The efficacy of the fibrinolytic therapy in pulmonary embolism was studied by Doppler echocardiography: the evolution of the cardiac and angiographic changes could be studied in parallel. Thirty patients with severe pulmonary embolism and vascular obstruction greater than 40% (67.2 +/- 9.9%) were examined prospectively by Doppler echocardiography before and after thrombolysis. The following parameters were studied: systolic pulmonary artery pressure calculated from the jet of tricuspid regurgitation and left and right ventricular diameters for the calculation of the ratio of the ventricular dimensions. All patients underwent Doppler echocardiography and pulmonary angiography immediately after thrombolysis. The average improvement of the percentage vascular obstruction was 37%. The hemodynamic and echocardiographic changes were globally favourable. The pulmonary artery systolic pressure fell from 51 +/- 10 to 33 +/- 6.7 to 25.3 +/- 6.3 mm and the ratio of ventricular dimension from 0.87 +/- 0.3 to 0.60 +/- 0.16 (p less than 0.001). Only 4 patients had pulmonary artery systolic pressures over 40 mmHg after therapy compared with 26 before therapy. However, the hemodynamic and angiographic correlations were poor (r = 0.37; p less than 0.001). In the 6 patients in whom treatment was ineffective according to angiographic criteria (less than 20% improvement of vascular obstruction), the echocardiographic changes were small or absent, the improvement in the ratio of ventricular dimensions being less than 20%. However, a satisfactory correlation was observed between the percentage improvement of the ratio of ventricular dimensions and that of vascular obstruction (r = 0.59; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)