Patent foramen ovale overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Ifeoma Odukwe, M.D. [2], Priyamvada Singh, M.B.B.S. [3], Kristin Feeney, B.S. [4]
Overview
A patent foramen ovale is a communication between the right and left atrium. Despite the communication between the two atria, it is not considered an atrial septal defect as the septal tissue is not missing. Patent foramen ovale is a congenital interatrial communication that is usually asymptomatic but has been associated with ischemic stroke due to paradoxical embolism, particularly in patients younger than 60 years.[1]
Historical Perspective
The first anatomic description of patent foramen ovale was made by Leonardi da Vinci in 1513. In 1877, Julius Friedrich Conheim first described an association between cryptogenic stroke and patent foramen ovale.
Pathophysiology
A patent foramen ovale is a flap-like structure in interatrial septum that is formed by failure of postnatal fusion of septum primum and septum secundum. It periodically opens and allows blood to shunt between the two atria. This flap-like structure functions like a one-way valve mechanism that only opens to allow blood to flow from the right atrium to the left atrium during times where there is an increase flow or pressure in the right atrium. Elevation of pressure in the pulmonary circulatory system (i.e.: pulmonary hypertension, cough or valsalva maneuver) can cause the foramen ovale to open.Patent foramen ovale allows intermittent right-to-left shunting of blood across the atrial septum. In the presence of a venous thrombus, this shunt may permit embolic material to bypass the pulmonary circulation and enter the systemic arterial circulation, resulting in paradoxical embolism and ischemic stroke.[2]Anatomical characteristics that may increase shunt flow and embolic risk include large shunt size, atrial septal aneurysm, long PFO tunnel, and the presence of a Eustachian valve, an embryologic remnant in the right atrium.[3]
Causes
The exact causes for patent foramen ovale is still not clear. However, it has been found to occur with increased frequencies in families and might have some genetic component to it.
Differentiating Patent Foramen Ovale from other Diseases
Patent foramen ovale is an inter-atrial communication. However, it is not formally classified as an atrial septal defect as no septal tissue is missing in them. It should be differentiated from the traditional types of atrial septal defect.
Epidemiology and Demographics
Patent foramen ovale is found in 25% of the population. The incidence decreases with increasing age, but the size increases with age. There is no difference in prevalence among men and women.
Patent foramen ovale is more frequently identified in younger patients with ischemic stroke of undetermined source compared with the general population. The likelihood that a PFO is pathogenic rather than incidental is higher in patients without traditional vascular risk factors.[4]
Risk Factors
There are no established risk factors for patent foramen ovale but because the disease occurs with an increased frequency in families, there may be at least in part a genetic component in the development of a patent foramen ovale.
Anatomical features associated with increased risk of paradoxical embolism in patients with patent foramen ovale include large right-to-left shunt, atrial septal aneurysm, long PFO tunnel, and the presence of a Eustachian valve.[1]
Screening
Routine screening of asymptomatic patients with patent foramen ovale is not recommended. It may be considered in patients with a history of cryptogenic stroke and recurrent decompression sickness in divers.
Natural History, Complications and Prognosis
A patent foramen ovale is often asymptomatic and may be an incidental finding on echocardiography. A PFO may be identified following the development of complications such as stroke, migraine, the platypnea orthodeoxia syndrome or decompression sickness. Decompression illness is associated with a 5 to 13 fold increased incidence of a patent foramen ovale. The risk increases with an increase in defect size. Device closure can be considered in divers with unexplained decompression illness, especially those who wish to continue diving. The number of ischemic brain lesions were twice as common among patients with a patent foramen ovale than in those without it.
Complications of patent foramen ovale include ischemic stroke resulting from paradoxical embolism.[1]The risk of stroke is influenced by patient age, absence of vascular risk factors, and the presence of high-risk anatomical features.[5]
Diagnosis
Diagnostic Study of Choice
Contrast-enhanced transesophageal echocardiography is the imaging modality of choice in diagnosing patent foramen ovale because of it's high sensitivity, superior image resolution, and ability to identify the origin of a right-to-left shunt.
History and Symptoms
Most individuals with patent foramen ovale are asymptomatic although some may present with rare symptoms like migraines, stroke, decompression illness and platypnoea orthodeoxia syndrome.
Physical Examination
There are no diagnostic findings in an isolated patent foramen ovale on physical examination.
Laboratory Findings
There are no diagnostic laboratory findings associated with patent foramen ovale.
Electrocardiogram
There are no diagnostic ECG changes for a patent foramen ovale but a crochetage pattern (An M-shaped bifid notch on the ascending branch, or on the zenith, of the R wave in inferior ECG lead) may be identified in some patients with patent foramen ovale.
X-ray
There are no diagnostic x-ray findings in a patent foramen ovale. Transesophageal echocardiography with a bubble study is the diagnostic modality of choice.
Echocardiography and Ultrasound
Transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and transcranial Doppler (TCD) are the commonly used diagnostic tools for patent foramen ovale. Transesophageal echocardiography is more sensitive in visualizing the interatrial septum, than transthoracic echocardiography and is the imaging modality of choice. A contrast medium such as agitated saline contrast is required. A diagnosis is made with the appearance of contrast bubbles in the left atrium a few heart beats after seen in the right atrium.
Transesophageal echocardiography with contrast and provocative maneuvers is the preferred diagnostic modality for identifying patent foramen ovale and for anatomical risk stratification. This technique allows detection of high-risk features, including shunt size, atrial septal aneurysm, long PFO tunnel, and the presence of a Eustachian valve. Evaluation should also exclude alternative cardioembolic sources.[6] Transcranial Doppler ultrasonography is a sensitive screening tool for detecting right-to-left shunting but lacks the anatomic detail required for comprehensive assessment.[1]
CT Scan
CT scans are not commonly used in the diagnosis of patent foramen ovale. When performed, a contrast agent jet from the left atrium to the right atrium toward the inferior vena cava with channel-like appearance of the interatrial septum may be seen.
MRI
Although not a standard modality used to diagnose patent foramen ovale, gadolinium can be injected in the antecubital fossa and the volume of flow across the patent foramen ovale can be calculated. Among patients with a patent foramen ovale, the volume of blood shunted between the right atrium and the left is 0.4 to 0.6 mL per heart beat.
Other Imaging Findings
There are no additional imaging findings associated with patent foramen ovale.
Other Diagnostic Studies
There are no other diagnostic studies associated with patent foramen ovale.
Treatment
Medical Therapy
The medical therapy for the patients with patent foramen ovale is controversial. Medical therapy with antiplatelet therapy (aspirin) or anticoagulant therapy (warfarin) could be considered in patients with recurrent strokes after index episode of cryptogenic stroke and unresponsive migraines. However, the relative effectiveness of aspirin or warfarin in these patients has not been proved.
Surgery
There is a lack of consensus regarding the effectiveness of percutaneous closure of patent foramen ovale. There are insufficient evidences to recommend device closure for a first stroke. PFO closure may be considered for recurrent cryptogenic stroke and high-risk patent foramen ovale (PFO) (atrial septal aneurysm). Some randomized controlled trials to compare the relative effectiveness of medical therapy versus percutaneous closure are on way and in future might be helpful in making therapeutic decisions.
Primary Prevention
There are no methods for the primary prevention of patent foramen ovale.
Secondary Prevention
In selected patients with ischemic stroke attributed to patent foramen ovale, percutaneous closure may be considered as part of secondary stroke prevention following appropriate patient selection and exclusion of alternative stroke mechanisms.[7]
References
- ↑ 1.0 1.1 1.2 1.3 Saver JL, Mattle HP, Thaler D. Patent Foramen Ovale Closure Versus Medical Therapy for Cryptogenic Ischemic Stroke: A Topical Review. Stroke. 2018 Jun;49(6):1541-1548. doi: 10.1161/STROKEAHA.117.018153. Epub 2018 May 14. PMID: 29760277.
- ↑ Yan C, Li H, Wang C, Yu H, Guo T, Wan L, Yundan P, Wang L, Fang W. Frequency and Size of In Situ Thrombus Within Patent Foramen Ovale. Stroke. 2023 May;54(5):1205-1213. doi: 10.1161/STROKEAHA.122.041524. Epub 2023 Mar 9. PMID: 36891906.
- ↑ Zhu J, Chen A, Zhu L, Li Y, Jiang Z, Ni D, Zheng Y, Liu X. Right Atrial Septal In Situ Microthrombus: A Potential Novel Cause of Patent Foramen Ovale-Associated Stroke. J Am Heart Assoc. 2024 Nov 19;13(22):e035838. doi: 10.1161/JAHA.124.035838. Epub 2024 Nov 7. PMID: 39508151; PMCID: PMC11681389.
- ↑ Alsheikh-Ali AA, Thaler DE, Kent DM. Patent foramen ovale in cryptogenic stroke: incidental or pathogenic? Stroke. 2009 Jul;40(7):2349-55. doi: 10.1161/STROKEAHA.109.547828. Epub 2009 May 14. PMID: 19443800; PMCID: PMC2764355.
- ↑ Kent DM, Ruthazer R, Weimar C, Mas JL, Serena J, Homma S, Di Angelantonio E, Di Tullio MR, Lutz JS, Elkind MS, Griffith J, Jaigobin C, Mattle HP, Michel P, Mono ML, Nedeltchev K, Papetti F, Thaler DE. An index to identify stroke-related vs incidental patent foramen ovale in cryptogenic stroke. Neurology. 2013 Aug 13;81(7):619-25. doi: 10.1212/WNL.0b013e3182a08d59. Epub 2013 Jul 17. PMID: 23864310; PMCID: PMC3775694.
- ↑ Mojadidi MK, Bogush N, Caceres JD, Msaouel P, Tobis JM. Diagnostic accuracy of transesophageal echocardiogram for the detection of patent foramen ovale: a meta-analysis. Echocardiography. 2014 Jul;31(6):752-8. doi: 10.1111/echo.12462. Epub 2013 Dec 23. PMID: 24372693.
- ↑ Kleindorfer DO, Towfighi A, Chaturvedi S, Cockroft KM, Gutierrez J, Lombardi-Hill D, Kamel H, Kernan WN, Kittner SJ, Leira EC, Lennon O, Meschia JF, Nguyen TN, Pollak PM, Santangeli P, Sharrief AZ, Smith SC Jr, Turan TN, Williams LS. 2021 Guideline for the Prevention of Stroke in Patients With Stroke and Transient Ischemic Attack: A Guideline From the American Heart Association/American Stroke Association. Stroke. 2021 Jul;52(7):e364-e467. doi: 10.1161/STR.0000000000000375. Epub 2021 May 24. Erratum in: Stroke. 2021 Jul;52(7):e483-e484. doi: 10.1161/STR.0000000000000383. PMID: 34024117.