If you’re involved in the world of diving, you may have heard of cases where divers have suffered from Decompression Sickness (DCS) after a dive, even if it wasn’t very deep or long, and if they followed proper diving techniques and stayed within non-decompression limits.

Some of these cases may be due to the individual having a Patent Foramen Ovale (PFO), possibly without even knowing it.

What is Patent Foramen Ovale or PFO?

A Patent Foramen Ovale (PFO) is a structural defect of the heart consisting of a small opening that connects the right and left atria.

In reality, the presence of a foramen ovale is normal during embryonic development and at birth, and it usually closes between 6 months and a year after birth. However, in approximately 25% of the population, this closure does not occur, resulting in a persistent communication between the two sides of the heart, known as a patent foramen ovale.

foramen oval

What risks are associated with Patent Foramen Ovale or PFO?

In most cases, the presence of a Patent Foramen Ovale (PFO) is asymptomatic and does not require specific treatment.

However, when the pressure in the right atrium increases, blood may pass from the right atrium to the left atrium, as occurs during exertion, coughing, or the Valsalva maneuver, which involves attempting to exhale against a closed glottis or with the mouth and nose closed. This maneuver is well-known in the diving community as it is often used to equalize pressure in the ears during immersion.

This shunt or passage of blood from the right atrium to the left atrium is associated with an increased risk of certain vascular disorders, such as paradoxical thromboembolism, strokes, or cerebrovascular accidents, and neurological decompression sickness in divers, with inner ear decompression sickness being particularly common within the latter.

During immersion, small bubbles form in the bloodstream, which, typically, are eliminated in the pulmonary filter as they travel with venous blood to the right side of the heart. However, due to the presence of a Patent Foramen Ovale, these bubbles can pass to the left side of the heart, from where the arteries carrying blood to the head originate, potentially leading to decompression sickness in brain structures and the inner ear.

Inner ear involvement is particularly common due to its vascularization characteristics and the direct formation of bubbles within it. The main symptom of inner ear decompression sickness is the onset of vertigo, followed by hearing loss and tinnitus.

foramen oval y buceo

Inner Ear Decompression Sickness and PFO

There is a strong correlation between inner ear decompression sickness (IEDS) and the presence of a patent foramen ovale (PFO), with a prevalence of up to 75% in the affected diver population.

Therefore, in a patient who has experienced IEDS, the presence of a right-to-left shunt must be investigated, the most common of which is a patent foramen ovale (PFO).

Among the possible diagnostic techniques to detect it, we can highlight:

  • Cardiac magnetic resonance imaging,
  • Transcranial Doppler,
  • Transthoracic echocardiogram,
  • Transesophageal echocardiogram.

The latter is the most commonly used diagnostic technique, due to its higher diagnostic sensitivity, especially when contrast bubble injection, typically agitated saline, is performed, and the arrival of bubbles in the left atrium is observed. Based on the amount of bubbles, the size of the PFO can also be estimated.

Prevention of inner ear decompression sickness with a diagnosis of PFO

Today, a PFO is not an absolute contraindication for diving. In fact, as we have seen, up to 25% of the population, and therefore up to 25% of divers, have some degree of PFO.

However, to prevent inner ear decompression sickness, especially when it has occurred before and the presence of a patent foramen ovale is diagnosed, conservative diving is recommended, meaning:

  • Compliance with all usual basic safety rules,
  • Not performing more than one dive per day,
  • Always diving within non-decompression limits,
  • Diving to a depth not exceeding 18 meters,
  • Performing decompression stops, even if not mandatory,
  • Diving with Nitrox, but using air tables.

Regarding individual risk factors, it is important to:

  • Maintain good health and physical condition,
  • Regularly train in diving techniques.

Surgical Treatment of Patent Foramen Ovale

Regarding the indication for surgical treatment of patent foramen ovale (PFO), there is some controversy. Although percutaneous closure of PFO (via the right femoral vein) is a relatively straightforward procedure with a complication rate of less than 1%, it is not without risks, and there are still no randomized studies supporting its systematic indication.

In the event that surgical treatment is chosen, it should be noted that after the procedure, the minimum time a diver should refrain from underwater activity is three to six months. After this period, tests should be conducted to confirm complete closure.

Feel free to schedule an appointment with us, and we will advise you on your specific case.