[The effect of asynchronous contraction of the myocardium on its mechanical function]

The effect of asynchronous excitation of adjacent portions of intact myocardium was simulated in two parallel connected papillary muscles from the rabbit heart right ventricle. Mechanical characteristics (length-force, force-rate, final systolic length-specific time of relaxation) of each of the muscles were recorded in simultaneous and asynchronous contractions. The asynchronism was found to exert a positive inotropic effect in each of the muscles and a negative one in the duplex. The asynchronism decelerated the temporal course of relaxation both in separate muscles and in duplex. The asynchronism-related mechanochemical dissociation seems to be the crucial phenomenon underlying the whole cycle of the mechanical phenomena.