Patent foramen ovale

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]

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]

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.

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]

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.

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.

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]

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]

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.

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]

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.

Most individuals with patent foramen ovale are asymptomatic although some may present with rare symptoms like migraines, stroke, decompression illness and platypnoea orthodeoxia syndrome.

There are no diagnostic findings in an isolated patent foramen ovale on physical examination.

There are no diagnostic laboratory findings associated with patent foramen ovale.

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.

There are no diagnostic x-ray findings in a patent foramen ovale. Transesophageal echocardiography with a bubble study is the diagnostic modality of choice.

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 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.

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.

There are no additional imaging findings associated with patent foramen ovale.

There are no other diagnostic studies associated with patent foramen ovale.

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.

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.

There are no methods for the primary prevention of patent foramen ovale.

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]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ifeoma Odukwe, M.D. [2], Priyamvada Singh, M.B.B.S. [3]; Kristin Feeney, B.S. [4]

The first anatomic description of patent foramen ovale was made by Leonardo da Vinci. He described it as a perforating channel from the left to the right chamber. Julius Friedrich Cohnheim first described the association between patent foramen ovale and stroke.

• In 1513, Leonardo da Vinci made the first anatomic description of patent foramen ovale. He wrote this in his notes: “I found from the left chamber to the right chamber a perforating channel, which I note here to see whether this occurs in other auricle (atria) of other hearts”.^[1]
• In 1564, the presence of foramen ovale at birth was first described by an Italian surgeon named Leonardi Botali.^[2]
• In 1877, Julius Friedrich Cohnheim, a German pathologist, first described the association between patent foramen ovale and stroke. This was based on a report he made from an autopsy he performed on a 35-year old woman who had a fatal stroke. He found a long thrombus in the lower extremity and a foramen ovale. He wrote in his report “I found a very large foramen ovale through which I could pass three fingers with ease. Now I could no longer ignore the fact that a torn-off piece of thrombus arising from the V. curalis, while traveling through the heart, passed out of the right atrium into the left atrium and to the A. Foss. Sylvii.”^[3][4]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ifeoma Odukwe, M.D. [2], Priyamvada Singh, M.B.B.S. [3], Kristin Feeney, B.S. [4]

During the 4th week of gestation, formation of the atrial septum begins. Formation of the septum primum and septum secundum leads to the development of a foramen ovale which allows blood to flow from the right atrium to the left atrium in the fetus. Fusion of both septa’s occurs after birth with increased left atrial pressure. The foramen ovale remains patent in some people due to failure of fusion of the septum primum and septum secundum. This permits blood flow from the right atrium to the left atrium during periods of increased right atrial pressure. Some conditions associated with patent foramen ovale include cryptogenic stroke, migraine with aura, and decompression sickness in divers.

• Atrial septation begins at about the 4th week of gestation. A crescent-shaped septum primum grows from the primordial atrial roof towards the endocardial cushion and partially divides the common atrium into right and left halves.^[1][2]
• Formation of the endocardial cushions occurs on the ventral and dorsal walls of the atrioventricular canal. Before the septum primum reaches the endocardial cushion, programmed cell death occurs in the more cranial part giving rise to perforations that become a large window called the ostium secundum/foramen secundum.
• Around day 33, a crescent-shaped septum secundum forms on the right side of the septum primum. It grows gradually and overlaps part of the ostium secundum/foramen secundum forming an oval-shaped, incomplete septal partition that becomes the foramen ovale. The foramen ovale permits blood to pass from the right atrium to the left atrium.
• A flap-like valve is formed by the remaining septum primum over the foramen ovale. Fusion of both septa’s occur after birth.

• In fetal circulation, oxygenated blood from the placenta flows through the umbilical vein to the inferior vena cava and makes its way into the right atrium. Due to greater right atrial pressure compared to left atrial pressure in utero, blood flows from the right atrium to the left through the foramen ovale. Blood from the left atrium flows into the left ventricle, into the aorta and to the systemic circulation. The deoxygenated blood from the systemic circulation travels back to the placenta through the umbilical arteries for oxygenation by the mother.^[2]
• At birth, oxygen fills the alveolus resulting in a drop in right heart pressure and pulmonary vascular resistance. The amount of blood entering the left atrium from the lungs increases leading to increased left atrial pressure. These mechanisms cause closure of the foramen ovale. In most individuals, the foramen ovale closes by age two.

• Soon after birth, as an infant takes its first breath, the negative intrathoracic pressure closes the foramen ovale. It may remain open in a number of people due to failure of fusion of the septum primum and septum secundum making the closure incomplete. This patent foramen ovale permits interatrial flow of blood from the right atrium to the left atrium during periods when the right atrial pressure exceeds that of the left atrium, for example, coughing, sneezing or straining^[3][4]
• It is undetected in a majority of people and may be seen during cardiac investigation.^[3]
• 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.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.^[5]

• F2 (prothrombin) and Apolipoprotein-C3 genes may be associated with patent foramen ovale.^[6]

Conditions associated with patent foramen ovale include:^[7][8][9]

• Cryptogenic stroke
• Migraine headache
• Atrial septal aneurysm
• Chiari network
• Obstructive sleep apnea
• Decompression sickness

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2], Kristin Feeney, B.S. [3], Ifeoma Odukwe, M.D. [4]

The exact cause of patent foramen ovale has not been identified.

The exact cause of patent foramen ovale has not been identified.

Cardiovascular	No underlying causes
Chemical/Poisoning	No underlying causes
Dental	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	No underlying causes
Ear Nose Throat	No underlying causes
Endocrine	No underlying causes
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	No underlying causes
Hematologic	No underlying causes
Iatrogenic	No underlying causes
Infectious Disease	No underlying causes
Musculoskeletal/Orthopedic	No underlying causes
Neurologic	No underlying causes
Nutritional/Metabolic	No underlying causes
Obstetric/Gynecologic	No underlying causes
Oncologic	No underlying causes
Ophthalmologic	No underlying causes
Overdose/Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	No underlying causes
Renal/Electrolyte	No underlying causes
Rheumatology/Immunology/Allergy	No underlying causes
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Miscellaneous	No underlying causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [3]

Patent foramen ovale must be differentiated from atrial septal defect, ventricular septal defect, patent ductus arteriosus, coarctation of the aorta, congenital aortic stenosis, and pulmonary stenosis.

Patent foramen ovale must be differentiated from atrial septal defect, ventricular septal defect, patent ductus arteriosus, coarctation of the aorta, congenital aortic stenosis, and pulmonary stenosis.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ifeoma Odukwe, M.D. [2], Priyamvada Singh, M.B.B.S. [3], Kristin Feeney, B.S. [4]

Approximately 1 in four healthy adults has a patent foramen ovale. The incidence decreases with increasing age, but the size increases with age. It is the most common cardiac finding in people less than 55 years with an unexplained cerebrovascular event. It is prevalent in men and women equally and has no racial predilection.

• The prevalence of patent foramen ovale is approximately 25,000 per 100,000 individuals worldwide..^[1]

• It is more common in those under the age of 30 and less common in those above 80 years.^[2]
• The incidence of patent foramen ovale varies with age:^[3]
  • 0-30 years: 34.3%
  • 40-80 years: 25.4%
  • 90+ years: 20.2%

• Patent foramen ovale size increases with age, from a mean of approximately 3mm in the first decade to approximately 6 mm in the 10th decade of life.^[3]
• In patients less than 55 years with an unexplained cerebrovascular event, patent foramen ovale is the most common cardiac finding seen. It is presumed to be caused by a paradoxical emboli.^[4]
• 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.^[5]

• There is no racial predilection to patent foramen ovale.^[6]

• Patent foramen ovale affects men and women equally.^[6]

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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]

There are no established risk factors for patent foramen ovale but the presence of congenital heart disease may be associated with an open 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]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [3]

The presence of a patent foramen ovale has been linked to decompression sickness, paradoxical embolism and migraine. There is a debate within the neurology and cardiology communities about the role of a patent foramen ovale in cryptogenic stroke. The prognosis of uncomplicated patent foramen ovale is generally good.

• In majority of people, the foramen ovale closes later in infancy but anatomic closure is incomplete in about 25% of the population.^[1]
• The size of a patent foramen ovale can range from 1 to 19mm. It is commonly larger in older adults.^[1]
• On the left atrial side, the opening tends to be crescentric in shape.^[1]

• Common complications of patent foramen ovale include:^{[2][3][4][5][6]}
  • Paradoxical embolism: This is from a venous thrombi leading to cerebral or peripheral stroke. The risk of a stroke is enhanced by the presence of some coexisting factors such as atrial septal defect, size of the patent foramen ovale, degree of the shunt, deep vein thrombosis, shunt at rest, and prothrombotic states.
  • Hypoxemia
  • Severe decompression sickness (due to paradoxical gas embolism) in divers.

• Overall, the prognosis of patients with patent foramen ovale is good.
• The prognosis is excellent for those who undergo closure.
• Asymptomatic patients have an excellent prognosis without undergoing treatment.
• Patients with patent foramen ovale may develop cryptogenic stroke due to paradoxical embolism.

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