What are the histopathological factors related to diastolic dysfunction in hypertrophic cardiomyopathy versus hypertensive asymmetric septal hypertrophy?
Diastolic dysfunction in hypertensive asymmetric septal hypertrophy is primarily driven by myocardial fibrosis, whereas in hypertrophic cardiomyopathy it is driven by myocyte disarray.
To clarify the histopathologic influence on diastolic function in the hypertrophied heart, we compared the echocardiographic and histopathologic findings in 9 controls, 10 patients with hypertrophic cardiomyopathy (HCM), and 8 hypertensive patients with asymmetric septal hypertrophy (HT-ASH). M-mode echocardiography was used to determine the left ventricular diastolic function. Mean diameter of myocytes, percentage of fibrosis and disarrangement were quantitatively calculated from right ventricular endomyocardial biopsy specimens. In both HT-ASH and HCM, the isovolumic relaxation time was significantly longer and the rapid filling volume tended to be smaller than in the controls. Histopathologically, the mean diameter of myocytes and percentage of myocardial interstitial fibrosis did not differ significantly between HT-ASH and HCM. However, quantitative disarrangement of myocytes in HCM was significantly greater than that in HT-ASH. Multiple regression analysis showed that the percentage of fibrosis was the most significant factor related to diastolic left ventricular dysfunction in HT-ASH, while disarrangement of myocytes was the most significant in HCM. We conclude that diastolic dysfunction in HT-ASH can be attributed to the percentage of fibrosis, and to disarrangement of myocytes in HCM.
Ohsato et al. (1992) studied this question.