Reduced Dose Bolus Alteplase vs Conventional Alteplase Infusion for Pulmonary Embolism Thrombolysis

An International Multicenter Randomized Trial

Study objective: To test the hypothesis that a reduced dose of bolus recombinant human tissue-type plasminogen activator (rt-PA) (0.6 mg/kg/15 min, maximum of 50 mg) would result in fewer bleeding complications than standard 100 mg of rt-PA administered as a continuous infusion over 2 h among hemodynamically stable patients with pulmonary embolism (PE). Subsidiary objectives were to compare the two rt-PA regimens with respect to the following: (1) the rate of other adverse clinical events; (2) the magnitude of change from baseline on perfusion lung scans, pulmonary angiograms, or echocardiograms; and (3) the differences in coagulation parameters over time.

Design: A double-blind, double-dummy, randomized, controlled trial.

Setting: Twenty-eight participating hospitals in the United States, Italy, and Canada.

Patients: Patients could be included if they had symptoms or signs of PE within 14 days of presentation as well as high-probability lung scans and/or pulmonary angiograms demonstrating PE.

Interventions: Randomization was undertaken with a 2:1 allocation ratio to rt-PA 0.6 mg/kg/15 min (maximum of 50 mg) or to 100 mg/2 h. Ninety patients were randomized, and 87 patients were treated: 60 with bolus rt-PA and 27 with 2-h rt-PA. All patients underwent baseline and 20- to 28-h follow-up perfusion lung scintigraphy. Patients at angiogram centers underwent baseline and 2-h follow-up angiography, while patients at echocardiogram centers underwent baseline, 3-h, and 20- to 28-h echocardiography. Forty-eight patients also participated in an ancillary study of serial fibrinogen and fibrin degradation product levels.

Results: In the first 14 days after randomization, there were six deaths: five (8.3 percent) in the bolus group vs one death (3.7 percent) in the 2-h group (p=0.66). There were two clinically suspected nonfatal recurrent PEs during the first 14 days after therapy, one in each treatment group. Overall, 14 patients suffered major or other important bleeding: 8 in the bolus group and 6 in the 2-h group (p=0.35). Changes in efficacy parameters (scans, angiograms, or echocardiograms) were similar in the two treatment groups. After initiation of therapy, patients who had received bolus rt-PA had less depression of fibrinogen levels (p=0.007) and smaller increases in fibrinogen degradation products (p=0.013) than patients who had received 100 mg of rt-PA over 2 h.

Conclusions: No significant differences were detected between the bolus rt-PA and 2-h rt-PA with respect to bleeding complications, adverse clinical events, or imaging studies. There was less fibrinogenolysis with the bolus dosing regimen.

Key Words: alteplase • bolus alteplase • bolus thrombolysis • pulmonary embolism • thrombolysis • tissue plasminogen activator

Submitted on February 4, 1994
Accepted on April 25, 2007

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