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, 42+/-17 years; 71% male), DE was 
compared with clinical and demographic variables, and patients were followed up 
for 681+/-249 days for adverse disease events. DE was identified in 111 (55%) 
HCM patients, occupying 9%+/-11% of left ventricular myocardial volume, 
including >25% DE in 10% of patients. The presence of DE was related to 
occurrence of heart failure symptoms (P=0.05) and left ventricular systolic 
dysfunction (P=0.001). DE was present in all patients with ejection fraction < 
or =50% but also in 53% (102/192) of patients with preserved ejection fraction 
(P<0.001); %DE was both inversely related to (r=-0.3; P<0.001) and an 
independent predictor of ejection fraction (r=-0.4; P<0.001). DE (7%+/-7% 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%; P=0.5).
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.