COMPARISON OF REST-REDISTRIBUTION TL-201 IMAGING AND REINJECTION AFTER STRESS-REDISTRIBUTION FOR THE ASSESSMENT OF MYOCARDIAL VIABILITY IN PATIENTS WITH LEFT-VENTRICULAR DYSFUNCTION SECONDARY TO CORONARY-ARTERY DISEASE

Thallium (Tl)-201 reinjection after stress-redistribution (RI) imaging has been proven to accurately identify ischemic and viable myocardium . Quantitative Tl-201 analysis after stress has also shown viable myoc ardium in most mild to moderate (51% to 85% of normal uptake) irrevers ible Tl-201 defects. However, if the main clinical question is whether a region is viable, and not whether there is inducible ischemia, a re sting protocol may be more appropriate. The aim of this study was to d etermine whether rest-redistribution (RD) quantitative Tl-201 single-p hoton emission tomographic imaging provides the same information on vi able myocardium as Tl-201 RI. Thus, 15 patients (mean age 58 +/- 9 yea rs) with chronic coronary artery disease and left ventricular dysfunct ion (election fraction 35 +/- 8%) were studied by both RI and RD Tl-20 1 single-photon emission tomography. Regional Tl-201 uptake was assess ed quantitatively using a 16-segment model. When Tl-201 Images were cl assified as normal/reversible (viable) or irreversible (nonviable), RI showed viable myocardium in 145 of 240 myocardial regions (60%), wher eas RD showed it in 103 of 240 myocardial regions (43%). The 2 imaging protocols provided concordant information in 176 of 240 myocardial re gions (73%). Among the 64 (27%) discordant regions, 53 (22%) were viab le by RI and nonviable by RD whereas 11 (5%) were viable by RD and non viable by RI (p <0.001). When the severity of Tl-201 activity was cons idered within irreversible Tl-201 defects, 55 of 64 discordant regions had only mild to moderate reduction with Tl-201 uptake (51% to 85% of normal uptake) by both RI and RD (68 +/- 10% vs 66 +/- 10%, p = NS). Among the 9 regions with severely reduced Tl-201 uptake ((less than or equal to 50% of normal uptake), RD suggested scar in 8 but RI indicat ed viable myocardium (mean Tl-201 uptake 40 +/- 9% with RD vs 57 +/- 9 % with RI; p <0.005). Thus, when the severity of Tl-201 activity was c onsidered within irreversible defects, the concordance between RI and RD Tl-201 imaging regarding viable myocardium increased to 93%, leavin g only 17 of 240 regions discordant (p = NS). These data indicate that RD quantitative Tl-201 imaging may be appropriate In patients with co ronary artery disease and left ventricular dysfunction when myocardial viability is in question.