RELATIONSHIP OF THE 3RD HEART-SOUND TO TRANSMITRAL FLOW VELOCITY DECELERATION

Background The third heart sound (S-3) occurs shortly after the early (E-wave) peak of the transmitral diastolic Doppler velocity profile (D VP). It is thought to be due to cardiohemic vibrations powered by rapi d deceleration of transmitral blood how. Although the presence, timing , and clinical correlates of the S-3 have been extensively characteriz ed, derivation and validation of a causal, mathematical relation betwe en transmitral flow velocity and the S-3 are lacking. Methods and Resu lts To characterize the kinematics and physiological mechanisms of S-3 production, we modeled the cardiohemic system as a forced, damped, no nlinear harmonic oscillator. The forcing term used a closed-form mathe matical expression for the deceleration portion of the DVP. We tested the hypothesis that our model's predictions for amplitude, timing, and frequency of S-3 accurately predict the transthoracic phonocardiogram , using the simultaneously recorded transmitral Doppler E wave as inpu t, in three subject groups: those with audible pathological S-3, those with audible physiological S-3, and those with inaudible S-3. Conclus ions We found excellent agreement between model prediction and the obs erved data for all three subject groups. We conclude that, in the pres ence of a normal mitral valve, the kinematics of filling requires that all hearts have oscillations of the cardiohemic system during E-wave deceleration. However, the oscillations may not have high enough ampli tude or frequency to be heard as an S-3 unless there is sufficiently r apid fluid deceleration (of the Doppler E-wave contour) with sufficien t cardiohemic coupling.