Assessment of the efficiency of ECG-Gated99mTc-MIBI SPECT for the evaluation of myocardial viability

In the field of nuclear cardiology, various methods have been employed to evaluate myocardial viability. It is more challenging when one wants to evaluate viability in the hibernating myocardium. Electrocardiographic (ECG)-gated Tc-MIBI SPECT has the unique capability of evaluating both perfusion and ventricular function (wall motion and thickness), simultaneously. We studied forty patients with coronary artery disease who had positive previous history of myocardial infraction. They all underwent ECG-gated99mTc-MIBI SPECT before and 2-3 months after coronary artery bypass rafting (CAB G). Global ejection fraction, segmental myocardial perfusion and ventricular wall motion were compared before and after operation. Assessment of perfusion, alone, in some myocardial segments such as apical, mid and basal segments of septum-demonstrated no statistical meaningful difference. There was no significant changes in septal wall motion. The pre and post operative mean ventricular ejection (E F) were 51.35% and 51%, respectively. (p=0/85). Regarding the severity of perfusion defeat as the only criterion for viability, a number of the myocardial segments were preoperatively evaluated as non-viable, that was not in agreement with the post-operative results, (in other words the myocardial viability was underestimated). Based on dual criteria (perfusion and wall motion) all the myocardial walls were viable on both pre and post operative scintigrams. We concluded that severity of myocardial perfusion defect was not a perfectly accurate rit erion for myocardial viability. Also ejection fraction was not appropriate for the evaluation of ventricular functional improvement after CAB G