Normal left ventricular muscle mass and mass/volume ratio after pediatric cardiac transplantation

The adaptive growth of the transplanted heart within the growing child may contribute to long-term cardiac performance. The ability 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 growth over a 3-year period after cardiac transplantation. This study was designed to assess changes in LV mass and mass/volume ratio and their relation to LV end-diastolic pressure (LVEDP) 1 to 4 years after cardiac transplantation.

Cardiac transplantation was performed in 18 patients, age 7 days to 18 years (median, 3.7 years). The indications for cardiac transplantation were cardiomyopathy (8 patients), hypoplastic left heart syndrome (7 patients), and postoperative structural congenital heart disease with ventricular failure (3 patients). 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 resistance (SVR) were measured. LV diastolic volume index (LVDVI), LV mass index, and mass/volume ratio were determined angiographically according to the method of Lange and Rackley. The data were analyzed by repeated-measures ANOVA. Least-squares means and group SEM were calculated. No change in cardiac index, SVR, or baseline LVEDP was noted. The LVEDP doubled after fluid challenge, suggesting a restrictive process. The LVDVI remained near 60 mL/m2. The LV mass/volume ratio remained one.

Appropriate increases in muscle mass occurred after cardiac transplantation, preserving normal mass/volume ratios despite somatic growth deficits associated with immunosuppressive therapy and denervation of the donor heart.