QUANTITATIVE-EVALUATION OF BLOOD-FLOW DISTRIBUTION TO EXERCISING AND RESTING SKELETAL-MUSCLES IN PATIENTS WITH CARDIAC DYSFUNCTION USING WHOLE-BODY TL-201 SCINTIGRAPHY

Background and hypothesis: Decreased blood flow to working muscles mak es an important contribution to exercise intolerance in patients with chronic heart failure. This study was undertaken to examine whether ma ldistribution of skeletal muscle blood flow is closely related to exer cise intolerance in patients with cardiac dysfunction. Method's: Whole -body thallium scintigraphy was performed during one-leg exercise in 1 1 patients with left ventricular (LV) dysfunction (LV ejection fractio n <45%). Blood flow distribution to the exercising and resting legs wa s quantified by expressing regional thallium counts as a percentage of the whole-body counts at rest, at the level of anaerobic threshold, a nd at peak exercise. Results: At anaerobic threshold, the thallium act ivity of exercising muscle increased from 4.2 +/- 0.7 to 14.0 +/- 2.5% (p < 0.05) in the thigh and from 1.7 +/- 0.3 to 4.1 +/- 0.9% (p < 0.0 5) in the calf, compared with the resting value. Consequently, the rat io of thallium activity between exercising and resting legs increased to 2.7 +/- 0.7 (p < 0.05) in the thigh and to 2.3 +/- 0.7 (p < 0.05) i n the calf. When plotted as a function of anaerobic threshold, thalliu m activity of the exercising thigh (r = 0.78, p < 0.05) and the thalli um ratio between exercising and resting thigh (r = 0.69, p < 0.05) dec lined with the reduction of exercise tolerance. These correlations wer e not observed in calves. Conclusion: Whole-body thallium scintigraphy demonstrated a maldistribution of leg blood flow in patients with red uced aerobic exercise capacity, suggesting that this abnormality could play an important role in exercising intolerance in these patients.