A study of heart sounds and murmurs by direct heart recordings.

A method is described for recording heart sounds and murmurs on the surface of the heart chambers and great vessels. Studies were performed on normal dogs and in those with murmurs of known origin, chiefly pulmonic and aortic stenosis. In addition, the reappearance of the murmurs in such cases was studied, following the release of caval occlusion. It was found that the systolic murmur of pulmonic stenosis returned almost immediately after release of caval occlusion, whereas the aortic murmurs did not return until usually from six to 10 beats after release. This may provide a basis for the differentiation of right heart and left heart murmurs by a carefully controlled Valsalva maneuver. DE ESPITE technical advances in phono-cardiography, the source of many heart murmurs remains obscure. One example is the basal systolic murmur in patients with atrial septal defects. To investigate further the origin of heart murmurs, an experimental technic has been developed in which sounds are recorded directly from the heart and great vessels in dogs. This technic has been used to record heart sounds in normal control animals, and immediately after the production of a defect in the atrial septum. In addition, in order to test the hypothesis that recording directly from the heart's surface would identify the site of origin of murmurs, experiments were carried out in which aortic or pulmonic stenosis was produced. In the course of these experiments, it was also possible to evaluate the test suggested by Zinsser and Kay' in which "right heart" and "left heart" murmurs may be differentiated by the length of time required for the murmur to return, following a Valsalva maneuver.