Identifying the cause of left ventricular systolic dysfunction after coronary artery bypass surgery: The role of myocardial contrast echocardiography

Abstract

Objective: Intraoperative myocardial contrast echocardiography was used to determine whether the identification of regional myocardial flow patterns during revascularization could predict myocardial contractile function immediately after separation from cardiopulmonary bypass (CPB) and at 1 month after coronary artery bypass grafting (CABG) surgery. Design: A prospective, open-labeled, longitudinal analysis. Setting: Two independent university hospitals. Participants: Twenty patients, during and up to 1 month after CABG. Interventions: The contrast agent Albunex (Mallenckrodt Medical, Inc, St Louis, MO) was injected into the aortic root during CPB. Measurements and Main Results: Myocardial contrast echo-cardiography opacification of flow was graded from intraoperative transesophageal echocardiographic images of the left ventricle in the short-axis, midpapillary view. The same myocardial images were also evaluated for regional wall motion abnormalities at 15, 30, and 60 minutes, 24 hours, 5 to 8 days, and 1 month after CPB. Logistic regression analysis was used to analyze the flow scores and regional function data from identical segments. Regional flow represented by contrast enhancement was assessed in 70% of the myocardial regions (55 of 80 possible segments; 95% confidence interval [CI], 61 to 76). Flow was more easily evaluated in the posterior region (95%) than in the anterior (70%) or septal regions (60%), and least likely evaluated in the lateral regions (50%). Regional wall motion was scored in 84% of the myocardial regions (469 of 560 possible regions). Function (segmental wall motion) was assessed in all regions with equal success. Segmental function and flow scores were matched to the same regions 66% of the time (53 of 80 possible series; 95% Cl, 55 to 76). Regional myocardial contrast flow patterns did not predict myocardial function at 15, 30, or 60 minutes after separation from CPB. However, contrast opacification of flow did predict regional myocardial function at 1 week ( p ≤ 0.05) and at 1 month ( p ≤0.01) after CABG surgery. The probability that myocardial function would be normal at 1 month was 0.62 when intraoperative flow opacification was abnormal and 0.98 when flow opacification was normal. For patients with normal flow, the estimated odds of having normal myocardial function were 3.33 times those of patients with abnormal flow at 1 week (odds ratio, 3.33; 95% CI, 1.09 to 10.19) and 18.5 timesthose of patients with abnormal flow at 1 month (95% Cl, 2.44 to 140.48). Conclusion: Intraoperative application of myocardial contrast echocardiography to determine regional flow patterns after revascularization may help differentiate conditions of left ventricular systolic dysfunction immediately after separation from CPB for CABG surgery and appear to predict myocardial function at 1 month.