Pulmonary Valve Stenosis and Pulmonary Embolism Risk
Pulmonary valve stenosis does increase the probability of pulmonary embolus, but only through a specific mechanism: paradoxical embolism when a patent foramen ovale is present. 1
The Mechanism of Increased PE Risk
The relationship between pulmonary valve stenosis and pulmonary embolism is indirect and conditional:
Severe pulmonary stenosis causes reduced right ventricular compliance, which elevates right atrial pressure. 1
When right atrial pressure exceeds left atrial pressure in the presence of a patent foramen ovale, right-to-left shunting occurs, leading to cyanosis. 1
This right-to-left shunting creates the pathway for paradoxical emboli—venous thrombi that bypass the pulmonary circulation and enter the systemic arterial circulation, potentially causing stroke or systemic embolization rather than traditional pulmonary embolism. 1
A case report documented a 62-year-old patient with severe pulmonary valve stenosis who developed a paradoxical arterial embolus, confirming this mechanism clinically. 2
Critical Distinction: Paradoxical vs. Traditional PE
The increased risk is for paradoxical embolism (systemic arterial embolization), not traditional pulmonary embolism. 1 This is a crucial distinction:
Traditional pulmonary embolism occurs when venous thrombi travel to and obstruct the pulmonary arteries 1
In pulmonary stenosis with patent foramen ovale, venous thrombi bypass the lungs entirely and enter systemic circulation 1
The clinical presentation differs: paradoxical emboli typically cause stroke or peripheral arterial occlusion rather than respiratory symptoms 2
Clinical Implications and Risk Stratification
The risk only exists when BOTH conditions are present: severe pulmonary stenosis AND patent foramen ovale. 1
Risk factors that must coexist:
- Severe pulmonary stenosis with elevated RV pressures (typically RV-to-pulmonary artery gradient >40 mmHg) 1
- Patent foramen ovale allowing right-to-left shunting 1
- Evidence of cyanosis or arterial desaturation 1
- Presence of venous thrombosis risk factors 3
Long-term follow-up data shows that patients with cyanosis before pulmonary stenosis repair have significantly increased cardiovascular complications (HR 5.23,95%CI 1.99-13.78, P=0.001), including thromboembolic events. 3
Common Pitfalls to Avoid
Do not assume pulmonary stenosis directly causes pulmonary embolism through pulmonary artery obstruction—the valve stenosis itself does not predispose to thrombus formation in the pulmonary arteries. 1, 4
Do not overlook the need to assess for patent foramen ovale in patients with pulmonary stenosis who develop unexplained neurological events or systemic embolization. 1, 2
When atrial communications are surgically closed during pulmonary stenosis repair, this should be done cautiously, as the atrial septal defect may allow necessary decompression of the right atrium in cases of significant postoperative tricuspid regurgitation or RV dysfunction. 1
Management Considerations
Patients with severe pulmonary stenosis and patent foramen ovale who are cyanotic represent a high-risk population requiring intervention. 1
- Balloon valvotomy is recommended for symptomatic patients with RV-to-pulmonary artery gradient >30 mmHg 1
- Asymptomatic patients with gradient >40 mmHg should also receive balloon valvotomy 1
- Closure of the atrial communication should be considered after relieving the pulmonary stenosis to eliminate the paradoxical embolism pathway 1