Pulmonary embolism (PE) is a potentially life-threatening condition caused by the obstruction of pulmonary arteries by thrombi. Patients with high-risk or intermediate-high-risk PE may require immediate reperfusion therapies, including percutaneous pulmonary thrombectomy. However, this procedure can be associated with significant hemodynamic and respiratory instability, potentially leading to shock, cardiac arrest, or the need for advanced support such as mechanical ventilation or extracorporeal membrane oxygenation (ECMO).

The mechanisms, timing, and causes of intraprocedural hemodynamic and respiratory deterioration during pulmonary thrombectomy are not well established. Factors such as catheter manipulation within the pulmonary arteries, increased pulmonary pressures, and the effects of anesthesia and mechanical ventilation may contribute to clinical instability. In addition, biomarkers such as NT-proBNP may reflect right ventricular strain and could help predict the risk of instability during the procedure.

The aim of this prospective observational study is to determine the incidence, causes, and timing of hemodynamic and/or respiratory instability during percutaneous pulmonary thrombectomy in patients with high-risk or intermediate-high-risk PE. The study will also compare the occurrence of instability between different thrombectomy devices (FlowTriever® and Indigo® systems) and evaluate the prognostic role of baseline NT-proBNP levels. Secondary objectives include the assessment of in-hospital and 30-day mortality and their underlying causes.

This study will include adult patients undergoing percutaneous pulmonary thrombectomy as part of routine clinical care. The results of this study may help improve risk stratification, guide procedural planning, and optimize the management of patients undergoing pulmonary thrombectomy, ultimately aiming to reduce morbidity and mortality.

Pulmonary embolism (PE) is a major cause of cardiovascular morbidity and mortality worldwide and represents the third leading cause of cardiovascular death. Patients with high-risk or intermediate-high-risk PE may develop significant hemodynamic compromise due to acute right ventricular overload and impaired pulmonary circulation. While anticoagulation remains the cornerstone of treatment, reperfusion therapies are recommended in selected patients, including systemic thrombolysis, catheter-directed therapies, and surgical embolectomy.

Percutaneous pulmonary thrombectomy has emerged as an increasingly used reperfusion strategy, particularly in patients with contraindications to thrombolysis or in whom rapid hemodynamic improvement is required. Despite its growing use, the intraprocedural course of these patients is not fully understood. During thrombectomy, mechanical manipulation within the pulmonary arteries, transient increases in pulmonary vascular resistance, and the effects of anesthesia and positive pressure ventilation may contribute to hemodynamic and respiratory instability. These complications may manifest as hypotension, shock, hypoxemia, need for vasopressor support, endotracheal intubation, cardiopulmonary resuscitation, or the requirement for extracorporeal membrane oxygenation (ECMO).

Currently, there is limited evidence regarding the incidence, timing, and underlying mechanisms of intraprocedural hemodynamic and respiratory deterioration during percutaneous pulmonary thrombectomy. In addition, the potential influence of procedural factors, such as the type of thrombectomy device used, has not been fully elucidated. The FlowTriever® (Inari Medical) and Indigo® (Penumbra) systems are among the most commonly used devices, yet comparative data regarding their safety profiles in terms of intraprocedural instability are scarce.

Furthermore, biomarkers reflecting right ventricular strain, such as N-terminal pro-B-type natriuretic peptide (NT-proBNP), may provide prognostic information in acute PE. However, their role in predicting intraprocedural instability during thrombectomy remains unclear and warrants further investigation.

This prospective observational study aims to comprehensively evaluate the incidence, causes, and timing of hemodynamic and/or respiratory instability during percutaneous pulmonary thrombectomy in patients with high-risk or intermediate-high-risk PE. The primary outcome is a composite of intraprocedural events including significant hypotension, escalation of vasopressor support, need for mechanical ventilation or intubation, cardiopulmonary resuscitation, and/or initiation of ECMO. The temporal relationship between instability and different procedural phases will also be analyzed.

In addition, the study will compare the incidence of intraprocedural instability between patients treated with different thrombectomy devices (FlowTriever® versus Indigo®), adjusting for baseline risk stratification. Secondary objectives include evaluating the prognostic value of baseline NT-proBNP levels for predicting intraprocedural instability and assessing in-hospital and 30-day mortality and their underlying causes.

By providing a detailed characterization of intraprocedural instability and its determinants, this study aims to improve risk stratification, optimize procedural planning, and guide clinical decision-making in patients undergoing percutaneous pulmonary thrombectomy. Ultimately, these findings may contribute to improving patient safety and clinical outcomes in this high-risk population.

Inclusion Criteria:

• Patients (aged ≥18 years) with high-risk or intermediate-high-risk pulmonary embolism
• Patients undergoing percutaneous pulmonary thrombectomy as part of routine clinical care

Exclusion Criteria:

• Age <18 years
• Low-risk pulmonary embolism
• Patients not undergoing percutaneous pulmonary thrombectomy
• Patients presenting with refractory shock upon arrival to the interventional suite

Adult patients with high-risk or intermediate-high-risk pulmonary embolism undergoing percutaneous pulmonary thrombectomy in routine clinical practice.

Individual participant data will not be shared due to institutional data protection policies and patient confidentiality considerations.