Abstract
Myocardial performance index (MPI) is a simple and reproducible method for the assessment of overall cardiac function. In this study, we evaluated the applicability and usefulness of pulsed-wave tissue Doppler echocardiography (TDE) as a tool to calculate MPI in comparision with a conventional Doppler method.
Twenty-five patients with previous myocardial infarction (MI) and 15 healthy subjects were included. In order to calculate MPI by TDE, isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVRT), and ejection time (ET) were measured at four different sites in the mitral annulus: septum, lateral, anterior, and inferior. MPI was calculated by dividing the sum of IVCT and IVRT by ET at each site of measurement. The mean MPI value was found by dividing the sum of these MPI values into four. The same parameters were measured using the mitral inflow and left ventricular outflow velocity time intervals by a conventional method.
MPI by TDE correlated well with conventional MPI in healthy subjects (r = 0.81, P < 0.0001). Although it continued to be statistically significant, the correlation between the two methods of measuring MPI, TDE and conventional, in patients with previous MI was not as high as it was in healthy individuals (P < 0.001, r = 0.62). This is due to the lesser degree of correlation between IVRT and IVCT values obtained by TDE and the conventional method (r = 0.49, P < 0.05; r = 0.56, P < 0.05; respectively).
In conclusion, this study has demonstrated that MPI could be measured by tissue Doppler and that it correlated well with conventional MPI. Moreover, MPI by TDE has the advantage of assessing both regional and global myocardial performance.
