A study of the subendocardial ultrastructural changes in the volume-overloaded left ventricular hypertrophy: a comparison of the effects of aortic and mitral regurgitation.

Ultrastructural changes of the subendocardial layer of the volume-overloaded left ventricle were studied in patients who underwent open heart surgery for chronic aortic valve disease (4 patients) and mitral valve disease (6 patients). Patients in these two entities were estimated to be in the same level of hemodynamic functional capacity. In aortic valve disease, the subendocardial layer of the hypertrophied left ventricle showed degeneration of cardiac muscle cells. Conversely, degeneration of cardiac muscle was rarely observed in those with mitral valve disease. Numerous small and medium sized mitochondria were observed in the subendocardial layer of the left ventricle in aortic valve and mitral valve diseases and suggested that the patients in both groups were well compensated at the time of surgery. Moderate to severe dilatation of tubules of the sarcoplasmic reticulum was observed with significantly higher incidence in the case of aortic valve disease. The hypertrophied myocardium as a result of aortic valve disease showed more ischemic damage than that due to mitral regurgitation, even with the same levels of hemodynamic functional capacity. These data suggest that the myocardium in cases of mitral regurgitation tolerates open heart surgery to a much greater extent and that the prognosis is better.