Update on PFO Study

[debersole]

As many of you know, Dr. Petar Denoble and I have been running a DAN sponsored study of PFO. I thought I'd update everyone on what we do and don't know about PFOs and diving.

First of all, PFOs are very common -- occurring in about 25% of the population. Secondly, they DO increase the risk of DCS -- probably by about 5 fold. Now, while that sounds impressive at first glance, you need to look at the ABSOLUTE risk of DCS. The best data we have is on recreational diving where the incidence of DCS is about 2 per 10,000 dives. Therefore, recreational divers with PFO probably have a risk of about 10 per 10,000 dives or 1 per 1000 dives (0.1%).

While PFO closure is a relatively minor procedure, the complication rate is in the range of 1-2% with complications ranging from minor things like palpitations and minor bleeding to severe problems like erosion of the device, device embolism, need for emergent surgery, etc.

Clearly, it doesn't make sense for someone who has never had a DCS event and has a risk of DCS of 0.1% to have a procedure that has a complication rate of 1-2% (10-20 times higher!). However, for divers that have had recurrent "unexpected" DCS, especially if they are technical or professional divers, closure may be a good alternative.

With this in mind, we developed a research protocol with the first enrollment about 3 years ago. We are looking for about 100 patients with DCS and a known PFO -- regardless of whether or not they elected to have it closed. We have enrolled 58 patients so far and have a mean follow-up of two years.

Preliminary findings suggest, as one would expect, more aggressive or frequent divers are more likely to opt for closure of their PFO while those that only do the occasional recreational dives are more likely to opt for conservative therapy.

Addiditonally, one of our co-investigators, Derrick Covington, will be reporting an abstract at next month's UHMS meeting that shows divers tend to change their diving styles once the diagnosis of PFO and DCS is made, regardless of whether or not their PFO was closed. Divers with uncomplicated closure did more dives afterwards while a number of them did fewer due to either closure complications or concomitant disease. Some divers with PFO who chose not to close but dive conservatively did more dives but used more nitrox and limited their depth and time.

In follow-up, three subjects have reported DCS events -- two with skin bends and one with spinal DCS. Obviously, these numbers are too small to make any conclusions, but we continue to follow the participants and are actively recruiting.

If you or any of your diving friends are interested in participating or simply learning more about the study, follow this link:

http://www.diversalertnetwork.org/re...of_pfo_closure

Thanks!
Doug

Douglas Ebersole, MD
Interventional Cardiology, Watson Clinic LLP
Lakeland, Florida

[apitkin]

Doug,

Thanks for a useful contribution to our knowledge on this difficult subject.

The finding that the diagnosis of a PFO alters behavior is very interesting indeed - that makes it even harder to design a study to answer the question of whether PFO closure reduces the risk of DCS.

Andy

[debersole]

Agreed. With the "aggressive" divers opting more often for closure while "less aggressive" divers opt more often for leaving it alone and then finding people altering their diving, making strong conclusions is going to be very difficult. The best study, of course, would have been a randomized study of closure vs. no closure but we don't have funding for a study of that size and complexity -- not to mention it would be hard to find people willing to be randomized.

Doug