Have the results of randomized clinical trials of pacing altered the practice of cardiac pacing?

Reduced ejection fraction, sudden cardiac death, and heart failure death in the mode selection trial (MOST): implications for device selection in elderly patients with sinus node disease

Sudden Cardiac Death in Elderly Pacemaker Patients.

BACKGROUND

The purpose of this study was to describe the incidence and predictors of sudden cardiac death (SCD) and heart failure (HF) death, and coexisting indications for ICDs and CRT, in patients with sinus node disease (SND) treated with pacemakers.

METHODS AND RESULTS

Baseline variables were used to predict SCD and HF death among 1,135 patients in the Mode Selection Trial, a 6-year trial of pacing mode in SND. There were 73 deaths among 177 patients with EF <or= 35% (41.2%), 46/156 (29.5%) with EF 36-49%, and 147/802(18.3%) with EF >or= 50%. SCD accounted for 21.9%, 23.9%, and 14.3% of deaths with EF <or= 35%, 36-49%, and >or= 50%. HF deaths accounted for 23.3%, 19.6%, and 3.4% of deaths with EF <or= 35%, 36-49%, and >or= 50%. EF <or= 35% predicted SCD (hazard ratio [HR] 3.68, 95% confidence interval [CI] 1.72-7.89, P = 0.002) and HF death (HR 10.17, 95% CI 3.35, 30.82, P = 0.001). Four-year SCD rate with EF <or= 35% was 15.5% (3.9% annually). Nearly one-fifth of patients qualified for ICDs (EF <or= 35%) and half of these had QRS >or= 120 ms. However, >40% died within 33 months (4-year noncardiac death rate approximately 22%).

CONCLUSIONS

Reduced EF predicts SCD and HF death in SND treated with pacemakers. SCD rates among patients with EF <or= 35% are similar to control arms of primary prevention ICD trials, but mortality rates are significantly higher. Whether ICDs or CRT to provide bradycardia support would prolong life in elderly patients with EF <or= 35% and SND merits prospective investigation.

Impact of rate-modulated pacing on quality of life and exercise capacity—Evidence from the Advanced Elements of Pacing Randomized Controlled Trial (ADEPT)

BACKGROUND

Ninety-nine percent of pacemakers implanted in the United States include an option for rate modulation.

OBJECTIVE

The purpose of this study was to determine whether dual-chamber rate-modulated pacing, when compared with dual-chamber pacing alone, improved quality of life.

METHODS

This was a single-blind randomized controlled trial comparing dual-chamber with rate-modulated dual-chamber pacing. Patients were enrolled between January 12, 2000, and January 10, 2002, with 1-year follow-up ending December 19, 2002. The study was a U.S. multicenter trial, with 95 sites participating. All patients received a rate modulation-capable dual-chamber pacemaker for standard indications. Patients were screened with an exercise test (Chronotropic Assessment Exercise Protocol) 1 month later. One thousand two hundred seventy-three patients were enrolled; 401 proved ineligible, and 872 (68%) made up the randomized patient cohort. Randomized patients had a mean age of 71 years, 64% were men, and 64% had sinus node dysfunction. Randomization was in a factorial design to (1) dual-chamber rate-modulated pacing versus dual-chamber pacing and (2) automatic mode switching versus no automatic mode switching. The present report is limited to the comparison of rate modulation with no rate modulation (DDDR vs. DDD). The primary endpoint was the score on the Specific Activity Scale, an activity-based cardiovascular disease-specific instrument at 1 year. Secondary endpoints included 6-month treadmill time and additional cardiovascular disease-specific, and generic health-related quality-of-life instruments at 1 year.

RESULTS

At 6 months, patients with rate modulation had a higher peak exercise heart rate (rate modulation 113.3 +/- 19.6, no rate modulation 101.1 +/- 21.1; P <.0001). Total exercise time was not different between groups. At 1 year, there were no significant differences between groups with respect to Specific Activity Scale or the secondary quality-of-life endpoints.

CONCLUSIONS

We conclude that rate modulation is ineffective in improving the functional status or quality of life of patients with a bradycardia indication for dual-chamber pacing.

Pacemakers and Defibrillators: Recent and Ongoing Studies That Impact the Elderly

Since the first implantation of a cardiac pacemaker in the second half of the 20th century, there have been evolutionary and revolutionary advances in the technology developed for patients with heart rhythm disturbances. These advances, however, have instead failed to demonstrate that mimicry of physiology by a pacing system would deliver a longer and better life to its recipient. Indeed, we are just now in the process of developing a new paradigm in pacing that may finally deliver physiology to the hyperbolically named "physiologic pacing." This article will discuss the reasons for the discrepancy between the earlier studies and the more recent ones, as well as a review of implantable cardioverter-defibrillator trials, keeping in focus the special needs of aged heart rhythm device recipients.

Reasons for escalating pacemaker implants

Surveys of pacing practice have shown a steady increase in pacemaker implantation rates in the past 15 years, despite no major changes in United States guidelines for permanent pacing. There are no data to explain why this is occurring. In this study, records were extracted from the National Hospital Discharge Survey to investigate this. There were 3 major findings. First, age-adjusted implantation rates increased progressively over the study period from 370 per million in 1990 to 612 per million in 2002. Second, it was found that the escalating implantation rate is attributable to increasing implantation for isolated sinus node dysfunction (SND). Implantation for SND increased significantly over the study period (by 102%), whereas implantation for all other indications did not. The increasing implantation for SND is due primarily to the increasing prevalence of SND, with a lesser increase in implantation rate relative to prevalence rate. The third major finding of this study is that there has been a progressive relative and absolute increase in the dual-chamber implantation rate. In 2002, 82.8% of all initial pacemaker implantations were dual-chamber devices. Furthermore, the National Hospital Discharge Survey data indicate that the major randomized pacing trials seem to have had no impact on pacing practice in the United States. In conclusion, age-adjusted implantation rates increased progressively over the study period. This escalating implantation rate is primarily attributable to increasing implantation for SND.

Clinical and Quality of Life Comparison of Accelerometer, Piezoelectric Crystal, and Blended Sensors in DDDR-Paced Patients with Sinus Node Dysfunction in the Mode Selection Trial (MOST)

INTRODUCTION

Permanent pacemakers are capable of increasing heart rate in response to physical activity by a variety of sensors including accelerometers, piezoelectric crystals, or blended sensors. The impact of these different physiologic sensors on cardiovascular events and quality of life is not known.

METHODS

Of 2,010 patients randomized in the Mode Selection Trial, 1,245 patients were selected with the most commonly used pacemakers with these three sensors. Clinical characteristics and quality of life were compared between groups at baseline, 3 months, and then yearly.

RESULTS

There were 449 patients with an accelerometer sensor device, 682 with a piezoelectric sensor, and 114 with a blended sensor. The groups were similar in terms of age (mean 74 years), gender, and cardiac risk factors but differences existed in weight, heart rate, mitral regurgitation, revascularization history, and drug therapy. The median ventricular pacing frequency was 80% (25th, 75th percentiles 42, 97). After a median follow-up of 33.1 months, the risk of death, heart failure hospitalization, atrial fibrillation, and the combined endpoint of mortality and stroke was not significantly different between the sensor types, after adjustment for baseline differences. Quality of life analyses demonstrated that patients with blended sensors had significantly worse (P < 0.01) physical function than did patients with the other two sensor systems. Moreover, patients receiving blended sensors had the poorest absolute scores, without reaching statistical significance, on 9 of 13 quality of life measures after adjusting for differences in the groups.

CONCLUSION

We found no significant differences among the three most utilized sensors in clinical endpoints. Those patients who received blended sensors had worse physical function quality of life scores. However, clinical selection of the most sophisticated sensor for the most ill patients cannot be excluded as an explanation of these results.

Body image changes associated with dual-chamber pacemaker insertion in women

PURPOSE

The study's purpose was to examine body image changes in subjects participating in a long-term multicenter pacemaker trial.

METHODS

At study closeout, 383 adults, all of whom had received a dual-chamber pacemaker, completed questionnaires evaluating what effect their pacemaker or pacemaker site and scar had on them or their spouses or significant others.

RESULTS

Most reported that their pacemaker did not change the way they or their spouses or significant others felt about their body (73.2% and 93.5%, respectively). Most (87.1%) denied feeling differently because of the pacemaker site and scar. Most were not concerned how their clothes fit or about wearing a swimsuit (92.0% and 90.7%, respectively). Women were more concerned about how the pacemaker site and scar made them feel about their body (P =.001), clothes fitting (P =.002), and wearing a swimsuit (P =.004). Men were more concerned with how their spouses or significant others perceived them postimplantation (P =.021).

CONCLUSIONS

Most subjects did not express undue concern about changes in body image.

An update on clinical trials in pacing: is dual chamber pacing better?

PURPOSE OF REVIEW

As pacemaker technology has increased in complexity and now offers a variety of additional capabilities, there is uncertainty as to which pacing mode offers more benefit-dual-chamber or single-chamber.

RECENT FINDINGS

Two large-scale randomized trials, the Canadian Trial of Physiologic Pacing and the Mode Selection Trial, demonstrated that dual-chamber pacing does not reduce the incidence of stroke or improve survival when compared with ventricular pacing. However, dual-chamber pacing does reduce the incidence of atrial fibrillation and in patients with sinus node dysfunction, reduces heart failure symptoms when compared with ventricular pacing. The modest results of these trials were unexpected when viewed in the context of the very favorable retrospective studies.

SUMMARY

A rethinking of the physiology of cardiac pacing has led to the concept that although atrioventricular synchrony supports an improvement in cardiac output and ventricular pressures, these favorable hemodynamics may be attenuated by ventricular dyssynchrony from right ventricular apical pacing. In patients with a reduced ejection fraction, this dyssynchrony may be especially detrimental. Two trials (DANPACE and SAVE-PACE) are currently underway that will clarify the clinical significance of reducing forced ventricular desynchronization. The results of these trials may direct pacemaker physicians away from the right ventricular apical lead toward a new imperative of atrioventricular and right ventricular-left ventricular synchrony.