Identification of viable myocardium early after acute myocardial infarction using closed-loop arbutamine echocardiography: comparison with positron emission tomography

Objective —This study sought to evaluate the safety and efficacy of arbutamine echocardiography in identifying contractile reserve and predicting functional improvement early after acute myocardial infarction (AMI). Methods and results — Seventeen patients with first AMI underwent arbutamine echocardiography 48 to 96 hours after AMI. Arbutamine was infused by a closed-loop delivery device. The heart rate slope was 4 beats/min and the heart rate target was 20 beats/min above baseline heart rate. A follow-up echocardiogram was obtained one month later. N-13 ammonia and F-18 FDG positron emission tomographic (PET) imaging were performed 6 ± 2 days after AMI, before coronary angiography. Mean duration of arbutamine infusion was 6 ± 2 min. There was no complication and there were no major side effects. Myocardial viability was identified with PET in 15 of the 17 patients. Contractile reserve was observed in 10 patients during arbutamine infusion. Functional recovery was identified in 12 patients. Sensitivity, specificity and accuracy of PET and arbutamine echocardiography for predicting functional recovery were 100%, 40%, 76% and 67%, 80%, 84%, respectively. Conclusions — Low-dose arbutamine stress testing is safe early after AMI. Contractile reserve can be rapidly identified by echocardiography and is specific, but moderately sensitive for predicting reversible dysfunction.