Myocardial performance index (MPI) has been regarded as an important parameter in the evaluation of ventricular systolic function in congestive heart failure. This study was designed to investigate the relationship between the ratio of isovolumic contraction time/left ventricular ejection time (IVCT/LVET), MPI, and LV systolic function. A total of 43 patients (patient group) with LV ejection fractions (LVEFs) <55% were compared with 43 patients (control group) with LVEF values >= 55%. LVEF was measured in all cases by 2-dimensional echocardiography via the modified Simpson method. Isovolumic relaxation time (IVRT), IVCT, LVET, ratio of IVCT/LVET, and MPI ([IVRT+IVCT]/LVET) were measured via Doppler echocardiography. The mean value for lVCT was found to be significantly higher (P<.001) and concomitant mean LVET value significantly lower (P=.027) in the patient group. Similarly, the mean value of MPI and the ratio of IVCT/LVET were found to be significantly higher (P<.001 for both) in the patient group. The value of the ratio of IVCT/LVET was found to have a significant negative correlation with the value of LVEF (r=-.947; P<.001) and a significant positive correlation with the value of MPI (r=.796; P<.001). The study reported here clearly demonstrates the noninferiority of the ratio of IVCT/LVET to MPI and the possibility of its substitution for MPI in the evaluation of LV systolic function.