Thallium-201 myocardial imaging to evaluate right ventricular overloading.

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Abstract
The usefulness of 201Tl myocardial imaging in assessing right ventricular (RV) overloading was evaluated and compared with the ECG and hemodynamic measurements. Multiple unprocessed photoscans were obtained using a .gamma. camera in 47 patients with chronic RV overload, including 28 subjects with pressure overload, 14 with volume overload and 5 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 was apparently 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. 201 Tl myocardial imaging apparently is sensitive and reliable in assessing RV overload.