Frequency spectrum of the aortic component of the second heart sound in patients with normal valves, aortic stenosis and aortic porcine xenografts: Potential for detection of porcine xenograft degeneration

Abstract

The frequency spectrum of the aortic component of the second sound (A 2) was measured noninvasively in 77 patients. Fourteen had a normal aortic valve, 14 had calcific aortic stenosis and 49 had an aortic porcine xenograft. Phonocardiograms were recorded on magnetic tape on line with a Spectral Dynamics signal processor with which the frequency spectrum and dominant frequency of A 2 were determined. In 14 patients with a normal aortic valve, the dominant frequency of A 2 was 53 ± 3 hertz (mean ± standard error of the mean); in 14 patients with aortic stenosis A 2 frequency was higher, 87 ± 5 hertz (p < 0.001). In 15 patients with a porcine aortic valve heterograft implanted for 18 months or less, A 2 frequency was 48 ± 5 hertz, which did not differ significantly from that of patients with a normal natural aortic valve. However, in 19 patients with an aortic porcine heterograft that was in place 5 to 7.5 years, the dominant frequency of A 2 was higher, 81 ± 4 hertz (p < 0.001), and within the range of that observed in patients with aortic stenosis. Among these 19 patients, 2 required replacement of the prosthetic aortic valve because of valve degeneration. The association of a higher than normal frequency of A 2 with a stiffened valve, such as occurs in aortic stenosis, is predictable on the basis of factors that affect the frequency of valve vibration and pressure fluctuations productive of sound. The data suggest that the frequency of A 2 may be of value in detecting degenerative changes of porcine aortic xenografts.