Thallium-201 myocardial imaging to evaluate right ventricular overloading.

The usefulness of thallium-201 myocardial imaging in assessing right ventricular (RV) overloading was evaluated and compared with the electrocardiographic and hemodynamic measurements. Multiple unprocessed photoscans were obtained using a gamma camera in 47 patients who had chronic RV overload, including 28 subjects with pressure overload, 14 with volume overload and five with pressure and volume overload.With pressure overload the degree of RV visualization (RVV) was correlated with elevation of RV systolic pressure. With volume overload the RV free wall was visualized in all patients, and RVV was correlated with the increment in pulmonary–to–systemic flow ratio. Pressure and volume overload could be differentiated from the morphologic characteristics of myocardial image. With pressure overload the interventricular septum appeared straight. With volume overload the RV cavity appeared to be dilated and the interventricular septum convex to the right ventricle.Myocardial images were compared with ECG findings of RV hypertrophy in cases with pressure overload. RVV intensity correlated with the number of criteria (Sokolow and Lyon) satisfied in each tracing. The sensitivity of myocardial imaging for diagnosis of RV pressure overload was 93.3%, higher than that of ECG criteria for RV hypertrophy. We conclude that thallium-201 myocardial imaging is sensitive and reliable in assessing RV overload.