To determine the changes in right heart hemodynamics and geometry early after surgery for chronic pulmonary hypertension due to large vessel thromboembolic occlusion, 30 patients were evaluated 8 +/- 8 days (mean +/- SD) before and 6 +/- 4 days after pulmonary thromboendarterectomy by two-dimensional echocardiography and right heart catheterization. Surgery resulted in an early significant improvement in hemodynamic variables including mean pulmonary artery pressure (48 +/- 12 to 28 +/- 8 mm Hg, p less than 0.001), right ventricular systolic pressure (76 +/- 20 to 47 +/- 15 mm Hg, p less than 0.001), pulmonary vascular resistance (935 +/- 620 to 278 +/- 252 dynes.s.cm-5, p less than 0.001) and cardiac index (2.0 +/- 0.5 to 2.9 +/- 0.6 liters/min per m2, p less than 0.001). Similarly, echocardiographic variables of right heart structures, which were well outside the normal range preoperatively, improved significantly early after thromboendarterectomy. These included diameters of the pulmonary artery (2.8 +/- 0.3 to 2.4 +/- 0.4 cm, p less than 0.001), inferior vena cava (2.9 +/- 0.6 to 2.2 +/- 0.4 cm, p less than 0.001) and right atrium (6.8 +/- 1.5 to 5.9 +/- 1.5 cm, p less than 0.001) as well as right ventricular short axis (4.5 +/- 0.8 to 3.7 +/- 0.8 cm, p less than 0.001) and long axis (8.7 +/- 0.9 to 8.1 +/- 0.9 cm, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)