Management of Right-to-Left Shunt Through Patent Foramen Ovale
For patients under 60 years old with cryptogenic stroke and PFO, percutaneous closure followed by antiplatelet therapy is strongly recommended over antiplatelet therapy alone, and weakly recommended over anticoagulation alone. 1
Clinical Context and Diagnosis
Right-to-left shunting through a PFO occurs when right atrial pressure exceeds left atrial pressure, allowing venous blood or thrombi to bypass pulmonary circulation and enter systemic circulation—termed paradoxical embolism 1. While shunting is typically left-to-right, pressure changes during the cardiac cycle and respiration create periods of right-to-left flow 1.
Diagnostic Approach
- Transesophageal echocardiography (TEE) has superior sensitivity compared to transthoracic imaging and is recommended for younger adults with unexplained cerebrovascular events 1
- Saline contrast study with Valsalva maneuver increases detection sensitivity by transiently elevating right atrial pressure 1
- Complete stroke workup required before attributing stroke to PFO:
- Prolonged rhythm monitoring to exclude atrial fibrillation
- TEE or alternative imaging to rule out aortic atherothrombosis or left atrial clot
- Carotid ultrasonography, CT, or MRI to exclude cerebrovascular disease 1
High-Risk Features
An atrial septal aneurysm (excessive bulging of fossa ovalis) often accompanies septal fenestrations and marks increased embolic risk 1
Treatment Algorithm for Cryptogenic Stroke with PFO
Scenario 1: All Options Available (Patient accepts any treatment)
Weak recommendation: PFO closure + antiplatelet therapy over anticoagulation 1
The evidence shows possible small reduction in stroke and decreased bleeding risk with closure versus anticoagulation, though the certainty is lower than for the comparison with antiplatelet therapy alone.
Scenario 2: Anticoagulation Contraindicated or Declined
Strong recommendation: PFO closure + antiplatelet therapy over antiplatelet therapy alone 1
This represents the highest quality evidence from 6 trials involving 3,560 patients. The substantial benefit in stroke reduction (high-quality evidence) outweighs procedure/device-related adverse events and risk of persistent atrial fibrillation 1.
Scenario 3: PFO Closure Contraindicated or Declined
Weak recommendation: Anticoagulation over antiplatelet therapy alone 1
This is the least robust recommendation and may change with further research.
Practical Considerations for PFO Closure
- Procedure duration: Under 2 hours
- Hospital stay: Typically 1 day
- Recovery: Most activities resumed within days; full recovery within weeks 1
- Post-procedure: Antiplatelet therapy (typically aspirin) continued for variable duration 1
Important Caveats
Age and Risk Factor Limitations
These recommendations apply primarily to patients under 60 years old 1. Applicability to older patients or those with traditional cerebrovascular risk factors (diabetes, hypertension, hyperlipidemia) is uncertain. In older patients, fewer cryptogenic strokes result from paradoxical emboli, so PFO closure benefits would be diminished 1.
Patient Selection
Patients with cryptogenic stroke and PFO are typically:
- Younger
- Less likely to have classic atherosclerotic risk factors
- More likely to have PFO than the general population 1
Shunt Size Considerations
While some data suggest larger shunts benefit more from closure, this association has low credibility due to confounding—studies with larger shunts also had fewer patients on anticoagulation in medical therapy arms 1.
Special Clinical Situations
Right-to-left shunting can cause acute hypoxemia in specific contexts beyond cryptogenic stroke:
- Right ventricular infarction with elevated right heart pressures 2, 3
- Severe right ventricular dysfunction creating biventricular output mismatch 4
- Platypnea-orthodeoxia syndrome 5
In these acute scenarios, treatment focuses on optimizing right ventricular function to minimize shunting, though closure may be needed if significant shunt persists 3.