[Power spectrum of heart murmurs: special reference to mitral regurgitant murmurs].

Abstract

Heart murmurs, especially the mitral regurgitant murmurs of 40 patients were analyzed using the fast Fourier transformation technique. 1. Three types of frequency spectral pattern of mitral regurgitation (MR) were demonstrated: A) broad, spanning 100 to 500 Hz, B) narrow, characterized by one giant peak, and C) two peaks. The reason for these patterns was not clear, but they may be related to various hemodynamic events. 2. The mean frequency (f) in MR was 295 +/- 38 Hz and it increased in proportion to the regurgitant grade: e.g., Sellers II, 258 +/- 27 Hz; Sellers III, 294 +/- 23 Hz; and Sellers IV, 311 +/- 65 Hz. The accumulated percentage of the 200-400 Hz component decreased, while that of the 400-600 Hz component increased. 3. The f in MR of various etiologies were as follows: It was higher in ruptured chordae tendineae, rheumatic cases and mitral valve prolapse syndrome, but was lower in papillary muscle dysfunction and dilated cardiomyopathy. In the latter two, the percentage of the 0-200 Hz component was greater than in other disorders. The degree of left ventricular dysfunction and of myocardial injury may be responsible for the changes in the propagation properties. In ventricular septal defect and aortic stenosis, the f was 306 +/- 12 Hz and 230 +/- 40 Hz, respectively. The frequency spectrum of the latter was lower than that of MR, which may be derived from the difference between ejection and regurgitant murmurs; whereas, that of ventricular septal defect was similar to that of rheumatic MR. 4. The relation between the frequency spectrum and the phase of systole was studied. In dilated cardiomyopathy and papillary muscle dysfunction, the f of each phase increased in late systole; whereas, the maximum f was in mid-systole in other disorders. 5. Administration of amyl nitrite resulted in a decreased f, an increased percentage of the 0-200 Hz component, and a decreased 400-600 Hz component. The spectral distribution shifted to the lower frequency region. Results of this study suggested that significant information can be obtained from the frequency analysis of heart murmurs.