[Estimation of left ventricular systolic function based on the electrocardiograms in cases with left bundle branch block].

The electrocardiographic features indicating left ventricular dysfunction were studied in 32 consecutive patients having left bundle branch block including 10 with idiopathic genesis without significant underlying disease, 6 with dilated cardiomyopathy, 8 with old myocardial infarction, and 8 with hypertensive heart disease. The patients were divided into two groups; those with favorable left ventricular systolic function and those with poor left ventricular systolic function evaluated by using non-invasive methods. Electrocardiographic findings were compared between these two groups. Ten patients had favorable and 22 poor left ventricular systolic function. One or more of the following electrocardiographic findings were observed in the poor group, but none in the favorable group: low voltage in the limb leads, prolonged intraventricular conduction (QRS duration wider than 0.17 sec), transitional zone between V5 and V6, depression of the ST-J point by more than 0.2 mV in V6, reverse progression of the R wave in V1-V5, marked left axis deviation (axis beyond: 30 degrees), left atrial overload (positive Morris index), PQ prolongation, and abnormal Q waves in I, aVL, V6. No significant differences in the distribution of these findings was observed in any of the underlying diseases. The clinical background of patients with left bundle branch block who had no significant underlying disease showed favorable left ventricular systolic function except the patients above 80 years of age, who showed poor left ventricular systolic function. In contrast, patients with underlying mild hypertensive heart disease may have a favorable left ventricular systolic function. Thus, left ventricular systolic function in patients with left bundle branch block may be suspected by observing these electrocardiographic findings.