[Clinical significance of stress thallium-201 myocardial scintigraphy for evaluation of right ventricular ischemia].

: Although stress thallium (T1)-201 myocardial imaging has been used for evaluation of the ischemic lesion of the left ventricle, there are few reports on the usefulness of this method for the assessment of the right ventricle in ischemic heart disease. The patients (pts) fell into three distinct groups according to the findings of the coronary arteriogram: normal control group (16 cases) without angiographically documented coronary artery disease; non-RCA group (16 cases) with a significant stenosis (greater than or equal to 75% narrowing) in the left coronary artery but free of a significant right coronary artery (RCA) stenosis; RCA group (28 cases) with a significant RCA stenosis regardless of the presence or absence of a significant left coronary artery lesion. After the pts were exercised to 80-85% of the expected maximum heart rate, immediate and delayed (3 to 4 hrs) T1-201 myocardial images were obtained. The images of the right ventricular free wall ( RVFW ) in 30 degrees and 60 degrees left anterior oblique (LAO) projections were evaluated visually with regard to the presence or absence of a defective T1-201 uptake, degree of the radioactivity and redistribution phenomenon of the RVFW . On immediate images, all normal controls and 13 pts in non-RCA group had continuous visualization of the RVFW . In RCA group, the RVFW was not visualized in five and 11 showed defective visualization of the RVFW in the 30 degrees LAO projection. In 60 degrees LAO projection, the RVFW was not visualized in six and five had defective visualization. On delayed images in RCA group, two pts who had no inferior myocardial infarction (MI) had redistribution of T1-201 into the RVFW . Defective visualization of the RVFW on the image was associated with location of the RCA lesion, history of inferior MI and degree of RCA stenosis. Collateral circulation seemed to protect the RVFW against the development of exercise-induced ischemia and affect the occurrence of redistribution of T1-201 into the RVFW . The RVFW findings on images improved the sensitivity for identifying the pts with RCA disease, compared with the LV findings alone. Thus, stress T1-201 myocardial imaging is able to visualize the myocardial blood flow of the RVFW and may provide a useful non-invasive method in the evaluation of right ventricular ischemia.