Myocyte nuclear area as a measure of left ventricular hypertrophy in transplant patients

Transplanted hearts have been reported to increase in size/weight in the first few months after transplant and to remain stable thereafter. An indirect way of assessing the changes in heart weight is through the changes in the area of the myocyte nucleus (MNA). We studied 20 patients who had undergone orthotopic heart transplantation more than 12 months previously; 10 had become hypertensive, and the remaining 10 were normotensive. Myocardial biopsies taken the first week after transplant and 6, 12, 24, and 52 weeks after transplant were assessed. Myocyte nuclear area was measured in 200 myocytes/biopsy with an image analyzer. Individual measurements showed a wide variation in MNA, with significant overlaps among the different biopsies. Assessment of MNA at one year showed increased MNA in 410 patients in the hypertensive group and 510 in the normotensive group. The remaining patients showed either no statistically significant changes in MNA or a significant (p < 0.0001) decrease in MNA. The presence of systemic hypertension was not a predictive factor for significant hypertrophy and, in some cases, not even for hypertrophy itself. We conclude that although there is often an increase in MNA of the transplanted heart at one year posttransplant, this increase is not systematic, and isolated morphometric results should be viewed cautiously.