Newer Studies of Selective Phonocardiography Including a New Method for the Identification of the Frequency Range of Extra Sounds

Problems dealing with the registration of either apical or basal diastolic murmurs of poor magnitude are discussed. Current methods of phonocardiography are reviewed. Eight normal subjects and thirty abnormal cases were studied by means of a variable band-pass filter with additional amplification. The various frequencies of the cardiac murmurs were analyzed. A band between 60 and 110 vibrations per second was found adequate for magnifying and recording murmurs caused by mitral stenosis. A band between 150 and 200 was found adequate for magnifying and recording murmurs caused by aortic defects or mitral insufficiency. A routine method of study of cardiac murmurs, called ``selective phonocardiography'' is outlined. It is based on the use of the two above bands, in addition to ``stethoscopic'' phonocardiograms. Incorporation of filters in the case of the phonocardiograph is recommended. A new method of study of the frequency of extra sounds is described. Preliminary observations are reported. A new technique of intracardiac(ic) phonocardiography during routine catheterization is described. Preliminary studies in animals are reported.