Risk mitigation in divers with persistent (patent) foramen ovale

Area of Science:

• Cardiovascular physiology in diving medicine.
• Diving safety and risk assessment.
• Interventional cardiology and its impact on recreational activities.

Background:

• Persistent (patent) foramen ovale (PFO) and atrial septal defects (ASDs) are right-to-left shunts that can contribute to decompression illness (DCI) in divers.
• Shunt-mediated DCI requires a right-to-left shunt, venous bubbles bypassing lung filtration, and supersaturated tissues for inert gas amplification.
• Two strategies exist for divers with shunts: closure of the shunt or extremely conservative diving practices.

Discussion:

• The study by Anderson et al. investigated the efficacy of PFO/ASD closure versus conservative diving in preventing recurrent DCI.
• Significant limitations include a small sample size, self-selected participants, lack of randomization, and inconsistent definitions.
• The study's primary endpoint showed no difference, with only two confirmed DCI events per group, highlighting the need for further research with larger, randomized cohorts.

Key Insights:

• PFO/ASD closure can reduce DCI risk to levels comparable to non-shunt divers if the procedure is effective.
• Conservative diving is only effective if dives are genuinely conservative, preventing bubble nucleation and amplification.
• DCI recurrence after closure can stem from residual shunts or other mechanisms like AGE or provocative dive profiles.

Outlook:

• Future research should focus on randomized controlled trials with robust methodologies to definitively assess PFO/ASD closure efficacy.
• Standardized protocols for conservative diving advice and adherence monitoring are crucial for evaluating this strategy.
• Understanding the specific mechanisms of DCI post-intervention requires detailed dive profiles, clinical data, and post-procedure assessments.