Phonocardiographic approach to the detection of right ventricular myocardial infarction

Right ventricular myocardial infarction (RVMI) is not as rare as was previously thought and, if present, is almost always complicated with inferior myocardial infarction (IMI). On the basis of hemodynamic criteria, RVMI was identified in 33.7 percent of 98 cases with IMI. RVMI may induce a low cardiac output, if not often, resulting in cardiogenic shock. It is clearly desirable therefore to have an early and sensitive diagnostic clue to the presence or possibility of RVMI. Although much investigative attention in the diagnosis of RVMI has been focused on electrocardiography, echocardiography, radionuclide ventriculography, technetium-99 m stannous pyrophosphate scintigraphy, and thallium-201 scintigraphy, there has been little study of phonocardiography (PCG). The present study was therefore undertaken in an attempt to assess whether or not PCG information is useful for the identification of RVMI. PCG recordings were made during unforced natural respiration for at least 8 consecutive beats. From among several PCG parameters, the delta QP2 interval was found to be the most reliable for the identification of RVMI in patients with IMI. The delta QP2 interval was defined as the difference between Max QP2 and Min QP2, where Max QP2 and Min QP2 represent the maximal and minimal interval between Q and P2, respectively. Using delta QP2 less than or equal to 10 msec, the sensitivity and specificity for the diagnosis of RVMI were 90.9% and 84.6%, respectively. These results were superior to those obtained by radionuclide ventriculography, electrocardiography and echocardiography. We consider therefore that PCG should be recorded as soon as possible in the presence of IMI, and conclude that a small range (less than or equal to 10 msec) of delta QP2 carries a reasonably high sensitivity and specificity for the diagnosis of RVMI.