I-123-IPPA SPECT for the prediction of enhanced left ventricular function after coronary bypass graft surgery

Fatty acids are the prime metabolic substrate for myocardial energy product ion. Hence, fatty acid imaging may be useful in the assessment of myocardia l hibernation. The goal of this prospective, multicenter trial was to asses s the use of a fatty acid, I-123-iodophenylpentadecanoic acid (IPPA), to id entify viable, hibernating myocardium. Methods: Patients (n = 119) with abn ormal left ventricular wall motion and a left ventricular ejection fraction (LVEF) < 40% who were already scheduled to undergo coronary artery bypass grafting (CABG) underwent I PPA tomography (rest and 30-min redistribution) and blood-pool radionuclide angiography within 3 d of the scheduled operat ion. Radionuclide angiography was repeated 6-8 wk after CABG. The study end point was a greater than or equal to 10% increase in LVEF after CABG. The n umber of IPPA-viable abnormally contracting segments necessary to predict a positive LVEF outcome was determined by receiver operating characteristic (ROC) curves and was included in a logistic regression analysis, together w ith selected clinical variables. Results: Before CABG, abnormal IPPA tomogr aphy findings were seen in 113 of 119 patients (95%), of whom 71 (60%) had redistribution in the 30-min images. The LVEF increased modestly after CABG (from 32% +/- 12% to 36% +/- 8%, P < 0.001). A greater than or equal to 10 % increase in LVEF after CABG occurred in 27 of 119 patients (23%). By ROC curves, the best predictor of a greater than or equal to 10% increase in LV EF was the presence of greater than or equal to 7 IPPA-viable segments (acc uracy, 72%; confidence interval, 64%-80%). Among clinical and scintigraphic variables, the single most important predictor also was the number of IPPA -viable segments (P = 0.008). The number of IPPA-viable segments added sign ificant incremental value to the best clinical predictor model. Conclusion: A substantial increase in LVEF occurs after CABG in only a minority of pat ients (23%) with depressed preoperative function. The number of IPPA-viable segments is useful in predicting a clinically meaningful increase in LVEF.