Proportion of viable myocardium is more reliable than semi-quantitative score in predicting functional recovery: a pilot study of PET myocardial viability imaging

PET myocardial viability imaging is the “gold standard” for the non-invasive assessment of myocardial viability. The research aims to find out the best methods of imaging interpretation in predicting the postoperative functional recovery. Twenty-one CAD patients with multi-vessel involvement were recruited. All patients underwent gated myocardial perfusion imaging(G-MPI) and FDG PET myocardial imaging within 2 weeks before coronary artery bypass grafting. The postoperative G-MPI was performed in all patients 3 months after the surgery. Out of the total 420 segments, 164 segments of ischemic myocardium were detected by preoperative G-MPI. Among them, 93 ischemic segments were identified as non-viable (difference score≥GT0) and the rest 71 segments were identified as viable(difference score<0). The proportion of viable segments (the ratio of viable segments versus ischemic segments) and summed difference score of metabolism to perfusion were calculated. The patients were further divided into 2 groups according to the proportion of viable myocardium: group I (the proportion≥GT50%, 12 cases) and group II (the proportion<50%, 9 cases) while another division was made according to SDS: group A (SDS≥GT0), group B (-5≤GTSDS<0) and group C (SDS<-5). The diagnostic accuracy of proportion of viable segments and SDS in predicting the post-revascularization improvement in the left ventricular ejection fraction by at least 5 or more ejection fraction units was 88.89% (8/9) and 55.56% (5/9) respectively. It is concluded that both approaches allow accurate evaluation of myocardial viability. Furthermore, the proportion of viable myocardium is more reliable in predicting the postoperative functional recovery.