Implantable Cardioverter Defibrillator Events in Patients with Asymptomatic Nonsustained Ventricular Tachycardia:

Abstract

Primary prevention trials have demonstrated that patients with coronary disease, reduced left ventricular function, and nonsustained ventricular tachycardia (NSVT) have improved survival with implantable cardioverter defibrillator (ICD) therapy, presumably secondary to effective termination of life-threatening arrhythmias. However, stored intracardiac electrograms were not always available and specific arrhythmias leading to ICD therapy were not always known. We examined the occurrence of ICD events in 51 consecutive patients who match the described patient profile to determine the frequency of appropriate and inappropriate ICD therapy. ICD detections were noted in 18 (35%) patients during a median follow-up period of 13.1 months. Appropriate therapy for sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) occurred in 11 (22%) patients, with appropriate shocks in 8 (16%) patients and appropriate antitachycardia pacing (ATP) in 4 (8%) patients. The time to first appropriate therapy occurred at a mean of 17 +/- 12 months (median 18 months, range 3-36 months). Inappropriate therapy occurred in 5 (10%) patients with inappropriate shocks in 4 patients and inappropriate ATP in 2 patients. Inappropriate therapy was delivered for supraventricular arrhythmias (SVAs) in 4 patients and for T wave oversensing in 1 patient. The reason for shock therapy was unknown in 1 patient (2%) due to ICD malfunction. The mean arrhythmia rate leading to appropriate therapy for VT/VF was 232 +/- 72 beats/min (range 181-400 beats/min), and the mean rate leading to inappropriate therapy for SVT was 168 +/- 10 beats/min (range 160-180 beats/min). Patients with coronary disease and asymptomatic NSVT commonly receive appropriate defibrillator therapy. These results support the need for ICD implantation for primary prevention, with attention to careful programming of the detection rate to prevent inappropriate therapy.

Appropriate and Inappropriate Ventricular Therapies, Quality of Life, and Mortality Among Primary and Secondary Prevention Implantable Cardioverter Defibrillator Patients

“…22 Inappropriate therapies due to misclassification of rapidly conducted SVTs occurred in 15% of both patient groups and accounted for more than one third of all therapies and Ϸ40% of all shocks in both groups. Although SVT discrimination was equivalently underutilized in the minority of patients with single-chamber ICDs in both groups, this is consistent with the reported rates of inappropriate therapies in other trials of secondary 16,23,24 and primary 16,19,21 prevention. These observations emphasize that despite increasingly sophisticated enhancements to single-and dual-chamber ICD systems that rely on rate-based detection, rejection of SVT while maintaining high sensitivity for true ventricular arrhythmias remains elusive.…”

“…16 Additionally, some studies have reported that the cycle lengths of appropriately detected VT may be longer in secondary than in primary prevention patients 16 and that the difference in cycle lengths between appropriately detected VT and inappropriately detected SVT may be greater in primary prevention patients. 16,21 One possible interpretation of these data are that rate-based programming to achieve the optimal balance between VT detection and SVT rejection is different between primary and secondary prevention patients. This is not supported by the present study.…”

Strategic Programming of Detection and Therapy Parameters in Implantable Cardioverter-Defibrillators Reduces Shocks in Primary Prevention Patients

“…The purpose of the PREPARE (Primary Prevention Parameters Evaluation) study was to adapt these strategies specifically to primary prevention patients both with and without Bi-V ICD indications. A treatment rate cutoff of 188 beats/min has been used to treat primary prevention patients in several large trials (2,6,15). In the latter 2 studies, investigators recommended a treatment cutoff between 170 and 180 beats/min for primary prevention patients in order to reduce the proportion of inappropriate therapies while still providing appropriate therapy.…”

Minimizing Inappropriate or “Unnecessary” Implantable Cardioverter-Defibrillator Shocks

“…21 These patients are those most likely to benefit from discrimination algorithms because lower programmed VT detection rates result in increased risk of unnecessary therapy for SVT.…”