Early postexercise thallium-201 reinjection after sublingual nitroglycerin augmentation: Effects on detection of myocardial ischemia and/or viability

Background: Thallium-201 (²⁰¹Tl) reinjection after conventional redistribution imaging is a standard procedure, resulting in enhanced ²⁰¹ Tl redistribution which is compatible with viable myocardium. Although this method significantly improves identification of viable myocardium, it increases the investigation time by approximately 1 h. Thus, this technique is suboptimal from the standpoint of patient convenience, since its routine performance may be impractical in a high-volume nuclear medicine laboratory. Hypothesis: This study was undertaken to evaluate the efficacy of an early ²⁰¹Tl reinjection and imaging protocol in combination with sublingual nitroglycerin, to detect myocardial ischemia and/or viability, and to reduce the need for conventional (4 h) redistribution imaging. Materials and Methods: In this study, 62 consecutive coronary patients, referred for the detection of possible myocardial ischemia and/or viability, were involved (mean age 55 years, range 41-70). Of those, 50 had previous angina attacks, with 42 having a history of previous myocardial infarction; 10 patients had coronary artery bypass grafting; and the remaining 2 had atypical chest pain. Immediately after the completion of the initial postexer-cise imaging, 0.3 mg sublingual nitroglycerin followed by the reinjection of 1 m Ci of ²⁰¹Tl were administered, and two further sets of images were acquired 1 h and 4h later. Results: In each set of i mages, a total of496 segments were analyzed. On postexercise imaging, 305 (61%) segments demonstrated defects of which 198 (65%) showed enhanced thallium uptake, 97 (32%) did not change, and 10(3%) showed reverse redistribution on 1 h reinjection imaging (IRI). Of the 97 persistent defects, only 17 (6%) showed fill-in of ²⁰¹ Tl on 4 h redistribution imaging (CRI), while 12 (4%) segments showed reverse redistribution. On the other hand, after analyzing the 62 patients of the 1 h IRI, 17 (27%) remained unchanged while in only 1 patient (6%) of 17 the diagnosis changed from myocardial necrosis to ischemia after analysis ofthe 4h CRI. Conclusion: These results indicate that early postexercise reinjection of ²⁰¹Tl in combination with sublingual nitroglycerin followed by l h image acquisition may prove useful for a comprehensive and convenient assessment of myocardial ischemia and/or viability.