Massive and Submassive Pulmonary Embolism: Diagnostic Challenges and Thrombolytic Therapy

Abstract

Pulmonary embolism (PE) remains a vexing entity as it offers both diagnostic and management challenges and has a high potential for lethality. The mortality rate for PE in hemodynamically stable patients has been estimated as below 5%, but when accounting for all patients, the International Cooperative Pulmonary Embolism Registry reports a 90-day mortality of 17.4%.1 Those patients with massive and submassive PE account for the increased mortality. Massive PE is defined by hemodynamic instability, which is a function of both embolus size and underlying cardiopulmonary status. Its diagnosis requires 1) sustained hypotension (systolic blood pressure below 90 mm Hg for at least 15 minutes or the need for inotropic support), 2) pulselessness, or 3) profound bradycardia (American Heart Association guidelines). Any combination of angiographic obstruction and cardiopulmonary function that causes hemodynamic decompensation qualifies as a massive PE.2 Submassive PE is characterized by a large clot burden without hemodynamic instability, but with signs of right ventricular dysfunction or evidence of myocardial necrosis. The diagnostic strategy for massive PE differs from nonmassive PE. The patient's hemodynamic compromise makes traditional diagnostic modalities (D-dimer, lower extremity ultrasound, computed tomography, etc.) problematic, as delaying treatment while awaiting testing may lead to further decompensation. Point-of-care echocardiography represents a more rapid approach to augment clinical evaluation and thus expedite treatment. Heparin (fractionated or unfractionated) represents the current emergent treatment of choice for PE diagnosed in the emergency department (ED). However, heparins function by preventing further clot formation and propagation while allowing the body's natural lytic systems to dissolve the clot that is present. Patients with massive PE are unlikely to benefit from heparin and may require more expeditious clot lysis. While thrombolytics have an established role in acute ST-elevation myocardial infarction, their role in the treatment of massive and submassive PE is more controversial. While recent studies have not shown significant mortality benefits with thrombolytics, they have shown improvements in long-term functional outcomes (e.g., exercise tolerance). This lecture endeavors to investigate ED echocardiography to diagnose massive and submassive PE and the role of thrombolytics in these critical diseases. Video is available at https://vimeo.com/73812907