Sudden Cardiac Death Despite a Functional Cardioverter‐Defibrillator: The Case for Early and Aggressive Therapy for Ventricular Tachycardia in Selected Patients

Abstract

We present three cases within 11 months at a single institution of sustained VT that fell below the programmed detection rate of the patients' implantable cardioverter-defibrillators (ICDs), two of which continued until converting to an agonal VF that did not meet criteria for detection, and a third case that could not be successfully defibrillated after a prolonged period of VT. These episodes may be under-recognized due to the dependence of device diagnostic storage on programming and the post-mortem effort that is often required to review these events. Some patients, likely those with the most advanced heart failure, may not tolerate sustained ventricular tachycardia (VT) and may even die from ventricular arrhythmias without ever having a rhythm that meets detection criteria in a ventricular fibrillation (VF) zone.

Failure to Treat Life-Threatening Ventricular Tachyarrhythmias in Contemporary Implantable Cardioverter–Defibrillators

“…Although low-frequency VF has been considered an agonal rhythm, metabolic changes during VT may produce de novo, low-frequency VF (patients 3, 7, and 9) because of local conduction block or hyperkalemia, resulting in long device-detected intervals because of undersensing or entrance block. 6 Patient 5’s first recorded rhythm was low-frequency VF, but recurrence of high-frequency VF promptly after the first defibrillation indicates that the presenting VF was not an agonal rhythm. In addition, prolonged VT may cause metabolic changes that facilitate early postshock recurrence of VT/VF (eg, catecholamine release, patients 4, 5, 7–9).…”

“…Manufacturers responded with improved technology; in this century, reports of failure to treat life-threatening VT or VF have been rare and limited to one 1 – 4 or a few patients. 5 , 6 …”

Failure to detect life‐threatening arrhythmias in ICDs using single‐chamber detection criteria

“…Montgomery et al. reported on three cases of sudden death due to sustained VT that fell below the programmed detection rate . Anguera et al.…”

“…A matter of concern is the anecdotal reports of sudden cardiac death despite a functional defibrillator . In this report, we describe another 24 patients with a fatal or near‐fatal arrhythmic event due to failure to detect ongoing life‐threatening ventricular tachyarrhythmias (VAs).…”

“…Abbreviations: -= unbinned interval; * = charging for shock delivery; Ars = atrial refractory sense, i.e., atrial event detected in the atrial refractory period; F = binned interval in VF zone; FF = far-field; ID = initial detection; mon = monitoring zone; PVT = polymorphic VT; VF = ventricular fibrillation; VS = ventricular sensed event; VT = ventricular tachycardia; VT2 = VT2 zone; sinus = sinus zone [Color figure can be viewed at wileyonlinelibrary.com] study, Tseng et al described six patients with sudden death despite a functional ICD 7. Undersensing of VF occurred in five patients; in one patient the VT was slower than the programmed detection rate.Montgomery et al reported on three cases of sudden death dueto sustained VT that fell below the programmed detection rate 8. Anguera et al reported a patient with sudden death due to PVT with an average cycle length of 329 ms that remained undetected as a consequence of undersensing due to intermittent high-amplitude R waves 6.…”