Diastolic Dysfunction and Its Histopathological Correlation in Obstructive Hypertrophic Cardiomyopathy in Children and Adolescents

Background: Histopathologic hallmarks of hypertrophic cardiomyopathy (HCM) include myocyte hypertrophy and disarray as well as interstitial and endocardial fibrosis. Published correlations between echocardiographic parameters and histopathologic findings are scarce. Methods: All patients aged <20 years (n = 45; 15 female patients; median age, 14 years) with obstructive HCM undergoing septal myectomy at the Mayo Clinic from 2003 to 2007 were identified. A retrospective review of echocardiographic data was performed, and these data were compared with the histologic findings from the myectomy specimens. Results: Histopathologic analysis of myectomy specimens revealed significant myocyte hypertrophy (100%), myocyte disarray (98%), interstitial fibrosis (95%), and subendocardial fibrosis (97%). On multivariate regression analysis, there was a significant relationship between the degree of myocyte disarray and echocardiographic markers of left ventricular diastolic dysfunction. Conclusion: The results of this study suggest that myocyte disarray is a key factor responsible for diastolic dysfunction in pediatric patients with obstructive HCM. These findings provide novel insights into the mechanism of diastolic dysfunction in HCM that warrant further study.