A new, noninvasive method to monitor the aging of bioprosthetic valves in the mitral position.

Bioprosthetic valves undergo a tissue degeneration of unpredictable onset and amount. This process alters the structure and function of the valve and consequently shortens its lifespan. The echocardiographic technique usually used in the follow-up of these patients does not provide accurate information concerning the amount of prosthesis tissue degeneration. A new technique has been developed based on the spectral analysis of the first heart sound, which enables the evaluation of prosthetic leaflet stiffness. The Young's modulus (E) and stress (s) of the valve leaflets were derived as functions of the inner diameter of the heterograft and its primary vibration frequency, which can be obtained from the frequency spectrum of the first heart sound. Thirty-six patients with a mitral bioprosthetic valve were studied. Fifteen had thickening or calcification, or both, of the valvular leaflets at echocardiographic examination. In patients with a normal valve, E and s showed a good correlation with the duration of implantation (r = 0.909, p < 0.001; and r = 0.828, p < 0.001; respectively). Patients with abnormal leaflets had values of E and s that were greater than the theoretical values expected for their duration of implantation. The procedure is sensitive, accurate and easy to perform, and enables monitoring of the aging of the prosthetic valve and early identification of valve tissue degeneration. Together with echocardiography, this procedure yields a more complete evaluation of prosthetic valves for the follow-up of patients.

Clinical value of the pitch of the third heart sound in ischemic heart disease.

The study investigates the genesis of the third heart sound (S3) in ischemic heart disease based on a mass-spring model. In such a system, the natural frequency of vibration, Fn, depends on the elastic constant, k, and the mass, m, according to the following relationship: Fn = 1/2 pi square root of k/m. To identify the cardiac structures representing k and m, the correlations between the energy of the S3 spectrum and the echocardiographic parameters were searched for. The results are consistent with a model in which k is represented by the thickness of the left ventricle and m by its blood content. The k/m ratio emerges as an important determining factor of the acoustic quality of S3, and yields information on the dysfunction of the left ventricle in ischemic heart disease.

Non-invasive estimation of the diastolic elastic and viscoelastic properties of the left ventricle.

The present study applies a non-invasive method to the quantitative evaluation of left ventricular stiffness in normal subjects and in patients with ischaemic heart disease (IHD). We have studied 20 patients with IHD and 25 healthy subjects. The third heart sound (S3) was detectable in all patients. We have correlated the energy spectrum of S3, divided into 15 Hz bands, with a series of echocardiographic parameters. The existence of a significant correlation between the spectrum energy and the diameter and thickness of the left ventricle at the moment of S3 allowed us to explore the possibility of interpreting the origin of S3 based on a mathematical model. Our hypothesis has been that, once the left ventricle starts vibrating, it behaves as a simple physical model composed of a mass and an elastic element. To this purely elastic model one can add a factor accounting for viscosity, with a damping effect, to obtain a more complex viscoelastic model. The stiffness coefficient 'k' was computed in both models from the peak frequency of S3 and the left ventricular mass at the moment of S3. Furthermore, in the viscoelastic model, the damping element 'c' was also computed. Both parameters--k and c--were significantly increased in the group with IHD compared with the control group. Although a simplification of the vibrating system, these models make it possible to obtain non-invasively information on the characteristics of the left ventricle through the combined use of echocardiography and spectral analysis of S3.

Idiopathic apical left ventricular aneurysm in hypertrophic cardiomyopathy. Report of 3 cases, and review of the literature.

In a review of 160 cases of hypertrophic cardiomyopathy which underwent hemodynamic studies, 3 cases of apical aneurysm of the left ventricle of unidentifiable etiology were found. Bearing in mind the rarity of apical idiopathic left ventricular aneurysms, the authors believe this association with hypertrophic cardiomyopathy is of some interest and point out the possible pathogenetic mechanisms.