Efficacy and Safety Evaluation of Low Dosage of Recombinant Tissue Plasminogen Activator (rt-PA) in the Treatment of Pulmonary Thromboembolism: A Multi-Center, Randomized Controlled Trial in China

Pulmonary thromboembolism (PTE) is a severe and common clinical problem with substantial morbidity and mortality both in US and in Europe. Used to be considered as a rare disease in China, PTE has been increasingly diagnosed in recent years due to the increased awareness and the improvement of imaging techniques. PTE is life threatening without proper intervention at the early onset. Effective treatment can decrease the mortality and the complication of chronic thromboembolic pulmonary hypertension (CTEPH).

Recombinant tissue-type plasminogen activator (rt-PA) is currently the most commonly used drug for PTE thrombolysis. Like most thrombolytic medications, rt-PA carries a risk of significant bleeding, which is dose dependent. Thus, optimal dosing that can maximize benefits and minimize risks is of great importance. There is substantial controversy and debate regarding the optimal rt-PA dosage for thrombolytic therapy and whether the same dose should be used in all patients. Low dose of intravenous rt-PA for thrombolysis after acute myocardial infarction (AMI) had been suggested by previous studies. Experimental and clinical studies have indicated that a lower dose of rt-PA bolus may be potentially safer, and yet equally effective then the 2-h 100 mg rt-PA continuous infusion for PTE.

Considering lower body weight in Chinese population, a lower dose of 50mg rt-PA/2h may exhibit similar efficacy and safety as 100mg/2-h rt-PA for treating acute PTE in this population. We, therefore, compared these two regimens in a multi-center, randomized, controlled trial. The efficacy was assessed by the improvement of the right ventricular function on echocardiograms, perfusion defect score of lung V/Q scans or quantitative computed tomographic (CT) evaluation, safety was evaluated by incidence of major or minor bleeding, death rate, and PTE recurrence on 24h,14d after treatment.

110 patients will be randomized in the study. The patients included in the study will be randomized, in a double blind fashion, to receive rt-PA 100mg 2h (55 patients) or rt-PA50mg 2h(55 patients).Study treatment should be administered within 72 hours from echocardiography. Echocardiography will be repeated at 24 hours and 14 days from rt-PA injection. A Follow-up visit at 14 days from randomization will include: clinical history, physical examination and ECG and an echocardiographic examination CTPA and V/Q scan.