Patent foramen ovale overview
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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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
There are no established measures for the secondary prevention of patent foramen ovale.