Relevance of Coronary Microvascular Flow Impairment to Long-Term Remodeling and Systolic Dysfunction in Hypertrophic Cardiomyopathy Original Research Article

Objectives This study sought to evaluate whether the entity of microvascular dysfunction, assessed by positron emission tomography (PET), predicts the long-term development of left ventricular (LV) remodeling and systolic dysfunction in hypertrophic cardiomyopathy (HCM). Background A subgroup of patients with HCM developed LV dilation and systolic impairment. A causal role of coronary microvascular dysfunction has been suggested as the underlying pathophysiological mechanism. Methods Fifty-one patients (New York Heart Association functional class I to II) were followed up for 8.1 ± 2.1 years after measurement of resting and dipyridamole (Dip) myocardial blood flow (MBF). Left ventricular systolic dysfunction was defined as an ejection fraction (LVEF) <50%. Results The Dip-MBF was blunted in HCM patients compared with a group of healthy control patients (1.50 ± 0.69 ml/min/g vs. 2.71 ± 0.94 ml/min/g; p < 0.001). At final evaluation, 11 patients (22%) had an LVEF <50%; in most (n = 7), systolic dysfunction was associated with a significant increase in LV cavity dimensions (>5 mm) during follow-up. These 11 patients showed lower Dip-MBF than the 40 with preserved LV function (1.04 ± 0.38 ml/min/g vs. 1.63 ± 0.71 ml/min/g, respectively; p = 0.001); Dip-MBF was particularly blunted in five patients with clinical progression to severe heart failure symptoms or death (Dip-MBF 0.89 ± 0.15 ml/min/g). At multivariate analysis, the two independent predictors of systolic dysfunction were Dip-MBF in the lowest tertile (<1.1 ml/min/g; relative hazard, 7.5; p = 0.038) and an end-diastolic LV dimension in the highest tertile (>45 mm; relative hazard, 12.3; p = 0.031). Conclusions Severe microvascular dysfunction is a potent long-term predictor of adverse LV remodeling and systolic dysfunction in HCM. Our findings indicate microvascular dysfunction as a potential target for prevention of disease progression and heart failure in HCM.