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Cardiac death and stored electrograms in patients with third-generation implantable cardioverter-defibrillators
E M Grubman1, B B Pavri, T Shipman
1Department of Medicine, Hospital of the University of Pennsylvania, Philadelphia 19104, USA.
Insights
Most deaths in implantable cardioverter-defibrillator (ICD) patients were not due to tachyarrhythmias, as indicated by intracardiac electrograms (EGMs). Stored EGMs revealed that wide EGMs, often showing electromechanical dissociation, were present in most cardiac deaths.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- High cardiac mortality persists in patients with implantable cardioverter-defibrillators (ICDs) despite their efficacy in terminating ventricular tachyarrhythmias.
- The precise mechanisms and modes of death in this patient population remain incompletely understood.
Purpose of the Study:
- To investigate the electrophysiologic events associated with mortality in patients with third-generation ICDs.
- To utilize terminal stored intracardiac electrograms (EGMs) for this analysis.
Main Methods:
- Retrospective analysis of clinical data and stored EGMs from 1,729 patients in the Ventritex Cadence ICD trial.
- Review of final recorded EGMs from 119 patients who died during 6 years of follow-up.
- Comparison with 50 control EGMs to establish normal EGM characteristics.
Main Results:
- Of 119 deaths, 83 were cardiac (70%), with 55 nonsudden and 28 sudden.
- Stored EGMs within 1 hour of death were absent in 46 (55%) of cardiac deaths, suggesting non-tachyarrhythmic causes.
- In 37 cardiac deaths with available EGMs, 33 (89%) showed wide EGMs (>158 ms), interpreted as ventricular tachycardia or fibrillation; 39% of these did not receive appropriate ICD therapy due to detection errors.
Conclusions:
- The majority of deaths (69%) in ICD patients were not immediately caused by tachyarrhythmias, as evidenced by the lack of relevant stored EGMs.
- When EGMs were recorded near death, wide waveforms suggestive of electromechanical dissociation were prevalent (89%).
- Overall, 94% of deaths were not directly attributable to immediate tachyarrhythmias based on EGM analysis.
Objectives:
We sought to utilize terminal stored intracardiac electrograms (EGMs) to study the electrophysiologic events that accompany mortality in patients with third-generation implantable cardioverter-defibrillators (ICDs).
Background:
Despite their ability to effectively terminate ventricular tachyarrhythmias, cardiac mortality in patients with ICDs remains high. The mechanisms and modes of death in these patients are not well understood.
Methods:
We retrospectively analyzed clinical data and stored EGMs from patients enrolled in the clinical trial of the Ventritex Cadence ICD. Of the 1,729 patients 119 died during 6 years of follow-up. The final recorded EGM was reviewed. Postimplant EGMs as well as 50 control EGMs were used to define normal EGM characteristics.
Results:
There were 36 noncardiac deaths (30%) and 83 cardiac deaths (70%). Of the cardiac deaths, 55 (66%) were nonsudden and 28 (34%) were sudden. When cardiac deaths were analyzed, 46 (55%) had no stored EGMs within 1 h of death, implying that the deaths were not directly related to tachyarrhythmias. In 37 cardiac deaths (18 nonsudden, 19 sudden), stored EGMs were present within 1 h of death. In these 37 deaths, the final EGM recorded was wide (>158 ms) in 33 (89%). Wide EGMs were interpreted as ventricular tachycardia in 27 and ventricular fibrillation in 6. In 13 of the 33 patients (39%) with wide EGMs, therapy was not delivered by the ICD, as it incorrectly detected a spontaneous termination of the arrhythmia. EGMs were significantly wider if recorded within 1 h, as compared with those recorded from 1 to 48 h before death (261+/-124 vs. 181+/-93 ms, p=0.04).
Conclusions:
Only 37 patients (31%) who died after placement of an ICD had a stored EGM within 1 h of the time of death, suggesting that the majority of deaths (69%) were not the immediate result of a tachyarrhythmia. When EGMs were recorded, they were wide in 89% of patients. These wide EGMs most likely represent intracardiac recordings of electromechanical dissociation. Thus, of the 119 deaths, 112 (94%) were not the immediate result of a tachyarrhythmia.