The Bilitch Registry

Development and Industrialization of the Implantable Cardioverter-Defibrillator: A Personal and Historical Perspective

The implantable cardioverter-defibrillator (ICD) is the standard of care for preventing sudden cardiac death. Contemporary ICDs are capable of providing a variety of therapeutic functions and can automatically gather and store diagnostic data that can guide both device and drug therapy and alert caregivers of impending battery depletion or lead problems. Moreover, much of the diagnostic data can be monitored remotely, so that many patients can be evaluated in their homes. This article, by a former chief executive officer of the first company to commercialize the ICD, traces the history of the device from its beginnings in the early 1980s.

Clinical experience with pacemaker pulse generators and transvenous leads: An 8-year prospective multicenter study

BACKGROUND

Pacemakers have improved the lives of patients worldwide. Unfortunately, the medical community has had little independent information regarding the performance of these vital medical devices.

OBJECTIVES

The purpose of this study was to examine the reasons pacemaker pulse generators and transvenous leads were removed from service. We evaluated the causes and major adverse clinical events associated with device end-of-service life behavior and how they were detected and managed.

METHODS

Pulse generator and lead data were entered prospectively using a web-based format. Normal battery depletion was signified by the elective replacement indicator appearing >3 years after implant. Lead failure was a device defect causing pacing, sensing, or fixation malfunction, high threshold, or abnormal impedance. Major adverse clinical events were death, angina, heart failure, syncope, and perioperative surgical complications.

RESULTS

From 1998 to 2006, 2,652 pulse generator and 615 leads were removed from service. The average pulse generator was implanted for 7.3 +/- 3.1 years (range <1 day to 26 years). The majority of pulse generators (n = 2,317 [87%]) were replaced for normal battery depletion. Severe and accelerated battery depletion, manufacturers' advisories, and electronic or connector defects accounted for 13% of pulse generator removals. The proportion of pulse generators removed from service as a result of manufacturers' advisories, electronic failure, and housing defects were 4%, 2%, and 1%, respectively. Models with rate response capability had shorter battery longevities than those without rate response capability. Major adverse clinical events due to pulse generator end-of-service life behavior were related to electronic and connector defects, and both normal and severe battery depletion. Median time to lead failure was 7.2 +/- 5.2 years. Insulation defects caused the majority of lead failures, and most of these leads used polyurethane materials. Lead failure was associated with a 16% incidence of major adverse clinical events. No major adverse clinical events occurred when impending lead failure was detected at routine follow-up. Lead extraction was associated with a 5.6% complication rate, including one death.

CONCLUSION

Overall pulse generator performance was satisfactory. Differences in battery longevity were observed among models. In some patients, elective replacement indicators signifying normal battery depletion resulted in major adverse clinical events. Pacemaker follow-up effectively identified pulse generator end-of-service life and often detected impending lead failure, thus avoiding major adverse clinical events. Long-term studies are needed to assess chronic lead performance so that appropriate clinical management strategies, including recommendations for lead extraction, can be developed.

Report of the NASPE Policy Conference on antibradycardia pacemaker follow-up: effectiveness, needs, and resources. North American Society of Pacing and Electrophysiology

On May 4-5, 1993, a policy conference was held in San Diego, California, under the sponsorship of the North American Society of Pacing and Electrophysiology (NASPE) to identify the fundamental goals of antibradycardia pacemaker follow-up, evaluate the effectiveness with which it achieves those goals, and formulate specific recommendations as to how it can be made more effective. The conference addressed clinical, administrative, and educational objectives, focusing on existing and potential resources for follow-up testing and the appropriate frequency of their application. The training of physicians and associated professionals engaged in follow-up also was addressed, as were regulatory and reimbursement issues. This report summarizes the conclusions and recommendations arrived at during the conference and subsequently approved by the NASPE Board of Trustees.

Upward bias in estimates of pacemaker reliability: effect of unreported patient mortality

OBJECTIVES

This study attempted to determine the effect of unreported patient deaths on estimates of pacemaker reliability.

BACKGROUND

The reliability of pacemakers is usually reported with reference to implant registration data and returned product analysis without censoring when follow-up data are missing.

METHODS

We studied 73 patients (mean [+/- SD] age 77 +/- 8 years) undergoing implantation of a ventricular-inhibited (VVI) pacemaker who were subsequently found to be at increased risk of experiencing premature pacemaker failure. Survival curves for patients and pacemakers were constructed by the Kaplan-Meier method with appropriate censoring at the time of unrelated death or elective explantation of a normal device. To examine the effect of unreported loss of follow-up data, patient mortality was then ignored, and follow-up for pacemakers without known failure was assumed to continue to the date of analysis.

RESULTS

There were 13 device failures, with a median pacemaker survival time of 37 months. Twenty-three patients died, all of causes unrelated to the pacemaker system; median patient survival time was only 44 months. Ignoring this attrition inflated follow-up time from 122 to 188 patient-years and reduced the apparent pacemaker failures at 30 months by almost half, from 37% to only 20%. Modeling the process shows that when the patient mortality rate is more than half the pacemaker failure rate, ignoring censoring inflates the device survival estimate by > or = 10% from the median survival onward.

CONCLUSIONS

When medical device survival curves are generated by implant registration data and returned product analysis, they should be adjusted for unreported loss of follow-up.