932-86 Importance of Collagen in Myocardial Ischemia and Remodeling of Abnormal Intramural Coronary Arteries (“Small Vessel Disease”) in Young Patients with Hypertrophic Cardiomyopathy and Sudden Cardiac Death

Abstract

Impaired coronary blood flow reserve and myocardial ischemia in the absence of epicardial coronary artery disease is a frequent and important pathophysiologic feature of hypertrophic cardiomyopathy (HCM). To provide the morphologic basis for such findings, we studied the hearts of 16 pts with HCM (ages 11–31 yrs; mean 20) who had died suddenly. Transmural sections of ventricular septum were studied (area 5.2 ± 2 cm 2 ) after staining with picrosirius-red; 9 ± 2 abnormal intramural coronary arteries (IMCAs)were analyzed per section. Compared to 16 structurally normal control hearts, IMCAs in HCM had substantially greater (12-fold) collagen volume fraction in media (2.5 ± 2-vs-0.2 ± 0.3%, p < 0.01), as well as larger outer diameter (120 ± 46-vs-82 ± 22 JLm, p < 0.01), luminal diameter (88 ± 33-vs-62 ± 19 JLm, p < 0.05), medial thickness (32 ± 20-vs-20 ± 6 JLm, p < 0.05) and also perivascular collagen area (41 ± 37-vs-18 ± 10 /!mZ, p < 0.05). The amount of perivascular collagen correlated directly with medial thickness (r = 0.88, P < 0.01) and volume of medial collagen (r = 0.57, p < 0.05). Thus, IMCAs in HCM are encased in perivascular collagen and also show greatly thickened media due in part to increased collagen. This substantial perivascular and medial collagen potentially impairs vasoreactivity, in turn resulting in diminished coronary blood flow and cell death. The findings provide a morphologic explanation for myocardial ischemia, mediated by “small vessel disease”, in pts with HCM.