Comparing Three Catheter Aspiration Strategies for Intermediate-High-Risk Acute Pulmonary Embolism

Background Acute pulmonary embolism (PE) is the third leading cause of cardiovascular death worldwide. Patients with intermediate-high-risk PE are haemodynamically stable but have imaging evidence of right ventricular dysfunction and elevated cardiac biomarkers, and remain at risk of early clinical deterioration. Anticoagulation alone may be insufficient to reduce thrombus burden, whereas systemic thrombolysis carries a substantial risk of major bleeding. Percutaneous catheter-based therapy has therefore become an important treatment option. Current aspiration catheters fall into two categories: small-bore systems (8-12 F), which are highly trackable into distal pulmonary artery branches but less efficient at removing large central thrombus, and large-bore systems (16 F or larger), which remove central thrombus efficiently but may be difficult to advance into distal vessels. A combined strategy, using a large-bore catheter first for central thrombus and a small-bore catheter subsequently for residual distal thrombus, is used in clinical practice, but its safety and effectiveness have not been systematically evaluated in a prospective study.

Objective This multicentre prospective observational cohort study will compare the safety and short-term effectiveness of three catheter-based aspiration strategies in adults with intermediate-high-risk acute PE: small-bore aspiration alone, large-bore aspiration alone, and combined large-bore plus small-bore aspiration.

Study design

Consecutive patients scheduled to undergo percutaneous catheter aspiration thrombectomy as part of routine care at five participating hospitals in China are screened and enrolled after providing written informed consent. Participants are assigned to one of three cohorts according to the catheter strategy actually used during the index procedure; the strategy is selected by the treating physician according to routine clinical practice and is not allocated by the study protocol.

Data collection Baseline demographic, clinical, laboratory, CTPA, and echocardiographic data are collected before the procedure. Procedural data include angiographic findings, technique used, procedure and fluoroscopy times, and intraoperative blood loss. Clinical assessments are performed at 24 hours, 48 hours, and 7 days (or before discharge), with follow-up visits (clinic or telephone) at 30 +/- 7 days and 90 +/- 14 days. All imaging and laboratory tests are performed as part of standard care; the study requires no additional invasive procedures or examinations.

Co-primary endpoints

(1) The composite rate of major adverse events within 7 days after the procedure. (2) The change in the right ventricular to left ventricular (RV/LV) diameter ratio on CTPA from baseline to 48 hours after the procedure, measured by an independent core laboratory.

Statistical analysis Approximately 225 participants will be enrolled (about 75 per cohort). The co-primary effectiveness endpoint will be analysed by analysis of covariance adjusted for baseline RV/LV ratio; the composite safety endpoint will be analysed using logistic regression or Cox proportional hazards models. Non-inferiority of the combined strategy versus large-bore aspiration alone will be assessed for the composite major adverse event endpoint, with a pre-specified non-inferiority margin of 8%, together with a superiority assessment for the change in RV/LV ratio. Baseline imbalances will be addressed by multivariable regression and, as sensitivity analyses, by propensity score matching or inverse probability of treatment weighting. Subgroup analyses by risk category, thrombus distribution, age, sPESI, and VTE-BLEED score, and multiplicity adjustment using Bonferroni or Benjamini-Hochberg methods, are pre-specified. Missing primary endpoint data will be handled by multiple imputation. An independent data and safety monitoring board will perform an interim safety review when 50% of the planned enrolment is reached.

Expected impact The results are expected to inform clinical selection of aspiration catheter size and strategy in intermediate-high-risk acute PE, and to support standardisation of percutaneous interventional management.