PFO Closure Shows Promise in Alleviating Unprovoked Decompression Sickness in Divers
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Catheter-based closure of patent foramen ovale (PFO) may alleviate decompression sickness in scuba divers by eliminating embolization of arterial bubbles, according to a case-controlled observational study published online March 19, 2014, ahead of print in JACC: Cardiovascular Interventions.
Researchers led by Josef Veselka, MD, PhD, of Motol University Hospital (Prague, Czech Republic), looked at 47 divers who participated between February 1, 2006, and April 30, 2013, in simulated dives in a hyperbaric chamber of either 18 m for 80 min or 50 m for 20 min. Patients were further categorized according to whether they had a PFO (n = 19) or had undergone PFO closure (n = 15). All patients performed the first dive (18 m), while 8 PFO patients and 5 closure patients performed the second dive (50 m).
On echocardiography, venous bubbles were detected with similar frequency in the PFO and closure group (74% vs 80%; P = 1.0). However, arterial bubbles were detected in 12% of the PFO group but none of the closure patients (P = 0.02).
In 21% of divers with PFO and detected arterial gas bubbles, neurological symptoms of decompression sickness were present (ie, headache, unusual fatigue, and transitory visual disturbances). Conversely, none of the divers in the closure group reported decompression sickness symptoms (P = 0.11).
Closure Group Shows No Symptoms
In the 50-m dive, venous bubbles were again detected with similar frequency in divers in the PFO vs closure group (88% vs 100%; P = 1.0). Arterial bubbles, meanwhile, were detected in 88% vs 0, respectively (P < 0.01). In 25% of divers with PFO and detected arterial gas bubbles, mild neurological symptoms of decompression sickness were present. No divers reported decompression sickness symptoms in the closure group (P = 0.49).
“In our study, no difference was found in the occurrence of venous bubbles between the PFO and closure groups,” the authors noted. “However, in the closure group, no arterial bubbles were detected. It is plausible, therefore, that the presence of a PFO plays a key role in paradoxical embolization of venous bubbles after scuba dives. Additionally, because PFO occlusion led to elimination of bubble occurrence in the medial cerebral artery, this closure strategy should have a role in the prevention of unprovoked [decompression sickness] recurrence in divers.”
They note that in divers with PFO, a paradoxical embolization may occur and cause various— mostly neurological or cutaneous decompression sickness—symptoms even after a dive with an appropriate decompression regimen. However, they add, “the management of divers with PFO remains unresolved. Routine screening for PFO in divers is currently not recommended in most countries. Suggested recommendations for divers with diagnosed PFO and a history of [decompression sickness] include the cessation of diving, a conservative approach to diving, and PFO closure.”
PFO Closure ‘The Thing to Do’
In an accompanying editorial, Alfred A. Bove, MD, PhD, of Temple University School of Medicine (Philadelphia, PA), notes that prior research has failed to demonstrate an association between PFO closure and reduced strokes or migraines in patients with the structural defect. Nevertheless, he adds, PFO closure “is the thing to do these days in the interventional laboratory.”
Whether this is warranted or not, he called the data from the current study “compelling.” Still, Dr. Bove cautions, “one should not conclude that commercial and technical divers who are exposed to risky dive profiles be screened for a PFO or have a PFO closed prophylactically, but commercial divers who have multiple recurrences of unexplained [deep compression sickness] should be screened for a PFO, and if found, a decision to close the shunt should be made by the diver and physician together. . . . “
In a telephone interview with TCTMD, Robert J. Sommer, MD, of Columbia University Medical Center (New York, NY), also found the data “highly compelling,” and observed, “If we’re going to use the presence of arterial bubbles as the equivalent of full-blown decompression illness, then I think the paper proves that closing the PFO eliminates that risk.”
Serious Divers Should Seek Screening
Furthermore, he said, the data should convince serious divers to seek screening for the presence of a PFO. “Now what to do after that is hard to say, because it’s different than patients who have had stroke or TIA because there, at least, there’s a medical option,” Dr. Sommer said. “Here, there’s no medical option.”
In his own experience, Dr. Sommer notes that he has seen professional divers from organizations such as the New York Police Department and the New York Fire Department who have experienced symptoms on the job and subsequently been found to have a PFO. “And then those patients come to me to get their PFOs closed because otherwise they would be classified as disabled,” and would not be allowed to dive again, he said.
Study Details
Mean age of patients was 32 years in the PFO group (74% men) and 38 in the closure group (80% men).
Venous bubbles were assessed by experienced echocardiographers using transthoracic echocardiography. Arterial bubbles were detected by means of transcranial color-coded ultrasound in the medial cerebral artery.
The PFO closure procedures were performed at a single center (with the exception of 2 divers) between February 1, 2006 and April 30, 2013. The Amplatzer septal occluder (AGA Medical Corporation, Golden Valley, MN) was used in 5 divers. In the remaining 15, the Occlutech Figulla PFO Occluder N (Occlutech GmbH, Jena, Germany) was used. In all cases, the indication for the procedure was a history of unprovoked decompression sickness (ie, without violation of decompression regimen) and the presence of a grade 3 PFO.
Sources:
1. Honěk J, Srámek M, Šefc L, et al. Effect of catheter-based patent foramen ovale closure on the occurrence of arterial bubbles in scuba divers. J Am Coll Cardiol Intv. 2014;Epub ahead of print.
2. Bove AA. The PFO gets blamed again. . . Perhaps this time it is real. J Am Coll Cardiol. Intv. 2014;Epub ahead of print.
Disclosures:
- Dr. Veselka reports no relevant conflicts of interest.
- Dr. Bove reports serving as a consultant for World Health Networks, Inc, serving as a consultant and owning stock in Insight Telehealth Systems LLC, and serving as a training director for Underwater Medicine Associates, Inc.
- Dr. Sommer reports having an equity interest in Coherex, a PFO closure device manufacturer, and being involved in the REDUCE trial, sponsored by St. Jude Medical, which is studying the PFO stroke relationship.
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