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
- Atrial septal defect (ASD)
- Eustachian valve: located at the junction of the inferior vena cava 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).
- Oxygenated blood comes from the placenta (lungs not used).
- Inferior vena cava carries oxygenated blood to the right atrium.
- Oxygenated blood is shunted through the foramen ovale and one-way valve (from right to left atrium, bypassing high-pressure pulmonary system).
- Aorta carries oxygenated blood to the rest of the body.
- Transition to ex-utero circulation:
- At birth:
- Lungs expand.
- Oxygen causes vasodilation of the pulmonary vascular bed, making it a low-pressure system.
- This causes the pressure gradient between the right and left atria to reverse.
- 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).
- At birth:
Normal closure of the foramen ovale, and a patent foramen ovale
Image by Lecturio.
Normal transition from in-utero cardiac circulation to ex-utero cardiac circulation
Image by Lecturio.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 or 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
- Tricuspid valve abnormalities
- Pulmonary hypertension
- Atrial septum aneurysm: aneurysm of the membrane of the fossa ovalis
- EA:
- Embryological malformation of the right atrium and tricuspid valve
- Leads to retrograde flow through the tricuspid valve
Diagnostic imaging
- Color-flow Doppler echocardiography is commonly used to identify PFOs.
- Contrast-enhanced 2-dimensional or 3-dimensional transesophageal echocardiography may identify small PFOs.
Transesophageal echocardiogram showing a patent foramen ovale in a patient who presented with cryptogenic ischemic stroke. The patent foramen is observed in the septum between the right atrium (RA) and left atrium (LA).
Image: “TEE showing a PFO in 62°” by Knebel, F. at al. License: CC BY 2.0, screenshot edited by Lecturio.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 (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.
References
- Snyder, B., & Neuman, T. (2016). Diving disorders. In J. E. Tintinalli et al. Tintinalli’s emergency medicine: A comprehensive study guide, 8e. New York, NY: McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1121493927
- Therrien, J., & Marelli, A. J. (2020). Congenital heart disease in adults. In L. Goldman MD, & A. I. Schafer MD (Eds.), Goldman-Cecil medicine (pp. 35-365.e4) https://www.clinicalkey.es/#!/content/3-s2.0-B9780323532662000618
- Suradi, Hussam S., MD, et al. (2016). Patent foramen ovale. Cardiology Clinics, 34(2), 231-240. doi:http://dx.doi.org/10.1016/j.ccl.2015.12.001
- Geva, T., Prof, Martins, J. D., M.D., & Wald, R. M., M.D. (2014). Atrial septal defects. Lancet, The, 383(9932), 1921-1932. doi:http://dx.doi.org/10.1016/S0140-6736(13)62145-5
- Dattilo, P. B., M.D., Kim, M. S., M.D., & Carroll, J. D., M.D. (2013). Patent foramen ovale. Cardiology Clinics, 31(3), 401-415. doi:http://dx.doi.org/10.1016/j.ccl.2013.05.002
