RAPID 2-STAGE ARTERIAL SWITCH OPERATION - EVALUATION OF LEFT-VENTRICULAR SYSTOLIC MECHANICS LATE AFTER AN ACUTE PRESSURE-OVERLOAD STIMULUS IN INFANCY

Background Banding of the pulmonary artery to induce left ventricular (LV) hypertrophy followed by arterial switch operation (ASO) within 2 weeks has been performed when a primary ASO was considered high risk b ecause of inadequate LV hypertrophy. Methods and Results Potential adv erse myocardial effects of the two-stage procedure were examined by co mparing outcome in 18 patients after a rapid two-stage ASO with 33 pat ients after a primary ASO. Regional wall motion was assessed. Echocard iographic and noninvasive pressure data were combined to obtain LV dim ension, wall thickness, mass, fractional shortening, rate-corrected me an velocity of shortening, and end-systolic wall stress. Afterload-adj usted velocity of shortening was obtained as a load-independent index of contractility. In the two-stage ASO group, the magnitude and rate o f hypertrophy after pulmonary artery banding were measured serially. N o wall motion abnormalities were seen in either group. Systolic dysfun ction due to higher afterload and lower contractility was observed in the two-stage ASO group. Contractility below the limits of normal was seen in 25% of two-stage ASO compared with 3% of primary ASO; however, symptomatic or progressive LV dysfunction was not observed. There was a significant inverse relation between the peak rate of hypertrophy i mmediately after banding and contractility at late exam. Lower ejectio n fraction before and early after pulmonary artery banding correlated with depressed contractility on late examination. Conclusions Myocardi al contractility is lower after the two-stage ASO than after a primary repair. Severe or progressive dysfunction was not seen. A very high p eak rate of hypertrophy and severe LV dysfunction after banding predic t a greater reduction in late contractility.