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AUTHOR AND EDITOR INFORMATION

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Author: Sandy N Shah, DO, MBA, Private Practice, Houston, Texas

Sandy N Shah is a member of the following medical societies: American College of Cardiology, American Heart Association, and American Osteopathic Association

Coauthor(s): Dawn M Calderon, DO, Co-Director of Center for Adults With Congenital Heart Disease, Clinical Associate Professor, Departments of Cardiology and Internal Medicine, Deborah Heart and Lung Center, Robert Wood Johnson School of Medicine

Editors: Park W Willis IV, MD, Sarah Graham Distinguished Professor of Medicine and Pediatrics, University of North Carolina at Chapel Hill School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Marschall S Runge, MD, PhD, Charles and Anne Sanders Distinguished Professor of Medicine, Chairman of Medicine, Vice Dean for Clinical Affairs, Chairman, Department of Medicine, University of North Carolina at Chapel Hill School of Medicine; Amer Suleman, MD, Consultant in Electrophysiology and Cardiovascular Medicine, Department of Internal Medicine, Division of Cardiology, Medical City Dallas Hospital; Park W Willis IV, MD, Sarah Graham Distinguished Professor of Medicine and Pediatrics, University of North Carolina at Chapel Hill School of Medicine

Author and Editor Disclosure

Synonyms and related keywords: patent foramen ovale, PFO, paradoxical embolism, atrial septum primum, atrial septum secundum, fossa ovalis, atrial septal aneurysm, right-to-left shunt, stroke, transient ischemic event, Valsalva maneuver, atrial septal aneurysm, cryptogenic stroke, paradoxical embolization

INTRODUCTION

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Background

Patent foramen ovale (PFO) is an anatomical interatrial communication with potential for right-to-left shunt. Foramen ovale has been known since the time of Galen. In 1564, Leonardi Botali, an Italian surgeon, was the first to describe the presence of foramen ovale at birth. However, the function of foramen ovale in utero was not known at that time. In 1877, Cohnheim described paradoxical embolism in relation to PFO.

Pathophysiology

PFO is a flaplike opening between the atrial septa primum and secundum at the location of the fossa ovalis that persists after age 1 year. In utero, the foramen ovale serves as a physiologic conduit for right-to-left shunting. Once the pulmonary circulation is established after birth, left atrial pressure increases, allowing functional closure of the foramen ovale. This is followed by anatomical closure of the septum primum and septum secundum by the age of 1 year.

The Mayo Clinic autopsy study revealed that the size of a PFO increases from a mean of 3.4 mm in the first decade to 5.8 mm in the 10th decade of life, as the valve of fossa ovalis stretches with age.1

With increasing evidence that PFO is the culprit in paradoxical embolic events, the relative importance of the anomaly is being reevaluated. James Lock, MD has postulated that PFO anatomy results in a cul-de-sac between the septa primum and secundum, predisposing individuals to hemostasis and clot formation. Any conditions that increase right atrial pressure more than left atrial pressure can induce paradoxical flow and may result in an embolic event.

This reasoning has greatly altered the previous conception of PFO and is changing current management of the condition.

Frequency

United States

PFO is detected in 10-15% of the population by contrast transthoracic echocardiography. Autopsy studies show a 27% prevalence of probe-patent foramen ovale.1 This difference is probably due to the ability to directly visualize PFO on autopsy study, while contrast echocardiography relies on detection of secondary physiologic phenomena.


CLINICAL

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History

  • Most patients with isolated patent foramen ovale (PFO) are asymptomatic.
  • Patients may have a history of stroke or transient ischemic event of undefined etiology.
  • Some present with migraine or migrainelike symptoms. Whether symptoms are due to transient ischemic attacks or paradoxical embolism is not clear.
  • Neurologic decompression sickness is seen with PFO in a small percent of scuba divers. Risk of nitrogen gas embolism across PFO increases in scuba divers. In unexperienced divers, PFO can worsen hypoxemia at great depth leading to death. 

Physical

No abnormal cardiac clinical findings are associated with isolated PFO.


DIFFERENTIALS

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Other Problems to Be Considered

  • Obstructive sleep apnea
  • Cardiac surgery
  • Hypoxemia increases in patent foramen ovale (PFO) due to transient elevation of right atrial pressure with an increase in right-to-left shunt resulting in systemic arterial desaturation.
  • In off-pump coronary artery bypass surgery, PFO increases the risk of postoperative atrial fibrillation and hypoxemia.


WORKUP

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Lab Studies

  • No specific lab tests are necessary to diagnose patent foramen ovale (PFO).

Imaging Studies

  • Echocardiography
    • In some instances, PFO is detectable with color flow Doppler imaging. A small "flame" of color signal may be seen in the middle region of the atrial septum.
    • Contrast echocardiography is usually required to detect small PFO. After obtaining optimal visualization of the atrial septum on transthoracic or transesophageal echocardiography, a bolus of agitated saline is injected into an antecubital vein. Subsequently, microbubbles appear in the right atrium. The study is positive for PFO if the microbubbles appear in the left atrium within 3 cardiac cycles of their appearance in the right atrium. Valsalva maneuver increases right atrial pressure and facilitates right-to-left shunting.
    • Transesophageal contrast echocardiography provides superior visualization of the atrial septum and therefore is preferred to transthoracic contrast echocardiography for detecting PFO. When clinically indicated, transesophageal contrast echocardiography is strongly recommended for patients whose findings on transthoracic echocardiography are negative.

Other Tests

  • No specific electrocardiographic findings are noted in PFO.


TREATMENT

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Medical Care

Most patients with a patent foramen ovale (PFO) as an isolated finding receive no special treatment. No consensus exists on treatment of PFO in patients with transient ischemic attack or stroke.

  • When PFO is associated with an otherwise unexplained neurologic event, traditional treatment has been antiplatelet (ie, aspirin) therapy alone in low-risk patients or combined with warfarin in high-risk individuals to prevent cryptogenic stroke. With administration of warfarin, the international normalized ratio (INR) is maintained at 2-3. Consultation with a neurologist is mandatory to direct this treatment.
  • The recurrence rate of stroke or transient ischemic attack has been reported to be as high as 3.4-3.9% per year.
  • In patients with atrial septal aneurysm and PFO, the risk of first recurrent stroke within 2 years has been reported to be as high as 9%, while the rate of subsequent stroke or transient ischemic attack recurrence within 2 years increases to 22%.

Surgical Care

Surgical closure of PFO with double continuous suture has resulted in elimination of residual shunt across the PFO.

  • Indication
    • PFO more than 25 mm in size
    • Inadequate rim of tissue around the defect
    • Percutaneous device failure
  • Advantages
    • Permanent closure of the defect.
    • Prevents future paradoxical emboli.
    • No long-term anticoagulation and its risks.
  • Disadvantages
    • General anesthesia
    • Open-heart surgery
    • Hospital stay for a few days
    • The usual risks of cardiac surgery

Percutaneous care

Percutaneous closure of PFO during cardiac catheterization is an emerging therapeutic option.

  • Indications
    • Recurrent cryptogenic stroke due to presumed paradoxical embolism through PFO failure of conventional drug therapy
    • Contraindications to anticoagulant treatment
    • Alternative to medical therapy or surgical closure - Cryptogenic TIA due to presumed paradoxical embolism through a PFO
    • Presumed paradoxical peripheral or coronary embolism through PFO
    • Cryptogenic stroke, TIA, or peripheral or coronary embolism due to presumed paradoxical embolism through a PFO that is associated with hypercoagulability state
      • Divers with a PFO who are at risk of clinical events that are related to paradoxical embolism through a PFO during decompression
      • Systemic deoxygenation due to right-to-left shunting through a PFO in the absence of severe pulmonary hypertension (eg, platypnea orthodeoxia, right ventricular infarction)
      • Migraine headache accompanied by aura
      • Posttraumatic fat embolism syndrome with cerebral embolism by way of PFO
  • The Federal Drug Administration (FDA) has approved 2 percutaneous devices for PFO closure.
    • CardioSEAL Septal Occlusion System (NMT Medical Inc, Boston, MA) is a double umbrella-shaped permanent implant. It is made up of metal framework to which polyester fabric is attached. The CardioSEAL implant is available in sizes 17 mm, 23 mm, 28 mm, and 33 mm.
    • Amplatzer PFO Occluder (AGA Medical Corp, Golden Valley, Minn) is a self-expanding wire mesh with double discs. It contains inner polyester fabric patches that, along with the wire mesh, cause the formation and accumulation of a blood clot, which seals the opening. After the device is in place, tissue will grow over it, and the device then becomes a part of the atrial septum. 
  • The procedure requires a hospital stay of 24-48 hours and prophylactic aspirin or warfarin for 6 months following the procedure. After more than 5 years of follow-up observation, the results are promising.


MEDICATION

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Most patients with a patent foramen ovale as an isolated finding receive no particular treatment.

Drug Category: Anticoagulants

Antiplatelet therapy and anticoagulation with warfarin can be indicated to prevent recurrent systemic thromboembolism.

Drug NameWarfarin (Coumadin)
DescriptionInterferes with hepatic synthesis of vitamin K-dependent coagulation factors. Used for prophylaxis and treatment of venous thrombosis, pulmonary embolism, and thromboembolic disorders.

Tailor dose to maintain an INR in the range of 2 to 3.
Adult Dose5-15 mg/d PO qd for 2-5 d; adjust dose according to desired INR
Pediatric DoseAdminister weight-based dose of 0.05-0.34 mg/kg/d PO; adjust dose according to desired INR
ContraindicationsDocumented hypersensitivity; severe liver or kidney disease; open wounds or GI ulcers
InteractionsDrugs that may decrease anticoagulant effects include griseofulvin, carbamazepine, glutethimide, estrogens, nafcillin, phenytoin, rifampin, barbiturates, cholestyramine, colestipol, vitamin K, spironolactone, oral contraceptives, and sucralfate

Medications that may increase anticoagulant effects of warfarin include oral antibiotics, capecitabine, phenylbutazone, salicylates, sulfonamides, chloral hydrate, clofibrate, diazoxide, anabolic steroids, ketoconazole, ethacrynic acid, miconazole, nalidixic acid, sulfonylureas, allopurinol, chloramphenicol, cimetidine, disulfiram, metronidazole, phenylbutazone, phenytoin, propoxyphene, sulfonamides, gemfibrozil, acetaminophen and sulindac
PregnancyX - Contraindicated; benefit does not outweigh risk
PrecautionsDo not switch brands after achieving therapeutic response; caution in active tuberculosis or diabetes; patients with protein C or S deficiency are at risk of developing skin necrosis


FOLLOW-UP

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In/Out Patient Meds

Aspirin or warfarin is required for 6 months following closure of patent foramen ovale (PFO) during cardiac catheterization.

Complications

  • Complications of catheter-based closure of PFO, such as embolism of device, device entrapment within the Chiari network, frame fracture, vessel damage, or perforation of atrial wall, may require further surgery.
  • Other possible complications include air embolism during device delivery, thrombus formation around the device, and infective endocarditis.


MISCELLANEOUS

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Medical/Legal Pitfalls

  • Patent foramen ovale (PFO) is often considered in the differential diagnosis of cryptogenic stroke. At present, no consensus guidelines exist for the treatment of PFO. The following issues remain unsettled:
    • Treatment of asymptomatic patients with PFO
    • Duration of medical therapy after stroke or transient ischemic event
    • Optimal time to close PFO
  • In the setting of PFO, risk of stroke recurrence is not trivial. Risk associated with long-term anticoagulation is also not trivial. Surgical closure reduces the risk of stroke recurrence from PFO and reduces the need for anticoagulation. Catheter-based techniques are an emerging option for closing PFO.

Special Concerns

  • Misconceptions: Clinicians must know what a PFO is and what it is not.
    • The defect in PFO is not a result of missing tissue; therefore, very specific hemodynamics must be present (ie, right atrial pressure exceeding left atrial pressure) for shunting to occur.
    • PFO is not associated with an increased risk of endocarditis. Antibiotic prophylaxis is not indicated.


ACKNOWLEDGMENTS

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The authors and editors of eMedicine gratefully acknowledge the contributions of previous author Ahmed Alghamdi, MD, MB, BCh, FRCP(C) to the development and writing of this article.


REFERENCES

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Patent Foramen Ovale excerpt

Article Last Updated: May 1, 2008