Background: Various interventional treatments for pulmonary embolism are under clinical investigation. This study aimed to assess the haemodynamic effects of transcatheter mechanical thrombectomy in acute pulmonary embolism (PE) with right heart overload.

Methods: In this prospective, open-label study, patients with acute symptomatic, computed tomography-documented PE with signs of right heart overload underwent catheter-based mechanical thrombectomy using the FlowTriever System. Right heart catheterization was performed immediately before and after thrombectomy and after three months. Transthoracic echocardiography was performed before thrombectomy, prior to discharge, and at three months. This analysis was done after the first 20 patients completed their three months of follow-up.

Results: From April 2021 to October 2022, 34 patients (38% female) underwent mechanical thrombectomy, of which 19 patients underwent right heart catheterization at three months. Most patients were at high (4/33, 12%) or intermediate-high (27/33, 82%) risk. Most patients (27/34, 79%) had bilateral pulmonary embolisms. The mean procedural time was 69 minutes (interquartile range [IQR]: 61-90), median intensive care unit stay was 2 days (interquartile range [IQR]: 1, 4). Prior to thrombectomy, systolic (sPAP) and mean pulmonary artery pressures (mPAP) were severely elevated (sPAP: 51.4±9.5 mmHg; mPAP: 29.7±9.1 mmHg). On table, mean sPAP and mPAP dropped by -13.7 mmHg (95% confidence interval [CI]: -17.2 to -10.2; p<0.001; n=31) and -7.6 mmHg (95% CI: -9.9 to -5.3; p<0.001; n=32), respectively (Figure). From post-thrombectomy to three months, mean sPAP (-6.0 mmHg, 95% CI: -9.7 to -2.3; p=0.003; n=17) continued to decrease. Systolic blood pressure increased by 7.5 mmHg (95% CI: 0.3 to 14.8; p=0.0426; n=33), and heart rate decreased by -15.4 b.p.m. (95% CI: -21.5 to -9.4; p<0.001; n=33) on table. Right ventricular/left ventricular ratio reduction was -0.33 (95% CI: -0.43 to -0.23; p<0.001; n=25). TAPSE increased from 16.4±6.2 mm pre-procedure to 19.9±3.9 mm before discharge (mean change: +3.5 mm; 95% CI: 1.3 to 5.7; p=0.003; n=24). There were no procedure-related major adverse events.

Conclusions: In PE with right heart overload, mechanical thrombectomy was safe and immediately reduced pulmonary artery pressures (PAP) and improved right heart function. The reduction in PAP was maintained at three months follow-up.