5 CASES OF INTERMITTENT LEFT ANTERIOR HEMIBLOCK

The first 5 cases of intermittent left anterior hemiblock (block in the anterior division of the left bundle branch) are reported. These cases can be considered exceptional experiments of nature, providing both invaluable evidence for the existence of left anterior hemiblock and useful material for studying, with great accuracy, the changes that this conduction disturbance produces on the previously normal or abnormal electrocardiogram in man. The three major electrocardiographic features of left anterior hemiblock are found to be: (1) An ÂQRS directed at approximately -60 °; (2) the presence of a Q1S3 pattern, simulating a counterclockwise rotation of the heart; and (3) a QRS widening of not greater than 0.02 sec. © 1969.