Myocardial Performance Index in Female Rats with Myocardial Infarction: Relationship with Ventricular Function Parameters by Doppler Echocardiography

Background The aim of the study was to analyze the myocardial performance index (MPI), its relationship with the standard variables of systolic and diastolic functions, and the influence of time intervals in an experimental model of female rats with myocardial infarction (MI). Methods Forty-one Wistar female rats were submitted to surgery to induce MI. Six weeks later, Doppler echocardiography was performed to assess infarct size (IS,%), fractional area change (FAC,%), ejection fraction biplane Simpson (EF), E/A ratio of mitral inflow, MPI and its time intervals: isovolumetric contraction (IVCT, ms) and relaxation (IVRT, ms) times, and ejection time (ET, ms); MPI=IVCT + IVRT/ET. Results EF and FAC were progressively lower in rats with small, medium and large-size MI ( P P P = .87), but different between large and medium-size MI (0.69 ± 0.08 vs 0.47 ± 0.07; P P P P P P P P P P P P P = .0534) and no correlation with IS (r = 0.26; p=0.144). Conclusions The MPI increased with IS, correlated inversely with systolic function parameters and had a non-linear relationship with diastolic function. These changes were due to the increase of IVCT and a decrease of ET, without significant influence of IVRT.