Quantification of heart sounds interference with lung sounds.

An index to quantify the contamination of lung sounds by heart sounds is described. Using the index, the efficacy of high pass filtering and adaptive filtering methods for the reduction of heart sounds is evaluated.

Noninvasive study of the presystolic component of the first heart sound in mitral stenosis.

Echophonocardiography and pulsed Doppler echocardiography were performed in 30 patients with mitral stenosis (19 with atrial fibrillation and 11 with sinus rhythm) to investigate the genesis of the presystolic component or small apical vibrations preceding the first heart sound in mitral stenosis. In 27 patients, mitral valve closure preceded or coincided with tricuspid valve closure regardless of the preceding RR interval. Of three patients whose tricuspid valve closed prematurely, two had a prolonged PR interval. The soft apical vibrations, which were recorded during the final rapid closing motion of the mitral valve echogram (B-C slope), began with the upstroke of the apexcardiogram. During this event the pulsed Doppler echocardiogram revealed a deceleration in the velocity of mitral inflow. In two exceptional patients with a prolonged PR interval, this apical sound was separated from a presystolic rumble that occurred during an accelerated phase of mitral inflow or at the A wave of mitral valve echograms. In conclusion, the tricuspid valve is not a factor contributing to the genesis of the small apical vibrations preceding the first heart sound in mitral stenosis. These vibrations are caused by acceleration of left ventricular contraction and deceleration of mitral inflow in the presence of a stenotic valve.

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.

Relation of intensity of cardiac sounds to age.

The absolute intensity of the first (S1), third (S3), and fourth (S4) heart sounds (in mm Hg) and the relative intensity of S4 compared with S1 were measured in 146 normal persons, aged 8 to 91 years, using an infinite time-constant, calibrated pressure mechanocardiograph applied to the chest wall with a loading pressure of 400 mm Hg. The absolute intensity of S1 (r = 0.28) and S3 (r = 0.43) decreases with age, but the absolute intensity of S4 does not increase with age (r = 0.06). Therefore, the relative intensity of S4 compared with S1 increases with age (r = 0.31). This finding may explain the increased frequency of S4 in qualitative phonocardiograms in older persons.

Phonometric study of the second heart sound in normal man.

The fast Fourier transform (FFT) was employed to analyze the frequency spectra of the second heart sound in 19 healthy subjects. The data obtained show that the second heart sound is mainly composed of low-frequency vibrations, and that the frequency vs. amplitude spectra for the various filters do not exceed 150 Hz. The different spectra obtained can represent a useful reference to compare with pathological acoustical findings.

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.