Objectives: The purpose of this study was to examine the temporal relation between the development of a third heart sound during the course of evolving heart failure and associated hemodynamic abnormalities.
Background: Although various theories have been proposed to explain the origin of the third heart sound, the exact origin of this sound remains unknown.
Methods: Studies were performed in seven dogs in which heart failure was produced by multiple sequential intracoronary micro-embolizations. Hemodynamic studies including ventriculography, pulsed wave Doppler echocardiography and intracardiac phonocardiography were performed at baseline, at the time at third heart sound was first heard and at 6 and 24 weeks after onset of the third heart sound.
Results: All dogs developed a third heart sound at 9 +/- 2 weeks after the initial embolization. The onset of the sound was accompanied by an increase in left ventricular chamber stiffness relative to the baseline value (0.25 +/- 0.03 vs. 0.14 +/- 0.01 mm Hg/ml) (p < 0.05) and mean deceleration of early mitral inflow velocity (1,040 +/- 90 vs. 590 +/- 40 cm/s per s) (p < 0.05).
Conclusions: These data indicate that the onset of a third heart sound during the course of evolving heart failure occurs coincident with the development of increased left ventricular chamber stiffness and the manifestation of rapid deceleration of early mitral inflow velocity. These findings are consistent with a myocardial vibratory origin of this sound.