Low-Dose Thrombolysis Improves Outcomes in Submassive PE
A small prospective, randomized trial finds low-dose TPA is safe and effective for treating moderate-sized pulmonary embolism.
Concern about intracranial hemorrhage limits the use of tissue plasminogen activator (TPA) in the treatment of submassive pulmonary embolism (PE). Researchers prospectively randomized 121 adults with symptomatic moderate PE to receive "safe dose" TPA plus anticoagulation with heparin or enoxaparin (thrombolysis group) or anticoagulation alone (control group).
"Safe dose" TPA was defined as 50 mg administered as a 10-mg bolus followed by a 40-mg infusion within 2 hours (or 0.5 mg/kg total dose for patients weighing <50 kg). Moderate PE was defined as >70% involvement of thrombus in at least two lobes or left or right main pulmonary arteries shown on angiography, or a high probability ventilation/perfusion scan showing mismatch in at least two lobes.
At a mean follow-up of 28 months, 58 of 61 patients in the thrombolysis group and 56 of 60 in the control group were available. Pulmonary hypertension was present in 16% of the thrombolysis group and 57% of the control group, and the composite endpoint of pulmonary hypertension and recurrent PE occurred in 16% and 63% of patients, respectively. Mean hospital length of stay was shorter in the thrombolysis group (2.2 vs. 4.9 days). There were no significant differences in mortality or bleeding complications between groups.
Comment: Because the lungs are the only organs that receive the entire cardiac output, it makes sense that concentrations of a fibrinolytic agent sufficient for effective lysis could be achieved in the pulmonary circulation with a lower total dose of TPA than is required for systemic lysis. Based on the findings of this randomized trial, "safe-dose" thrombolysis with TPA is a reasonable option for symptomatic patients with submassive PE.
Published in Journal Watch Emergency Medicine February 1, 2013
Sharifi M et al. Moderate pulmonary embolism treated with thrombolysis (from the "MOPETT" trial). Am J Cardiol 2013 Jan 15; 111:273. (http://dx.doi.org/10.1016/j.amjcard.2012.09.027)
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