What is it?
A patent foramen ovale, sometimes known as a persistent foramen ovale or PFO, is a small hole between the atria of the heart. It is required during intrauterine development of a foetus and should close shortly after birth. In 20-25% of the population this does not occur and the small hole remains open or ‘persists’. It is very common (1 in 4 approximately) and rarely causes any problems throughout life however can become problematic when considering SCUBA diving.
What’s the problem with scuba diving?
During scuba diving inert gases (usually nitrogen) build up in the tissues. Occasionally, these bubbles can cause Decompression Illness.
There are two types of Decompression Illness (DCI): Decompression Sickness and Arterial Gas Embolism.
Arterial Gas Embolism happens when a bubble of inert gas escapes and lodges into a smaller blood vessel causing the blood supply to be interrupted. This can happen anywhere in the body but most commonly occurs in the blood supply of the brain causing stroke like symptoms.
If you have a PFO, an Arterial Gas Embolus is more likely as the hole in the heart can act as a “bypass” mechanism for bubbles into the arterial blood system. Therefore, making it more likely that you will get Decompression Illness.
How do I know if I have a PFO?
As PFO’s rarely cause a problem in daily life, many people do not know they have one. Most of the divers we see only discover they have a PFO after being treated for Decompression Illness. Many of these divers got Decompression Illness despite doing relatively safe and otherwise benign dives. There has been shown to be a link between having a PFO and suffering from migraines with aura. Therefore, if you have migraines it is important to discuss this with a diving doctor before going diving.
If it is thought that you may have a PFO and want to dive you can continue to do so, but there are some restrictions (see below). Alternatively, you can see a cardiologist with an interest in diving. They can perform further tests to determine if you have a PFO. One of these is a bubble contrast echo. This is a special type of scan where tiny bubbles are injected into your blood stream to see if they cross the heart through a PFO. Unfortunately, these consultations and instigations for PFO in relation to diving are not funded by the NHS so you will have to pay to be seen as a private patient.
So, can I dive with a PFO?
The United Kingdom Diving Medical Committee (UKDMC) and the South Pacific Underwater Medical Society (SPUMS) have issued a joint statement on diving with a PFO. If you are diagnosed with a PFO there are three potential options; stop diving, dive more conservatively (see restrictions) or consider a procedure to close the PFO. These options should be discussed with your cardiologist with an interest in diving.
Due to the increased risk of DCI there are some restrictions if you want to continue diving but do not wish to have your PFO closed.
Examples of these are:
- Restricting depth to less than 15m
- Reducing dive times to well within no decompression limits
- Diving no more than once per day
- Using nitrox with air diving planning tools
- Lengthening of the safety stop
- No heavy lifting or strenuous activity for at least three hours after diving