Submassive Pulmonary Embolism: Risk Evaluation and Role of Fibrinolysis

Submassive pulmonary embolism (PE) is characterized by hemodynamic stability with evidence of right ventricular dysfunction or myocardial necrosis, and represents a heterogeneous population at risk for adverse outcomes. Although patients with this subtype of PE are at higher risk of death, it is unclear whether escalation of care with fibrinolytic therapy mitigates this risk. The controversial role of fibrinolytic therapy for submassive PE is driven by a paucity of data, conflicting results from clinical trials, and lack of reliable positive predictive markers of mortality in this population. When compared with anticoagulation therapy alone, systemic fibrinolytic therapy leads to a more rapid improvement in pulmonary artery hemodynamics, restoration of right ventricular function, improved lung perfusion, and fewer episodes of clinical deterioration. The clinical significance of these findings remains uncertain because fibrinolytic therapy has not been demonstrated to improve mortality or reduce recurrent PE in patients with submassive PE. However, it is unclear whether this reflects methodological limitations such as small sample size and rescue fibrinolytic therapy in those assigned placebo, the absence of benefit in all patients with submassive PE, or the benefit is limited to an undefined, high-risk subset. The decision to administer adjunctive fibrinolytics in patients with submassive PE should be made on an individual basis, with serious consideration given to those with severe PE-related clinical manifestations and an acceptable risk of bleeding.