Lung uptake of thallium-201: a marker of defect reversibility?

High lung uptake of thallium-201 at stress is reported to be associated with a large number of perfusion defects and poor prognosis. This study was performed to assess whether the reversibility of stress perfusion defects was related to lung uptake. Gated planar thallium scans at stress and at redistribution from 102 consecutive patients with essentially normal left ventricular ejection fraction (using 99mTc gated blood pool ventriculography) were graded in terms of defect size. Lung and myocardial uptake of thallium were quantitated by region of interest methods relative to the given activity in a previously validated method. There was no significant correlation (non-parametric) between lung uptake and degree of redistribution (p = ns, rs = 0.140). There was a weak but positive correlation between lung uptake and defect size (p < 0.05, rs = 0.188). Both exercise time and double product showed a negative correlation with lung uptake (e.g. for double product, p < 0.0005, rs = -0.541). In conclusion, contrary to our expectation, lung uptake is not related to the degree of redistribution. High lung uptake seems to reflect poor cardiovascular reserve.