Obstructive Sleep Apnea can be Provocative for Right-to-Left Shunting Through a Patent Foramen Ovale

STUDY OBJECTIVES: Under particular conditions, a patent foramen ovale (PFO) can potentially give rise to ischemic stroke by means of paradoxical embolization, due to right-to-left shunt. Our study aimed to evaluate the presence of right-to-left shunt in patients with obstructive sleep apnea syndrome (OSAS) and diagnosed PFO during sleep. DESIGN AND SETTING: Assessment of provocative-only PFO and concomitant OSAS. Evaluation of right-to-left shunting during sleep by means of transcranial doppler with contrast medium injected in the cubital vein. PARTICIPANTS: 10 consecutive patients affected by PFO detectable only under Valsalva maneuver during wakefulness and affected by OSAS (mean age 52.8 +/- 10.7 years). INTERVENTIONS: Patients underwent transcranial doppler with injection of agitated saline solution mixed with air during normal breathing and during periods of apnea/hypopnea in nocturnal sleep. MEASUREMENTS AND RESULTS: Right-to-left shunt was present in 9 patients out of 10 and appeared during obstructive apneas longer than 17 seconds. In 1 out of 10 patients, only hypopneas occurred and no right-to-left shunt could be shown. The number of microembolic signals detected during periods of nocturnal apnea was positively correlated with the number detected during Valsalva maneuver in wakefulness (p<0.0001). CONCLUSIONS: In the nocturnal sleep period, right-to-left shunt can occur during single obstructive apneas in patients with OSAS and concomitant presence of PFO. This can be a risk factor for cerebrovascular diseases. This risk could probably increase proportionally to the respiratory disturbance index of these patients.