A low-cost, high-fidelity FM wireless precordial radiostethoscope for continuous monitoring of heart and breath sounds.

We constructed and tested an inexpensive (less than $50) FM wireless, acoustically shielded, precordial radiostethoscope that enables the anesthetist to follow the heart tones and breath sounds of the patient regardless of the anesthetist's location in the operating room. We compared our acoustically shielded device with a similar, but acoustically unshielded, commercially available device. We found the sound quality of our radiostethoscope to be superior to that of the commercial device; the signal-to-noise ratio of our device was 7.6 for heart tones and 8.4 for breath sounds, whereas the commercial device had a signal-to-noise ratio of 2.7 and 3.9 for heart tones and breath sounds, respectively. Our device offers all of the advantages of a radiostethoscope and has the added advantages of low cost and high fidelity.

Investigation of genesis of gallop sounds in dogs by quantitative phonocardiography and digital frequency analysis.

Several investigators have noted external gallop sounds to be of higher amplitude than their corresponding internal sounds (S3 and S4). In this study we hoped to determine if S3 and S4 are transmitted in the same manner as S1. In 11 closed-chest dogs, external (apical) and left ventricular pressures and sounds were recorded simultaneously with transducers with identical sensitivity and frequency responses. Volume and pressure overload and positive and negative inotropic drugs were used to generate gallop sounds. Recordings were made in the control state and after the various interventions. S3 and S4 were recorded in 17 experiments each. The amplitude of the external S1 was uniformly higher than that of internal S1 and internal gallop sounds were inconspicuous. With use of Fourier transforms, the gain function was determined by comparing internal to external S1. By inverse transform, the amplitude of the internal gallop sounds was predicted from external sounds. The internal sounds of significant amplitude were predicted in many instances, but the actual recordings showed no conspicuous sounds. The absence of internal gallop sounds of expected amplitude as calculated from the external gallop sounds and the gain function derived from the comparison of internal and external S1 make it very unlikely that external gallop sounds are derived from internal sounds.

Delayed timing of heart and arterial sounds in patients with implanted pacemakers.

We have recorded the timing of the heart sounds and the arterial sounds with reference to the onset of each cardiac cycle in 16 patients before and after implantation of a pacemaker prosthesis, and in an additional 18 patients after pacemaker implantation only. The interval between the QRS complex and the Korotkoff sound at diastolic pressure (QKd) is markedly prolonged, from 206 to 294 msec., a change corresponding to 10 standard errors of the mean difference. Likewise, the Q-Korotkoff interval at systolic pressure (QKs) is prolonged from 329 to 414 msec. The interval between the QRS complex and the onset of the first sound (S1) is prolonged by approximately 90 msec., whereas the interval between the QRS and the second heart sound (S2) is prolonged by 70 msec. We noted an associated increase in heart rate, a slight decrease in systolic pressure, an increase in diastolic pressure, a decrease in pulse pressure, and a slight decrease in the deltaP/deltat at the brachial artery measured indirectly and noninvasively.