King1 and King and McEachern2 described a group of physical signs by means of which they were able to recognize bundle branch block in 85 per cent of patients with this condition. These signs consist of a visible or palpable double apical impulse, reduplication of the first sound at the apex, an asynchronous first sound and murmur and asynchronous systolic murmurs. The abnormal impulse was found in over 80 per cent of their patients and was regarded as the most important sign. A reduplicated first sound was present in 56 per cent of their patients, and the other signs mentioned occurred less frequently. In a number of patients they obtained graphic evidence of the presence of a double systolic apical impulse by photographing the movements of a straw or its shadow attached to the chest wall at the site where the abnormal impulse was seen or felt.
LEWIS JK. NATURE AND SIGNIFICANCE OF HEART SOUNDS AND OF APEX IMPULSES IN BUNDLE BRANCH BLOCK. Arch Intern Med (Chic). 1934;53(5):741-761. doi:10.1001/archinte.1934.00160110110010