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Scuba and PFO The following an updated and expanded piece from my "Ask RSD" column in "Rodale's Scuba Diving": What is patent foramen ovale (PFO)? PFO, a type of atrial septal defect, is an abnormal opening between the right and left upper chambers of the heart. It is normal for blood to flow through a small opening between these two chambers during fetal development when the lungs are inoperative and blood is oxygenated by the mother. At the moment of birth, however, changes in chamber pressures cause this membranous opening to close, shunting blood to the now functioning lungs. While usually permanently sealed by the 3rd month of life, this does not always occur; about one in every four persons has an incomplete closure of varying size. Without complete closure, blood can flow from the right to the left side of the heart without passing through the lungs. This causes a decrease in the amount of oxygen reaching the body and may limit exercise tolerance, sometimes severely. In the absence of shifts in the pressure gradient in these upper chambers of the heart, however, the majority of otherwise healthy persons with PFO, many with only small openings, are unaware they have the condition. It typically requires no treatment in the adult. Of significance to divers with PFO is the increase in right chamber pressure which occurs with common equalization techniques like the Valsalva maneuver. Under this condition, nitrogen bubbles that can form in the venous bloodstream during decompression may pass directly into the arteries without the filtering action of the lungs. Divers with PFO can develop decompression illness (DCI) manifestations ranging from relatively harmless skin rashes to serious neurological problems such as vertigo or paralysis. Bubbles passing into the brain can obstruct blood vessels, resulting in lesions of various size. Studies of high frequency divers have documented an increased likelihood of large and/or multiple brain lesions, and shown that a high percentage of divers who had otherwise unexplained incidents of DCI turned out to have PFO. In addition, The risk of severe decompression sickness (DCS) appears to be about three to five times greater in those with PFO as compared to the general diving population, although the relationship is much weaker for only mild cases. Despite research findings of increased risk of DCI in divers with PFO, the risk is still low. Most dive medicine experts do not recommend echocardiogram as a routine procedure in healthy divers. However, scuba enthusiasts with PFO will want to be aware of a relatively recent study in the American Journal of Cardiology showing that the size of a PFO in some divers increased over time. While this finding needs replication, it is potentially disturbing. The presence and nature of a PFO is best established by transesophageal echocardiogram (TEE) with bubble contrast. This allows bubbles passing from the right to the left to side of the heart to be observed. Even a small number of bubbles are a matter of concern. The basic procedure is described here----> http://en.wikipedia.org/wiki/Echocardiography. At this examination procedures such as Doppler color flow imaging also may be performed, although this is not common. If repair is indicated, the procedure selected depends upon a number of factors including the size of the opening. There are several approaches, including suturing of the defect or placing a tissue patch over it, although preferred where possible is the non-surgical placement of a blocking device such as the Amplatzer PFO Occluder described here----> http://www.fda.gov/cdrh/mda/docs/p000039.html At some point following
the repair TEE with bubble contrast likely will be repeated. With these
findings and other information regarding fitness to dive, including general
health and exercise tolerance, the diver and his physician can decide
on the best course of action. Given an uncomplicated and successful closure
in an otherwise fit individual, return to diving typically can be expected
within 6-12 weeks. © Doc Vikingo 2005 Back
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