A new review article highlights approaches for mechanical circulatory support in patients with high-risk acute pulmonary embolism (PE).
Pulmonary embolism with hemodynamic significance is widely underdiagnosed, and the mortality rate can be as high as 30%, but new therapeutic developments offer promise. “Over the past few years, a renewed interest in mechanical circulatory support (MCS; both percutaneous and surgical) for acute RVF has emerged, increasing viable treatment options for high-risk acute PE,” wrote the authors of the review, which was published online in Interventional Cardiology Clinics.
Poor outcomes are often driven by RVF, which is tricky to diagnose and manage, and it stems from a sudden increase in pulmonary vascular resistance (PVR) following PE. “The mechanism for increased PVR in acute PE is multifactorial, including direct blood flow impedance, local hypoxia-induced vasoconstriction, and platelet/thrombin-induced release of vasoactive peptides. The cascade of events that then leads to RVF includes decreased RV stoke volume, increased RV wall tension, and RV dilation,” the authors wrote.
The authors noted that diuretics help to correct changes to RV geometry and can improve left ventricle filling, which improves hemodynamics. Diuretics can be used in patients who are hypotensive and volume overloaded, but vasopressors should be employed to support blood pressure.
When using mechanical ventilation, strategies such as low tidal volumes, minimization of positive end expiratory pressure, and prevention of hypoxemia and acidemia should be employed to prevent an increase of pulmonary vascular resistance, which can worsen RV failure.
Pulmonary vasodilators aren’t recommended for acute PE, but inhaled pulmonary vasodilators may be considered in hemodynamically unstable patients.
Surgically implanted right ventricle assistance device are generally not used for acute RV failure in high-risk PE, unless the patient has not improved after medical management.
Percutaneous devices
Percutaneous mechanical circulatory support devices can be used for patients experiencing refractory shock. The review highlighted three such devices, including the Impella RP, tandem-heart right ventricular assist devices (TH-RVAD) or Protek Duo, and venoarterial extracorporeal membrane oxygenation (VA-ECMO), but they are not without limitations. “Challenges to using these devices in patients with acute PE include clot dislodgement, vascular complications, infections, device migration, and fracture of individual elements,” the authors wrote.
The Impella RP is easy to deploy and bypasses the RV, but it can’t provide blood oxygenation and may cause bleeding or hemolysis. TH-RVAD oxygenates the blood and bypasses the RV, but suffers from a large sheath size. VA-ECMO oxygenates the blood but may cause bleeding.
There are important differences among the mechanical support devices, according to Jonathan Ludmir, MD, who was asked to comment. “In reality, if someone has a large pulmonary embolism burden, to put in the Impella RP or the Protek Duo would be a little bit risky, because you’d be sometimes putting the device right where the clot is. At least what we do in our institution, when someone is in extremis despite using [intravenous] medications like vasopressors or inotropes, VA-ECMO is kind of the go to. This is both the quickest and probably most effective way to support the patient. I say the quickest because this is a procedure you can do at the bedside.”