Abstract
Interatrial septal murmurs were investigated by means of intracardiac phonocardiography and hemodynamics.
1) The murmur was detected in 77% of total 31 cases of secundum type ASD.
2) The murmur was localized at the site of septal defect and usually not transmitted widely because of the low intensity. It was essentially continuous, starting from late systole and continuing to diastole, and lowto medium-pitched. The systolic component was dominant at the left side of the septum, whereas the diastolic accentuation was observed at the right side of it. Respiration influenced the intensity and it was usually louder in expiration. Methoxamine intensified the murmur.
3) Hemodynamic study disclosed that the determinant was the interatrial (left-to-right atrial) pressure gradient mainly observed during the phase of v wave. Occasionally, pressure gradient of a waves was present with concomitant atrio-systolic murmur. The significance of the hemodynamic determinant was discussed.
4) The audibility of the interatrial septal murmurs by precordial auscultation depends on several factors which are discussed in detail. Rare instance, in which the murmur appeared in the 3rd left interspace, was demonstrated, and discussion was made on the detection of the murmur and its topographic localization.
5) Other diastolic murmurs, particularly that of relative tricuspid stenosis, were also investigated in order to differentiate from the interatrial septal murmurs.
6) The clinical meaning of the interatrial septal murmurs was mentioned.
