TL-201 LUNG UPTAKE AND PEAK TREADMILL EXERCISE FIRST-PASS EJECTION FRACTION

Increased thallium-201 lung uptake immediately after exercise has been shown (1) to be a marker for extensive coronary artery disease, (2) t o correlate with low rest and exercise left ventricular ejection fract ion by supine gated blood pool scintigraphy, and (3) to be a powerful independent predictor of future cardiac events, Exercise left ventricu lar ejection fraction measured during upright exercise by the first-pa ss technique has also been shown to be a powerful independent prognost ic variable, Combined perfusion and exercise left ventricular ejection fraction can be acquired by using the technetium gsm-based myocardial perfusion agents and offers an alternative protocol to stress/redistr ibution thallium imaging, It is therefore clinically important to unde rstand the relation between exercise lung heart thallium uptake and ex ercise left ventricular ejection fraction, Accordingly, both these mea surements were acquired in 38 patients with documented coronary artery disease who underwent two treadmill exercise studies, Parameters obta ined from the first-pass study that are known to affect lung thallium uptake were correlated with exercise lung/heart thallium ratios; lung/ heart ratios were used in a model to predict exercise left ventricular ejection fraction values, Exercise left ventricular ejection fraction and peak filling rate showed significant negative correlations with t hallium lung/heart ratio, but the first-pass variables examined were n ot independently predictive of thallium lung uptake, The chance of fin ding an abnormal thallium lung/heart ratio at exercise LVEF of 40% is only 52%, whereas the chance of finding an abnormal ratio at exercise LVEF of 30% is 74%. These data suggest that, although there is an over all significant inverse correlation between exercise left ventricular ejection fraction and lung/heart thallium ratio, moderately reduced ex ercise left ventricular ejection fraction values cannot be reliably pr edicted from lung/heart thallium ratios.