CARDIAC DEATH AND STORED ELECTROGRAMS IN PATIENTS WITH 3RD-GENERATIONIMPLANTABLE CARDIOVERTER-DEFIBRILLATORS

Objectives. We sought to utilize terminal stored intracardiac electrog rams (EGMs) to study the electrophysiologic events that accompany mort ality in patients with third-generation implantable cardioverter-defib rillators (ICDs). Background. Despite their ability to effectively ter minate ventricular tachyarrhythmias, cardiac mortality in patients wit h ICDs remains high. The mechanisms and modes of death in these patien ts are not well understood. Methods. We retrospectively analyzed clini cal 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 E GMs as well as 50 control EGMs were used to define normal EGM characte ristics. 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 s tored EGMs within 1 h of death, implying that the deaths were not dire ctly 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 nide (>158 ms) in 33 (89%). Wide EG Ms were interpreted as ventricular tachycardia in 27 and ventricular f ibrillation in 6. In 13 of the 33 patients (39%) with wide EGMs, thera py was not delivered by the ICD, as it incorrectly detected a spontane ous termination of the arrhythmia. EGMs were significantly wider if re corded within 1 h, as compared with those recorded from 1 to 48 h befo re 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 I h of the time of death, suggesting that the majority of death s (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 dissoci ation. Thus, of the 119 deaths, 112 (94%) were not the immediate resul t of a tachyarrhythmia. (C) 1998 by the American College of Cardiology .