A discussion this week included the management of massive and submassive pulmonary embolism (PE).
Reference: Aggarwal V, et al. Acute management of pulmonary embolism. American College of Cardiology. 2017 Oct 24.
Summary: The severity of PE is stratified into massive (PE causing hemodynamic compromise), submassive (PE causing right ventricular dysfunction demonstrable by echocardiography, computed tomography or elevated cardiac biomarkers) and non-massive or low-risk (PE without evidence of RV dysfunction or hemodynamic compromise). The International Cooperative Pulmonary Embolism Registry (ICOPER) demonstrated 90-day mortality rates of 58.3% in patients with massive PE versus 15.1% in sub-massive PE.
Anticoagulation therapy is the primary treatment option for most patients with acute PE. The utilization of factor Xa antagonists and direct thrombin inhibitors, collectively termed Novel Oral Anticoagulants (NOACs) are likely to increase as they become incorporated into societal guidelines as first line therapy.
Inferior vena cava filters
The role of inferior vena cava filters (IVCF) in the contemporary management of acute VTE has not been truly defined owing to a paucity of high quality evidence. At present the benefit of IVCF use seems to be in reducing the risk of acute PE in patients who have a clear contraindication to anticoagulation in the form of active bleeding.54,55 In the absence of such a contraindication there appears to be no clear benefit and non-retrieval of IVCF exposes the patient to risk of recurrent VTE, PTS and other mechanical complications such as filter fracture or migration.
Percutaneous Mechanical Thrombectomy (PMT) for Massive and Submassive Acute PE
Several percutaneous approaches have been used alone or in combination in patients with an absolute contraindication to thrombolysis: thrombus fragmentation, aspiration thrombectomy, rheolytic thrombectomy, and suction embolectomy.
Caution must be exercised during the placement of all catheters into the pulmonary arterial circulation. Ensuring proper positioning is vital in order to prevent the risk of catastrophic vessel injury as well as distal embolization of thrombus when using high-pressure injection systems. For this reason, the American College of Cardiology (Aggarwal et al, 2017) advocate the use of available computed tomography to help guide the optimal placement of any drug delivery system. Suction embolectomy devices such as the Greenfield catheter benefit from being large bore catheters capable of achieving thrombus removal without the side effects associated with fragmentation and rheolytic techniques. Despite this, technical difficulties related to catheter size have precluded its widespread adoption.
Ultrasound-Assisted CDT (UA-CDT) for Acute PE
For patients without an absolute contraindication to systemic thrombolysis, UA-CDT can be considered. Low energy ultrasound disaggregates fibrin within acute thrombi, this is exploited by the EKOS device (EkoSonic, Bothell, WA), which combines emission of low energy ultrasound and infusion of a thrombolytic agent via a multi side-hole containing catheter. This strategy has been evaluated in the ULTIMA (Ultrasound-Assisted, Catheter-Directed Thrombolysis for Acute Intermediate-Risk Pulmonary Embolism) trial, which demonstrated superiority to anticoagulation alone in improving hemodynamics without a significant increase in bleeding complications.