Magnetic resonance tagging and echocardiographic response to dobutamine and functional improvement after reperfused myocardial infarction

Objective Our objective was to compare the qualitative response to low-dose dobutamine by echocardiography (DSE) with the quantitative response of magnetic resonance myocardial tagging (DMRT) in the prediction and evaluation of functional improvement after reperfused myocardial infarction (MI). Methods Twenty-two patients with a reperfused first MI (aged 51 2 years, 20 male, 13 anterior MI) were studied. On day 3 I after MI, patients underwent both DSE and DMRT at baseline and during infusion of 5 mug/kg/min and 10 mug/kg/min of dobutamine. The patients returned at week 8 1 for follow-up echocardiogram and MRT at rest. Two experienced observers interpreted the DSE for the presence of contractile reserve and functional improvement in dysfunctional segments. By DMRT, a 5% increase in percent intramyocardial circumferential shortening at peak response to dobutamine was defined as evidence of contractile reserve. Functional improvement by echocardiography was defined as the gold standard. Results Ejection fraction improved from 46% +/- 10% at week 1 to 51% +/- 12% at week 8 (P < .001) in the patients. Sixty-seven transmural segments with baseline dysfunction matched between imaging modalities by location were studied. For 51 (76%) of the segments, echocardiography and MR tagging were concordant in the assessment of functional improvement (K value 0.52). Twenty-nine segments (43%) demonstrated improvement by echocardiography, whereas 33 segments (49%) improved by MR tagging. With improvement of function by echocardiography as gold standard, the sensitivity and specificity of DMRT for prediction of functional improvement was 86% and 69%, respectively, with an overall accuracy of 76%. The sensitivity, specificity, and accuracy of DSE was 86%, 87%, and 85%, respectively. Overall accuracy was similar between techniques. Conclusions Both DSMRT and DSE are sensitive and accurate techniques for predicting functional improvement after reperfused MI.