STATUS OF THE LEFT-VENTRICLE AFTER ARTERIAL SWITCH OPERATION FOR TRANSPOSITION OF THE GREAT-ARTERIES - HEMODYNAMIC AND ECHOCARDIOGRAPHIC EVALUATION

Background: The potential for improved preservation of systemic ventri cular function represents an important reason for the increasing popul arity of the arterial switch operation. In support of this expectation , prior studies in patients early after arterial switch operation have found normal ventricular contractility and function. This study was c onducted to extend those observations to up to 10 years of follow-up a nd to directly examine the effects of a coexisting ventricular septal defect or short-term preparatory banding of the pulmonary artery befor e the arterial switch operation. Methods: Patients operated on from 19 83 through 1991 were included. Echocardiographic and catheterization d ata were collected as part of a prospective evaluation of outcome in a ll patients who undergo the arterial switch operation at Boston Childr en's Hospital, with inclusion of data from the most recent catheteriza tion only. Echocardiograms performed at least 6 months after the opera tion were included, with assessment of both the most recent status as well as serial trends. Whenever possible, echocardiographic evaluation included data necessary to perform analysis of ventricular mechanics including indices of afterload, preload, and contractility. Comparison was made to normal values and between subgroups defined on the basis of an arterial switch operation with or without ventricular septal def ect and those who had a rapid two-stage arterial switch operation. Res ults: Invasive measures of left and right ventricular filling pressure s, cardiac index, and pulmonary vascular resistance did not differ amo ng the three groups. Overall, echocardiographic left ventricular end-d iastolic dimension, wall thickness, mass, afterload (end-systolic wall stress), function (fractional shortening and rate corrected velocity of fiber shortening), contractility (stress-velocity and stress-shorte ning relations), and preload were normal, and none of these variables was different between the groups with and without a ventricular septal defect. Serial evaluation indicated a slight but significant trend to ward ventricular dilatation, perhaps related to a relatively high inci dence of at least mild aortic regurgitation (30%). In contrast, in the rapid two-stage group the echocardiographic indices of left ventricul ar function (fractional shortening and velocity of fiber shortening) a nd contractility (stress-velocity and stress-shortening relations) wer e found to be mildly but significantly reduced compared with normal su bjects and with the other arterial switch operation groups. Over the d uration of follow-up encompased by this study, no tendency toward prog ressive depression of function was seen. Conclusions: As the length of observation after the arterial switch operation continues to increase , left ventricular size, mass, functional status, and contractility co ntinues to be normal, with no evidence of time-related deterioration o f function. As previously reported, the rapid two-stage arterial switc h operation does represent a higher risk for mild impairment of myocar dial mechanics.