Preoperative Correction of Tc-99-m-MIBI SPECT by F18-FDG Cardiac PET/CT for Myocardial Viability Before CABG

Özet

Objectives: Coronary artery bypass graft (CABG) surgery has been safely practiced on cases with poor left ventricular ejection fraction (LVEF). Although adversely effects of surgery with higher mortality and morbidity rates, preoperative myocardial viability defines outcome. Thus, it is crucial to determine preoperative left ventricular myocardial tissue viability for acceptable postoperative results in this group of patients. This multi-center prospective study focuses of assessment of myocardial perfusion and viability by comparison of two different nuclear medicine imaging techniques; technetium 99-m-methoxy-isobutyl-isonitrile single photon emission computed tomography (Technetium99-m-MIBI SPECT) and cardiac fluorodeoxyglucose positron emission tomography-computed tomography (F18- FDG Cardiac PET/CT). Materials and Methods: Study is performed by ethical approval and Helsinki protocols. Each patient was evaluated by Technetium-99-m-MIBI SPECT and F18- FDG Cardiac PET/CT for myocardial viability detection prior to CABG surgery. Technetium-99-m-MIBI SPECT and F18-FDG Cardiac PET/CT was evaluated in 191 cases preoperatively. These 191 cases (mean age 64±9.1 and male n=103, 53.9%) with LVEF ≤35% were evaluated for coronary revascularization preoperatively. Results: Study data accumulated from cases of CABG (n=191) with preoperative LVEF measurements between 35% to 20% (n=154, 80.6%) and lower than 20% (n=37, 19.3%). Technetium-99-m-MIBI SPECT imaging was performed before F18-FDG Cardiac PET/CT in all cases. By these evaluations, 1896 segments were detailed in total. For Technetium-99-m-MIBI SPECT, 1036 segments displayed normal Technetium-99-m-MIBI uptake (≥70%, classification 2). On the other hand, 860 segments displayed reduced Technetium-99-m-MIBI uptake with different degrees (<70%). Elaborations of the latter data, scar tissue with absent Technetium-99-m-MIBI uptake (≤30%) was imaged in 441 (23.2%, classification 0), reduced Technetium-99-m-MIBI uptake from 30% to 69% in 419 (22%, classification 1). One thousand and thirty-six segments with normal Technetium-99-m-MIBI uptake (≥70%) revealed myocardial viability by F18- FDG C-PET/CT in 1036 segments. Predictive value for viability of Technetium-99-m-MIBI SPECT therefore presents a value in 100% in this group. On the other end of the SPECT images, 441 cases with Technetium-99-mMIBI uptake ≤30% (which otherwise would be accepted as poor candidates for revascularization) presented viability with FDG uptakes in 285 cases. One hundred and fiftysix segments from the latter group were verified by FDG uptake as nonviable. The predictive value for Technetium99-m-MIBI SPECT for this group on myocardial viability presents a rate in 35.3%. Regression analysis revealed a weak linear correlation between segmental F18-FDG and Tc-99-m-MIBI uptake with a correlation coefficient of 0.30 (n=441, p<0.05). Conclusion: Prior to coronary artery bypass graft surgery decision for cases with reduced preoperative left ventricular ejection fraction, cardiac PET/CT using F18-FDG predicts myocardial viability more effectively when compared with Tc-99-m-MIBI SPECT alone. After a report of a severe hypoperfusion by Tc-99-m-MIBI SPECT analyse, it is suggestible to applicate to F18-FDG cardiac PET/ CT as a last resort. The latter technique is more accurate at elaborating and corroborating myocardial viability. We believe that avoiding from surgery by Tc-99-m-MIBI SPECT is a premature decision.