Comparison of thallium deposition with segmental perfusion in pigs with chronic hibernating myocardium

摘要

Comparison of thallium deposition with segmental perfusion in pigs with chronic hibernating myocardium. Am J Physiol Heart Circ Physiol 295: H2522-H2529, 2008. doi:10.1152/ajpheart.00761.2008.梀iable, chronically dysfunctional myocardium with reduced resting flow (or hibernating myocardium) is an important prognostic factor in ischemic heart disease. Although thallium-201 imaging is frequently used to assess myocardial viability in patients with ischemic cardio-myopathy, there are limited data regarding its deposition in hibernating myocardium, and this data suggest that thallium retention may be supernormal compared with control myocardium. Accordingly, pigs (n = 7) were chronically instrumented with a 1.5 mm Delrin stenosis on the proximal left anterior descending coronary artery (LAD) to produce hibernating myocardium. Four months later, severe an-teroapical hypokinesis was documented with contrast ventriculogra-phy (wall motion score, 0.7 +- 0.8; normal = 3), and microsphere measurements confirmed reduced resting flow (LAD subendocardium, 0.78 +- 0.34 vs. 0.96 +- 0.24 ml-min"1^-1 in remote; P < 0.001). Absolute deposition of thallium-201 and insulin-stimulated [18F]-2 fluoro-2-deoxyglucose (FDG) were assessed over 1 h and compared with resting flow (n = 704 samples). Thallium-201 deposition was only weakly correlated with perfusion (r2 = 0.20; P < 0.001) and was more homogeneously distributed (relative dispersion, 0.12 +- 0.03 vs. 0.29 +- 0.10 for microsphere flow; P < 0.01). Thus after 1 h relative thallium-201 (subendocardium LAD/remote, 0.96 +- 0.16) overestimated relative perfusion (0.78 +- 0.32; P < 0.0001) and underestimated the relative reduction in flow. Viability was confirmed by both histology and preserved FDG uptake. We conclude that under resting conditions, thallium-201 redistribution in hibernating myocardium is nearly complete within 1 h, with similar deposition to remote myocardium despite regional differences in flow. These data suggest that in this time frame thallium-201 deposition may not discriminate hibernating myocardium from dysfunction myocardium with normal resting flow. Since hibernating myocardium has been associated with a worse prognosis, this limitation could have significant clinical implications