Hemodynamic changes due to intraoperative testing of the automatic implantable cardioverter defibrillator: implications for anesthesia management.

During the insertion of an automatic implantable cardioverter defibrillator, repeated induction of ventricular tachycardia or ventricular fibrillation and subsequent defibrillation is performed to determine the defibrillation threshold. In this study, the influence of these testing episodes on myocardial function was investigated in 13 patients under general anesthesia. Preoperative ejection fraction (EF) was 41 (14 to 84) % (median and range). Testing was performed 3 (2-5) times. During these testing episodes the patients received a total of 4 (2-8) countershocks. Patients with a preoperative EF < 30% (N = 5) showed a significant reduction of cardiac index (CI) from 2.2 (1.5-3.3) L/min/m2 before testing to 1.5 (1.3-2.3) L/min/m2 after the last testing episode, and of left ventricular stroke work index (LVSWI) from 32 (14-53) g.m/m2 before testing to 22 (7-43) after the last testing episode. These changes were not related to the total fibrillation time or the cumulative defibrillation energy. Patients with a preoperative EF > 30% (N = 8) showed no significant changes of CI (2.15 [1.8-3.0] L/min/m2 v 2.15 [1.7-3.0] L/min/m2) or LVSWI (35 [28-48] g.m/m2 v 33.5 [27-52] g.m/m2). Comparison of the two patient groups revealed similar hemodynamic baseline values, but significant differences in LVSWI after the last testing episode. Defibrillation testing may produce a further reduction in myocardial performance in patients with preexisting poor cardiac function.