Right and left ventricular flow during mechanical alternans

Pulmonary and aortic blood flow simultaneous with right and left ventricular isometric tension were measured in anesthetized dogs during mechanical alternans induced by rapid atrial driving. It was found that any steady state of mechanical alternation can be altered to another steady state by a single premature or delayed beat. The relationship between the force of the alternating beats was not necessarily equal in the two ventricles. Pulmonary and aortic flow changed markedly with changing steady states of mechanical alternation, at the same heart rate, within a wide range of flow levels. Moreover, inequality between the mechanical alternation of the two ventricles was at times associated with disparity of aortic and pulmonary flow. The possible mechanism and clinical significance are mentioned.