Introduction
Acute pulmonary embolism (PE) can be stratified as high-risk or massive PE, intermediate-risk or submassive PE, and low-risk or non-massive PE, with nearly 300,000 deaths per year attributable to PE1. Right ventricular dysfunction (RVD) and the presence of hemodynamic instability are powerful predictors of poor prognosis of patients with acute PE2. In particular, patients with acute high-risk PE defined as cardiogenic shock and systemic hypotension, are at particularly increased risk of early death, and require emergency treatment to restore circulation. Overall, in-hospital mortality rates for massive PE range from 25% for patients with cardiogenic shock (CS), to 65% for those that required cardiopulmonary resuscitation (CPR), while in-hospital mortality rate in stable patients with PE was 8.1% 3.
Although systemic anticoagulation remains the cornerstone of therapy for acute symptomatic pulmonary embolism, the morbidity and mortality associated with high-risk PE and intermediate-high risk PE warrant treatment beyond anticoagulation alone. More aggressive therapeutic options include systemic intravenous thrombolysis (Class IB), surgical embolectomy (Class IC) and catheter-directed thrombolysis needed (CDT) (Class IIa) according to European Society of Cardiology guidelines4.
However, the clinical course of high-risk PE can rapidly progress before surgical or catheter-directed treatment. Many patients are not amenable to reperfusion therapies or fail to improve after these treatments due to major hemodynamic instability and cardiogenic shock. Based on the ICOPER Registry, two-thirds of patients with massive PE did not receive any thrombolysis or surgical embolectomy5. For those patient group, veno- arterial extracorporeal membrane oxygenation (VA-ECMO) is one of the most reliable and quickest way to decrease RV overload, improve RV function and hemodynamic status, restore tissue oxygenation and may be considered as either a bridge to reperfusion therapy such as surgical embolectomy or CDT6.
The general aim of catheter-directed therapy in the setting of hemodynamically compromised patients with acute PE is to debulk and/or redistribute the obstructive clot rendering it less hemodynamically significant. In recent years, interest has risen in a variety of endovascular strategies based on catheter-based technologies for thrombus removal in patients with high-risk PE. The EKOS EkoSonic Endovascular System (EKOS, Boston Scientific, USA) is a catheter-based system that uses high frequency, low-energy ultrasound waves to aid in the delivery and uptake of thrombolytic agent within the clot.
Existing data regarding the utility of ECMO in the setting of high-risk PE mainly come from case reports or small series(6-8). The impacts of VA-ECMO in conjunction with EKOS acoustic pulse thrombolysis (APT) on survival have not been investigated in massive PE. Therefore, we present a serie of patients with high risk PE showing hemodynamic collapse that required cardiopulmonary resuscitation, who were successfully treated with VA-ECMO as an adjunct to APT.