Hole in heart worsens sleep apnea: study

NEW YORK (Reuters Health) - Sleep apnea -- frequent, short periods during sleep when breathing stops -- may be much worse in people with a relatively common heart defect called patent foramen ovale or PFO, a study by Swedish researchers has found.

In PFO, an opening between the heart's two upper chambers that normally closes during fetal development remains open. PFO is present in 25 percent of the adult population, and the defect may allow deoxygenated blood to pass through the hole in the heart.

Obstructive sleep apnea (OSA) affects up to 15 percent of middle-aged adults and produces varying degrees of low blood-oxygen levels (also called oxygen desaturation).

In a sleep apnea study, Dr. Magnus C. Johansson of Sahlgrenska University Hospital, Ostra and colleagues found that oxygen desaturation was more common, and occurred in proportion to the frequency of breathing disturbances, in patients with PFO.

From a larger group of 209 diagnosed with OSA, the Swedish group identified 15 OSA patients with frequent desaturation, and matched them with 15 OSA patients with few episodes of desaturation. The 30 subjects were then screened for the presence of PFO.

The presence of PFO was more common in patients with more episodes of desaturation than in those with fewer episodes of desaturation, Johansson and colleagues report in the European Respiratory Journal.

Sixty percent of apnea subjects with frequent episodes of desaturation had a large patent foramen ovale compared with just 13 percent of those with few desaturation episodes.

The authors conclude that shunting of deoxygenated or "blue" blood through the PFO contributes to low blood-oxygen levels in sleep apnea subjects with this heart defect. "Moreover, this may be the mechanism that explains the increased risk of stroke that is seen in OSA," they write.

If this link could be established, closing the PFO using a catheter technique may be a potential treatment option in the future, they conclude.

SOURCE: European Heart Journal, January 2007.