Comparative study of single-injection, single-acquisition Tc-99m-MIBI gated SPET and stress-rest perfusion SPET for the evaluation of myocardial viability after bypass surgery in coronary artery disease

In patients without previous myocardial infarction, the single-injection st ress perfusion/rest function (SISPRF) approach using stress technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (S PET) can substitute for conventional stress-rest myocardial perfusion imagi ng for the assessment of myocardial viability. This study compared pre-oper ative single-injection, single-acquisition Tc-99m-MIBI gated SPET and conve ntional stress-rest imaging for the prediction of myocardial viability in p atients who underwent coronary artery bypass surgery (CABG). Rest thallium- 201 SPET followed by stress 99mTc-MIBI gated SPET was performed in 20 patie nts (nine with previous myocardial infarction (MI) and 11 without previous MI). The study was performed before and 3 months after CABG, and viability assessment was validated by wall motion improvement after CABG. A four-poin t scoring system (0-3 for normal to absent tracer uptake) for 17 segments o f the left ventricular myocardium was used for the assessment of stress and rest uptake. Wall motion, wail thickening and perfusion status were analys ed by semi-quantitative visual assessment. On gated SPET, perfusion defect reversibility was considered present when a definite perfusion defect was o bserved and wall motion or thickening was normal or showed only a mild decr ease. In patients with a previous MI, the left ventricular ejection fractio n improved significantly after CABG (46% +/- 7% vs 42% +/- 11% before CABG, P < 0.05). In patients without previous MI, the ejection fraction improved significantly after CABG (50 <plus/minus> 12% vs 44% +/- 16% before CABG, P < 0.05), In patients with previous MI, positive predictive values using t he stress-rest reversibility and SISPRF approaches were 91% and 90%, respec tively, and corresponding negative predictive values were 25% and 18%. In p atients without previous MI, positive predictive values using the stress-re st and SISPRF approaches were 70% and 61%, respectively, and corresponding negative predictive values were 63% and 14%. It is concluded that SISPRF SP ET study is of similar value to conventional stress-rest perfusion study in predicting wall motion improvement in patients with a previous MI, but tha t it is of limited value in predicting the myocardial viability of patients without previous MI, owing to a lower predictive value.