Right ventricular (RV) function influences left ventricular (LV) diastolic filling in various clinical and experimental models. The influence of RV systolic function on LV diastolic performance was examined in patients with severe RV pressure overload. Eighty-two patients with pulmonary vascular or parenchymal disease who were referred for heart-lung or lung transplant evaluation were studied. All patients had radionuclide angiography from which RV ejection fraction and LV peak filling rate were measured. Most patients (n = 51) had right-sided cardiac catheterization. In 24 patients (group 1), RV ejection fraction was < 30%, whereas in 58 (group 2), it was > 30%. Mean pulmonary artery pressure was greater in group 1 than in 2 (57 +/- 16 vs 34 +/- 20 mm Hg; p < 0.0001). Pulmonary artery wedge pressure was also greater in group 1 than in 2 (14 +/- 9 vs 7 +/- 2 mm Hg; p < 0.0001), whereas peak filling rate was decreased (2.16 +/- 0.88 vs 2.97 +/- 0.79 end-diastolic volumes/s; p < 0.0001). LV ejection fraction was normal in all patients. There was an inverse relation between RV ejection fraction and pulmonary artery wedge pressure (r = 0.45; p < 0.001; SEE 5.3). There was a direct relation between RV ejection fraction and LV peak filling rate (r = 0.49; p < 0.0001; SEE 1.34). In patients with RV pressure overload, RV systolic function is related to LV diastolic performance. This effect is most likely mediated by ventricular interdependence.