Relationship of basal-septal fibrosis with LV outflow tract obstruction in hypertrophic cardiomyopathy: insights from cardiac magnetic resonance analysis.

Abstract

Myocardial fibrosis is frequently observed and may be associated with the prognosis in patients with hypertrophic cardiomyopathy (HCM); however, the clinical pathophysiological features, particularly in terms of fibrosis, of hypertrophic obstructive cardiomyopathy (HOCM) remain unclear. This study aimed to determine a role of local fibrosis in HOCM using cardiac magnetic resonance (CMR). 108 consecutive HCM patients underwent CMR. HOCM was defined as a left ventricular outflow tract (LVOT) pressure gradient ≥30mmHg at rest. Myocardial mass and fibrosis mass by late gadolinium-enhancement CMR (LGE-CMR) were calculated and the distribution/pattern was analyzed using the AHA 17-segment model. LV ejection fraction (LVEF) was significantly higher in patients with HOCM (n=19) than in those with nonobstructive HCM (n=89) (P<0.05). Both total myocardial and fibrosis masses in LV were similar in the two groups (P=0.385 and P=0.859, respectively). However, fibrosis in the basal septum was significantly less frequent in the HOCM group than in the nonobstructive HCM group (P<0.01). The LVOT pressure gradient was significantly higher in the basal-septal non-fibrosis group than in the fibrosis group (23.6±37.3 vs. 4.8±11.4mmHg, P<0.01). Multivariate analysis revealed that basal-septal fibrosis was an independent negative predictor of LVOT obstruction in addition to the local wall thickness and LVEF as positive predictors in HCM patients. In conclusion, a significant association was observed between LVOT obstruction and basal septal fibrosis by LGE-CMR in HCM patients. In addition to negative impact of basal-septal fibrosis, basal-septal hypertrophy and preserved global LV contractility may be associated with the pathophysiological features of LVOT obstruction.