PFO a Higher Danger to Divers Than Thought

A PFO (a patent foramen ovale) is a common heart defect. It's a small opening between the left and right atrium of the heart that usually closes after birth. If it stays open, arterial blood can flow between the chambers, avoiding the lungs and causing nitrogen-loaded blood to recirculate more easily. Therefore, nitrogen absorbed during a dive is less easily off-loaded on ascent.

Previous studies have indicated that PFO prevalence is higher among divers who experienced DCI than those who did not, Hyun-Jong Lee, MD, a professor at Sejong University in South Korea, wrote in the current Annals of Internal Medicine. The researchers studied 100 experienced divers who completed more than 50 dives annually, dividing them into two groups. During a follow-up of 28.7 months, 12 divers in the PFO group had PFO-related DCI events. The incidence of DCI was 12.8%, which is higher than reported in previous literature.

"Our results indicated that DCI events with mild symptoms occurred frequently in divers with PFO, and many divers did not recognize them as DCI," Lee and colleagues wrote. Divers with a PFO, they concluded, should adhere to a conservative diving protocol or avoid diving altogether.

Lee and colleagues noted that routine PFO screening is not recommended for divers without previous DCI episodes.

Some divers who suffer minor DCS events thought to be caused by a PFO prefer to resort to surgery and have them closed up. There was even talk a few years ago about including screening for PFO in diving medicals.

Bill Schlegel, MD, a cardiologist and long-time Undercurrent contributor, sent us an article about the association of PFOs with unprovoked DCS hits. The article in JACC: Cardiovascular Imaging reports that in a recent study, 829 divers were enrolled in the Decompression Illness Prevention in Divers with a Patent Foramen Ovale registry between January 2006 and December 2018. An analysis showed that those who were screened and then underwent PFO closure were less likely to experience unprovoked decompression sickness (DCS) than those who took a conservative approach to management.

Schlegel, who is also associated with DAN, tells us in 30 years of diving medicine, he's seen three people who had undeserved DCS hits where a thorough medical workup found that the cause could have been a PFO. "We plugged two of them. One declined the procedure and decided to stop diving. Two others, both of whom had serious but transient neurologic 'hits,' had the closure, and both did well. One of them has returned to occasional diving, conservatively."

Closing the hole these days is much easier than in the past. There are various patented closure devices to plug PFOs delivered into the heart on the end of a catheter. The device is pushed through the PFO and deployed. It expands, locks into place, and plugs the hole. The catheter is then removed. The patient ends up only with a small puncture at the site where the catheter entered.

(A few paragraphs are abridged from an article in Undercurrent November 2021)

See also: https://tinyurl.com/3fx3tke8