A successful aortic coarctectomy performed beyond early infancy is followed, even in the long term, by persistence of left ventricular hypertrophy and by diastolic dysfunction, although systolic function is often increased. In this study we investigated whether earlier coarctectomy provides better preservation of left ventricular function. Experimental studies on the myocardial response to pressure overload show that neonates and young infants develop a functionally advantageous combination of myocytic hyperplasia (together with mild hypertrophy) and increased angiogenesis. Older patients, in contrast, generate myocytic hypertrophy in isolation, setting the scene for ventricular dysfunction. Cross-sectional echo-Doppler evaluation of left ventricular size, shape, mass and systolic and diastolic function was made in 13 patients a mean of 44±36 months (range 11 days-10 years) after successful coarctectomy in the first year of life. They were compared to 11 age, body surface area and gender-matched control subjects. In all patients, left ventricular mass normalized for body surface area was significantly greater than in the control group (66.2±12.3 vs 43±l2 p=0.0001). There was no correlation between left ventricular mass normalized for body surface area and age at operation, follow-up duration, degree of residual isthmic gradient, peak systolic wall stress, systolic blood pressure or left ventricular shape. No significant differences were noted between the two groups in regard to transverse diameter of the aortic arch, left ventricular afterload (meridional end-systolic wall stress), volume and shape (both in systole and diastole), systolic performance (fractional shortening and ejection fraction) and contractility (rate-corrected velocity of fiber shortening to meridional end-systolic wall stress relationship). Furthermore, no significant differences were found with respect to indices of mitral (including peak filling rate normalized to mitral stroke volume) and pulmonary venous flow, suggesting normal diastolic function. Repair of aortic coarctation in the first year of life promotes a more complete recovery of left ventricular function (particularly diastolic) than that reported after coarctectomy at older age, despite persistence of moderate ventricular hypertrophy.