The registration of heart sounds from the exposed heart and large vessels. A demonstration

For a number of reasons it was questionable whether the heart sounds recorded from the resonant thoracic wall are composed of the same vibrations as those actually arising within the heart. To assist in answering this question a method of registering the sounds from different spots on the exposed heart and large vessels was devised. The apparatus consists of a sound receptor stitched to the heart, and a recording Frank capsule. The sound receptor consists of a light segment capsule 2 cm. in diameter and similar to the miniature myocardiograph recently described. 1 It differs in that it has only one arm connected with a trapezoidal plate which pivots on the segment capsule. When stitched to any portion of the heart this arm transmits the sound vibrations to a tensely stretched, heavy rubber diaphragm covering the segment capsule. The interior of the receptor communicates by tubing with a Frank segment capsule covered by a light film of dried rubber cement to which a tiny mirror is allowed to adhere. By leaving a side-tube open to an adequate degree, as is customary in sound registration, the gross mechanical changes are eliminated.

In comparing the sounds thus derived from the ventricle and the aorta essential differences were found, especially in the first sound. The first ventricular sound consists of three elements:

1. One or two initial vibrations which begin during auricular relaxation and precede by a variable interval the rise of intraventricular pressure.

2. The main vibrations composed of 7 to 13 irregular vibrations which begin with the onset of the intraventricular pressure rise.

3. The final vibrations, variable in number, which occur during the ejection period of the heart.

The first aortic sound is also divisible into three components, the second and third of which give the group a configuration essentially different from that of the first ventricular sound.