In this large HCM cohort with no or only mild symptoms, myocardial fibrosis detected by CMR was associated with greater likelihood and increased frequency of ventricular tachyarrhythmias (including NSVT) on ambulatory Holter ECG. Therefore, contrast-enhanced CMR identifies HCM patients with increased susceptibility to ventricular tachyarrhythmias.

Although diverse, patterns of LV hypertrophy are usually not extensive in HCM, involving < or = 50% of the chamber in about one-half the patients, and are particularly limited in extent in an important minority. Contiguous portions of anterior free wall and septum constituted the predominant region of wall thickening, with implications for clinical diagnosis. These observations support an emerging role for CMR in the contemporary evaluation of patients with HCM.

Background-Contrast-enhanced cardiovascular magnetic resonance with delayed enhancement (DE) can provide in vivo assessment of myocardial fibrosis. However, the clinical significance of DE in hypertrophic cardiomyopathy (HCM) remains unresolved. Methods and Results-Cine and cardiovascular magnetic resonance with DE were performed in 202 HCM patients (mean age, 42Ϯ17 years; 71% male), DE was compared with clinical and demographic variables, and patients were followed up for 681Ϯ249 days for adverse disease events. DE was identified in 111 (55%) HCM patients, occupying 9%Ϯ11% of left ventricular myocardial volume, including Ͼ25% DE in 10% of patients. The presence of DE was related to occurrence of heart failure symptoms (Pϭ0.05) and left ventricular systolic dysfunction (Pϭ0.001). DE was present in all patients with ejection fraction Յ50% but also in 53% (102/192) of patients with preserved ejection fraction (PϽ0.001); %DE was both inversely related to (rϭϪ0.3; PϽ0.001) and an independent predictor of ejection fraction (rϭϪ0.4; PϽ0.001). DE (7%Ϯ7% of left ventricle) was present in 54 patients who were asymptomatic (and with normal ejection fraction). Over the follow-up period, the annualized adverse cardiovascular event rate in patients with DE exceeded that in patients without DE but did not achieve statistical significance (5.5% versus 3.3%; Pϭ0.5). Conclusions-In a large HCM cohort, DE was an independent predictor of systolic dysfunction but with only a modest relationship to heart failure symptoms. These data suggest an important role for myocardial fibrosis in the clinical course of HCM patients but are not sufficient at this time to consider DE as an independent risk factor for adverse prognosis.

Background-Whether morphological abnormalities of the mitral valve represent part of the hypertrophic cardiomyopathy (HCM) disease process is unresolved. Therefore, we applied cardiovascular magnetic resonance to characterize mitral valve morphology in a large HCM cohort. Methods and Results-Cine cardiac magnetic resonance images were obtained in 172 HCM patients (age, 42Ϯ18 years; 62% men) and 172 control subjects. In addition, 15 HCM gene-positive/phenotype-negative relatives were studied. Anterior mitral leaflet (AML) and posterior mitral leaflet lengths were greater in HCM patients than in control subjects (26Ϯ5 versus 19Ϯ5 mm, PϽ0.001; and 14Ϯ4 versus 10Ϯ3 mm, PϽ0.001, respectively), including 59 patients (34%) in whom AML length alone, posterior mitral leaflet length alone, or both were particularly substantial (Ͼ2 SDs above controls