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Decompression Illness in Divers With or Without Patent Foramen Ovale
Quick Takes
- In a single-center prospective cohort study of 100 divers who did >50 dives per year, the incidence of PFO was 68% (including 37% [54% of all PFOs] high-risk and 31% [46% of all PFOs] low-risk).
- Multivariable analysis revealed that high-risk PFO was independently associated with an increased risk for PFO-related DCI.
Study Questions:
Is there an association between patent foramen ovale (PFO) and decompression illness (DCI) in scuba divers?
Methods:
The DIVER-PFO (Decompression Illness in Divers With or Without Patent Foramen Ovale) study was a single-center prospective cohort study between August 2015 and February 2021, which recruited 100 volunteer adult divers who did >50 dives per year. Transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and transcranial Doppler (each with agitated saline contrast without and with Valsalva maneuver) were performed to determine the presence of a PFO, and patients with PFO were divided into high-risk (atrial septal aneurysm or hypermobility, PFO size ≥2 mm, or left-to-right shunt at rest) and low-risk groups. Follow-up was using a self-reported questionnaire while blinded to PFO status; all reported symptoms were adjudicated in a blinded manner. The primary endpoint was the 3-year cumulative incidence of PFO-related DCI defined as cutaneous or neurological DCI events, DCI symptoms requiring hyperbaric therapy, DCI symptoms within 30 minutes after surfacing, or unexplained death within 2 weeks after diving. Logistic regression analysis was performed to determine the odds ratio of PFO-related DCI.
Results:
PFO was seen in 68 divers (68%; 37 [54% of all PFOs] high-risk and 31 [46% of all PFOs] low-risk). During a mean follow-up of 28.7 months, PFO-related DCI occurred in 12 divers in the PFO group (all cutaneous or neurological, no deaths, and only one diver who underwent hyperbaric treatment). The incidence of a DCI event per 10,000 dives was 0 in non-PFO divers vs. 8.4 in high-risk PFO divers vs. 2.0 in low-risk PFO divers (p = 0.001). Multivariable analysis showed that high-risk PFO was independently associated with an increased risk for PFO-related DCI (odds ratio, 9.34; 95% confidence interval, 1.95-44.88; p = 0.005).
Conclusions:
High-risk PFO was associated with an increased risk for DCI in scuba divers. The authors conclude that this indicates that divers with high-risk PFO are more susceptible to DCI than what has been previously reported and should consider either refraining from diving or adhering to a conservative diving protocol.
Perspective:
DCI occurs when inhaled nitrogen that is dissolved in tissue or blood under high pressure during a dive subsequently forms gas bubbles when the diver ascends, mechanically affecting tissue or inhibiting blood flow; if present, a PFO can enable the embolization of venous nitrogen bubbles to the arterial system. Although previous studies also have documented a higher incidence of PFO in divers who experience DCI than in those who do not, in this prospective cohort study, both the divers and the adjudicating neurologist were blinded to the presence of PFO during the study. Interestingly, although only 1 of 12 divers who were diagnosed in this study with DCI had a history of prior DCI, 11 of 12 reported having experienced similar symptoms in the past, suggesting that mild symptoms might occur frequently but go unreported.
The study found a higher incidence of PFO (68%) in divers compared to usual population reports (20-34%), which could have represented selection bias (divers who had past symptoms were more motivated to volunteer for the study) or a truly elevated prevalence of PFO among people who dive >50 times per year (possibly mediated by frequent Valsalva maneuver performed during normal diving descents). The small sample size in this study might have been insufficient to detect a role of low-risk PFO in DCI events. Decisions regarding how to best mitigate DCI risk for divers with high-risk PFO probably should weigh the severity as well as the incidence of clinical events.
Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Sports and Exercise Cardiology, Congenital Heart Disease, CHD and Pediatrics and Imaging, CHD and Pediatrics and Quality Improvement, Echocardiography/Ultrasound, Nuclear Imaging, Sports and Exercise and Congenital Heart Disease and Pediatric Cardiology, Sports and Exercise and Imaging
Keywords: Aneurysm, Congenital Abnormalities, Decompression, Diagnostic Imaging, Diving, Echocardiography, Echocardiography, Transesophageal, Foramen Ovale, Patent, Hyperbaric Oxygenation, Nitrogen, Risk Factors, Sports, Ultrasonography, Doppler, Transcranial, Valsalva Maneuver
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