Rapid two-stage arterial switch operation. Evaluation of left ventricular systolic mechanics late after an acute pressure overload stimulus in infancy.

Abstract

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 because of inadequate LV hypertrophy. Potential adverse myocardial effects of the two-stage procedure were examined by comparing outcome in 18 patients after a rapid two-stage ASO with 33 patients after a primary ASO. Regional wall motion was assessed. Echocardiographic and noninvasive pressure data were combined to obtain LV dimension, wall thickness, mass, fractional shortening, rate-corrected mean velocity of shortening, and end-systolic wall stress. Afterload-adjusted velocity of shortening was obtained as a load-independent index of contractility. In the two-stage ASO group, the magnitude and rate of hypertrophy after pulmonary artery banding were measured serially. No wall motion abnormalities were seen in either group. Systolic dysfunction 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 immediately after banding and contractility at late exam. Lower ejection fraction before and early after pulmonary artery banding correlated with depressed contractility on late examination. Myocardial contractility is lower after the two-stage ASO than after a primary repair. Severe or progressive dysfunction was not seen. A very high peak rate of hypertrophy and severe LV dysfunction after banding predict a greater reduction in late contractility.