One in four people have an opening between the left and right chambers of the heart – called a Patent foramen ovale or PFO. Normally this is not a problem, a flap covers the opening and generally remains closed because of greater pressure in the left chamber than the right. In scuba divers though, it is a worry.
After and whilst ascending from a dive, nitrogen bubbles are formed in the blood of a diver’s veins and carried back to the heart. In a diver with a PFO, the bubbles can pass to the left chamber of the heart and be carried in the arteries back around the body. If they get into the tissues then the diver might get decompression sickness (the bends), even when diving within the normal decompression limits.
One of the treatments for a PFO is to close it using a catheter based procedure. A catheter is a flexible hollow tube which can be used to move a closure-device in place in the heart. In a study available this week in the journal JACC: Cardiovascular Interventions, doctors report that closing a PFO in this way completely eliminates arterial bubbles after a dive. This compares to a control group where after an 18 m dive 32% of them had bubbles in their arteries, and after a 50 m dive 88% exhibited arterial bubbles. No difference was found in the presence of bubbles in veins in either groups.
The dives were simulated in a hyperbaric chamber: 34 divers “dived” to 18 m for 80 min, and 13 divers to 50 m for 20 min.
Jakub Honek et al, Effect of Catheter-Based Patent Foramen Ovale Closure on the Occurrence of Arterial Bubbles in Scuba Divers, JACC: Cardiovascular Interventions (2014), http://dx.doi.org/10.1016/j.jcin.2013.12.199.