Comparison of rest-redistribution thallium-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 myocardium in most mild to moderate (51% to 85% of normal uptake) irreversible TI-201 defects. However, if the main clinical question is whether a region is viable, and not whether there is inducible ischemia, a resting protocolmay be more appropriate. The aim of this study was to determine whether rest-redistribution (RD) quantitative Tl-201 single-photon emission tomographic imaging provides the same information on viable myocardium as Tl-201 RI. Thus, 15 patients (mean age 58 ± 9 years) with chronic coronary artery disease and left ventricular dysfunction (ejection fraction 35 ± 8%) were studied by both RI and RD Tl-201 single-photon emission tomography. Regional Tl-201 uptake was assessed quantitatively using a 16-segment model. When Tl-201 images were classified as normal/reversible (viable) or irreversible (nonviable), RI showed viable myocardium in 145 of 240 myocardial regions (60%), whereas RD showed it in 103 of 240 myocardial regions (43%). The 2 imaging protocols provided concordant information in 176 of 240 myocardial regions (73%). Among the 64 (27%) discordant regions, 53 (22%) were viable by RI and nonviable by RD, whereas 11 (5%) were viable by RD and nonviable by RI (p < 0.001). When the severity of Tl-201 activity was considered 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 (≤50% of normal uptake), RD suggested scar in 8 but RI indicated viable myocardium (mean Tl-201 uptake 40 ± 9% with RD vs 57 ± 9% with RI; p < 0.005). Thus, when the severity of TI-201 activity was considered within irreversible defects, the concordance between RI and RD Tl-201 imaging regarding viable myocardium increased to 93%, leaving only 17 of 240 regions discordant (p = NS). These data indicate that RD quantitative Tl-201 imaging may be appropriate in patients with coronary artery disease and left ventricular dysfunction when myocardial viability is in question.