Aim. To evaluate the changes in intracardiac hemodynamics, identify the markers of cardiac insufficiency and myocardial lesions in the patient presenting with acute massive pulmonary embolism (AMPE) before and after catheter fragmentation with thrombolysis. Material and methods. The study involved 102 patients at the mean age of 56 years including 52 (51%) men and 50 (49%) women. The mean period between the first manifestations of AMPE and  the beginning of the study was 6.7 days. All the patients underwent fragmentation of thromboemboli in the main pulmonary arteries. Half of the total therapeutic dose of a thrombolytic agent was administered directly into the thromboeboli and the other half by means of intravenous infusion during 30—60 minutes. Two groups of the patients were formed. Group one (n=46) included the patients with moderate pulmonary hypertension (30—50 mm Hg), group 2 (n=56) was comprised of those with severe pulmonary hypertension (50—80 mm Hg). Results. In the early period after the onset of the treatment, 77 (75.4%) patients showed regression of the clinical manifestations of acute respiratory insufficiency accompanied by stabilization of  arterial pressure. The frequency of the respiratory movements decreased from 23.5±2.99 to 16.7±2.1  (p<0.05). Moreover the initially elevated troponin I level decreased to the normal value; this observation was of significance for the clinical prognosis. The initially enhanced mean blood level of brain natriuretic peptide (BNP) was documented in 65 (63.7%) patients. The treatment resulted in the normalization of the plasma BNP level in the patients of group 1 and its appreciable decrease in group 2.  Systolic pressure in the pulmonary artery in the patients of group 1 decreased from 41.6±5.23  to  33.3±5.1 mm Hg  (p<0.05), the mean arterial pressure fell down from 29.75±7.7  to  22.6±8.3  mm Hg  (p<0.05). In group 2, systolic and total pressure in the pulmonary artery decreased from 66.5±12.9 to 40.6±8.8  mm Hg  (p<0.05) and from 46.4±13.4  to 25.3±8.4 mm Hg respectively (p<0.05). The Miller index score decreased from 24.53±2.25 to 15±3.8 (p<0.05) in the patients of group 1 and from 26.2±3.1  to  16.1±5.02 (p<0.05) in group 2. Conclusion. Catheter fragmentation supplemented by thrombolysis promoted the recovery of the disturbed right ventrivular function and caused the regression of cardiac insufficiency in 55% and 65.7% of the patients presenting with acute massive pulmonary embolism respectively. This treatment may be prescribed to  all the patients with this condition including those with stable hemodynamics and in the absence of signs of right ventricular dysfunction for the purpose of more active recanalization of the pulmonary artery, restoration of  heart linear dimensions, and prevention of the development of left-ventricular type chronic cardiac failure and pulmonary hypertension.