Cardiac vibrational intensity and cardiac output

Abstract

1. 1. An electronic heart sound meter has been devised to convert the complex pattern of low-frequency cardiac vibrations picked up at the chest wall into a simple “resultant frequency.” 2. 2. The “resultant frequency” varies during each heart cycle in a manner similar to the ventricular volume curve. 3. 3. Simultaneous records of the high-frequency ballistocardiograph and the heart sound meter made on rested, supine subjects show a close correlation between the cardiac output as calculated by Starr's formula, 11 (I+J) C 3 2 A and an “output” calculated from the formula, S=f1 2−f2 2 in which f 1 is the maximum “resultant frequency” occurring at commencement of systole, and f 2 is the minimum “resultant frequency” at the end of systole. 4. 4. Records of the ballistocardiograph and the heart sound meter taken immediately after exercise do not give comparable calculations of cardiac output. However, heart sound meter data after moderate exercise, after anoxia produced by breathing nitrogen, and after the Flack Test show qualitative and quantitative trends comparable to data obtained by other procedures.