An estimation of the left ventricular diastolic function from the spectral analysis of the fourth heart sound. A Doppler validated study in hypertrophic cardiomyopathy

: Hypertrophic cardiomyopathy (HCM) is a typical primary cardiac disease characterized by diastolic abnormal function due to both prolonged relaxation and decreased compliance (Sanderson et al., 1977; Spirito & Maron, 1990). Since the contribution of the atrial systole to ventricular filling is usually increased, the appearance of a fourth heart sound (S4) is a common finding in HCM. This sound is related to the ventricular compliance and to the atrial contractility. It is generated during the rapid setting into vibration of the left ventricular walls that results from the rapid rush of the blood due to the atrial contraction (Nishimura et al., 1989; Tavel, 1978). The aim of this study is to look for relationships between the frequency peak of S4 and various mono- and two-dimensional echocardiographic parameters in order to identify those cardiac structures involved in its genesis and obtaining an estimation of the stiffness of the acoustic vibrating system with a simply vibratory model (Baracca et al., 1991).