Determinants of the amplitude of the aortic component of the second heart sound in aortic stenosis

A mathematical model of aortic valve vibration

It has been shown experimentally that the second heart sound is produced by diastolic vibrations of the closed aortic valve. In the present paper a mathematical model of this vibration is developed from first principles. The model assumes a one dimensional but non-linear fluid behavior. The problem is coupled through a non-linear, planar valve. A solution is obtained using the method of characteristics developed in finite difference form. The resulting valve frequency and amplitude are in good agreement with patient data. The model predicts a strong dependency of response on the valve forcing function and valve stiffness; and a weaker dependency of response on valve mass.

Frequency analysis approach to the origin of the first and second heart sounds

Catheter-tipped micromanometers were used to simultaneously record left ventricular and aortic pressures, and left ventricular and aortic internal phonocardiograms in order to determine if they had a common mode of origin and propagation. Spectrographic analysis showed that even with high-pass filtration the phonocardiogram obtained with a commonly used system (Millar) contained large amounts of energy in the subaudible frequency range (below 40 Hz). It was possible to derive close facsimiles of the phonocardiograms by double differentiation of the corresponding pressure pulse and conversely to derive the pressure pulse by double integration of the phonocardiograms. The propagation velocities of the first heart sound, second heart sound, and the foot of the aortic pressure pulse were found to be similar and were respectively, 4.3 +/- 0.2, 4.6 +/- 0.3, and 4.2 +/- 0.2 m/sec (+/- SE). These data support the concept that the low frequency pressure variations produced by the heart, which predominate in the left ventricular and aortic pressure pulse waveforms, are generated and propagated in the same manner as the high frequency pressure variations, which are the first and second heart sounds.

Invasive and noninvasive phonocardiography and orifice-view aortography in the diagnosis of left ventricular outflow obstruction

Phonocardiography and orifice-view aortography for the detection of valvular and subvalvular stenosis is reviewed. Intracardiac phonocardiography may be useful in detecting a left ventricular outflow tract obstruction, and in distinguishing it from other conditions that can produce an apparent pressure gradient during cardiac catheterization. The frequency analysis of heart sounds on noninvasive phonocardiograms may be useful in identifying subclinical aortic stenosis. Orifice-view aortography can show the anatomy of deformed aortic valves and is useful in measuring the orifice area. In patients with heavily calcified valves, plain orifice-view roentgenograms may enable one to assess the valve area. Therefore the use of these techniques in selected patients may help establish a definitive diagnosis.