Rationale:
Patients with acute pulmonary embolism (PE) and an intermediate risk constellation show signs of myocardial damage and right ventricular dysfunction in biomarkers and cardiac imaging with (still) existing hemodynamic stability. An individualized therapeutic approach in those patients adapted to risk stratification as well as detection of an imminent acute decompensation is not existing. The aim of this prospective, descriptive "single-center/single-arm" study was to evaluate the effectiveness and safety of interventional mechanical thrombectomy using the FlowTriever system (Inari Medical, California) in patients with acute PE and an intermediate risk constellation.

Methods:
Patients with symptomatic, CT pulmonary angiogram confirmed acute PE who had imaging signs of right ventricular distress and elevated cardiac biomarkers were treated with interventional mechanical thrombectomy using the FlowTriever system after evaluation by the in-house PE-response team. Endpoints were procedural success in terms of a decrease in pulmonary artery (PA) pressure, oxygen demand and normalization of oxygen saturation and heart rate, as well as periprocedural safety with regard to device- or access route-associated complications, blood loss and post-interventional renal function.

Results:
In the first observation period between 07/2021 and 05/2022, a total of 19 patients with acute pulmonary artery embolism and an intermediate risk constellation were treated with the FlowTriever system. A remarkable procedural success was shown in terms of a significant decrease in the invasively measured systolic PA pressure (56 mmHg to 45 mmHg), periprocedural normalization of oxygen saturation (91.7% to 97%) with a simultaneous reduction in oxygen demand (5.1 l to 1.9 l) and normalization of the heart rate (97/min to 90/min). Furthermore, a normalization of cardiac biomarkers and the clinical condition could be documented in the short term.

Conclusion:
Interventional mechanical thrombectomy using the FlowTriever system is highly effective and safe to use in patients with acute PE and intermediate risk. Clinical benefits and a significant reduction in PA pressure, oxygen demand and heart rate are directly evident periprocedurally. In particular, patients with an intermediate high risk, pronounced symptoms and imminent decompensation as well as patients with contraindications for pharmacological lysis therapy can be offered an innovative and effective therapy. Further prospective, randomized and controlled trials with regard to possible advantages in terms of mortality and subsequent morbidity are urgently needed.