MYOCARDIAL VIABILITY IN PATIENTS WITH CHRONIC CORONARY-ARTERY DISEASE- COMPARISON OF TC-99M-SESTAMIBI WITH THALLIUM REINJECTION AND [F-18]FLUORODEOXYGLUCOSE

Background Tc-99m-sestamibi and thallium imaging have similar accuracy when used for diagnostic purposes, but whether sestamibi provides acc urate information regarding myocardial viability in patients with chro nic coronary artery disease has not been established. Since there is m inimal redistribution of sestamibi over time, it may overestimate nonv iable myocardium in patients with left ventricular dysfunction, in who m blood flow may be reduced at rest. Methods and Results We studied 54 patients with chronic coronary artery disease with a mean ejection fr action of 34+/-14%. Patients underwent stress/redistribution/reinjecti on thallium tomography and, within a mean of 5 days, same-day rest/str ess sestamibi imaging using the same exercise protocol and with patien ts achieving the same exercise duration. Of the 111 reversible thalliu m defects on either the redistribution or reinjection study, 40 (36%) were determined to be irreversible on the rest/stress sestamibi study, whereas only 3 of 63 irreversible thallium defects despite reinjectio n (5%) were classified to be reversible by sestamibi imaging. The conc ordance regarding reversibility of myocardial defects between thallium stress/redistribution/reinjection and same day rest/stress sestamibi studies was 75%. A subgroup of 25 patients also underwent positron emi ssion tomography (PET) studies with O-15-labeled water and [F-18]fluor odeoxyglucose (FDG) at rest after an oral glucose load. As in the over all group of 54 patients, there was concordance between thallium and s estamibi imaging regarding defect reversibility in 51 of 73 regions (7 0%). In the remaining 22 discordant regions (30%), 18 (82%) appeared i rreversible by sestamibi imaging but were reversible by thallium imagi ng. Myocardial viability was confirmed in 17 of 18 regions, as evidenc ed by normal FDG uptake (10 regions) or FDG/blood flow mismatch (7 reg ions) on PET. These regions were present in 16 of the 25 patients stud ied (64%). We then explored methods to improve the sestamibi results. First, when the 18 discordant regions with irreversible sestamibi defe cts were further analyzed according to the severity of defects, 14 (78 %) demonstrated only mild-to-moderate reduction in sestamibi activity (51% to 85% of normal activity), suggestive of predominantly viable my ocardium, and the overall concordance between thallium and sestamibi s tudies increased to 93%. Second, when an additional 4-hour redistribut ion image was acquired in 18 patients after the injection of sestamibi at rest, 6 of 16 discordant irreversible regions (38%) on the rest/st ress sestamibi study became reversible, thereby increasing the concord ance between thallium and sestamibi studies to 82%. Conclusions These data indicate that same-day rest/stress sestamibi imaging will incorre ctly identify 36% of myocardial regions as being irreversibly impaired and nonviable compared with both thallium redistribution/reinjection and PET, However, the identification of reversible and viable myocardi um can be greatly enhanced with sestamibi if an additional redistribut ion image is acquired after the rest sestamibi injection or if the sev erity of reduction in sestamibi activity within irreversible defects i s considered.