Simulation of mechanoenergetics of asynchronously contracting ventricle.

We simulated mechanoenergetics of ventricular asynchronous contraction using a model comprising two compartmentalized asynchronous time-varying elastic elements, E1 and E2. Their elastances [e1(t) and e2(t)] waxed and waned cyclically with a variable time lag (tau). The pressure-volume area (PVA1 or PVA2) circumscribed by the maximum (emax) and minimum e1(t) or e2(t) lines and the contracting pressure-volume trajectory of E1 or E2 quantifies the mechanical energy generated by a contraction of E1 or E2. Similarly, the PVA circumscribed by the resultant Emax (ventricular contractility index) line, the end-diastolic pressure-volume (P-V) line, and the systolic P-V trajectory quantifies the mechanical energy of the entire ventricle. PVA of the ventricle is equal to the sum of PVA1 and PVA2. We found that Emax decreased with increases in tau despite constant emax, and hence ventricular PVA decreased with increases in tau. This simulation helps us to better understand the mechanism of decreased oxygen consumption with increasing ventricular asynchrony reported in the literature.