Barbara Corti, Francesco Grigioni, Alberto Foà, Franco Cecchi, Giuseppe Galati, Iacopo Olivotto, Emanuele Pilato, Massimiliano Lorenzini, Elena Biagini, Ferdinando Pasquale, Ornella Leone, Valentina Agostini, Claudio Rapezzi, Galati, Giuseppe, Leone, Ornella, Pasquale, Ferdinando, Olivotto, Iacopo, Biagini, Elena, Grigioni, Francesco, Pilato, Emanuele, Lorenzini, Massimiliano, Corti, Barbara, Foà, Alberto, Agostini, Valentina, Cecchi, Franco, and Rapezzi, Claudio
Background— Although noninvasively detected myocardial fibrosis (MF) has clinical implications in hypertrophic cardiomyopathy, the extent, type, and distribution of ventricular MF have never been extensively pathologically characterized. We assessed the overall amount, apex-to-base, circumferential, epicardial–endocardial distribution, pattern, and type of MF in 30 transplanted hearts of end-stage, hypertrophic cardiomyopathy. Methods and Results— Visual and morphometric histological analyses at basal, midventricular, and apical levels were performed. Overall MF ranged from 23.1% to 55.9% (mean=37.3±8.4%). Prevalent types of MF were as follows: replacement in 53.3%, interstitial-perimyocyte in 13.3%, and mixed in 33.3%. Considering left ventricular base-to-apex distribution, MF was 31.9%, 43%, and 46.2% at basal, midventricular, and apical level, respectively ( P Conclusions— In end-stage, hypertrophic cardiomyopathy patients undergoing transplantation, more than one-third of the left ventricular myocardium was replaced by fibrosis, mainly of replacement type. MF preferentially involved the left ventricular apex and the midwall. Inferior and anterior walls and septum were maximally involved, whereas inferolateral and right ventricular were usually spared. These observations reflect the complex pathophysiology of hypertrophic cardiomyopathy and may provide clues for the timely recognition of disease progression by imaging techniques capable of quantifying MF.