Glucose-loading thallium-201 myocardial SPECT

This study was designed to evaluate the feasibility of assessing myocardial viability using glucose loading followed by ²⁰¹Tl SPECT. Methods: First, the effect of insulin on the kinetics of ²⁰¹Tl uptake was evaluated in isolated perfused rat hearts. Second, glucose-loading ²⁰¹Tl myocardial SPECT was performed in 13 nondiabetic patients with histories of anterior myocardial infarction. Thirty minutes before acquiring rest ²⁰¹Tl SPECT, 20 g of glucose were intravenously injected into the fasting subjects. Thallium perfusion defects were compared to those of conventional rest- redistribution SPECT images obtained within a 2-wk interval. SPECT images were divided into 21 segments, and a defect score in 17 segments was calculated as a sum of the semiquantitative defect scores (0 = normal; I = mildly decreased uptake; 2 = severely decreased uptake; 3 = absence of uptake). Results: Thallium-201 uptake in isolated hearts showed a significant increase of 26% after insulin loading. Eleven (24%) of 45 segments showing perfusion defects on the conventional rest SPECT images demonstrated ²⁰¹Tl uptake on glucose-loading SPECT imaging. Defect scores decreased significantly on the glucose-loading SPECT images (9.9 ± 2.2 in early images; mean ± s.e.) compared with the conventional rest-redistribution SPECT images (12.6 ± 6.9 in delayed images, p < 0.05). Conclusion: Glucose- loading SPECT represents a superior method for assessing myocardial viability using ²⁰¹Tl.