Mechanism of sustained mechanical alternans. Effect of variations in ventricular billing volume.

Abstract

This study investigates the phenomenon of sustained mechanical alternans (SMA) through the use of quantitative criteria. Discrete analysis is used to demonstrate that the hemodynamic variables during SMA are governed by a simple mathematical relation. The analysis shows that the value of the slope created by the two alternating beats on the stroke volume (SV)-enddiastolic volume (EDV) found to agree with data in the literature. In 10 other dogs, mitral flow and aortic flow were measured in 55 series of SMA. In 51 series, was greater than 1. Because the experimental slope in the presence of one contractile state, y, is smaller than or equal to 1, the possibility that one contractile state is involved in this series is rejected. On the other hand, when two contractile states are involved, the slope that the two successive beats create on the SV-EDV plane, 7, is determined by connecting the two SV-EDV relations. This slope tends to be greater than 1. Thus, in these 51 series, SMA cannot be explained as a result of the Frank-Starling mechanism and variations in FV but as a result of two alternating contractile states. In the other four series, the value of 3Y can be compatible either with the presence of one contractile state or with two alternating contractile states. This quantitative analysis enables the classification of the various types of SMA into subcategories with well-defined features. The quantitative analysis presented here shows that the common genesis of SMA is an alternating contractile state. (Circulation Research 1991;69:26-38

Phantom Systole: A Failed Ejection Phenomenon between Pulsus Alternans and Systolic Aortic Regurgitation

“…2 Regarding its pathophysiology, it was initially believed that PA was a consequence of hemodynamic changes that influenced the filling volume of each cardiac cycle. However, Adler et al 3 demonstrated, in a mathematical experimental model with comparative data of filling and systolic volumes obtained from canine hearts, that the mechanisms responsible for generating PA or sustained mechanical alternans could be classified into two main categories, myocardial and hemodynamic.…”