Improvement in contractility of infarct zone after dobutamine infusion predicts good (TIMI II or III) flow in infarct related artery.

ABSTRACT

Eighteen patients of 'Q' wave acute myocardial infarction (AMI) (age 50 +/- 6.2 years), underwent dobutamine stress echocardiography (DSE) before hospital discharge (7.2 +/- 1.3 days after AMI) to find out the correlation between response of infarct zone to dobutamine infusion and TIMI grade flow in infarct related artery (IRA). The aim of study was to test the hypothesis that infarct zone which shows improvement in contractility after dobutamine infusion has viable myocardial tissue and would have good flow (TIMI II or III) in IRA. Echocardiographically, improvement in contractility in the centre of infarct zone by at least 1 grade (on a scale of 4) was termed as positive response on DSE. The mean dose of dobutamine was 19.4 micrograms/kg/min. Ten patients had positive response on DSE; 8 of them had good antegrade flow in IRA. Eight patients had no improvement in contractility of infarct zone on DSE; 6 of them had poor flow in IRA. Clinical markers of reperfusion (relief of chest pain, early ST settlement, peak CPK-MB levels), age of patient, site of AMI, time to thrombolysis, resting left ventricular ejection fraction, wall motion score of the infarct zone and presence of collaterals were not significantly different in patients with good or poor flow in IRA. Thus, improvement in contractility of infarct zone after dobutamine infusion can predict good flow (TIMI II or III) in IRA with 80 percent sensitivity, 75 percent specificity, 80 percent diagnostic accuracy, 80 percent positive predictive value and 75 percent negative predictive value.