Heart Sounds in Bundle Branch BlockObservations on 244 Cases

摘要

The heart sounds in 244 cases of bundle branch block observed during the years 1926-1963 were measured in the quantitative symbol phonocardiograms and electrophonocardiograms. Splitting of the first sound occurs rarely in both right and left bundle branch block and is most likely to be detected at the apex. In the QSPcg's. splitting of the second sound occurred in about 40% of Series A (1926-1952) and 80% of Series B (1952-1963) at the left border of the sternum near the fourth inter costal space with the patient in the sitting position. In Series B, auscultation with the patient in the dorsal recumbent posture, splitting was detected in only 60% at this area. The tables depict the frequency of splitting at all areas of auscultation. The left ventricular components of both the first and second sounds are shorter than normal. A first sound of markedly reduced loudness occurs with somewhat increased frequency in left bundle branch block. The range of loudness of the first sound is otherwise normal in both types. The right ventricular component (tricuspid and pulmonic) is a short thud which is rather faint in about twothirds of cases and about half the loudness of a normal first sound in the remaining third. The interval of quiet between the 2 components does not vary with respiration but the loudness of the pulmonic component increases during inspiration and decreases during expiration, sometimes to the point of extinction. Left bundle branch block is strongly suggested when the pulmonic component precedes the aortic. A rare exception occurs when pulmonary arterial pressure is high enough to make the pulmonic component in the case of right bundle branch block louder than the aortic which precedes it. In about a third of cases of right bundle branch block, physiologic splitting of the first sound could be detected which indicates that this type of split does not depend upon asynchronism of the ventricles. In about 20% of cases with satisfactory electrophonocardiograms, splitting was absent although it was detected by clinical auscultation in the sitting postion. This probably results from the fact that during clinical auscultation the pulmonic component of the second sound became inaudible in about 30% of cases when the position was changed from sitting to dorsal recumbent. The electrophonocardiograms were recorded in this latter posture. The absence of splitting in any posture in some instances is due to the faintness of the right ventricular components of the first and second sounds. In others, it may be due to the fact that the electrocardiogram may present the pattern of bundle branch block but the mechanical events may not be correspondingly asynchronous.