The value of semi-quantitative myocardial metabolic-perfusion scores in coronary artery bypasses grafting

Objective: Coronary artery bypass grafting (CABG) is the preferred method of coronary revascularization in the coronary artery disease (CAD) patients with multi-vessel involvement. The study was aimed to evaluate the role of semi-quantitative assessment of myocardial viability scores using PET in CABG. Methods: Twenty-one consecutive patients with multi-vessel CAD were recruited from the department of cardiac/thoracic surgery. All patients underwent gated myocardial perfusion imaging (G-MPI) and 18F-fluorodeoxyglucose (FDG) myocardial PET imaging to assess the extent and severity of ischemia as well as the myocardial viability. The images were interpreted according to the semi-quantitative method issued by American Society of Nuclear Cardiology (ASNC) imaging guidelines using a 20-segment nomenclature. Summed rest score (SRS) and summed difference score (SDS) were calculated accordingly. All patients were scheduled for CABG within 2 weeks after the radionuclide myocardial imaging. The follow-up G-MPI was performed in all patients in the 3rd month after the surgery. Results: Out of the total 420 segments, 164 segments had abnormal myocardial perfusion by preoperative G-MPI. Among them, 93 segments were identified as non-viable (with difference score≥0) and the remaining 71 viable (with difference score <0). Based on their SDS, the patients were divided into 3 groups: group A (SDS≥0, n=5), group B (-5≤SDS<0, n8) and group C (SDS < -5, n=8). The mean change of global left ventricular ejection fraction (LVEF) after CABG in the three groups were -3.6%, 3.38% and 6.88% respectively. Conclusion: Assessment of myocardial viability by PET imaging is valuable in predicting whether the CAD patients may benefit from CABG. (authors)