Low-dose dobutamine echocardiography predicts the early response of dysfunctioning myocardial segments to coronary artery bypass grafting

Dobutamine echocardiography has recently been introduced for use in identification of viable myocardium in patients with acute myocardial infarction and prediction of the response of dysfunctioning myocardial segments to coronary angioplasty. The aim of this study was to evaluate whether this test may be used to predict the early response of dysfunctioning myocardial segments to surgical revascularization. We studied 30 patients with three-vessel disease and chronic, stable angina pectoris during coronary artery bypass grafting (CABG). Patients were monitored by intraoperative transesophageal echocardiography in the transgastric short-axis view at the papillary muscle level. The left ventricle was divided into eight segments; and 240 myocardial segments were analyzed. Percentage of systolic wall thickening (PSWT) was calculated in each segment at baseline (early after pericardiectomy), before bypass during dobutamine infusion (5 µg/kg/min), and after separation from cardiopulmonary bypass. Segments showing PSWT <30% at baseline were considered dysfunctional. Segments showing an increase in PSWT >10% during dobutamine infusion were considered responders. Segments showing an increase in PSWT <10% during dobutamine infusion were considered nonresponders. At baseline, 161 (67%) of 240 segments had PSWT <30% (dysfunctioning segments). During dobutamine, 98 (60%) of these segments increased PSWT >10% (from 11.3% ± 7.6% to 24.2% ± 12.0%, p < 0.01; responder segments), and 63 (40%) increased PSWT <10% (from 10.2% ± 4.9% to 8.3% ± 5.5%, p value not significant [NS]; nonresponder segments). After CABG, responder segments showed a significant increase in PSWT in comparison with baseline values (from 11.3% ± 7.6% to 24.4% ± 14.0%; p < 0.01). Segments not responding to dobutamine showed no significant changes in PSWT after CABG (from 10.2% ± 4.9% to 9.3% ± 6.6%; p = NS). Seventy-nine normai segments (PSWT 43.9% ± 12.6%) showed a slight but significant reduction in wall thickening both during dobutamine (PSWT 33.6% ± 14.0%, p 0.01 vs baseline) and after CABG (PSWT 32.8% ± 14.6%; p < 0.01 vs baseline), suggesting that compensatory hyperfunction was present at baseline. Estimation of clinica! accuracy for transesophageal echocardiography dobutamine-stress test yielded to 91% sensitivity, 93% specificity, 97% positive predictive value, 79% negative predictive value, and 92% overall accuracy.