Collagen remodeling and cardiac dysfunction in patients with hypertrophic cardiomyopathy: The significance of type III and VI collagens

Background: The relationship between the extent of myocardial interstitial fibrosis, the percentage of each type of collagen, and cardiac function in patients with hypertrophic cardiomyopathy (HC) has not been established. Hypothesis: The study aimed to establish that increases in some types of collagen may correlate with cardiac dysfunction. Methods: Mallory-Azan staining and immunohistochemical staining by the avidin-biofin-complex (ABC) method using anticollagen antibodies were performed on the myocardial biopsy specimens in 35 patients with HC, and the percentage and type of collagen present was determined. Left ventricular (LV) function was evaluated by cardiac catheterization and ventriculography. Results: The percentage of myocardial interstitial fibrosis correlated highly with indices of LV diastolic and systolic function. The amount of type III collagen correlated significantly with the peak negative dp/dt, the rapid filling volume/stroke volume, and the ejection fraction (EF). Significant correlations also were noted between the amount of type VI collagen and peak negative dp/dt, peak positive dp/dt, and EE Type I collagen did not correlate with any of the LV function indices, and type IV collagen correlated only with peak ejection rate. Type V collagen did not accumulate substantially in the myocardial interstitium. Conclusions: The progression of myocardial interstitial fibrosis in the HC heart adversely impacts both the diastolic and systolic function of the LV. Increases in the percentage of type III and VI collagen correlate with cardiac dysfunction.