Date: 29 Apr 2011

Washout of 82Rb as a marker of impaired tissue integrity, obtained by list-mode cardiac PET/CT: relationship with perfusion/metabolism patterns of myocardial viability

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Abstract

Purpose

Myocardial washout of the potassium analogue 82Rb may indicate tissue impairment. Few studies have evaluated its usefulness for viability assessment, and controversial results were reported. We revisited this topic using list-mode positron emission tomography (PET)/CT.

Methods

A total of 22 patients with chronic ischemic cardiomyopathy (ICM) and 11 control subjects with normal CT coronary angiogram were studied. Rest 82Rb PET/CT studies were acquired in list mode and resampled to static, gated, and dynamic images. Using a 17-segment model, 82Rb washout was determined by monoexponential fitting of myocardial time-activity curves. In ICM patients, 18F-fluorodeoxyglucose (FDG) studies were obtained in the same session and segments were classified as normally perfused, mismatch, or matched defect.

Results

82Rb washout was minimal and homogeneous in control subjects. Normally perfused segments of ICM did not differ (p = 0.33). ICM patients had a left ventricular ejection fraction (LVEF) of 25 ± 12%, 25/353 mismatched, and 46/353 matched defect segments. 82Rb washout was higher in hypoperfused vs normal segments (p < 0.05), but not different between mismatch and matched defect (p = 0.18). Intraindividual analysis in nine patients showing both FDG mismatch and matched defect confirmed absence of differences. Overall, segmental 82Rb washout correlated inversely with 82Rb uptake (r = −0.70; p < 0.05) and less well with FDG uptake (r = −0.31; p < 0.05).

Conclusion

Using state-of-the-art PET/CT technology for myocardial viability assessment, 82Rb washout does not distinguish between perfusion/metabolism patterns of hibernating myocardium and scar. Tissue integrity may be at least partially impaired in hibernation.