Key Points:
- Mortality in high-risk PE remains unacceptably high (25%) despite advances in medical and interventional therapies.
- The FLAME study was a prospective, multi-center non-randomized observational study to describe the outcomes of patients undergoing mechanical thrombectomy and other modern therapies and generate evidence in high-risk PE. The primary outcome was a composite of all-cause mortality, bailout to alternate thrombus removal strategy, clinical deterioration, and major bleeding.
- Compared with a pre-established performance goal of 32%, patients treated with Flowtriever had a significant reduction in the primary endpoint. There was also significant reduction in in-hospital mortality (1.9% compared to 28.5%). There was no increase in adverse events in the FlowTriever group.
- Randomized evidence will be required to follow-up this observational study, but FlowTriever appears to be a safe, effective treatment which may reduce mortality in high-risk PE.
Mortality in high-risk pulmonary embolism (PE) has unfortunately remained stagnant at 25% over the past 20 years; this high mortality is felt to be driven by RV failure. Systemic thrombolysis is generally indicated based on limited data, but it is associated with high bleeding risk. Developing an RCT in this patient population has been challenging due to the high illness severity and difficulty with randomization. In a breaking presentation at the 2023 ACC Conference today, Dr. Mitchell J. Silver (OhioHealth Heart and Vascular) and his team presented their study: “Outcomes in High-risk Pulmonary Embolism Patients Undergoing FlowTriever Mechanical Thrombectomy,” or the FLAME study.
The FLAME study (NCT04795167) was designed as a prospective, multi-center non-randomized observational study to describe the outcomes of patients undergoing mechanical thrombectomy and other modern therapies and generate evidence in high-risk PE. Therapies were physician-dictated. Enrollment was conducted in a concurrent, non-randomized fashion; patients with high-risk PE were followed through discharge or for 45 days. The three arms included the FlowTriever arm, the Context arm (including non-FlowTriever therapies for PE), and Prior Therapy (including patients who were treated with advanced therapies who subsequently developed high-risk PE). The inclusion criteria comprised any adults with high-risk PE with PE-related shock. The exclusion criteria included: OHCA with GCS<8, cardiac arrest with ongoing CPR >30 minutes, contraindication to anticoagulation, and either intracardiac thrombus or clot-in-transit.
A total of 53 FlowTriever patients and 61 Context patients were examined. In the FlowTriever arm, the average age was 65, and 49% were women. 42% had a contraindication to thrombolysis and 92.5% had a central PE. In the Context arm, the majority (69%) had systemic thrombolysis, 23% had anticoagulation alone, and the remainder had other mechanical interventions. The primary outcome was a composite of all-cause mortality, bailout to alternate thrombus removal strategy, clinical deterioration, and major bleeding; the primary endpoint was compared to a performance goal of 32% which was established from a meta-analysis. A pre-specified interim analysis was planned at 50 FlowTriever patients enrolled. In the Flowtriever arm, the primary endpoint occurred in 17% of patients, which was significantly lower than the pre-specified performance goal (p<0.01). The Context arm had a primary composite rate of 64%. On secondary outcome analysis, the FlowTriever arm had an in-hospital mortality of 1.9% compared to the 28.5% performance goal and 29.5% in the Context arm. The FlowTriever arm had no reports of device-related tricuspid valve injuries, cardiac injuries, or pulmonary vascular injuries. 1.9% of patients suffered a stroke (compared to 6.6% in the Context arm). 22.6% had a device-related complication, which was predominantly hemoglobin decrease or anemia. 30.2% had a serious adverse event compared to 60.7% in the Context population.
When discussing the clinical implications of the study at ACC, Dr. Silver stated: “Large-bore mechanical thrombectomy with the FlowTriever device likely reduces mortality in high-risk PE patients by rapidly unloading the RV…and quickly reverses the shock-death spiral and simultaneously improves oxygenation…a care pathway similar to STEMI and stroke may benefit PE patients.”
