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¹²³I-IPPA SPECT for the Prediction of Enhanced Left Ventricular Function After Coronary Bypass Graft Surgery

Section of Cardiology, Baylor College of Medicine and Methodist Hospital, Houston, Texas
Hospital Hotel-Dieu De Montreal, Montreal, Quebec, Canada
Section of Cardiology, University of Alabama at Birmingham, Birmingham, Alabama
Medco Research, Inc., Research Triangle Park, North Carolina

Correspondence: For correspondence or reprints contact: Mario S. Verani, MD, Baylor College of Medicine and Methodist Hospital, 6550 Fannin, SM 677, Houston, TX 77030.

ABSTRACT

Fatty acids are the prime metabolic substrate for myocardial energy production. Hence, fatty acid imaging may be useful in the assessment of myocardial hibernation. The goal of this prospective, multicenter trial was to assess the use of a fatty acid, ¹²³I-iodophenylpentadecanoic acid (IPPA), to identify viable, hibernating myocardium. Methods: Patients (n = 119) with abnormal left ventricular wall motion and a left ventricular ejection fraction (LVEF) < 40% who were already scheduled to undergo coronary artery bypass grafting (CABG) underwent IPPA tomography (rest and 30-min redistribution) and blood-pool radionuclide angiography within 3 d of the scheduled operation. Radionuclide angiogra-phy was repeated 6–8 wk after CABG. The study endpoint was a 10% increase in LVEF after CABG. The number 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 with selected clinical variables. Results: Before CABG, abnormal IPPA tomography 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 10% increase in LVEF after CABG occurred in 27 of 119 patients (23%). By ROC curves, the best predictor of a a 10% increase in LVEF was the presence of 7 IPPA-viable segments (accuracy, 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 significant incremental value to the best clinical predictor model. Conclusion: A substantial increase in LVEF occurs after CABG in only a minority of patients (23%) with depressed preoperative function. The number of IPPA-viable segments is useful in predicting a clinically meaningful increase in LVEF.

Key Words: fatty acids • myocardial hibernation • myocardial viability • myocardial metabolism