Cardiology > Patent Foramen Ovale (PFO)   

Background 

I) Definition 

A patent foramen ovale (PFO) is a persistent communication between the right and left atria due to the failure of postnatal closure of the foramen ovale, a fetal interatrial shunt. Normally, the foramen ovale closes shortly after birth as left atrial pressure exceeds right atrial pressure. However, in about 25–30% of the population, incomplete anatomical fusion leads to a PFO. While most individuals remain asymptomatic, PFO can be implicated in paradoxical embolism, cryptogenic stroke, decompression illness, and migraine with aura. 

Classification/Types 

By Size: 

• • Small (<2 mm): Often clinically insignificant 

• • Moderate (2–4 mm): May allow intermittent right-to-left shunting 

• • Large (>4 mm): Higher risk for paradoxical embolism 

By Hemodynamic Behavior: 

• • Non-shunting (closed at rest): Opens only under transient pressure changes (e.g., Valsalva) 

• • Shunting (open at rest): Constant or provoked right-to-left flow 

• • PFO with atrial septal aneurysm (ASA): Redundant, hypermobile septum with exaggerated movement—significantly increases stroke risk 

Pathophysiology 

In fetal life, the foramen ovale allows oxygenated blood from the placenta to bypass the non-functioning fetal lungs. After birth, pulmonary circulation increases left atrial pressure, functionally closing the foramen. In PFO, the septum primum and secundum fail to fuse, creating a flap-like opening. While typically left-to-right, increased right atrial pressure (e.g., with Valsalva, coughing, pulmonary embolism, or pulmonary hypertension) can transiently reverse flow, allowing unfiltered venous emboli to enter systemic circulation (paradoxical embolism). 

Epidemiology 

• • Present in ~25–30% of the general population 

• • Identified in up to 50% of patients with cryptogenic stroke 

• • Higher prevalence in younger stroke patients (<55 years) 

• • Associated with migraine with aura, decompression illness, and platypnea-orthodeoxia syndrome 

Etiology 

I) Causes 

• • Congenital failure of postnatal closure of the foramen ovale 

II) Risk Factors 

• • Atrial septal aneurysm 

• • Large PFO size 

• • History of cryptogenic stroke or embolism 

• • Prothrombotic states (e.g., Factor V Leiden, protein C/S deficiency) 

• • Scuba diving or high-altitude exposure (for decompression illness) 

Clinical Presentation 

I) History (Symptoms) 

• • Asymptomatic: Most common presentation 

• • Cryptogenic stroke or TIA: Sudden-onset neurologic deficit without identifiable cause 

• • Unexplained systemic embolism: Especially in absence of peripheral DVT 

• • Migraine with aura: Often in younger patients; association under investigation 

• • Platypnea-orthodeoxia syndrome: Dyspnea and hypoxia worse in upright position 

• • Decompression sickness: In divers due to arterialization of venous bubbles 

II) Physical Exam (Signs) 

• • Typically unremarkable 

• • May have subtle hypoxemia in platypnea-orthodeoxia 

• • No characteristic heart murmur unless coexistent with other defects 

Differential Diagnosis (DDx) 

• • Atrial septal defect (ASD) 

• • Cryptogenic ischemic stroke from other sources 

• • Pulmonary arteriovenous malformations 

• • Paradoxical embolism from DVT 

• • Inherited or acquired hypercoagulability 

• • Primary pulmonary hypertension 

Diagnostic Tests 

Initial Evaluation 

• • ECG: Often normal; may show atrial enlargement or arrhythmias 

• • Chest X-ray: Usually normal 

• • Transthoracic echocardiogram (TTE): May miss small PFOs 

• • TTE with bubble contrast (bubble study): Detects microbubble passage from RA to LA (during Valsalva) 

Advanced Imaging 

• • Transesophageal echocardiography (TEE): Gold standard; superior sensitivity for PFO detection and anatomical details 

• • Transcranial Doppler with contrast: Non-invasive; detects cerebral microembolic signals 

• • Cardiac MRI/CT: May assist with anatomical visualization but less commonly used 

• • Lower extremity Doppler ultrasound: If paradoxical embolism suspected 

Treatment 

I) Acute Management 

• • Ischemic stroke or TIA: Standard acute stroke protocols including thrombolysis (if eligible) 

• • Antiplatelet therapy: Aspirin or clopidogrel for secondary prevention 

• • Anticoagulation: If associated with DVT or hypercoagulable state 

II) Definitive/Long-Term Management 

• • Medical management: Antiplatelet or anticoagulant therapy based on individual risk 

• • PFO closure: Considered in patients <60 years with cryptogenic stroke and high-risk PFO anatomy 

• • Transcatheter device closure preferred over surgery 

• • Especially indicated if recurrent stroke on medical therapy or large PFO with ASA 

• • Avoidance of provocative activities: For decompression illness (e.g., scuba diving) 

Medications 

Device Therapy 

• • PFO closure devices: Amplatzer, Gore Helex, or Occlutech occluders 

• • Implantable loop recorder: For cryptogenic stroke workup to rule out paroxysmal atrial fibrillation 

Patient Education, Screening, Vaccines 

• • Educate on symptoms of stroke and importance of timely evaluation 

• • Advise on avoiding activities that increase right atrial pressure (e.g., heavy lifting, dehydration in divers) 

• • Routine vaccinations: Influenza, COVID-19 

• • Genetic counseling if coexisting inherited thrombophilia 

• • Discuss contraceptive options in women with hypercoagulability 

Consults/Referrals 

• • Neurologist: For evaluation of stroke/TIA 

• • Interventional cardiologist: For consideration of PFO closure 

• • Hematologist: If thrombophilia or hypercoagulable state suspected 

• • Pulmonologist: If unexplained hypoxia or platypnea-orthodeoxia 

• • Dive medicine specialist: If decompression illness involved 

Follow-Up 

Short-Term 

• • Follow-up echocardiography after closure to assess residual shunt 

• • Monitor for arrhythmias post-device placement 

• • Reassess neurologic symptoms and functional recovery 

Long-Term 

• • Annual follow-up if PFO remains unrepaired and associated with neurologic or embolic events 

• • Surveillance imaging after closure at 6–12 months 

• • Reassessment of antiplatelet or anticoagulant needs based on evolving risk 

Prognosis 

• • Asymptomatic individuals: Excellent prognosis, no treatment needed 

• • Cryptogenic stroke: PFO closure significantly reduces risk of recurrence in selected patients 

• • With coexisting ASA or large shunt: Higher recurrence risk, may benefit from closure 

• • Decompression illness or platypnea-orthodeoxia: Prognosis improves with closure and activity modification