Thallium-201: quantitation of right ventricular hypertrophy in chronically hypoxic rats

Sprague Dawley rats were divided into two groups. Ten were kept in room air and 10 in hypobaric hypoxia (air at 380 mm Hg). After two weeks all were injected intravenously with 50 muCi of 201Tl and sacrificed. The right and left ventricles were separated, weighed, and measured for radioactivity in a gamma well counter. Left and right ventricular mass ratios (MR) correlated with 201Tl radioactivity ratios (TAR) in both control and hypoxic rats: r = 0.962 where MR = 0.863 TAR + 0.27. Myocardial 201Tl uptake reflects and quantitates normal and abnormal ventricular mass, the abnormal mass in this model consisting of right ventricular hypertrophy associated with hypoxic pulmonary hypertension.