Patent Foramen Ovale and Scuba Diving

Introduction

Patent Foramen Ovale (PFO) is a relatively common cardiac abnormality that occurs when a hole remains open between the left and right atria of the heart. This opening allows blood to flow directly between the two upper chambers, bypassing the lungs. While PFO is often asymptomatic and typically harmless in everyday life, it can pose certain risks for scuba divers. This entry will explore the potential implications of PFO on scuba diving, diving-related conditions associated with PFO, and considerations for safe diving practices for individuals with PFO.

Patent Foramen Ovale: Background and Physiology

The foramen ovale is a small opening between the left and right atria that is essential for fetal circulation. In utero, the fetus receives oxygen-rich blood from the placenta rather than the lungs. The foramen ovale allows this oxygen-rich blood to bypass the fetal lungs and be distributed directly to the rest of the body. After birth, the lungs begin to function, and the foramen ovale typically closes within a few months due to increased blood pressure in the left atrium.

However, in about 25% of the population, the foramen ovale does not close completely, resulting in a patent (or open) foramen ovale. In most cases, the pressure difference between the left and right atria keeps the hole closed during normal activities, and the PFO remains asymptomatic.

PFO and Scuba Diving: Decompression Sickness and Arterial Gas Embolism

Scuba diving introduces unique physiological challenges, including exposure to increased ambient pressure and the risk of decompression sickness (DCS) and arterial gas embolism (AGE). DCS occurs when a diver ascends too quickly or fails to perform adequate decompression stops, causing dissolved inert gases, primarily nitrogen, to form bubbles in body tissues and blood vessels. AGE, on the other hand, results from a gas bubble entering the arterial circulation, often due to lung over-expansion injuries or rapid ascent.

In individuals with PFO, the risk of developing DCS and AGE may be higher. During diving, the presence of a PFO may allow gas bubbles to bypass the lungs, where they would typically be filtered out, and instead enter the arterial circulation. This right-to-left shunt of blood can lead to the formation of larger gas bubbles, which may cause more severe symptoms of DCS or AGE.

PFO and Scuba Diving: Risk Assessment and Management

Although the presence of PFO increases the risk of DCS and AGE, it does not mean that individuals with PFO cannot dive safely. Rather, it requires a thorough assessment of the risks and careful management of diving practices. Divers with PFO should consult with a diving medicine specialist to evaluate their individual risk and determine if they can safely participate in scuba diving.

Several factors may influence the risk of DCS and AGE in divers with PFO, including the size of the opening, the presence of other medical conditions, and the specific diving profiles (depth, time, ascent rate, and decompression stops). Divers with PFO may be advised to follow more conservative diving practices, such as shallower dives, longer surface intervals, slower ascent rates, and the use of enriched air nitrox to reduce nitrogen loading.

PFO Closure: Surgical and Nonsurgical Options

In some cases, divers with PFO may be advised to undergo a procedure to close the opening. There are both surgical and nonsurgical options for PFO closure. Nonsurgical closure, known as percutaneous PFO closure, involves the insertion of a closure device through a catheter to seal the opening. This minimally invasive procedure has a high success rate and

low complication rate, making it an attractive option for many individuals. Surgical closure, although less common, may be recommended in cases where nonsurgical closure is not suitable or when other heart conditions require surgical intervention.

Following PFO closure, divers should consult with their diving medicine specialist to reassess their risk and determine when they can safely return to diving. A period of recovery and monitoring is typically required to ensure proper healing and the absence of complications.

Pre-Dive Screening for PFO

Given the potential risks associated with PFO and scuba diving, some divers may wonder if they should be screened for the condition before diving. While routine screening for PFO in all divers is not currently recommended, those with a history of unexplained DCS or AGE incidents or a family history of PFO may consider undergoing testing. Screening for PFO can be conducted through noninvasive methods, such as transthoracic echocardiography with a bubble study or transesophageal echocardiography.

Conclusion

Patent Foramen Ovale, while a common and often asymptomatic cardiac abnormality, can pose unique risks for scuba divers due to the potential for right-to-left shunting of blood and gas bubbles. Divers with PFO should work closely with a diving medicine specialist to assess their risk and develop an appropriate diving plan that minimizes the chances of developing DCS or AGE. In some cases, PFO closure may be recommended to further reduce risk. Ultimately, with proper risk assessment and management, many individuals with PFO can continue to enjoy the underwater world through safe scuba diving practices.

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