Physiology of the Third Heart Sound: Novel Insights from Tissue Doppler Imaging

Background The third heart sound (S 3 ) is thought to be caused by the abrupt deceleration of left ventricular (LV) inflow during early diastole, increased LV filling pressures, and decreased LV compliance. We sought to determine whether the ratio of early mitral inflow velocity to diastolic velocity of the mitral annulus (E/E') could confirm the proposed mechanism of the S 3 . Methods A total of 90 subjects underwent phonocardiography, echocardiography, tissue Doppler imaging, and left-sided heart catheterization. Results Phonocardiography detected an S 3 in 21 patients (23%). Subjects with an S 3 had lower ejection fraction ( P = .0006) and increased E deceleration rate ( P P P 3 confidence score correlated with E/E' ( r = 0.46; P r = 0.43, P = .0001). Of the echocardiographic variables, only E/E' was independently associated with the S 3 confidence score ( P = .009), independently of invasively determined LV filling pressures ( P = .001). Conclusions The most important determinants of the pathologic S 3 are an increased deceleration rate of early mitral inflow, elevated LV filling pressures, and abnormal compliance of the myocardium as measured by tissue Doppler imaging.