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.