What are the causes and management of pulmonary embolism?

Causes and Management of Pulmonary Embolism

Pulmonary embolism (PE) is primarily caused by thrombotic occlusion of pulmonary arteries, but can also result from various non-thrombotic sources including air, fat, amniotic fluid, septic material, tumor cells, and foreign bodies, each requiring specific management approaches. 1, 2

Thrombotic Pulmonary Embolism

Causes

• Venous thromboembolism (VTE) is the most common cause of PE, typically originating from deep vein thrombosis in the lower extremities 2
• Risk factors include recent surgery, trauma, malignancy, and estrogen exposure 3
• PE incidence is approximately 60-120 per 100,000 people annually, with 60,000-100,000 deaths per year in the US 2

Management of Thrombotic PE

• Anticoagulation is the cornerstone of treatment for hemodynamically stable patients 2, 3
• Direct oral anticoagulants (DOACs) such as apixaban, edoxaban, rivaroxaban, or dabigatran are first-line therapy with lower bleeding rates (0.6% reduction) compared to traditional heparin/warfarin regimens 2
• For patients with systolic BP <90 mmHg, systemic thrombolysis is recommended, associated with a 1.6% absolute reduction in mortality 2
• Heparin is indicated for prophylaxis and treatment of venous thrombosis and PE 4
• Duration of anticoagulation is typically at least 3 months, with consideration for indefinite treatment in patients with ongoing risk factors 3

Non-Thrombotic Pulmonary Embolism

Septic Embolism

• Most commonly associated with right-sided endocarditis, particularly in intravenous drug users 1
• Also seen with infected indwelling catheters, pacemaker wires, septic thrombophlebitis, and organ transplants 1
• Typically presents with fever, cough, and hemoptysis 1
• Management includes antibiotic treatment targeting the responsible organism, with occasional surgical removal of the embolic source 1

Foreign Material Embolism

• Caused by broken catheters, guidewires, vena cava filters, embolization coils, and endovascular stent components 1
• Increasing incidence due to more widespread use of interventional medical techniques 1
• Management involves intravascular retrieval of foreign objects when possible to prevent further thrombosis and sepsis 1

Fat Embolism

• Common with pelvic or long bone fractures, prosthetic joint placement, and also seen in lipid/propofol infusions, bone marrow procedures, sickle cell disease, fatty liver, and liposuction 1
• Clinical syndrome presents 12-36 hours after injury with altered mental status, respiratory distress, and petechial rash 1
• Pathogenesis involves both vascular obstruction and inflammatory cascade activation 1
• Treatment is primarily supportive as the condition is often self-limiting 1

Venous Air Embolism

• Results from air entrainment into the venous system during procedures or from environmental exposure 1
• Lethal volume estimated at 200-300 ml (3-5 ml/kg) when injected at 100 ml/s 1
• Causes obstruction of right ventricular outflow tract or pulmonary arterioles 1
• Management includes preventing further air entry, positioning patient in left lateral decubitus head-down position, and hemodynamic support 1

Amniotic Fluid Embolism

• Rare but catastrophic complication unique to pregnancy 1
• Occurs in 1/8,000-1/80,000 pregnancies with high maternal (80%) and fetal (40%) mortality rates 1
• Presents as a complex phenomenon with varying degrees of organ dysfunction 1

Tumor Embolism

• Seen in up to 26% of autopsies but rarely identified before death 1
• Most commonly associated with prostate and breast carcinomas, followed by hepatoma, stomach, and pancreatic cancers 1
• Radiologically mimics pneumonia, tuberculosis, or interstitial lung disease 1
• Limited treatment success with chemotherapy 1

Talc Embolism

• Occurs when oral medications containing fillers (talc, starch, cellulose) are ground and injected intravenously 1
• Common with abuse of amphetamines, methylphenidate, hydromorphone, and dextropropoxyphene 1
• Leads to entrapment in pulmonary vasculature causing thrombosis and intravascular granuloma formation 1

Hemodynamic Considerations in PE

• Right ventricular failure due to acute pressure overload is the primary cause of death in severe PE 5
• The abrupt increase in pulmonary vascular resistance leads to right ventricular dilation and dysfunction 5
• Systemic hypotension in PE can compromise coronary perfusion to the overloaded right ventricle, potentially causing right ventricular ischemia 5
• Sustained hypotension is a defining feature of massive PE with a 90-day mortality rate of 52.4% versus 14.7% in normotensive patients 5

Risk Stratification and Advanced Management

• PE is categorized as low-risk, intermediate-risk, or high-risk based on hemodynamic status and right ventricular function 6
• Intermediate-risk (submassive) PE presents the most challenging management decisions 6
• For hemodynamically unstable patients, consider mechanical circulatory support with veno-arterial extracorporeal membrane oxygenation in addition to anticoagulation and thrombolysis 7
• Chronic thromboembolic pulmonary hypertension is a rare but serious long-term complication, developing in approximately 3.8% of patients within 2 years after PE 5, 3