Clinical Characteristics and Acute Management of Pediatric Pulmonary Embolism

Background: Pediatric pulmonary embolism (PE) is rare in children, but the incidence is rising. Despite the associated significant morbidity and mortality, there is limited data to guide the care of children and adolescents who present with PE. There is a demonstrated need to standardize evaluation and management of pediatric PE, and for further research to investigate the safety and efficacy of therapeutic options.

Aims: The primary aim was to describe the clinical characteristics of pediatric patients presenting with acute PE. Secondary aims were to describe the treatment of pediatric PE and to define bleeding complications in those who received systemic thrombolysis.

Methods: A single center, retrospective review was performed including patients <21 years of age who received primary treatment for acute PE at the Children's Hospital of Philadelphia (CHOP) between 1/1/2003 and 8/1/2021. Patients were initially identified based on international classification of diseases (ICD) 9 and 10 codes for PE and verified with manual chart review. Exclusion criteria included: septic emboli, initial treatment for PE at an outside institution, absence of a radiologically confirmed PE, and cardiac disease as a comorbid condition. Data collection included patient demographics, comorbidities, risk factors for VTE, acute diagnostic evaluation, management including anticoagulation and utilization of advanced procedures, and bleeding using International Society of Thrombosis and Hemostasis consensus definitions. Subjects were classified by PE severity: high-risk (cardiac arrest, shock, or persistent hypotension); intermediate risk (right heart strain by imaging or cardiac biomarkers and without high-risk features); and low risk (without right heart strain or high-risk features). Descriptive statistics were used to summarize demographic and clinical characteristics. Data analysis was performed using Stata 16.

Results: There were 154 children and adolescents who met inclusion criteria during the study period (Table 1). The majority (127/154, 82%) were 12 years of age or older at the time of PE and infants were disproportionately found to have high-risk PE. Most (131/154, 85%) subjects had a provoked PE. Most had low-risk PE, but 47/154 (31%) met intermediate or high-risk criteria. Demographic and clinical characteristics by risk category are presented in Table 1.

Initial inpatient anticoagulation is summarized in Table 1. Enoxaparin was the most common initial anticoagulant (90/154, 58%). Two patients did not receive any anticoagulation due to high bleeding risk.

Of the 24 subjects who received systemic thrombolysis, 21 received concomitant anticoagulation: eight with therapeutic intensity enoxaparin, six with therapeutic intensity unfractionated heparin (UFH), five with decreased intensity UFH, and two with therapeutic intensity bivalirudin. Clinically relevant bleeding occurred in 4/24 subjects during systemic thrombolysis: three clinically relevant non-major bleeding events on UFH and one major bleeding event. The major bleeding event was a pulmonary hemorrhage in a subject with metastatic cancer and IVC thrombosis whose anticoagulation was held prior to a surgical procedure and then experienced cardiac arrest due to PE. She received systemic thrombolysis, was cannulated onto extracorporeal membrane oxygenation(ECMO), however unfortunately died. Six subjects (4%) experienced in-hospital or 30-day post-discharge mortality, at a median of 21.5 (IQR: 0 - 45) days after the PE: three high risk, two intermediate risk, one low risk. All subjects who died had other comorbidities, however PE was felt to contribute to death in four subjects.

Conclusions: We describe the clinical characteristics and acute management of a large cohort of children and adolescents with PE. Nearly one-third of patients had intermediate or high-risk PE, which was associated with a mortality of 11%. Major bleeding was rare during systemic thrombolysis, despite the majority receiving concomitant therapeutic intensity anticoagulation. Future work will focus on bleeding and long-term outcomes after advanced therapies compared to anticoagulation alone.

Raffini:Childrens Hospital of Philadelphia: Current Employment; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech, Inc.: Membership on an entity's Board of Directors or advisory committees; Boeringer Ingelheim: Membership on an entity's Board of Directors or advisory committees.

Certain anticoagulants and thrombolytic agents are not FDA approved in pediatric patients but are frequently used in clinical practice and are discussed in this abstract.