Precordial-Intracardiac Phonocardiographic Correlative Study of Ventricular Septal Defect

Precordial and intracardiac phonocardiographic correlation was investigated in 28 cases with ventricular septal defect (VSD) to confirm the diagnostic value of intracardiac phonocardiography and to clarify the clinical as well as physiological significance of the point of maximum intensity (PMI) of the regurgitant systolic murmur of VSD. At the same time, the teleological use of catheterization was documented and the recent concept of the auscultatory area was modified.(1) The regurgitant systolic murmur of VSD was localized within the right ventricle (RV) or partially transmitted toward the pulmonary artery (PA) and had the PMI somewhere in the RV. The murmur was pansystolic in timing and had a wide frequency span. A few exceptional cases were described, but the murmur of these cases became typical following the administration of methoxamine. The findings due to the associated anomalies were documented. The fact that the presence of regurgitant systolic murmur within the RV is the most sensitive diagnostic clue of VSD was confirmed.(2) The PMI of the regurgitant systolic murmur within the RV was so localized that it was easy to locate the site of the septal defect in almost all cases.(3) The localized PMI within the RV was the best site for the sampling of any measurements. The oxygen content was significantly high at this point when compared to those of randam sampling. This fact enables us to utilize teleologically the catheterization to detect the shunt. Methoxamine administration made the oxygenation of the sample conclusive in doubtful cases.(4) In a dorsoventral projection to the chest wall, intracardiac PMI of the regurgitant systolic murmur coincided with the precordial PMI in all cases. Therefore, the sampling at the site immediately beneath the precordial PMI was also recommended instead of the intracardiac PMI whenever the intracardiac phonocardiography was not available. Moreover, the site of septal defect could be anticipated in many cases with a reasonable accuracy based on this topographical correspondence of both PMIs.(5) The correspondence of the 2 (intracardiac and precordial) PMIs suggests that there is a direct transmission of the murmur from the origin to the chest wall. In this regard, the present authors made a minor modification to the "revised auscultatory areas" for the sake of the regurgitant systolic murmur of VSD and reserved a name of "interventricular septal area" to the precordial PMI.