PFO Closure May Prevent Decompression Sickness in Divers With Large Shunts

In scuba divers with large patent foramen ovale (PFO), transcatheter closure seems to prevent decompression sickness (DCS), a new study suggests.

“According to our data, PFO closure is recommended in divers with a high-grade PFO, with a history of unprovoked DCS, or at the diver’s preference,” investigators led by Jakub Honĕk, MD, PhD (Motol University Hospital, Prague, Czech Republic), write. “Besides protection from DCS, PFO closure also offers the diver lifelong protection from PFO-associated stroke.”

This is not the first time PFO closure has been studied in divers, with a 2011 study showing that PFO closure in this population may prevent symptomatic and asymptomatic neurological events over 5 years, said Amar Krishnaswamy, MD (Cleveland Clinic, OH), who was not involved in either study. However, the perspective of PFO closure has changed substantially over the past several years, with it now widely accepted as a means to prevent PFO-associated stroke and studies are ongoing to show its potential in reducing migraines.

“Generally speaking, there is more interest and understanding in how we distinguish an inconsequential versus a consequential PFO,” he said. “A lot of that understanding has come from the fact that the earlier PFO trials for stroke didn't seem to demonstrate that closure of the PFO made a difference, and then the more-contemporary trials, that really had better patient and PFO selection, have demonstrated that closing PFOs to reduce stroke in appropriately selected patients is important.”

In divers specifically, Krishnaswamy said, the concern of a large shunt would be that if “some of the small gas bubbles in tissue sort of become elaborated and enter the venous circulation, then . . . go across the PFO and enter the arterial circulation, that's what contributes in large part to decompression illness.”

Implications for Professional, Amateur Divers Alike

For the study, published as a research letter in the September 1, 2020, issue of the Journal of the American College of Cardiology, Honĕk and colleagues included 829 individuals who were prospectively enrolled in the DIVE-PFO registry between 2006 and 2018. Among them, 702 had follow-up data and continued diving.

High-grade PFO (≥ grade 3) was identified in 153 divers (22%), 55 of whom underwent PFO closure with either the Amplatzer Septal Occluder (18%; Abbott) or the Occlutech Figulla PFO Occluder N (82%; Occlutech GmbH). Minor bleeding was the only procedural complication, noted in two cases (3.6%). The rest of the divers were advised to dive within the limits of recreational diving.

Over a mean follow-up period of about 7 years, those in the closure group did more diving (30,684 vs 25,328 new dives; P < 0.001). However, while unprovoked DCS (primary endpoint) occurred in 11 people who did not have their PFOs closed, there was no DCS reported in those divers who did (P = 0.012).

“The implication that PFO closure prevents unprovoked DCS is valid both for professionals and amateur (recreational) divers,” Honĕk told TCTMD in an email. “It must be a shared decision of the diver and the specialist to go forward with the procedure. In my opinion, amateur divers that wish to continue with frequent unrestricted diving after they have suffered from an unprovoked episode of decompression sickness should be considered for PFO closure. Typically, DCS cases are seen on a diving vacation where the divers often do between two to five dives every day for a week. In professionals, I think the decision is quite clear—if they want to continue working as divers and their diving profiles and frequency cannot be adapted, they should undergo PFO closure.”

Krishnaswamy agreed that these data are relevant to all kinds of divers but would have more-profound implications for those who rely on diving for a paycheck. “If you've got the man or woman who is diving once every 2 years when they go to the Caribbean, I don't know whether this small risk, as small as it is for PFO closure, makes it worth it,” he said. On the otherhand, it might “mean something more for professional divers, diving instructors, or individuals who are in the Navy or the military, for whom diving is an important part of life and security.”

The population ripe for future study would be those who dive often and also have a large PFO, according to Krishnaswamy. “If another trial were to be done, having a brain MRI as a substudy or part of the outcome measures could be an important part of analyzing this as well,” he said.

Additionally, research on PFO closure different populations may affect the US Food and Drug Administration’s stance, with implications for reimbursement. “The way the FDA approval and insurance funding is currently written is that PFO closure is considered for patients with prior stroke, no other factors, and large shunting,” Krishnaswamy added. “But the group of patients who may be excluded from that, and for whom we sometimes have difficulties in obtaining insurance coverage, are the group of patients who have nonstroke arterial emboli that we're attributing to a PFO. . . . So, I think that this is an important thing for insurance providers and FDA to understand.”

Honĕk said his team plans to publish more on this population soon. “One important point is that the strategy of screening for PFO, risk stratifying, and even performing PFO closure in some divers works, and that screening for PFO should be more encouraged,” he concluded.