Echocardiography for Technical Divers – Does It Make Sense?

I was recently asked by a diver whether it makes sense that his diving school requires him to undergo an echocardiography (heart ultrasound) before taking a technical diving course beyond Advanced Nitrox. The reasoning given was to check for a patent foramen ovale (PFO) — a small opening in the heart that, in theory, could allow bubbles to pass into the arterial circulation and increase the risk of decompression sickness.

Lediwrack, Walensee.

At first glance, this seems plausible. Especially in technical diving, where high inert gas saturations are achieved and the risk of decompression sickness is naturally greater than in recreational diving, one wants to avoid any additional risk. But the question arises: Is such a recommendation actually justified – and how do professional associations evaluate this approach?

According to the 2025 Joint Position Statement on Atrial Shunts and Diving from the South Pacific Underwater Medicine Society (SPUMS) and the UK Diving Medical Committee (UKDMC), the answer is clear: routine screening of all divers is not recommended.

For technical divers, however, the story is more nuanced.

What is a PFO?

Before birth, every baby has a natural opening between the right and left atria of the heart called the foramen ovale. It allows blood to bypass the lungs in the womb, since oxygen comes from the placenta, not breathing. After birth, when the lungs take over, this opening normally closes. In about 25% of people, however, it remains partially open. This is called a patent foramen ovale (PFO). For most people, a PFO causes no problems and they live their entire lives without ever knowing it exists.

However, a PFO can play a role in diving: it can act as a kind of ‘shortcut’ through which venous gas bubbles, which are normally filtered out in the lungs, enter the arterial circulation directly. This increases the risk of certain forms of decompression sickness, especially with neurological symptoms, when there are many bubbles present. However, a PFO alone does not make diving unsafe – the real risk lies in the formation of bubbles. That is why the focus is on well-thought-out decompression strategies and safe behaviour after the dive.

How is a PFO detected?

If a diver and their doctor decide to investigate a PFO, this is done using contrast echocardiography:

Contrast bubbles

1. Saline solution is shaken with a little air to create bubbles. This bubble mixture is injected into a vein and thus enters the right atrium.

2. Echocardiographic methods

   Transthoracic echocardiography (TTE): The examination is performed externally via the chest. It is non-invasive and comfortable, but less sensitive, especially for small PFOs.

   Transoesophageal echocardiography (TEE): A flexible probe is inserted into the oesophagus, which runs directly behind the heart. It provides a much clearer image and is the most sensitive method for detecting a PFO. However, it is less comfortable as the patient has to swallow the probe (usually with sedation or local anaesthesia).

3. Provocation manoeuvre

   A PFO only opens when the pressure in the right atrium increases. The patient is therefore asked to push hard (Valsalva manoeuvre). This increases the pressure in the right atrium for a short time, which can cause a PFO to open.

Important: A simple ultrasound without contrast agent is not sufficient. The results must always be evaluated in conjunction with the diving history.

What the Experts Say

The 2025 consensus clearly states:

• Routine echocardiography for all divers is not indicated.

• Screening should only be considered for divers with specific histories, such as neurological decompression sickness (DCS) or unexplained stroke.

• Even if a PFO is present, many divers will never experience a problem.

In other words: international experts do not recommend echocardiography as a blanket requirement.

But — and this is where nuance matters — for technical divers, screening could have value as an educational tool. Knowing whether you have a PFO may not change whether you dive, but it can make you more aware of behaviors that significantly increase risk.

The Real Issue: Bubble Formation

The main factor that increases the risk of decompression sickness is not whether someone has a PFO, but how many bubbles form in the body during and after a dive.

If bubbles are kept to a minimum through careful dive practices, the chance of them causing harm — even in someone with a PFO — is greatly reduced.

Consequences of a PFO

PFO screening for technical divers should not primarily be carried out with the aim of immediately treating any findings with closure. Rather, it serves to specifically sensitise technical divers with PFO to the following safety measures (based on the SUHMS guidelines):

• Only one dive per day

• Avoid cold and dehydration

• Avoid excessive skin warming after diving (sunbathing, sauna, hot shower)

• Allow sufficient waiting times when moving to higher altitudes (e.g. mountain passes)

• No exertion or pressing manoeuvres at the end of the dive

  • Avoid physical work underwater and currents at the end of the dive

  • Remove equipment in the water and have helpers lift you out.

  • Effortless exit onto land or into the boat.

  • Avoid carrying heavy equipment around.

• Absolutely no diving when you have a cold! Coughing or sneezing promotes the passage of bubbles through the PFO.

An absolute no-go for technical divers with PFO

Never inflate a buoy (DSMB) with your mouth! This pressure manoeuvre opens any PFO – precisely when supersaturation and the likelihood of venous gas bubbles are at their highest.

The message is clear: a PFO should motivate you to be more disciplined when technical diving – not to stop diving altogether.

Possible disadvantages of mandatory screening

Mandatory echocardiography for all technical divers could also have undesirable consequences:

• A negative result could give a false sense of security and lead to more important factors for preventing decompression sickness, such as consistent dive planning, the use of adequate decompression gases, long decompression stops, good hydration, etc., being neglected.

• Small, clinically insignificant shunts, which would never cause a problem, could lead to divers being excluded.

• The examination is expensive and – from a global perspective – not available everywhere, which can create unnecessary financial and organisational hurdles. In Switzerland, however, we are in the comfortable position that these arguments are hardly relevant.

Conclusion

Echocardiography should not be mandatory for technical divers. If it is performed, it should not be with the aim of possible PFO closure or to exclude those affected, but as a tool for education and awareness – with a focus on even safer diving strategies.

Reality confirms this impression: in almost all cases where a PFO was detected after a decompression incident, there were already clear errors in the dive planning or execution. The PFO was at most an additional contributing factor. At the same time, experience shows that there are numerous highly experienced divers who have made many challenging and deep dives in their careers, have a PFO – and yet have never suffered a decompression incident.