Patent foramen ovale.

Patent foramen ovale is common in the general population and even more common in patients with cryptogenic stroke or stroke of unknown cause. The most common causes of stroke in people over the age of 50 are atherosclerosis and atrial fibrillation. In patients under the age of 50 who develop stroke of undetermined cause, one should entertain the possibility of a patent foramen ovale. (1) The foramen ovale is open during embryonic development and should close by the neonatal period. In 26 to 29% of the population, it remains open after birth and continues to be patent through life, creating a shunt between the two atria. Valsalva maneuver from straining may raise the right atrial pressure and cause a right-to-left shunt. What is the best approach to managing patients with this cardiac defect? Surgical closure, percutaneous transcatheter closure, antiplatelet agents and anticoagulants have all demonstrated benefit in its management. (2)

We do know of an association between patent foramen ovale and stroke. Forty percent of all ischemic strokes are of unknown cause. The presence of atrial septal aneurysm and patent foramen ovale together worsen the risk of stroke. (3) Twenty-eight percent of patients with cryptogenic stroke have atrial septal aneurysm. (1) Some investigators believe that the larger the patent foramen ovale, the greater the risk of cryptogenic stroke. The cardiac defect may predispose the patient to atrial dysrhythmias of the heart which increase the chance of stroke. (3) The assumption is that an embolus moves from the right atrium to the left atrium in these patients, and this results in a stroke. It is conceivable that surgeons have reduced the morbidity and mortality from patent foramen ovale through the surgical closure procedure, despite the risk of the procedure itself. The procedure permanently closes the patent foramen ovale and lowers, if not eliminates, the possibility of paradoxical embolism originating somewhere else in the body and subsequently crossing the atrial septum to the left heart. It further obviates the need for subsequent anticoagulant therapy. This problem of paradoxical embolism is of great concern in patients with patent foramen ovale who take oral contraceptives, smoke cigarettes, have a history of venous thromboembolism, have certain coagulation disturbances or who are pregnant. (2) Fat emboli and air emboli are possibilities in paradoxical emboli which may traverse a patent foramen ovale, and this includes deep sea divers who suffer from decompression sickness. (4) In any event, recurrent paradoxical embolism with patent foramen ovale and atrial septal aneurysm may make surgical closure the best approach. (4) Percutaneous transcatheter closure of patent foramen ovale may be an alternative to surgery or to the use of long-term anticoagulation in patients with patent foramen ovale and paradoxical embolism. This procedure has a high success rate and few complications or recurrences of systemic emboli. (5)

The diagnosis of patent foramen ovale, like many other medical conditions today, has become much easier. Transesophageal echocardiography is the best method to evaluate adults with suspected paradoxical embolism. The latter procedure suggests that right-to-left atrial shunting occurs with Valsalva. Right ventricular infarction and acute respiratory failure may create a right-to-left shunt through elevation of right atrial pressure. (1) Much of our data regarding the prevalence of the condition comes from autopsy examinations; however, the use of transesophageal echocardiography has become an important tool, not only in clinical research trials, but also in the daily evaluation and management of these cases.

In conclusion, patent foramen ovale is a common medical condition which requires adequate medical and surgical evaluation. We have accomplished much with good diagnostic cardiology and surgery and will likely continue to make great strides in enhancing the quality of life for these patients.

References

1. Wu L, Malouf JMD, Dearani D. Patent foramen ovale in cryptogenic stroke: Current understanding and management options. Arch Intern Med 2004;164:950-956.

2. Dearani J, Ugurlu B, Danielson G, et al. Surgical patent foramen ovale closure for prevention of paradoxical embolism--related cerebrovascular ischemic events. Circulation 1999;100:171-175.

3. Homma SMD, Sacco R, DiTullio M, et al. Effect of medical treatment in stroke patients with patent foramen ovale. Circulation 2002;105:2625.

4. Meir B, Lock J. Contemporary management of patent foramen ovale. Circulation 2003;107:5.

5. Martin F, Sanchez P, Doherty E, et al. Percutaneous transcatheter closure of patent foramen ovale in patients with paradoxical embolism. Circulation 2002;106:1121.

Michael Koger, Sr., MD

From University of Alabama, Tuscaloosa, AL.

Reprint requests to Michael Koger, Sr., MD, PO Box 21260, Tuscaloosa, AL 35402. Email: [e-mail]

Accepted July 1, 2005.