Objectives: In patients with depressed systolic function after recent acute myocardial infarction (AMI), improvement of global left ventricular (LV) systolic function using low-dose dobutamine (LDD) may be influenced by factors different from those observed in patients with chronic ischemic cardiomyopathy (CIC). The aim of this study was to analyze, by means of myocardial perfusion-gated single photon emission computed tomography, segmental thickening (STh), LV volumes and ejection fraction (EF), at baseline and during LDD infusion in patients with systolic dysfunction early after AMI, and compare these results with those in patients with CIC.
Methods: Prospective, multicenter study. Eighty-nine patients {mean 60.7 years [standard deviation (SD)=12.9]} with coronary artery disease and LVEF less than or equal to 40% were investigated with resting gated single photon emission computed tomography with LDD, 41 patients between 5 and 8 days post-AMI, and 48 patients with CIC.
Results: Post-AMI the patients had lower LVEF, worse STh scores, and a greater number of segments with severely diminished thickening than patients with CIC. In post-AMI patients, contractile reserve in segments with severely impaired baseline thickening was predictive of a more than or equal to 5% increase in LVEF [odds ratio (OR): 3.77], whereas in patients with CIC the predictors were global contractile reserve (OR: 2.45) and a lower resting end-diastolic volume (OR: 0.98).
Conclusion: Improvement of LVEF with LDD in patients with systolic dysfunction early after AMI depended essentially on contractile reserve in segments with severely impaired baseline thickening, whereas in patients with CIC it depended on overall LV contractile reserve and the presence of less ventricular remodeling.