RIGHT TO LEFT SHUNTING THROUGH PATENT FORAMEN OVALE DURING SIMULATED EPISODES OF OBSTRUCTIVE SLEEP APNEA

Background: Paradoxical embolism through a patent foramen ovale (PFO) may cause cryptogenic stroke (CS). Obstructive sleep apnea (OSA) is associated with increased risk of CS, but the underlying mechanisms remain unclear. We hypothesized that changes in left and right atrial (LA, RA) pressure gradients (PG) during simulated apnea episodes (Mueller maneuver, MM) may promote increased PFO opening and right-to-left shunting during OSA.
Methods: CS patients requiring PFO closure underwent simultaneous measurement of intrathoracic pressure and LA/RA pressures using high-fidelity micromanometry at rest and during MM (inspiration against closed glottis) and Valsalva maneuvers (VM).
Results: Ten patients (age 55±11 years, 2 women) were studied. During the onset of MM (Figure, orange arrow), RA pressure transiently but consistently (n=9/10 patients) exceeded LA in response to the steep decline of intra-thoracic pressure (mean gradient from RA to LA: -2.7±1.5 to -0.8±2.0 mmH, p<0.0001; maximum gradient from RA to LA: 1.7±2.2 to 4.9±3.5 mmHg, p<00001). RA-LA PG was more positive during MM than at baseline, and RA-LA PG was comparable between MM and VM.
Conclusions: Onset of MM causes transient reversal in the normal RA to LA pressure gradient, likely as a result of increased blood return to the RA from extra-thoracic veins. Exuberant MM responses, as observed in OSA, may promote paradoxical embolism by enhancing flow across PFO in susceptible patients.