SAFETY AND DIAGNOSTIC YIELD OF NONINVASIVE VENTRICULAR STIMULATION PERFORMED VIA TIERED THERAPY IMPLANTABLE DEFIBRILLATORS

Extensive electrophysiological testing is critical for the effective u tilization of sophisticated tachycardia detection and termination algo rithms available in tiered therapy ICDs. To evaluate the safety and di agnostic yield of electrophysiological testing via noninvasive ventric ular stimulation, we performed 294 electrophysiological studies in 154 patients (age 65 +/- 10; left ventricular ejection fraction 0.36 +/- 0.15) with tiered therapy ICDs. Stimulation was performed under methoh exital anesthesia. A total of 918 sustained ventricular tachyarrhythmi as were induced (3.1 +/- 2.5 per procedure): monomorphic VT, 550; vent ricular putter, 74; and VF, 246. The results of invasive and noninvasi ve programmed stimulation were compared for 79 patients who herd both studies under similar treatment. Overall concordance was 83%, and did not differ significantly between patients who had the noninvasive stim ulation via epicardial or endocardial pacing leads. VF could be induce d in 206 of 257 studies (82%) and it was less likely to be induced in patients on amiodarone (74% vs 85%; P = 0.02), or beta blockers (55% v s 83%; P = 0.017). No patient presented a serious complication Minor c omplications occurred during 39 studies: transient laryngospasm in 1, unintended delivery of an ICD shock to a conscious patient in 4; induc tion of sustained atrial fibrillation in 8; need for external rescue d efibrillation shocks in 13; and delivery of inappropriate shocks for s upraventricular rhythms in 14 studies. Noninvasive ventricular stimula tion performed under methohexital anesthesia is safe. Its diagnostic y ield compares favorably with that of conventional electrophysiological studies. VF can be induced in a majority of patients. There is good c orrelation between invasive and noninvasive programmed stimulation for induction of VT. Noninvasive ventricular stimulation may emerge as st andard procedure for the initial program ming and follow-up of ICDs.