[Dilated cardiomyopathy: electrocardiographic forms].

The shape of the QRS complex was analyzed in 90 cases of dilated cardiomyopathy and was divided into 6 electrocardiographic types which may be interpreted as follows: A predominant S wave in V2, V3 and V4 leads, surrounded by a reduced QRS voltage in the other leads was the most frequent characteristic pattern, being found in 31 cases (34.4%). This pattern coexisted with a lack of R wave progression from V1 to V4, with primary disorders of ST-T and with alterations in P wave. The deep S wave is probably due to a growth of vectors in the base of the left ventricle and in the septum in response to lesions in the rest of the myocardium. Second in frequency (22.2%) came left bundle branch block, with 20 cases. If to these are added the 19 cases of left anterior half-block observed, dilated cardiomyopathy appears as the major cause of the cardiac pathology that partially or completely interrupts the left branch. These cases also show that the lesions predominate in the left ventricle. The 14 cases (15.5%) of QS with elevated and convex ST-T betray extensive areas of fibrosis or necrosis. This pattern is characteristically located at the apex of the heart and associated with ventricular tachycardia. In 11 cases (12.2%) the QRS complex was normal in shape but associated with depressed ST-T and atrial disorders. This shows that the ventricular myocardium which produces QRS is neither badly damaged nor hypertrophic, but that repolarization is highly sensitive to the constant alterations of the subendocardial layers observed in dilated cardiomyopathy. Left ventricular hypertrophy was seen in 9 cases (10%).(ABSTRACT TRUNCATED AT 250 WORDS)