Assessment of left ventricular function from the electrocardiogram in left bundle branch block

Abstract

The QRS duration, maximum right precordial S amplitude, sum of amplitudes of the maximum right precordial S and T wave and T wave polarity in lead I have been analyzed in order to identify electrocardiographic predictors of left ventricular end-diastolic volume index and ejection fraction in 165 patients with complete left bundle branch block and various forms of heart disease. Multivariate analysis selected the duration, maximal amplitude of the S wave and polarity of the T wave in decreasing order of discriminatory power, which correctly identify 76.6% of the patients with a normal end-diastolic volume index ⩽ 90 ml/m 2 and a normal ejection fraction ⩾ 60% ( n = 64) and 73.3% of those with an end-diastolic volume index > 90 ml/m 2 or an ejection fraction < 60% ( n = 101). The comparisons of the QRS duration with the end-diastolic volume index and the ejection fraction give the best single correlations: r = 0.57 and −0.63, respectively. Multiple correlations lead to no substantial improvement of the r values: 0.06 and −0.65, respectively. A QRS duration < 140 msec is almost always predictive of the presence of a normal end-diastolic volume index and a normal ejection fraction (sensitivity 100%, specificity 91.9%, positive predictive value 73.3%). A QRS duration > 170 msec is most accurate in predicting depressed left ventricular ejection fraction < 55% (sensitivity 36.5%, specificity 98%, positive predictive value 92%). Thus, only the QRS duration provides a useful reference and guide for the evaluation of left ventricular function in the presence of left bundle branch block.