Prediction of global left ventricular function after bypass surgery in patients with severe left ventricular dysfunction. Impact of pre-operative myocardial function, perfusion, and metabolism

Abstract

Aims: Previous studies have compared the accuracy of various tests of viability for the prediction of recovery of regional left ventricular function; global left ventricular recovery has been less well studied, although it has important prognostic and functional ramifications. We sought to identify the relative contribution of ischaemia, regional and global contractile reserve, perfusion and metabolic function to changes in left ventricular volumes and global function after coronary artery bypass surgery in patients with severe left ventricular dysfunction.

Methods and results: Dipyridamole stress Rb-82, fluorodeoxyglucose positron emission tomography and low and high-dose dobutamine-atropine stress echocardiography were obtained in 66 patients with left ventricular impairment. Myocardial segments were considered viable if ischaemia or either metabolic or contractile reserve were present, on positron emission tomography or dobutamine echocardiography. Resting left ventricular function was reassessed after surgery (mean 10+/-3 weeks) in the 59 patients who had not suffered a major peri-operative event; functional improvement was defined by a 5% increment of ejection fraction. Myocardial viability was found in 37 (63%) patients using positron emission tomography and in 42 (71%) patients using dobutamine echocardiography; post-operative functional improvement was noted in 28 (47%) patients. In univariate analyses, predictors of global post-operative functional recovery included: the extent of viability according to positron emission tomography [OR (odds ratio): 2.08 for each additional viable segment, 95% CI (confidence interval): 1.33-3. 25, P=0.001] or dobutamine echocardiography (OR: 2.06 for each additional viable segment, 95% CI: 1.28-3.30, P=0.003) and the increase in ejection fraction with low-dose dobutamine (OR: 1.9 for each 1% increase in ejection fraction with low dose dobutamine, 95% CI 1.39-2.61, P<0.0001). In a multivariate model which included evidence of viability by either technique, and change in ejection fraction with low-dose dobutamine echocardiography, only change in ejection fraction with low-dose dobutamine echocardiography was predictive of post-operative left ventricular functional recovery (adjusted OR: 1.81, 95% CI: 1.30-2.52, P=0.0005).

Conclusion: Among patients with severe left ventricular dysfunction who are referred for surgical revascularization, the overall accuracies of positron emission tomography and dobutamine echocardiography for the prediction of post-operative myocardial recovery are comparable. However, the strongest predictor of overall improvement of post-operative left ventricular function is an increase of ejection fraction with a low-dose dobutamine infusion.