Mitral valve regurgitation and systolic performance: a model approach

A quite common and surgically correctable cardiac pathology is represented by mitral insufficiency. The LV contractile state of patients with chronic mitral regurgitation (CMR) is hard to evaluate because of the elevated preload, the low impedance regurgitant leak, the elevated systolic wall stress and the consequently depressed myocardial pump function. A mathematical model for the study of the interaction between the insufficient mitral valve (MV) and the global cardiovascular system has been carried out. The developed non-linear, time-varying, lumped parameter model has been used to evaluate the interplay between the entity of the mitral regurgitation and LV contractility, left atrium compliance, systemic and pulmonary arterial loads. The model has been studied in the two phases of systole: the “isovolumic” contraction and the ejection. The resulting system of non-linear, time-varying state equations has been solved with a Runge-Kutta-Fehlberg sixth-order method. The low impedance systolic leak masks the depressed contractility furnishing ejection-fraction (EF) values in the normal range, up to E_max reduced to 1/3 of its normal value. The increasing in left atrium pressure, as a consequence of mitral regurgitation, has been pointed out, displaying its dependence on the pulmonary impedance. The importance of LV viscous resistance for both the entity of regurgitation and the guaranteed cardiac output has been investigated