Low dose 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 wheter tihs test could be used to predict the early response of dysfunctioning myocardial segements to coronary artery bypass grafting(CABG).

We studied in 23 patients with multi-vessel disease during CABG. Myocardial segments were monitored by intraoperative transesophageal echocardiography(TEE) in the transgastric short-axis view at papillary muscle level. The left ventricle was divided into five segments and sixty eight myocardial segments in 23 patients were analyzed. Percentage of systolic wall thickening(PSWT) was calculated in each segment for three times: at basline(early after pericardiectomy);before bypass during dobutamine infusion(3-5ug/kg/min);and after seperation from cardiopulmonary bypass. Segments showing baseline PSWT >_30% were considered normal and those < 30% were dysfunctional. Segments showing an increase in PSWT >_10% during dobutamine infusion were considered responders and those < 10% nonresponders.

AT baseline, 24%(36%) of 68 segments had PSWT > 30%(normal) and 44(68%) had PSWT < 30%(dysfuctioning segments). During dobutamine infusion, 21(47.7%) among 44 dysfunctional segments showed increase in PSWT >_10%(from 12.3±7.2% to 33.5±11.8%, p<0.01 ; responder segments), and 23(52.3%) showed increase in PSWT < 10%(from 14.7±6.5% to 17.4±7.4%, p=NS ; nonresponder segments). After CABG, responder segments showed a significant increase in PSWT in comparison with baseline values(from 12.3±7.2% to 32.1 ±11.0%,p<0.01). Segments not responded to dobutamine showed no significant changes in PSWT after CABG(from 14.7±6.5% to 16.0±8.2%, p=NS). Twenty-four normal segments (PSWT 41.9±6.2%) showed a slight but significant reduction in PSWT both during dobutamine infusion(38.7±6.9%;p<0.05) and after CABG(38.9±6.3%, p<0.05), suggesting that compensatory hyperfunction was present at baseline. Estimation of clinical accruacy of low dose dobutamine TEE yieded to 69% sensitivity, 93.9% specificity, 95.2% positive predictive value, 60.9% negavive predictive value, and 77.3% overall accuracy. In both responders and nonresponders of dysfunctioning segments, there was a correlation between PSWT during dobutamine infusion and that after CABG(r=0.61, r=0.63, respectively).

Low dose dobutamine TEE test well predicts the early response of dysfunctioning myocardial segments to CABG.