exacerbate heart failure. Cardiac resynchronization therapy (CRT) has been shown to be associated with improved outcomes among patients with reduced left ventricular ejection fraction who need frequent RV pacing, but the patterns of use of CRT vs dual chamber (DC) devices and the associated outcomes among these patients in clinical practice is not known.

OBJECTIVE

To assess outcomes, variability in use of device type, and trends in use of device type over time among patients undergoing implantable cardioverter defibrillator (ICD) implantation who were likely to require frequent RV pacing but who did not have a class I indication for CRT.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used the National Cardiovascular Data Registry (NCDR) ICD Registry. A total of 3100 Medicare beneficiaries undergoing first-time implantation of CRT defibrillator (CRT-D) or DC-ICD from 2010 to 2016 who had a class I or II guideline ventricular bradycardia pacing indication but not a class I indication for CRT were included. Data were analyzed from August 2018 to October 2019.

EXPOSURES

Implantation of a CRT-D or DC-ICD.

MAIN OUTCOMES AND MEASURES

All-cause mortality, heart failure hospitalization, and complications were ascertained from Medicare claims data. Multivariable Cox proportional hazards models and Fine-Gray models were used to evaluate 1-year mortality and heart failure hospitalization, respectively. Multivariable logistic regression was used to evaluate 30-day and 90-day complications. All models accounted for clustering. The median odds ratio (MOR) was used to assess variability and represents the odds that a randomly selected patient receiving CRT-D at a hospital with high implant rates would receive CRT-D if they had been treated at a hospital with low CRT-D implant rates.

RESULTS

A total of 3100 individuals were included. The mean (SD) age was 76.3 (6.4) years, and 2500 (80.6%) were men. The 1698 patients (54.7%) receiving CRT-D were more likely than those receiving DC-ICD to have third-degree atrioventricular block (828 [48.8%] vs 432 [30.8%]; P < .001), nonischemic cardiomyopathy (508 [29.9%] vs 255 [18.2%]; P < .001), and prior heart failure hospitalizations (703 [41.4%] vs 421 [30.0%]; P < .001). Following adjustment, CRT-D was associated with lower 1-year mortality (hazard ratio [HR], 0.70; 95% CI, 0.57-0.87; P = .001) and heart failure hospitalization (subdistribution HR, 0.77; 95% CI, 0.61-0.97; P = .02) and no difference in complications compared with DC-ICD. Hospital variation in use of CRT was present (MOR, 2.00), and the use of CRT in this cohort was higher over time (654 of 1351 [48.4%] in 2010 vs 362 of 594 [60.9%] in 2016; P < .001).

CONCLUSIONS AND RELEVANCE

In this cohort study of older patients in contemporary practice undergoing ICD implantation with a bradycardia pacing indication but without a class I indication for CRT, CRT-D was associated with better outcomes compared with DC devices. Variability in use of device type was observed, and the rate of CRT implantation increased over time.

Gene therapy to restore electrophysiological function in heart failure

INTRODUCTION

Heart failure (HF) is a major public health epidemic and a leading cause of morbidity and mortality in the industrialized world. Existing treatments for patients with HF are often associated with pro-arrhythmic activity and risk of sudden cardiac death. Therefore, development of novel, effective and safe therapeutic options for HF patients is a critical area of unmet need.

AREAS COVERED

In this article, we review recent advances in the emerging field of cardiac gene therapy for the treatment of tachy- and bradyarrhythmias in HF. We provide an overview of gene-based approaches that modulate myocardial conduction, repolarization, calcium cycling and adrenergic signaling to restore heart rate and rhythm.

EXPERT OPINION

We highlight major advantages of gene therapy for arrhythmias, including the ability to selectively target specific cell populations and to limit the therapeutic effect to the region that requires modification. We illustrate how advances in our fundamental understanding of the molecular origins of arrhythmogenic disorders are allowing investigators to use targeted gene-based approaches to successfully correct abnormal excitability in the atria, ventricles and conduction system. Translation of various gene therapy approaches to humans may revolutionize our ability to combat lethal arrhythmias in HF patients.

Characteristics of the electrocardiogram in patients with continuous-flow left ventricular assist devices

BACKGROUND

Electrocardiograms (ECGs) are routinely obtained in patients with advanced congestive heart failure (CHF) before and after surgical implantation with a left-ventricular assist device (LVAD). As the number of patients with CHF is increasing, it is necessary to characterize the changes present in the ECG of patients with LVADs.

METHODS

ECGs of 43 patients pre- and postimplantation of a HeartMate II LVAD were compared to characterize the presence of an LVAD using the following six criteria (LVADS2 ): low limb-lead voltage, ventricular pacing, artifact (electrical), duration of the QRS > 120 milliseconds, ST-elevation in the lateral leads, and splintering of the QRS complex. Additionally, 50 ECGs of non-LVAD patients coded as "lateral myocardial infarction (MI)" and 50 ECGs coded as "ventricular pacing" were chosen at random and scored. Odds ratios were calculated using Fisher's exact test. Logistic regression models were built to predict the presence of an LVAD in all patients.

RESULTS

Univariate analysis of the pre- and post-LVAD ECGs confirmed that all criteria except the "Duration of QRS > 120 milliseconds" characterized the ECG of a patient with an LVAD. Electrical artifact and low limb-lead voltage yielded the greatest association with an LVAD-ECG.

CONCLUSIONS

The ECG of a patient with end-stage CHF significantly changes with LVAD implantation. The LVADS2 criteria provide a framework towards characterizing and establishing a new baseline of the ECG in a patient with a continuous-flow LVAD.

Pacemakers and implantable cardioverter defibrillators--general and anesthetic considerations

A pacemaking system consists of an impulse generator and lead or leads to carry the electrical impulse to the patient's heart. Pacemaker and implantable cardioverter defibrillator codes were made to describe the type of pacemaker or implantable cardioverter defibrillator implanted. Indications for pacing and implantable cardioverter defibrillator implantation were given by the American College of Cardiologists. Certain pacemakers have magnet-operated reed switches incorporated; however, magnet application can have serious adverse effects; hence, devices should be considered programmable unless known otherwise. When a device patient undergoes any procedure (with or without anesthesia), special precautions have to be observed including a focused history/physical examination, interrogation of pacemaker before and after the procedure, emergency drugs/temporary pacing and defibrillation, reprogramming of pacemaker and disabling certain pacemaker functions if required, monitoring of electrolyte and metabolic disturbance and avoiding certain drugs and equipments that can interfere with pacemaker function. If unanticipated device interactions are found, consider discontinuation of the procedure until the source of interference can be eliminated or managed and all corrective measures should be taken to ensure proper pacemaker function should be done. Post procedure, the cardiac rate and rhythm should be monitored continuously and emergency drugs and equipments should be kept ready and consultation with a cardiologist or a pacemaker-implantable cardioverter defibrillator service may be necessary.

Cycle length restitution in sinoatrial node cells: a theory for understanding spontaneous action potential dynamics

Normal heart rhythm (sinus rhythm) is governed by the sinoatrial node, a specialized and highly heterogeneous collection of spontaneously active myocytes in the right atrium. Sinoatrial node dysfunction, characterized by slow and/or asynchronous pacemaker activity and even failure, is associated with cardiovascular disease (e.g. heart failure, atrial fibrillation). While tremendous progress has been made in understanding the molecular and ionic basis of automaticity in sinoatrial node cells, the dynamics governing sinoatrial nodel cell synchrony and overall pacemaker function remain unclear. Here, a well-validated computational model of the mouse sinoatrial node cell is used to test the hypothesis that sinoatrial node cell dynamics reflect an inherent restitution property (cycle length restitution) that may give rise to a wide range of behavior from regular periodicity to highly complex, irregular activation. Computer simulations are performed to determine the cycle length restitution curve in the computational model using a newly defined voltage pulse protocol. The ability of the restitution curve to predict sinoatrial node cell dynamics (e.g., the emergence of irregular spontaneous activity) and susceptibility to termination is evaluated. Finally, ionic and tissue level factors (e.g. ion channel conductances, ion concentrations, cell-to-cell coupling) that influence restitution and sinoatrial node cell dynamics are explored. Together, these findings suggest that cycle length restitution may be a useful tool for analyzing cell dynamics and dysfunction in the sinoatrial node.

Atrioventricular nodal ablation in atrial fibrillation: a meta-analysis of biventricular vs. right ventricular pacing mode

AIMS

For patients with refractory atrial fibrillation (AF) undergoing atrioventricular nodal ablation (AVNA), initial single-chamber right ventricular (RV)-only pacing is standard. Given the deleterious effects of chronic RV-only pacing, the impact of an initial biventricular (BiV) pacing strategy post-ablation is of interest.

METHODS AND RESULTS

We conducted a meta-analysis to determine the effect of BiV vs. RV-only pacing in patients undergoing AVNA for refractory atrial fibrillation. A search of multiple electronic databases identified 921 reports, which included four randomized controlled trials (n = 534). Mean New York Heart Association (NYHA) class was 2.3 and mean left ventricular ejection fraction (LVEF) was 44%. When compared with RV-only pacing, BiV pacing was not associated with reduced mortality [risk ratio 0.85, 95% confidence interval (CI) 0.40-1.82, P = 0.68]. In three studies comprised of patients with left ventricular systolic dysfunction (mean EF 41 ± 3%), BiV pacing demonstrated a non-significant reduction in cardiac mortality (risk ratio 0.59, 95% CI 0.25-1.39; P = 0.23). Compared with RV-only pacing, BiV pacing was associated with significant improvement in symptoms [Minnesota Living with Heart Failure Questionnaire (MLWHFQ) 2.72 points fewer, 95% CI 1.45-3.99] and increased LVEF (+2.6%, 95% CI 1.69-3.44), but no significant change in 6 min walk distance (6MWD) (5.02 ms more, 95% CI -1.56 to 11.59; P = 0.13).

CONCLUSIONS

In patients with refractory AF undergoing AVNA, BiV pacing was not associated with significantly improved survival when compared with RV-only pacing. A modest, but significant improvement in structural and functional response to BiV pacing was observed.

Chronic kidney disease and mortality in implantable cardioverter-defibrillator recipients

Incidence of sudden cardiac death (SCD) in end-stage renal disease (ESRD) remains high. Limited data is available about whether implantable cardioverter-defibrillators (ICDs) can prevent arrhythmic death in patients with chronic kidney disease (CKD). The purpose of this retrospective study was to determine the impact of CKD on all-cause and sudden cardiac death in ICD recipients. We evaluated 441 consecutive patients who underwent ICD implantation at our center between 1994 and 2002. We found that mortality rate was higher in patients with eGFR <60 mL/min and those with ESRD on hemodialysis (43%, n = 69/162 and 54%, n = 12/22, resp.) than in patients with eGFR ≥60 mL/min (23%, n = 58/257; P < .0005). The SCD rate was also higher in the patients with ESRD (50%) than in CKD patients not on dialysis (10.2%; P < .0005). Mortality rate for single-chamber ICDs was 56.8% in comparison with dual-chamber ICDs (38.1%) and for biventricular ICDs (5.0%) (P < .0005).

Conventional versus biventricular pacing in heart failure and bradyarrhythmia: the COMBAT study

BACKGROUND

Worsening in clinical and cardiac status has been noted after chronic right ventricular pacing, but it is uncertain whether atriobiventricular (BiVP) is preferable to atrio-right ventricular pacing (RVP). Conventional versus Multisite Pacing for BradyArrhythmia Therapy study (COMBAT) sought to compare BiVP versus RVP in patients with symptomatic heart failure (HF) and atrioventricular (AV) block.

METHODS AND RESULTS

COMBAT is a prospective multicenter randomized double blind crossover study. Patients with New York Heart Association functional class (FC) II-IV, left ventricular ejection fraction (LVEF) <40%, and AV block as an indication for pacing were enrolled. All patients underwent biventricular system implantation and then were randomized to receive successively (group A) RVP-BiVP-RVP, or (group B) BiVP-RVP-BiVP. At the end of each 3-month crossover period, patients were evaluated according to Quality of Life (QoL), FC, echocardiographic parameters, 6-Minute Walk Test (6MWT), and peak oxygen consumption (VO(2 max)). Sixty patients were enrolled, and the mean follow-up period was 17.5 +/- 10.7 months. There were significant improvements in QoL, FC, LVEF, and left ventricular end-systolic volume with BiVP compared with RVP. The effects of pacing mode on 6MWT and VO(2 max) were not significantly different. Death occurred more frequently with RVP.

CONCLUSION

In patients with systolic HF and AV block requiring permanent ventricular pacing, BiVP is superior to RVP and should be considered the preferred pacing mode.

Calmodulin kinase II is required for fight or flight sinoatrial node physiology

The best understood "fight or flight" mechanism for increasing heart rate (HR) involves activation of a cyclic nucleotide-gated ion channel (HCN4) by beta-adrenergic receptor (betaAR) agonist stimulation. HCN4 conducts an inward "pacemaker" current (I(f)) that increases the sinoatrial nodal (SAN) cell membrane diastolic depolarization rate (DDR), leading to faster SAN action potential generation. Surprisingly, HCN4 knockout mice were recently shown to retain physiological HR increases with isoproterenol (ISO), suggesting that other I(f)-independent pathways are critical to SAN fight or flight responses. The multifunctional Ca(2+) and calmodulin-dependent protein kinase II (CaMKII) is a downstream signal in the betaAR pathway that activates Ca(2+) homeostatic proteins in ventricular myocardium. Mice with genetic, myocardial and SAN cell CaMKII inhibition have significantly slower HRs than controls during stress, leading us to hypothesize that CaMKII actions on SAN Ca(2+) homeostasis are critical for betaAR agonist responses in SAN. Here we show that CaMKII mediates ISO HR increases by targeting SAN cell Ca(2+) homeostasis. CaMKII inhibition prevents ISO effects on SAN Ca(2+) uptake and release from intracellular sarcoplasmic reticulum (SR) stores that are necessary for increasing DDR. CaMKII inhibition has no effect on the ISO response in SAN cells when SR Ca(2+) release is disabled and CaMKII inhibition is only effective at slowing HRs during betaAR stimulation. These studies show the tightly coupled, but previously unanticipated, relationship of CaMKII to the betaAR pathway in fight or flight physiology and establish CaMKII as a critical signaling molecule for physiological HR responses to catecholamines.

Innovation focus: the patient with arrhythmia

Great strides have been made over the last two decades in the management of patients with rhythm disorders. Despite this, however, the remaining critical problems of stroke related to atrial fibrillation or as a result of radiofrequency ablation require innovative solutions to fully realize the potential of these recent advances. Similarly, implanted cardiac devices have revolutionized the care of patients with bradyrhythmias and tachyarrhythmias. Dyssynchronus ventricular pacing associated with present devices; however, results in heart failure, tricuspid regurgitation, and inappropriate device therapy once again create a demand for creative solutions. While not technically an arrhythmia, epilepsy management today is riddled with many of the problems that plagued cardiac arrhythmia management previously, and thus an appreciation of the similarities in requirement for investigative solutions may yield groundbreaking solutions. In this paper, we describe some novel methods to reduce complications associated with rhythm disorders and their treatment and apply the lessons learned from cardiovascular arrhythmia management to the brain. These include: a method to reduce coagulum formation and thus subsequent thromboembolism with indwelling catheters specifically during radiofrequency ablation procedures; a technique to ligate the left atrial appendage through percutaneous subxiphoid pericardial access; development and testing of a novel intramyocardial pace-sense lead, particularly used in a unique anatomic location (the atrioventricular septum) to allow pacing the ventricles in a relatively synchronous manner without crossing the tricuspid valve or entering the coronary sinus; finally, novel modifications of the cardiovascular mapping and ablation techniques used for the management of the central nervous system disorders primarily via the venous drainage of the brain. Innovative and potential solutions to treat the patient with arrhythmia are presented.

New developments in antibradycardic devices

With increasing advances in technology, cardiac pacemakers have become highly sophisticated devices that allow diagnostic and therapeutic functions beyond conventional antibradycardic therapy. This review discusses the most promising developments in antibradycardic device therapy, such as novel diagnostic functions, telemonitoring, autoadjustment of programmed parameters, algorithms for support of intrinsic atrioventricular conduction, pacing algorithms for the prevention of atrial arrhythmias and cardiac resynchronization therapy. A short overview of the basic principles of antibradycardic device therapy is also provided.

Is dual-chamber programming inferior to single-chamber programming in an implantable cardioverter-defibrillator? Results of the INTRINSIC RV (Inhibition of Unnecessary RV Pacing With AVSH in ICDs) study

BACKGROUND

The INTRINSIC RV (Inhibition of Unnecessary RV Pacing with AVSH in ICDs) study tested the hypothesis that dual-chamber rate-responsive (DDDR) with atrioventricular search hysteresis (AVSH) 60-130 programming is not inferior to single-chamber (VVI)-40 programming in an implantable cardioverter defibrillator with respect to all-cause mortality and heart failure hospitalizations using an equivalence margin of 5%.

METHODS AND RESULTS

At 108 centers, 1530 patients with an implantable cardioverter defibrillator indication received a VITALITY AVT (Guidant Corporation, St. Paul, Minn) implantable cardioverter defibrillator programmed consistently to DDDR AVSH 60-130 for the first week. Of those, 988 patients with <20% right ventricular pacing at 1 week were randomized to DDDR AVSH 60-130 or to VVI-40 programming. Among those randomized, 502 were assigned to DDDR AVSH and 486 to VVI. Groups were similar with regard to coronary disease (68%), gender (21% female), and New York Heart Association functional class >I (79%). A total of 32 patients (6.4%) in the DDDR AVSH arm and 46 patients (9.5%) in the VVI arm died or were hospitalized for heart failure during a mean follow-up of 10.4 months (relative risk=0.67, P=0.072 in favor of DDDR AVSH). DDDR AVSH was not inferior to VVI programming (P<0.001). All-cause mortality was not significantly different between the DDDR AVSH arm (3.6%) and the VVI arm (5.1%; P=0.23). The mean percent right ventricular pacing in the DDDR AVSH arm was 10% (median 4%) versus 3% (median 0%) in the VVI arm.

CONCLUSIONS

In the INTRINSIC RV trial, among those randomized, DDDR AVSH was associated with similar outcomes as with VVI backup pacing.

Cardiac resynchronization therapy: redefining the role of device therapy in heart failure

That cardiac dyssynchrony can contribute to a decline in cardiac efficiency has been recognized in one form or another for at least 50 years. Although revascularization and beta-blockers can improve cardiac synchrony, there was little interest in or awareness of this clinical entity until the advent of specific, highly effective therapy using atriobiventricular pacing, often described as cardiac resynchronization therapy. Over the last few years, significant advances in cardiac resynchronization therapy technology and the publication of large-scale clinical trials using cardiac resynchronization therapy devices in patients with heart failure have led to the widespread use of these devices. This review will briefly describe the complex nature of cardiac dyssynchrony, what is known about its epidemiology, the effects of cardiac resynchronization therapy, appropriate patient selection, practical aspects, such as implantation and monitoring, and some still unanswered questions.

Upgrade of a single chamber endo-epicardial to a triple chamber biventricular implantable cardioverter-defibrillator

In patients with heart failure implanted with conventional pacemakers, cardiac resynchronization therapy results in significant benefits. The upgrade of previously implanted devices to biventricular pacing may be technically challenging. We report one case of upgrade to biventricular pacing and describe the related technical implications and the therapeutic solutions adopted.

The benefit of upgrading chronically right ventricle–paced heart failure patients to resynchronization therapy demonstrated by strain rate imaging

BACKGROUND

RV pacing induces conduction delay (CD), mechanical dyssynchrony, and increased morbidity in patients with HF. CRT improves HF symptoms and survival, but sparse data exist on its direct effect on chronically RV-paced HF patients.

OBJECTIVES

To assess the benefit of cardiac resynchronization therapy (CRT) in chronically right ventricle (RV)-paced heart failure (HF) patients.

METHODS

We studied 12 consecutive patients with class III HF who had a previously implanted pacemaker or implantable cardioverter-defibrillator. These individuals were chronically RV paced and referred for upgrade to a biventricular device by their primary cardiologists. Tissue Doppler and strain rate imaging (TDI and SRI, respectively) were performed immediately before each upgrade and 4-6 weeks afterward to quantify changes in regional wall motion and synchrony with CRT.

RESULTS

CRT significantly reduced the mean QRS duration (205 ms to 156 ms; P<.0001), and it increased the ejection fraction (30.7%+/-5.1% to 35.8%+/-5.1%; P<.01). Left ventricular end-systolic and end-diastolic dimensions were also significantly reduced. Clinically, patients improved by an average of one New York Heart Association (NYHA) functional class after upgrade (P = .006). The parameter exhibiting greatest improvement was the coefficient of variation (CoV: standard deviation/mean) of time to peak systolic strain rate, a marker of ventricular dyssynchrony, which decreased from 34.3%+/-13.0% to 19.0%+/-6.6% (P<.01). Reduction in CoV of time to peak systolic strain rate was maximally seen in the midventricle (38.2%+/-19.6% to 16.5%+/-9.7%; P<.01).

CONCLUSIONS

Upgrading chronically RV-paced HF patients to CRT improves global and regional systolic function. TDI and SRI provide compelling evidence that this benefit parallels that seen in HF patients with CD unrelated to RV pacing, which implies that biventricular pacing synchronizes mechanical activation in different myocardial regions in patients upgraded from RV pacing as well.

COMBAT-conventional versus multisite pacing for bradyarrhythmia therapy: rationale of a prospective randomized multicenter study

COMBAT is a prospective, multicenter, randomized, blinded clinical study, with crossover design. The main objective is the comparative evaluation of atrio-biventricular versus conventional atrioventricular stimulation (atrio and right ventricle) in patients with heart failure and bradycardia as the primary indication for pacemaker implantation. After successful atrio-biventricular system implantation, patients will be randomized into two groups: group A--atrioventricular conventional pacing and group B--atrio-biventricular pacing. Both groups will be programmed in DDD mode with AV delay optimized by echocardiogram. After 3 months, New York Heart Association functional class, ventricular arrhythmia density and complexity, echocardiography outcomes, 6-min hall walk distance, quality of life and peak oxygen consumption will be assessed in all patients. Then, all patients will crossover to the other pacing regimen, with an additional AV delay adjustment by echo. Patients will be followed up for another 3 months at the end of which all evaluations will be repeated. Patients will then crossover back to their original pacing regimen for a further 3 months. At the end of this 9-month period, patients will be reprogrammed according to their optimal pacing regime. In an extended follow-up, patient survival will be evaluated after 24 months of the optimal pacing therapy.

Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV):. Design and Clinical Protocol

Implantable cardioverter defibrillators (ICDs) reduce sudden arrhythmic death risk but when these devices are programmed DDD and pace in the right ventricle (RV), they can be associated with increased mortality and heart failure morbidity compared to an ICD programmed to back-up RV. An ideal ICD would provide effective treatment for life-threatening tachyarrhythmias, reduce unnecessary RV pacing and maintain AV synchrony. The Inhibition of Unnecessary RV Pacing with AV Search Hysteresis (AVSH) in ICDs (INTRINSIC RV) study will assess whether an ICD programmed to DDDR with AVSH is equal to an ICD programmed to VVI with regard to mortality, heart failure hospitalizations, and several predefined secondary enpoints. AVSH allows intrinsic AV conduction beyond the programmed AV delay to help minimize ventricular pacing. INTRINSIC RV, a multi-center, randomized, prospective trial will enroll >1,200 participants who receive a Guidant VITALITY AVT ICD. ICDs are programmed initially to DDDR AVSH 60-130. Then, after a week, if the %RV pacing <20%, patients are randomized to VVI-40 or DDDR 60-130 with AVSH. Those with RV pacing > or =20% are placed in an obvservational arm and programmed ad libitum by the treating physician. Patients are followed for one year. This large, randomized, controlled, clinical trial will address whether DDDR with AVSH programming is equivalent to VVI programming in an ICD with regard to mortality and heart failure hospitalization.

Biventricular implantable cardioverter defibrillators improve survival compared with biventricular pacing alone in patients with severe left ventricular dysfunction

INTRODUCTION

Biventricular cardiac pacemakers provide important hemodynamic benefit in selected patients with heart failure and severe left ventricular (LV) dysfunction. Nevertheless, these patients remain at high mortality risk. To address this issue, we examined mortality outcome in patients with heart failure treated with biventricular pacemakers alone and those treated with biventricular implantable cardioverter defibrillators (ICDs).

METHODS AND RESULTS

The study population consisted of 126 consecutive patients with LV dysfunction and heart failure who received either a biventricular ICD (n = 62) or a biventricular pacemaker (n = 64) between January 1998 and December 2002. A minimum 12 months of follow-up was obtained in all survivors. ICD indications were conventional in all patients. Kaplan-Meier actuarial method and log rank statistics were used to calculate and compare survival rates in both groups. Comparison of mortality rates utilized Chi-square test. The two groups had similar clinical and demographic features, LV ejection fraction, and medication use. Average follow-up times were 13 +/- 11.8 months (range 4-60) and 18 +/- 13.2 months (range 0.5-53) for biventricular ICD and pacemaker groups, respectively. Overall mortality rate was significantly lower in the biventricular ICD group (13%, 8 deaths) compared to the pacemaker group (41%, 26 deaths) (P = 0.01). Further, the predominant survival benefit for ICD-treated patients becomes evident after the first 12 months of follow-up.

CONCLUSION

The findings in this study, although necessarily limited in their interpretation by the absence of treatment randomization, suggest that biventricular ICDs offer a survival benefit compared to biventricular pacing alone. Furthermore, this benefit may be most apparent if other clinical factors do not preclude patient survival >1 year postimplant.

Natriuretic peptides and the prevalence of congestive heart failure in patients with pacemakers

AIM

The aim of the study was to investigate the diagnostic potential of natriuretic cardiac peptide measurement in the context of left ventricular dysfunction and comorbidities in a pacemaker population.

MATERIAL AND METHODS

Ninety-five consecutive patients with pacemakers were included in the study. All patients underwent echocardiography and were asked to complete the Minnesota Living with Heart Failure Questionnaire (MLHFQ). Brain natriuretic peptide (BNP), N-terminal proatrial natriuretic peptide (N-ANP) and atrial natriuretic peptide levels in plasma were measured.

RESULTS

Twenty-six percent of patients had reduced systolic left ventricular function; only 16 patients had a history of congestive heart failure. BNP was abnormally elevated in 64%, N-BNP in 72% and N-ANP in 96% of patients. Both BNP (r = 0.30; P < 0.01) and N-ANP (r = 0.39; P < 0.0005) correlated with MLHFQ. The strongest correlation was found between N-ANP and the ejection fraction (r = 0.6; P < 0.0001). Patients were stratified in a high-risk group and a low risk-group according to their N-ANP (N-ANP > 5000 fmol L(-1); n = 63 and N-ANP < 5000 fmol L(-1), n = 32) and BNP levels (BNP > 400 pg mL(-1); n = 17 and BNP < 400 pg mL(-1), n = 78). N-ANP was correlated with hypertension (P < 0.003) and atrial fibrillation (P < 0.03), and BNP with mitral insufficiency (P < 0.002).

CONCLUSIONS

Cardiac natriuretic peptides are markedly elevated in the majority of patients with pacemakers. The prognostic significance of BNP and N-ANP in left ventricular dysfunction warrants close follow-up schedules.

Development of circulatory-renal limitations to angiotensin-converting enzyme inhibitors identifies patients with severe heart failure and early mortality

OBJECTIVES

This study examined the hypothesis that patients who develop angiotensin-converting enzyme inhibitor intolerance attributable to circulatory-renal limitations (CRLimit) have more severe underlying disease and worse outcome.

BACKGROUND

Although the renin-angiotensin system contributes to the progression of heart failure (HF), it also supports the failing circulation. Patients with the most severe disease may not tolerate inhibition of this system.

METHODS

Consecutive inpatient admissions to the cardiomyopathy service of the Brigham and Women's Hospital between 2000 and 2002 were reviewed retrospectively for initial profiles, discharge medications, and documented reasons for discontinuation of angiotensin-converting enzyme inhibitors. Outcomes of death and transplantation were determined.

RESULTS

Of the 259 patients, 86 were not on an angiotensin-converting enzyme inhibitor at discharge. Circulatory-renal limitations of symptomatic hypotension, progressive renal dysfunction, or hyperkalemia were documented in 60 patients (23%); other adverse effects, including cough, in 24 patients; and absent reasons in 2 patients. Compared with patients on angiotensin-converting enzyme inhibitors, patients with CRLimit were older (60 vs. 55 years; p = 0.006), with longer history of HF (5 vs. 2 years; p = 0.009), lower systolic blood pressure (104 vs. 110 mm Hg; p = 0.05), lower sodium (135 vs. 138 mEql/l; p = 0.002), and higher initial creatinine (2.5 vs. 1.2 mg/dl; p = 0.0001). Mortality was 57% in patients with CRLimit and 22% in the patients on angiotensin-converting enzyme inhibitors during a median 8.5-month follow-up (p = 0.0001).

CONCLUSIONS

Development of CRLimit to angiotensin-converting enzyme inhibitor intolerance identifies patients with severe disease who are likely to die during the next year. New treatment strategies should be targeted to this population.

Prevention and management of chronic heart failure with electrical therapy

Sudden cardiac death is responsible for >40% of patients with heart failure losing their lives. Thus, the prevention of life-threatening cardiac arrhythmias is a major goal in the management of heart failure. In several randomized clinical trials, electrical therapy with the implantable cardioverter defibrillator (ICD) has proved superior to medical antiarrhythmic therapy in both the secondary and primary prevention of sudden cardiac death in patients with reduced left ventricular function. In addition to the severity of left ventricular dysfunction, the etiology of the cardiomyopathy appears to be a determinant in the benefit derived from this form of electrical therapy. Whereas patients with ischemic cardiomyopathy clearly show improved survival with ICD therapy, outcome data in patients with nonischemic cardiomyopathy are less convincing. The major challenge lies in the risk stratification of patients with heart failure for arrhythmic death. Catheter ablation is another form of electrical therapy that can help in the treatment of patients with heart failure. In patients with a tachycardia-mediated cardiomyopathy because of drug-refractory atrial fibrillation with rapid ventricular response, catheter ablation of the atrioventricular node and pacemaker implantation can effectively restore a physiologic heart rate, often with dramatic regression of left ventricular dysfunction. In patients with frequent ICD therapies because of frequent recurrences of ventricular tachyarrhythmias, catheter ablation of ventricular tachycardia can be an effective adjunctive therapy. New catheter ablation techniques and new atrial pacing algorithms can also significantly reduce the atrial fibrillation burden in patients with heart failure who are particularly susceptible to decompensation because of atrial fibrillation. Pacing for hemodynamic benefit in heart failure has evolved from dual-chamber pacing modes with optimized atrioventricular delay to biventricular pacing resulting in cardiac resynchronization. This new treatment modality for advanced heart failure has been shown to result in significant symptomatic and hemodynamic improvement.

Left ventricular septal and apex pacing for optimal pump function in canine hearts

OBJECTIVES

The goal of this study was to test the hypothesis that left ventricular (LV) pump function is optimal when pacing is performed at the LV near the sites where the impulses exit the Purkinje system.

BACKGROUND

Pacing at the conventional site, the right ventricular (RV) apex, adversely affects hemodynamics. During normal sinus rhythm (SR), electrical activation of the working myocardium starts at the LV septal endocardium and spreads from apex to base.

METHODS

Experiments were conducted in anesthetized open-chest dogs with normal ventricular conduction to investigate hemodynamic effects of pacing at various epicardial LV sites, the RV apex, and combinations of these sites (n = 11) and of RV and LV septal pacing (n = 8). The LV septal endocardium was reached via the RV by puncturing through the septum with a barbed electrode. Left ventricular systolic (LVdP/dtpos and stroke work) and diastolic (LVdP/dtneg and Tau) function were assessed using pressure-volume relations (conductance catheter technique).

RESULTS

Left ventricular systolic and diastolic function were highly dependent on the site of pacing, but not on QRS duration. Left ventricular function was maintained at SR level during LV septal, LV apex, and multisite pacing, was moderately depressed during pacing at epicardial LV free wall sites, and was most severely depressed during RV apex pacing. On average, RV septal pacing did not improve LV function, compared with RV apex pacing, but in each experiment one (variable) RV pacing site was found, which only moderately reduced LV function.

CONCLUSIONS

During ventricular pacing, LV pump function is maintained best (i.e., at SR level) when pacing at the LV septum or LV apex, potentially because pacing from these sites creates a physiological propagation of electrical conduction.

Cardiac size, autonomic function, and 5-year follow-up of chronic heart failure patients with severe prolongation of ventricular activation

BACKGROUND

Chronic heart failure is characterized by left ventricular dilation and abnormalities of cardiac autonomic function. Up to 20% of patients with chronic heart failure have QRS prolongation, which can lead to asynchronous left ventricular contraction. We tested the hypotheses that in patients with chronic heart failure, QRS > 150 ms is a risk factor for additional abnormalities of ventricular morphology, heart rate variability, and increased mortality.

METHODS AND RESULTS

In 184 patients with left ventricular ejection fraction < 35%, QRS duration was > 150 ms in 53, and </= 150 ms in 131. We evaluated patients with baseline chest radiographs, echocardiograms, and Holter recordings. Patients with QRS duration above and below 150 ms were similar in age, sex, functional class, renal function, serum sodium, and ejection fraction. In patients with QRS > 150 ms, left ventricular end-diastolic and end-systolic diameters were greater than patients with QRS duration </=150 ms (P <.01). Patients with QRS > 150 ms had less low frequency R-R interval spectral power (P <.04). At 5 years 60% of patients with QRS > 150 ms had died compared with 35% of patients with QRS </=150 ms (P <.001). This increase in mortality was predominantly the result of an increase in progressive heart failure.

CONCLUSIONS

Chronic heart failure patients with QRS duration > 150 ms have exaggerated disturbance of cardiac autonomic function, and left ventricular remodeling and significantly higher mortality than patients with QRS duration </= 150 ms.

Ventricular resynchronization: a promising therapy for heart failure

Primarily a disease of the elderly, heart failure continues to be an ever-increasing health care problem given the growth in the number of individuals over age 65. Although there have been many advances in the pharmacologic management of heart failure, there continues to be a significant number of patients with persistent symptoms despite maximal therapy and it is likely that this group of patients will only continue to increase in number. Given this, significant research has gone into exploring new modalities, such as device therapies, to treat heart failure. Of these, ventricular resynchronization has emerged as one of the most promising. This review will examine the most important aspects of ventricular resynchronization therapy including: the significance of ventricular dyssynchrony, the role of traditional pacemakers, the effects on contractile function and reverse remodeling, and the currently accepted indications for resynchronization devices. Additionally, various aspects of completed and ongoing trials will be discussed.

Management of arrhythmias in heart failure

Arrhythmias often complicate the management of heart failure and contribute to mortality and morbidity. Implantable cardioverter defibrillators are the best protection from death caused by ventricular arrhythmias, but their benefit will probably be less in heart failure populations than has been observed in trials that have not focused on heart failure populations. Implantable cardioverter defibrillators are first-line therapy for high-risk patients who have been resuscitated from sustained ventricular tachycardia or ventricular fibrillation, who have inducible ventricular tachycardia in the setting of previous myocardial infarction, or who have unexplained syncope. Amiodarone is the major pharmacologic option for treatment of symptomatic arrhythmias. In selecting therapy, the severity of heart failure and cause of heart failure are important considerations. Atrial fibrillation occurs with increasing frequency as the severity of heart failure increases. Anticoagulation and rate control are important. Attempted maintenance of sinus rhythm with amiodarone or dofetilide is a reasonable consideration for selected patients, although the benefit of treatment strategies that seek to maintain sinus rhythm has not been demonstrated. Ongoing trials will provide further guidance for arrhythmia management.

Hemodynamic implications of left bundle branch block

Left bundle branch block (LBBB), traditionally viewed as an electrophysiologic abnormality, is increasingly recognized for its profound hemodynamic effects. LBBB causes asynchronous myocardial activation, which, in turn, may trigger ventricular remodeling. Exercise nuclear studies frequently show reversible perfusion defects in the absence of obstructive coronary artery disease and some patients with intermittent LBBB develop angina coincident with the onset of LBBB. It is uncertain, however, if these phenomena are because of myocardial ischemia or ventricular asynergy. LBBB is associated with impaired systolic and diastolic function. In patients with dilated cardiomyopathy (DCM), LBBB is accompanied by progressive left ventricular (LV) dilatation and mitral regurgitation. It is not known whether LBBB is the cause or the consequence of LV dilatation. DCM patients with LBBB, as compared to those with normal intraventricular conduction, are more likely to have a nonischemic etiology, profound LV dilatation, lower ejection fraction, increased symptomatology, and shorter survival. Patients with DCM and acceleration-dependent LBBB may benefit from restoration of a narrow QRS complex by suppressing the heart rate with beta-blocker. There is extensive research underway in patients with DCM and LBBB to evaluate the short and long-term effects of normalization of ventricular activation sequence with high septal, LV, or biventricular pacing.

Biventricular pacing in severe heart failure patients reverses electromechanical dyssynchronization from apex to base

Biventricular (BV) pacing is an emerging treatment for patients with severe dilated cardiomyopathy and ventricular asynchrony. Radionuclide angioscintigraphy has shown that BV can reduce activation delays between left (LV) and right ventricles (RV), but alterations of electromechanical asynchrony between the LV base and apex have not been previously described. Radionuclide angioscintigraphy with Tc99m red cell labeling was performed in 21 patients, 64 +/- 17 years of age, in NYHA functional Class III or IV, and with a mean QRS duration of 180 +/- 15 ms. Right (RVEF) and LV ejection fraction (LVEF), and the synchronization between LV apex and base (Tab) in the left lateral view, were measured by a phase analysis program (1) at baseline, (2) on day 8 after BV pacemaker implantation (D8), and (3) at 12-month follow-up in BV (M12). BV pacing reversed Tab from 42 +/- 47 ms at baseline to -57 +/- 75** on D8, and -37 +/- 76** on M12. LVEF increased from 17.8 +/- 6.3% to 19.9 +/- 8.3 on D8, and 24.2 +/- 10.8* on M12, and RVEF increased from 27.6 +/- 16% to 29.9 +/- 16 on D8 and 34.1 +/- 12.1* on M12 (*P < 0.05, **P < 0.001). A close correlation was found between early LV apex-to-base resynchronization induced by BV and late increase in LVEF (r = 0.59**). In parallel with its known interventricular resynchronization effect, BV pacing reverses the apex-to-base ventricular activation sequence, causing early contraction of the LV base followed by the apex. These changes persisted up to 12 months along with an improvement in LV systolic function.

Mitral regurgitation after atrioventricular node catheter ablation for atrial fibrillation and heart failure: acute hemodynamic features

BACKGROUND

Radiofrequency catheter ablation of the atrioventricular node and pacemaker insertion have been associated with occasional development of mitral regurgitation (MR). Ventricular pacing might result in MR if (1) left ventricular (LV) compliance is decreased and/or (2) mitral valve leaflet apposition is disturbed. We studied acute hemodynamic changes resulting from initiation of ventricular pacing in patients undergoing ablation.

METHODS AND RESULTS

Thirteen patients (10 men and 3 women) with a mean age of 73.4 +/- 8. 6 years, with chronic atrial fibrillation and congestive heart failure, had permanent ventricular pacemaker insertion with lead placement at the right ventricular (RV) apex. The following hemodynamic recordings were obtained before ablation (during atrial fibrillation) and then immediately after ablation (during RV pacing): heart rate, mean arterial pressure, LV end-diastolic pressure (LVEDP), mean pulmonary capillary wedge pressure, V-wave amplitude, and cardiac index. Presence of MR was assessed by V-wave amplitude and the results of LV angiography. In patients who had MR, recordings were also obtained during temporary ventricular pacing from the RV outflow tract (RVOT). As a group there were no significant changes in any hemodynamic measurement. Before ablation, mild MR by LV angiogram was present in 5 patients, but none had large V-wave amplitude. After ablation, mild MR was present by LV angiogram in 6 patients, and in 3 of these patients large V-wave amplitude developed (mean amplitude 42.7 +/- 2.2 mm Hg; assigned to group 1). This was associated with a rise in LVEDP in 1 patient (consistent with reduced LV compliance), but LVEDP was unchanged in the other 2 patients (suggesting abnormal mitral valve leaflet apposition). All patients in group 1 exhibited a fall in V-wave amplitude when the pacing site was moved to the RVOT.

CONCLUSIONS

Both reduced LV compliance and disturbed mitral valve leaflet apposition contribute to MR after ablation. MR is reduced by pacing from the RVOT.

Outcome of patients with nonischemic dilated cardiomyopathy and unexplained syncope treated with an implantable defibrillator

OBJECTIVES

The purpose of this study was to determine the outcome of patients with nonischemic dilated cardiomyopathy, unexplained syncope and a negative electrophysiology test who are treated with an implantable defibrillator.

BACKGROUND

Patients with nonischemic cardiomyopathy and unexplained syncope may be at high risk for sudden cardiac death, and they are sometimes treated with an implantable defibrillator.

METHODS

This study prospectively determined the outcome of 14 consecutive patients who had a nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test and who underwent defibrillator implantation (Syncope Group). Nineteen consecutive patients with a nonischemic cardiomyopathy and a cardiac arrest who were treated with a defibrillator (Arrest Group) served as a control group.

RESULTS

Seven of 14 patients (50%) in the Syncope Group received appropriate shocks for ventricular arrhythmias during a mean follow-up of 24+/-13 months, compared with 8 of 19 patients (42%) in the Arrest Group during a mean follow-up of 45+/-40 months (p = 0.1). The mean duration from device implantation until the first appropriate shock was 32+/-7 months (95% confidence interval [CI], 18 to 45 months) in the Syncope Group compared to 72+/-12 months (95% CI, 48 to 96 months) in the Arrest Group (p = 0.1). Among patients who received appropriate shocks, the mean time from defibrillator implantation to the first appropriate shock was 10+/-14 months in the Syncope Group, compared with 48+/-47 months in the Arrest Group (p = 0.06). Recurrent syncope was always associated with ventricular tachyarrhythmias.

CONCLUSIONS

The high incidence of appropriate defibrillator shocks and the association of recurrent syncope with ventricular arrhythmias support the treatment of patients with nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test with an implantable defibrillator.

Acute effects of intraoperative multisite ventricular pacing on left ventricular function and activation/contraction sequence in patients with depressed ventricular function

INTRODUCTION

We hypothesized that simultaneous right and left ventricular apical pacing would result in improvement in left ventricular function due to improved coordination of segmental ventricular contraction. Structural changes in ventricular muscle present in dilated cardiomyopathy compromise ventricular excitation and mechanical contraction.

METHODS AND RESULTS

Eleven patients with depressed left ventricular function having cardiac surgery underwent epicardial multisite pacing with continuous transesophageal echocardiographic imaging. Quantitative measurement of percent fractional area change was performed, and segmental changes in contraction sequence resulting from simultaneous right and left ventricular pacing were assessed by application of phase analysis to recorded transesophageal images. There was no statistically significant difference between the paced QRS duration achieved with simultaneous right and left ventricular apical pacing and the native QRS duration (139+/-39 msec vs 106+/-18 msec, P = NS), but all other paced modes resulted in longer QRS durations. Percent fractional area change improved with simultaneous right and left ventricular apical pacing but not with other paced modes (41.5+/-11.9 vs 34.3+/-9.7, P < 0.01). Phase analysis demonstrated a resequencing of segmental left ventricular activation/contraction when compared to baseline ventricular activation.

CONCLUSION

Simultaneous right and left ventricular apical pacing results in acute improvements in global ventricular performance in patients with depressed ventricular function. Improvements may result from pacing-induced global coordination through recruitment of left and right ventricular apical and septal segments critical to effective ventricular contraction.

Chronic treatment with carbachol sensitizes the myocardium to cAMP-induced arrhythmia

BACKGROUND

The present study investigated biochemical and functional consequences of chronic activation of the inhibitory Gi alpha-coupled adenylyl cyclase pathway in the heart.

METHODS AND RESULTS

Rats (220 to 260 g) were treated with 4-day infusions of the M-cholinoceptor agonist carbachol (9.6 mg/kg per day) or vehicle. An additional group that received the beta-adrenoceptor agonist isoprenaline (2.4 mg/kg per day) served as control. The main finding was that chronic infusion of carbachol led to a marked increase in isoprenaline- or forskolin-induced arrhythmia in electrically driven papillary muscles (in vitro). Compared with control, the potency of isoprenaline and forskolin to induce arrhythmia in cardiac preparations from carbachol-treated rats was increased 36- and 2.2-fold and the efficacy was increased 7.3- and 2.3-fold, respectively. The potency of carbachol to antagonize the isoprenaline- and forskolin-induced arrhythmia was decreased 30-fold. These changes were accompanied by a decrease in left ventricular M-cholinoceptor density by 15% (P < .05) and a decrease in pertussis toxin-sensitive G proteins (Gi alpha) by 26% (P < .05) without a decrease in the corresponding mRNAs. beta-Adrenoceptor density and basal and stimulated adenylyl cyclase activity remained unchanged. In contrast, isoprenaline infusion induced a decrease in arrhythmogenic potency of forskolin (P = NS), which was accompanied by a decrease in beta-adrenoceptor density, an increase in Gi alpha protein and mRNA levels, and a decrease in basal and stimulated adenylyl cyclase activity.

CONCLUSIONS

Chronic parasympathetic activation sensitizes the myocardium to cAMP-induced arrhythmia. These changes may be due to quantitative alterations in functional Gi alpha.

Four chamber pacing in dilated cardiomyopathy

A 54-year-old man received a four chamber pacing system for severe congestive heart failure (NYHA functional Class IV). His ECG showed a left bundle branch block (200-msec QRS duration) with 200-msec PR interval, normal QRS axis, and 90-msec interatrial interval. An acute hemodynamic study with insertion of four temporary leads was performed prior to the implant, which demonstrated a significant increase in cardiac output and decrease of pulmonary capillary wedge pressure. A permanent pacemaker was implanted based on the encouraging results of the acute study. The right chamber leads were introduced by cephalic and subclavian approaches. The left atrium was paced with a coronary sinus lead, Medtronic SP 2188-58 model. An epicardial Medtronic 5071 lead was placed on the LV free wall. The four leads were connected to a standard bipolar DDD pacemaker, Chorus 6234. The two atrial leads were connected via a Y-connector to the atrial channel of the pacemaker with a bipolar pacing configuration. The two ventricular leads were connected in a similar fashion to the ventricular channel of the device. The right chamber leads were connected to the distal poles. The left chamber leads were connected to the proximal poles of the pacemaker. Six weeks later, the patient's clinical status improved markedly with a weight loss of 17 kg and disappearance of peripheral edema. His functional class was reduced to NYHA II. Four chamber pacing is technically feasible. In patients with evidence of interventricular dyssynchrony, this original pacing mode probably provides a mechanical activation sequence closer to the natural one.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-chamber ventricular pacing is not associated with worsening heart failure in sick sinus syndrome

Ventricular pacing (with loss of normal atrioventricular synchrony) has been considered to have a role in the development or progression of congestive heart failure (CHF) in patients with sick sinus syndrome (SSS). No rigorous study has tested this hypothesis. Five hundred seven consecutive patients with SSS who received an initial pacemaker from January 1980 to December 1989 were studied. Atrial or dual-chamber pacemakers were implanted in 395 patients and ventricular pacemakers in 112. After a mean follow-up of 65 +/- 37 months, 97 patients (19%) developed new CHF or increased their New York Heart Association functional class. By univariate analysis, preimplant predictors for these events were left ventricular dysfunction (p < 0.001), valvular heart disease (p = 0.004), peripheral vascular disease (p = 0.005), diabetes (p = 0.02), coronary artery disease (p = 0.02), high New York Heart Association functional class (p = 0.03) and complex ventricular arrhythmia (p = 0.03). By multivariate analysis (logistic regression), the only predictors for CHF were valvular heart disease (p = 0.002; odds ratio [OR] 2.51), peripheral vascular disease (p = 0.003; OR 1.7) and complex ventricular arrhythmia (p = 0.027; OR 2.74). When the analysis was restricted to patients who had preimplant assessment of left ventricular function, independent predictors for CHF were left ventricular dysfunction (p < 0.001; OR 1.66), and complex ventricular arrhythmia (p < 0.001; OR 1.75). In conclusion, progressive or new-onset CHF is a consequence of the underlying cardiovascular disease. In the present population of patients with SSS, ventricular pacing mode was not associated with an increased incidence of CHF.