NORMAL LEFT-VENTRICULAR MUSCLE MASS AND MASS VOLUME RATIO AFTER PEDIATRIC CARDIAC TRANSPLANTATION/

Background The adaptive growth of the transplanted heart within the gr owing child may contribute to long-term cardiac performance. The abili ty to achieve increased ventricular volume and appropriate muscle mass in the face of immunosuppression and cardiac denervation has not been studied. We previously reported normal left ventricular (LV) volume g rowth over a 3-year period after cardiac transplantation. This study w as designed to assess changes in LV mass and mass/volume ratio and the ir relation to LV end-diastolic pressure (LVEDP) 1 to 4 years after ca rdiac transplantation. Methods and Results Cardiac transplantation was performed in 18 patients, age 7 days to 18 years (median, 3.7 years). The indications for cardiac transplantation were car diomyopathy (8 p atients), hypoplastic left heart syndrome (7 patients), and postoperat ive structural congenital heart disease with ventricular failure (3 pa tients). The mean follow-up was 48 months, with a range from 29 to 70 months. Serial annual catheterizations were performed after 1 year (16 patients), 2 years (18 patients), 3 years (15 patients), and 4 years (8 patients). Cardiac index (Fick), LVEDP (baseline and after 10-mL/kg saline infusion delivered over 5 minutes), and systemic vascular resi stance (SVR) were measured. LV diastolic volume index (LVDVI), LV mass index, and mass/volume ratio were determined angiographically accordi ng to the method of Lange and Rackley. The data were analyzed by repea ted-measures ANOVA. Least-squares means and group SEM were calculated. No change in cardiac index, SVR, or baseline LVEDP was noted. The LVE DP doubled after fluid challenge, suggesting a restrictive process. Th e LVDVI remained near 60 mL/m(2). The LV mass/volume ratio remained on e. Conclusions Appropriate increases in muscle mass occurred after car diac transplantation, preserving normal mass/volume ratios despite som atic growth deficits associated with immunosuppressive therapy and den ervation of the donor heart.