Investigation of Cardiovascular Sound with Esophageal Phonocardiography

Abstract

Esophageal phonocardiography (ePCG) has the advantage that certain heart sounds are picked up near their sites of origin, whereas in conventional surface phonocardiography (sPCG) attenuation of the vibration occurs in the pathway to the microphone. The disadvantage of directional sensitivity of an accelerometer-type microphone has been eliminated by constructing biaxial microphones; with the aid of an electronic axes rotation, optimal recording of heart vibrations in the horizontal plane is achieved. ePCG has clinical value because of diagnosing mitral valve regurgitation (MR) better than conventional PCG, especially in patients having prosthetic valves in both mitral and aortic orifices where left ventricular angiography is not easily accomplished. Regarding the level of the microphone in the esophagus it has been established that various significant vibration patterns can be recorded at different heights. This variety of patterns is also explained by the distance to specific sources: heart sounds generated in the vicinity of the microphone are better detected with respect to others having a more distant origin. In this way the method contributes to the discussion about valvular components contained in the first heart sound. In the investigation simultaneous recordings with M-mode echocardiogram and pulsation curves have been obtained. More than 60 patients and normal subjects were examined. In 9 patients with prosthetic valves in both mitral and aortic orifices and 8 patients with mitral valve prolapse, MR was proved by ePCG in respectively 4 and 2 cases while sPCG failed to do so.