Abstract

Submassive pulmonary embolism (PE) is common and depending on the degree of hemodynamic compromise can carry a 25-65% mortality. The mainstay of treatment is fibrinolytic therapy, although data is limited and based on several small randomized controlled trials that enrolled less than 800 patients in total. A meta-analysis of these trials revealed fibrinolysis is at best moderately effective and does not consistently lower mortality in the setting of massive PE.¹ Furthermore, contraindications are common that would leave a large portion of patients untreated if no other treatment modalities are explored. Similar to the failure of fibrinolytics in the setting of cardiogenic shock in an acute myocardial infarction, presumably from the inability to deliver an adequate dose of the drug to the site of thrombus; they may also fail in patients with PE due to circulatory shock. Alternative treatment modalities in this setting include surgical embolectomy which is logistically difficult. Furthermore, patients are commonly believed to be too sick for surgery because of common comorbid conditions. Other alternatives include catheter based thrombectomy or fragmentation of the thrombus, which has been performed for 40 years. Success is variable, complications are common, and, aside from case series, no solid data is available to support routine use of this technique. Finally, assuming fibrinolytics are generally effective, yet peripherally administered agents may not reach the thrombus at high enough concentrations, it only seems intuitive to attempt local delivery of the fibrinolytic agent to where the thrombus is present.