EFFECTS OF ELECTROPHYSIOLOGIC STUDIES RESULTING IN ELECTRICAL COUNTERSHOCK OR BURST PACING ON LEFT-VENTRICULAR SYSTOLIC AND DIASTOLIC FUNCTION

To determine the acute effects of electrophysiologic study on left ventricular systolic and diastolic function in patients requiring termination of induced tachyarrhythmias by either electrical countershock or burst pacing, we examined 16 patients (11 men and five women), aged 43 to 78 years (mean 58 .+-. 13), undergoing programmed electrical stimulation. Indices of systolic and diastolic left ventricular function were measured by M-mode echocardiography before and within 1 minute after termination of 22 episodes of induced tachyarrhythmias by defibrillation (n = 16) and burst pacing (n = 6). The left ventricular septal and posterior endocardial surfaces were digitized immediately below the mitral valve leaflets, and indices of systolic and diastolic function were calculated. The results showed a significant impairment in both systolic and diastolic function after termination of tachyarrhythmias by defibrillation, as seen by a decrease in the shortening fraction (23.7 .+-. 7.6% to 19.8 .+-. 7.8%; p < 0.005) and a decline in the peak rate of increase in left ventricular diameter during diastole called dD/dtmax (87.4 .+-. 36.1 mm/sec to 71.5 .+-. 28.9 mm.sec; p < 0.01), respectively. In addition, indices of systolic and diastolic function measured at baseline were predictive of impairment in diastolic function, as seen by modest but highly significant correlations between the absoluble change in dD/dtmax after defibrillation versus the peak velocity of fiber shortening (r = -0.69; p < 0.005) and dD/dtmax (r = -0.60; p < 0.02) measured at baseline. Left ventricular function after termination of tachyarrhythmias by burst pacing was not significantly altered. Although electrophysiologic study with the induction of sustained ventricular tachyarrhythmias has been performed safely, the potential for left ventricular dysfunction from hemodynamic instability and electrical countershock exists. Burst pacing termination of ventricular tachycardia appears to be devoid of deleterious effects on left ventricular function and should be employed whenever hemodynamic stability permits.