By Lauretta Ihonor, medwireNews Reporter
Clinically significant shunting of blood through a patent foramen ovale (PFO) is more common among patients with severe obstructive sleep apnea (OSA) than in the general population, study findings indicate.
However, the nocturnal blood oxygen desaturation that occurs in OSA patients with PFO-related shunting does not appear to improve after the defect is surgically closed, say the authors.
Zarrin Shaikh (Royal Brompton Hospital and Imperial College, London, UK) and team therefore surmise: "PFO closure is not recommended for treating intermittent hypoxia in OSA."
The findings arise from the assessment of 100 patients with severe OSA (defined as an apnea-hypopnea index [AHI] of >30 events per hour) and 50 healthy controls.
PFOs and shunting were detected by contrast transthoracic echocardiography and transcranial Doppler.
This revealed significantly higher rates of PFO with clinically noticeable (large) shunting among OSA patients than among controls, at respective rates of 18% (n=18) and 6% (n=3).
PFO, irrespective of shunt size, was also more common among OSA patients than controls; however, this finding was nonsignificant.
"The increased prevalence of large PFO may be explained by mechanisms that alter the anatomical configuration of the interatrial septum, ultimately stretching pre-existing PFO and increasing the size of shunt," say Shaikh et al in Chest.
Blood oxygen desaturation (reflected by oxygen desaturation index (ODI)/AHI ratios) was significantly higher among OSA patients with clinically significant PFO-related shunts compared with those without such shunts.
This, say the authors, suggests that shunting through a PFO worsens desaturation in OSA patients.
When six of the 18 patients with large PFO-related shunts underwent percutaneous PFO closure, ODI/AHO ratio did not change significantly.
These patients also reported no change in preoperative daytime sleepiness and general quality of life after PFO closure.
Shaikh et al say that although PFO closure "can be safely performed, it is also technically difficult, due to body habitus and the frequency of lipomatous hypertrophy of the secundum septum."
They therefore conclude that surgical PFO closure is best avoided in patients with OSA and PFO.
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