What is a thromboembolic event?

What is a Thromboembolic Event?

A thromboembolic event occurs when a blood clot (thrombus) forms in a blood vessel and either obstructs blood flow at that site or breaks off and travels through the circulation to block a vessel elsewhere in the body, causing tissue ischemia or infarction. 1

Types of Thromboembolic Events

Thromboembolic events are broadly categorized into two main types:

Venous Thromboembolism (VTE)

• Deep vein thrombosis (DVT): Formation of thrombi in the deep veins, most commonly in the large veins of the legs or pelvis 2, 3
• Pulmonary embolism (PE): Occurs when thrombi dislodge from clots in vein walls and travel through the heart to pulmonary arteries 2, 3
• VTE affects approximately 300,000-600,000 individuals in the U.S. annually and represents a major source of morbidity and mortality 1, 4
• The 30-day mortality of patients suffering a thrombotic event exceeds 25% 1

Arterial Thromboembolism

• Stroke: Ischemic stroke occurs when a thrombus or embolus blocks cerebral arteries 1
• Myocardial infarction: Thrombotic occlusion of coronary arteries 5
• Acute limb ischemia: Sudden decrease in limb perfusion due to arterial thrombosis or embolism 5
• Systemic embolism: Thrombi originating from cardiac sources (such as prosthetic heart valves or atrial fibrillation) that travel to peripheral arteries 1

Clinical Manifestations

The symptoms and signs of thromboembolic events vary by location:

• DVT: Leg swelling, pain, warmth, and erythema 6
• PE: Sudden dyspnea, chest pain, hemoptysis, or sudden death 2
• Stroke: Focal neurological deficits, altered consciousness 1
• Acute limb ischemia: Pain, pallor, pulselessness, paresthesias, paralysis 5

Risk Factors

For Venous Thromboembolism

• Acquired factors: Surgery, trauma, hospitalization, immobilization, cancer, long-haul travel, obesity, major medical illness, contraceptive use 1, 3, 7
• Patient characteristics: Advanced age (incidence increases substantially beyond age 60), previous VTE 1, 7
• Hereditary factors: Factor V Leiden, prothrombin mutations, deficiencies in natural anticoagulants (antithrombin, Protein C, Protein S) 1

For Arterial Thromboembolism

• Cardiac sources: Atrial fibrillation, mechanical heart valves, left ventricular dysfunction 1
• Vascular factors: Atherosclerosis, hypertension, hypercholesterolemia, diabetes, smoking 1
• Procedural complications: Endovascular procedures carry an 8-11% risk of thromboembolic complications 1

Clinical Significance

Morbidity and Mortality

• VTE: Approximately 20% of individuals who have a VTE event die within 1 year, often from the provoking condition 7
• Recurrence: In the absence of continued anticoagulation, VTE recurs in approximately 20% of patients within 5 years and 30% within 10 years 1
• Long-term complications: Post-thrombotic syndrome affects approximately 30% at 10 years, with 10% suffering venous stasis ulceration 1
• Endovascular procedures: High rates of thromboembolic events (8.2-19% depending on procedure type) with subsequent morbidity and death 1

Diagnostic Approach

• The symptoms and signs are nonspecific and require objective testing 6
• Clinical probability scores combined with D-dimer testing identify low-probability patients where imaging can be safely avoided 1, 6
• Imaging confirmation is essential before initiating anticoagulation due to bleeding risks 1

Common Pitfalls

• Assuming all thromboembolic events originate from the suspected source: Thorough investigation is essential, as many events arise from other sources beyond the obvious (e.g., prosthetic valve thromboembolism may originate elsewhere) 1
• Underestimating recurrence risk: The risk of recurrent VTE is highest in the first year after initial event, necessitating appropriate duration of anticoagulation 1
• Missing provoked versus unprovoked classification: This distinction critically influences recurrence risk and duration of anticoagulation therapy 2