Can Atrial Fibrillation Cause Pulmonary Embolism?
Atrial fibrillation does not directly cause pulmonary embolism, but it is an independent risk factor for deep vein thrombosis (DVT) and subsequent PE, particularly in the setting of stroke, immobility, or other prothrombotic conditions. 1
The Mechanistic Relationship
AF as a Risk Factor for Venous Thromboembolism
- AF is independently associated with increased DVT risk in stroke patients, where it was the only significant risk factor in multivariate analysis for venous thromboembolic complications 1, 2
- The American Stroke Association identifies advanced age, immobility, paralysis of the lower extremity, severe paralysis, and atrial fibrillation as associated with increased risk of deep vein thrombosis in stroke patients 1
- AF patients have a 6-7 fold increased risk of VTE during the first 30 days after AF diagnosis (40.2 vs 5.7 per 1000 person-years in men; 55.7 vs 6.6 in women), which decreases substantially after anticoagulation is initiated 3
The Bidirectional Association
- PE and AF share common risk factors including advanced age, obesity, heart failure, and inflammatory states, making it difficult to establish pure causality 4
- PE can trigger AF through right-sided pressure overload or inflammatory cytokines, while AF may lead to right atrial appendage clot formation and thereby PE 4
- However, a large Swedish registry study found that after adjustment for age and comorbidity, AF without anticoagulation was not independently associated with increased PE risk (HR 1.03, CI 0.94-1.13) 5
Clinical Context: When AF Increases PE Risk
High-Risk Scenarios
In stroke patients with immobility:
- Pulmonary embolism accounts for approximately 10% of deaths after stroke, and AF is a recognized risk factor in this population 1
- The combination of AF plus immobility creates a particularly high-risk state for venous thromboembolism 1
In cancer patients:
- The European Society of Cardiology notes that AF in cancer patients is associated with a two-fold higher risk of systemic thromboembolism 1
- Cancer patients with new-onset AF have a two-fold increased risk of thromboembolism compared to those without AF 1
Early after AF diagnosis:
- VTE risk is highest in the first 30 days after AF diagnosis before anticoagulation is typically initiated, then decreases substantially 3
Protective Factors
- Patients with AF and PE have significantly lower incidence of DVT (21% vs 44% in controls), suggesting some PE cases in AF patients may originate from right atrial thrombi rather than leg veins 6
- Anticoagulation for AF stroke prevention simultaneously reduces VTE risk, which explains why VTE rates normalize after 9 months of treatment 3
Clinical Implications for Management
Prophylaxis Considerations
- Anticoagulants are effective in preventing DVT and PE among bedridden patients with recent stroke, and this is particularly important when AF is present 1
- The American Stroke Association recommends prophylactic anticoagulation for stroke patients with AF who are immobilized 1
Risk Stratification
- CHA2DS2-VASc score correlates with PE risk in AF patients and may be more sensitive than CHADS2 for predicting PE 4, 6
- Consider cancer type, stage, immobility, and history of DVT when assessing PE risk in AF patients, as these factors have additive effects 1
Key Clinical Pitfalls
- Do not assume AF alone causes PE in the absence of other risk factors - the association is largely explained by shared comorbidities and age 5
- Do not withhold anticoagulation in elderly AF patients due to PE concerns - therapeutic anticoagulation for AF stroke prevention simultaneously reduces VTE risk 3
- Recognize that the first month after AF diagnosis carries the highest VTE risk before anticoagulation is established 3
- In cancer patients with AF, bleeding risk may exceed thrombotic risk depending on cancer type, requiring individualized assessment 1