Large-bore mechanical thrombectomy for intermediate- and high-risk pulmonary embolism: interim outcomes from the European cohort of the FLASH registry

Abstract Background/Introduction Mechanical thrombectomy is utilized for the treatment of acute pulmonary embolism (PE), but reported outcomes are limited in the European patient population. Purpose To report interim results from the European cohort of a large, prospective all-comer registry of mechanical thrombectomy for PE treatment. Methods The FLASH registry is a multinational, prospective, observational study of safety and effectiveness outcomes for PE treatment using a large-bore mechanical thrombectomy system. FLASH is currently enrolling up to 200 patients in Europe. The primary endpoint is a composite of Major Adverse Events (MAEs) within 48 hours, including device-related deaths, major bleeding, and intraprocedural AEs. Additional assessments include invasive hemodynamics, hospital resource usage, and dyspnea improvement. Results Interim results through 48 hours post-thrombectomy are presented for the first 29 patients enrolled in the European cohort across 4 institutions. Mean patient age was 64.9±14.5 years, 51.7% of patients were male, 10.3% were contraindicated for thrombolysis, 51.7% had concomitant deep vein thrombosis, and 79.3% had centrally located thrombus involving one or both main pulmonary arteries. Per ESC guidelines, 58.6% of patients were classified as high-risk. The remaining 41.4% of patients were classified as intermediate-risk, with 31.0% being intermediate-high-risk. Pre-thrombectomy, the median RV/LV ratio from a composite of computed tomography and echocardiography was 1.31 [IQR: 1.08-1.44], and 38.9% of patients who had cardiac index (CI) measured were in cardiogenic shock (CI ≤2 L/min/m²). Procedural characteristics included a median thrombectomy time of 39 minutes [IQR: 26-49]. Extracorporeal membrane oxygenation was used in 6.9% of patients. Post-thrombectomy, the median length of stay in the intensive care unit (ICU) was 1 overnight [IQR: 0-2], and 48.1% of patients required no overnight ICU stay. In addition, hemodynamic variables, vitals, dyspnea symptoms, and reliance on supplemental oxygen all improved significantly post-thrombectomy (Table 1). Acute safety and mortality outcomes were highly favorable following the procedure (Table 2). All patients survived through 48 hours post-thrombectomy. There were no MAEs (0%), no major access site complications (0%), and no device-related Serious AEs (0%) through 48-hour follow-up. Conclusions Interim results from the first 29 patients in the European cohort of the FLASH registry suggest that large-bore mechanical thrombectomy can be safely performed in both intermediate- and high-risk PE patients, with no MAEs or mortalities observed through 48 hours. Significant improvements observed in multiple hemodynamic and dyspnea-related variables further suggest that thrombectomy can offer effective reperfusion treatment for acute PE.