BACKGROUND: The dilated phase of hypertrophic cardiomyopathy (HCM) has a poor 
prognosis. For correct recognition of such patients, we compared the findings in 
cardiac delayed enhancement (DE)-magnetic resonance imaging (MRI) between HCM 
and dilated cardiomyopathy (DCM) patients.
METHODS AND RESULTS: Sixty-five patients (HCM 39, DCM 26) underwent 
gadolinium-DTPA-enhanced MRI. The HCM patients were divided into those with 
preserved (HCM-P, n = 30) and those with impaired systolic function (HCM-I, n = 
9). DE-MRI demonstrated focal or diffuse DE at the left ventricular (LV) wall in 
60% of HCM-P and 100% of HCM-I, but in only 12% of DCM. The DE distributed 
mainly septal to the anterior wall of LV, but the DE volume against whole LV 
muscle volume was much larger in HCM-I than in HCM-P and DCM (4.1 +/- 6.1% in 
HCM-P, 14.6 +/- 11.9% in HCM-I, and 0.8 +/- 2.4% in DCM, means +/- SD, P < .05). 
In HCM, there were weak but significant correlations between DE volume, and LV 
end-diastolic volume and LV end-systolic volume. In HCM-P, the percent of length 
shortening in the segments with DE was lower than that without DE.
CONCLUSIONS: The HCM patients had more DE than the DCM patients, and DE volume 
correlated to lower global and local LV function. DE-MRI may be useful to 
evaluate myocardial damage in HCM patients, and to differentiate the dilated 
phase of HCM from DCM.