Electrocardiographic features differentiating dilated cardiomyopathy from hypertrophic cardiomyopathy.

To determine the usefulness of electrocardiographic (ECG) features in differentiating between hypertrophic cardiomyopathy with features mimicking dilated cardiomyopathy (D-HCM) and true dilated cardiomyopathy (DCM), we compared ECGs of 52 consecutive patients (11 with D-HCM, 41 with DCM). Left atrial dimension, left ventricular internal dimension, and septal and posterior wall thickness were employed as echocardiographic indexes, while QRS duration, amplitude of RV5 or V6 + SV1, number of abnormal Q waves, P-terminal force in V1, and frontal plane QRS axis were used as ECG parameters. The patients with D-HCM demonstrated a larger number of abnormal Q waves (P < .0001), greater prolongation of QRS duration (P < .0001), and lower amplitude of RV5 or V6 + SV1 (P < .0001). In all cases of D-HCM, atrial overload was observed and abnormal QRS axis in 9 (82%) of the 11 patients. These features were noted in 21 (51%) and 17 (41%), respectively, of the 41 DCM patients (P < .005 and P < .05, respectively). Despite significant differences in the echocardiographic parameters between D-HCM and DCM, excluding left ventricular end-diastolic dimension, ECG abnormalities were more significant between the two groups. The results indicate that ECG features are extremely useful in differentiation between DCM and D-HCM.