Wall-motion analysis during low-dose dobutamine echocardiography (LDDE) is a semiquantitative measure of left ventricular contractile reserve after myocardial infarction (MI). The Doppler echocardiographic myocardial performance index (MPI) is a quantitative measure of combined left ventricular systolic and diastolic function. We sought to characterize the changes in MPI during LDDE in control subjects and patients with MI, and to describe the relation of these changes to changes in regional systolic function.Methods
MPI was obtained at rest and during LDDE (10 μg/kg/min) in 25 healthy volunteers (group 1) and 50 patients with a recent MI. Patients were divided into two subsets; those with (n = 23; group 2A) and those without (n = 27; group 2B) a contractile reserve defined as an improvement of wall motion in more than two contiguous infarct-zone segments during LDDE. ΔMPI was defined as the change from rest to LDDE.Results
MPI decreased significantly during LDDE in groups 1 and 2A, whereas MPI increased in group 2B (ΔMPI = 0.12 ± 0.04 and 0.10 ± 0.08 vs −0.03 ± 0.08, P < .0001). On multivariate analysis, Δwall-motion score index predicted ΔMPI (β = 0.65, P < .0001) independently of age, sex, and the dobutamine-induced change in heart rate and systolic blood pressure.Conclusions
Data suggest that the change in MPI during LDDE may provide a simple and quantitative measure of overall left ventricular functional reserve in patients with a recent MI.