Small vessel disease: Another component of the hypertrophic cardiomyopathy phenotype not necessarily associated with fibrosis

Abstract

Background: Hypertrophic cardiomyopathy (HCM) is characterized by myocardial disarray, small vessel disease (SVD), and fibrosis. The relationship between SVD and replacement-type fibrosis is still unclear. Methods: Histopathologic assessment of replacement-type fibrosis and SVD in HCM patients with either end-stage heart failure (HF) or sudden cardiac death (SCD). Chronic ischemic heart disease (IHD) patients served as controls. Results: Forty HCM hearts, 10 HF and 30 SCD, were studied. Replacement-type fibrosis was detected in all HF and in 57% of SCD cases. In SCD, replacement-type fibrosis was associated with older age, greater septal thickness, SVD prevalence, and score (all p < 0.05). Prevalence of SVD did not show significant differences among SCD, HF, and IHD (73%, 100% and 95%, respectively), while SVD score was higher in HF than IHD and SCD (2.4, 1.95, and 1.18, respectively) and in areas with replacement-type fibrosis vs. those without in HF (3.4 vs. 1.4) and SCD (1.4 vs. 0.8) (all p < 0.05). Conclusions: SVD is a frequent feature in HCM independent of the clinical presentation. A higher SVD score is observed in HCM-HF and in areas with replacement-type fibrosis. Although SVD is part of the HCM phenotype, further remodeling of the microcirculation might occur secondarily to fibrosis.