Background.

Pulmonary embolism is a common cause of acute right heart failure. Thrombolysis not always is successful or may be contraindicated. According to current guidelines, extracorporeal membrane oxygenation (ECMO) may be considered in patients with refractory circulatory collapse or cardiac arrest. Yet, ECMO carries a substantial risk of bleeding, especially after lysis, and not always restores sustained hemodynamic stability. Surgical pulmonary embolectomy in this situation is recommended, but the complication rates are high. Therefore, there is a need for less invasive therapies. The Inari FlowTriever® is a large‐bore (up to 24 French) aspiration mechanical thrombectomy device, which allows both extraction and detachment of pulmonary emboli.

Methods.

Consecutive patients with massive central pulmonary embolism were included in this prospective observational trial if they had right heart failure with refractory cardiac shock and emergency implanted veno-arterial ECMO. The femoral vein was sonographically imaged before puncture to avoid additional thrombus mobilization. The 24-French Triever Aspiration Catheter was used in all patients. A maximum of 7 aspiration attempts (max. 420 ml blood loss) were performed until angiographic reperfusion of the central pulmonary arteries. In case of three unsuccessful aspiration attempts, the FlowTriever catheter with three self-expanding nitinol mesh disks designed to engage, disrupt, and deliver the clot to the aspiration catheter was also used. When a "lollipop" was stuck on the aspiration catheter, ECMO flow was briefly reduced during retrieval to prevent thrombus aspiration by the ECMO. Anticoagulation was continued during and after the procedure, and the venous puncture was closed with a Z-suture.

Results.

Four patients (3 males, mean age 57 ± 2 years) presented with central pulmonary embolism and, in each case, leading (sub-)total occlusion of the left pulmonary artery. Three of them had been resuscitated. One had received ineffective intravenous thrombolysis, whereas this was contraindicated in the other patients.

Immediately after thrombus extraction, mean pulmonary arterial pressure dropped from 43 ± 6 mmHg to 20 ± 4 mmHg. Right ventricular end-diastolic diameter decreased from 53 ± 7 mm to 38 ± 5 mm and tricuspid annular plane systolic excursion increased from 13 ± 2 mm to 17 ± 2 mm. Mean lactate dropped from 55 ± 17 mg/dl to 7 ± 1 mg/dl within twelve hours after the procedure. Catecholamines were rapidly reduced in all patients, and ECMO was explanted after an average of 61 ± 16 hours. No procedure-associated deterioration or complications occurred and all patients could be discharged from the ICU in hemodynamically and respiratory stable condition after 10 ± 2 days. All patients were discharged from the hospital in stable general condition.

Conclusion

With this proof of concept series, we provide a new strategy for the treatment of very high-risk pulmonary embolism in patients on VA-ECMO with persisting right ventricular failure, which has been an unmet need before. FlowTriever® large‐bore mechanical aspiration can be safely applied in this collective of critically ill patients and resulted in discharge without procedure-related complications.