Deactivation in the rabbit left ventricle induced by constant ejection flow

A study of pressure generated by the left ventricle after ejection with constant flow for different values of the ejection flow, flow duration, time of flow arrest, and ventricular volume is discussed. It was found that pressure after ejection, normalized with respect to isovolumic pressure, is regenerated according to a model consisting of an elastance, a resistance, a series elastance, and an additional deactivation component. Deactivation is defined as the difference between the value 1 and the plateau value of the normalized pressure after constant flow ejection. It is shown that this plateau value is constant after constant flow ejection until the minimum in isovolumic dP/dt, i.e. during physiological systole. The plateau value is uniquely related to the value of the normalized pressure with a time constant of 10.44+or-0.09 ms which agrees with the series-elastance time constant of 10.35+or-0.26 ms.