The detection of interatrial flow patency in awake and anesthetized patients: A comparative study using transnasal transesophageal echocardiography

The Valsalva maneuver in the awake patient and the ventilation maneuver in the tracheally intubated anesthetized patient are two provocation methods t o detect a patent foramen ovale (PFO) by means of contrast transesophageal echocardiography. In 60 patients undergoing posterior fossa surgery, a cont rast agent was administered via a peripheral vein during a Valsalva maneuve r immediately before anesthesia induction, followed by central venous admin istration during a ventilation maneuver in the same patients when anestheti zed and endotracheally intubated. We evaluated both maneuvers with a 32-ele ment monoplane transnasal transesophageal echocardiography probe to trace t he atrial flow of the contrast agent in a 90 degrees bicaval view. A maneuv er was rated positive when more than four bubbles appeared in the left atri um during the first three cardiac cycles after intrathoracic pressure relea se. The right atrial cross-sectional area before pressure release, and the peak septal excursion during atrial contrast opacification, were measured. McNemar's test was used to assess a paired dichotomous response on the two maneuvers for a significant difference. In 56 patients, the ventilation man euver was significantly (P < 0.037) more often positive for PFO (n = 14) th an the Valsalva maneuver (n = 7). Although there was no difference in the m ethods regarding the peak septal excursion, the mean right atrial area befo re pressure release was significantly smaller during the ventilation maneuv er than during the Valsalva maneuver (11.2 <plus/minus> 3.1 cm(2) vs 14.4 /- 3.3 cm(2), n = 42, P < 0.05). In the patients with a positive ventilatio n, but a negative Valsalva maneuver, the discrepancy was even larger (10.9 <plus/minus> 4.4 cm2 vs 16.3 +/- 4.2 cm(2), n = 7, P<0.001). We conclude th at the ventilation maneuver is superior to the Valsalva maneuver in detecti ng PFO. Our data suggest that a peak pressure of 30 cm H2O during the venti lation maneuver achieves a more pronounced reduction in right atrial load a nd allows right atrial pressure to exceed left atrial pressure when intrath oracic pressure is released.