Right ventricular ejection fraction from equilibrium krypton-81m blood pool scans: a noninvasive predictor of pulmonary arterial hypertension

Based on the relation between the impedance to right ventricular ejection and ejection fraction of the right ventricle (RVEF) we tested the hypothesis that radionuclide RVEF correlates inversely with pulmonary artery pressure and allows the noninvasive prediction of pulmonary hypertension. A recently developed improved equilibrium right ventricular blood pool imaging technique using ultrashort-lived krypton-81m and simultaneous right heart catheterization were combined for assessment of right ventricular systolic performance in relation to right ventricular loading in a heterogeneous group of cardiopulmonary disorders. The study group included 9 patients with pulmonary artery hypertension secondary to left ventricular dysfunction, 5 with primary pulmonary hypertension, 5 with corrected tetralogy of Fallot, and 10 normal subjects. Linear regression analysis between radionuclide RVEF and simultaneously recorded hemodynamic measurements of right ventricular loading revealed a significant inverse correlation with mean PA pressure (r = -0.87; P less than 0.001), with total pulmonary resistance index (r = -0.81; P less than 0.001) and with pulmonary vascular resistance index (r = -0.78, P less than 0.01). The sensitivity and specificity of a resting RVEF less than 40% to indicate pulmonary hypertension (mean PA pressure greater than 20 mmHg) were 71% and 100%, respectively; positive and negative predictive values were 100% and 80%, respectively. Thus, radionuclide RVEF as a parameter of right ventricular systolic performance is predominantly dependent on right ventricular afterload and has the potential for the noninvasive prediction of pulmonary hypertension in a heterogeneous group of cardiopulmonary disorders.