[Comparative studies on right ventricular pressure and volume overloading by thallium-201 myocardial scintigraphy]

Thallium-201 myocardial scintigraphy was performed in 44 patients with various heart diseases including mitral stenosis (MS), atrial septal defect (ASD), primary pulmonary hypertension (PPH), and left atrial myxoma. The morphological findings of right ventricular (RV) free wall on the scintigram and RV/IVS (interventricular septum) uptake ratio of the images obtained from the left anterior oblique projection were studied in the patients with RV pressure or volume overloading. The RV free wall was visualize by scintigraphy in 13 out of 22 patients (59%) with MS, and in 15 out of 17 patients (88%) with ASD. In 5 patients with PPH or left atrial myxoma, the RV free wall was visualized in all cases. The patterns of RV free wall image were classified into three types. Type I with the smaller right ventricle than left ventricle was mainly seen in cases of MS, and type II with the dilated right ventricle was seen in cases of ASD and PPH. The RV free wall was visualized in most of the patients with MS whose RV systolic pressure (RVSP) was higher than 35 mmHg and mean pulmonary artery pressure (PAMP) was 20 mmHg or more, and with ASD whose RVSP was higher than 30 mmHg and PAMP was 10 mmHg or more. The ratio of radioactivity on the RV free wall and interventricular septum (RV/IVS uptake ratio) was calculated using 45 degree left anterior oblique view images. The RV/IVS uptake ratio ranged from 0.38 to 0.73 in the cases with MS, from 0.40 to 0.77 in the cases with ASD, and from 0.64 to 0.79 in the cases with PPH. In two cases with left atrial myxoma, the ratio was 0.50 and 0.55, respectively. The RV/IVS uptake ratio was compared to various hemodynamic parameters in right ventricular overloading. In the cases with MS, the RV/IVS uptake ratio was closely correlated with RVSP (r = 0.93: p less than 0.001), PAMP (r = 0.92; p less than 0.001), pulmonary capillary wedge pressure (PCWP) (r = 0.83: p less than 0.01), RV work index (RVWI) (r = 0.82: p less than 0.001), and pulmonary vascular resistance (PVR) (r = 0.71: p less than 0.01), respectively. In the cases with ASD, the RV/IVS uptake ratio was closely correlated with RVSP (r = 0.89: p less than 0.001), PAMP (r = 0.68: p less than 0.01), PVR (r = 0.77: p less than 0.01), and a left-to-right shunt ratio (r = 0.785: p less than 0.001). It was concluded that the analysis of thallium-201 myocardial scintigraphy is valuable as a non-invasive technique for the qualitative and quantitative estimation of RV pressure or volume over-loading.U