Overview

Definition

Patent foramen ovale (PFO) is a persistent, post-natal communication between the atria due to the failure of the closure of the foramen ovale during the transition from in-utero to ex-utero neonatal circulation.

Epidemiology

• Autopsy studies show a prevalence rate of approximately 27% in the general population.
• Often associated with other cardiac anomalies:
  • Atrial septal aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms
  • Atrial septal defect Atrial Septal Defect Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial Septal Defect (ASD)
  • Eustachian valve: located at the junction of the inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels and right atrium
  • Ebstein’s anomaly (EA): congenital apical displacement of the septal and posterior tricuspid valve leaflets and an abnormal anterior leaflet

Embryology

• In-utero circulation: Pulmonary vasculature is a high-pressure system due to lack of oxygen (vasoconstriction).
  1. Oxygenated blood comes from the placenta Placenta The placenta consists of a fetal side and a maternal side, and it provides a vascular communication between the mother and the fetus. This communication allows the mother to provide nutrients to the fetus and allows for removal of waste products from fetal blood. Placenta, Umbilical Cord, and Amniotic Cavity ( lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs not used).
  2. Inferior vena cava carries oxygenated blood to the right atrium.
  3. Oxygenated blood is shunted through the foramen ovale and one-way valve (from right to left atrium, bypassing high-pressure pulmonary system).
  4. Aorta carries oxygenated blood to the rest of the body.
• Transition to ex-utero circulation:
  • At birth: 
    1. Lungs expand.
    2. Oxygen causes vasodilation of the pulmonary vascular bed, making it a low-pressure system.
    3. This causes the pressure gradient between the right and left atria to reverse.
    4. The one-way valve shuts against the septum secundum and closes the foramen. 
  • After several months: 
    • Becomes an anatomical closure (fossa ovalis)
    • Incomplete closure leads to persistent communication between the atria (PFO).

Clinical Presentation and Imaging

Isolated PFO

• Frequently asymptomatic
• Cryptogenic strokes:
  • Occurring in the absence of blood clots in the heart
  • Caused by an embolus that passes from the left to the right side of the heart without going through the natural filter of the lung vasculature (paradoxical embolus)
  • Present with signs of transient ischemic attack Transient ischemic attack Transient ischemic attack (TIA) is a temporary episode of neurologic dysfunction caused by ischemia without infarction that resolves completely when blood supply is restored. Transient ischemic attack is a neurologic emergency that warrants urgent medical attention. Transient Ischemic Attack (TIA) or ischemic stroke Ischemic Stroke An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke including headache, hemisensory deficits, paresis, and ataxia
• Vascular headaches:
  • Caused by hypo-oxygenation of the brain 
  • Due to right-to-left shunting of oxygenated blood through the PFO
• Less common manifestations:
  • Decompression sickness with nitrogen gas embolism when emerging from deep-sea scuba diving 
  • Myocardial or other systemic infarctions

Patent foramen ovale associated with other cardiac anomalies

• Often associated with pathological processes that cause elevated pulmonary vascular pressure:
  • Pulmonary stenosis Pulmonary stenosis Valvular disorders can arise from the pulmonary valve, located between the right ventricle (RV) and the pulmonary artery (PA). Valvular disorders are diagnosed by echocardiography. Pulmonary stenosis (PS) is valvular narrowing causing RV outflow tract obstruction. Pulmonary Stenosis
  • Tricuspid valve abnormalities
  • Pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Pulmonary Hypertension 
• Atrial septum aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms: aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms of the membrane of the fossa ovalis
• EA:
  • Embryological malformation of the right atrium and tricuspid valve
  • Leads to retrograde flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure through the tricuspid valve

Diagnostic imaging

• Color- flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure Doppler echocardiography is commonly used to identify PFOs.
• Contrast-enhanced 2-dimensional or 3-dimensional transesophageal echocardiography may identify small PFOs.

Management

• Isolated asymptomatic PFO: no treatment indicated
• Isolated PFO associated with an otherwise unexplained stroke:
  • All patients: lifestyle modifications aimed at reducing heart disease and risk of strokes including diet, exercise, and smoking cessation
  • Low risk for recurrent stroke: antiplatelet agents Antiplatelet agents Antiplatelet agents are medications that inhibit platelet aggregation, a critical step in the formation of the initial platelet plug. Abnormal, or inappropriate, platelet aggregation is a key step in the pathophysiology of arterial ischemic events. The primary categories of antiplatelet agents include aspirin, ADP inhibitors, phosphodiesterase/adenosine uptake inhibitors, and glycoprotein IIb/IIIa inhibitors. Antiplatelet Agents (e.g., aspirin, clopidogrel)
  • High risk for recurrent stroke: aspirin + warfarin
• Open surgical closure or percutaneous closure: indicated in patients with recurrent stroke, large PFOs, contraindications to anticoagulant therapy, etc.