Controlled contrast transcranial Doppler and arterial blood gas analysis to quantify shunt through patent foramen ovale.
OBJECTIVE
A right-to-left shunt can be identified by contrast transcranial Doppler ultrasonography (c-TCD) at rest and/or after a Valsalva maneuver (VM) or by arterial blood gas (ABG) measurement. We assessed the influence of controlled strain pressures and durations during VM on the right-to-left passage of microbubbles, on which depends the shunt classification by c-TCD, and correlated it with the right-to-left shunt evaluation by ABG measurements in stroke patients with patent foramen ovale (PFO).


METHODS
We evaluated 40 stroke patients with transesophageal echocardiography-documented PFO. The microbubbles were recorded with TCD at rest and after 4 different VM conditions with controlled duration and target strain pressures (duration in seconds and pressure in cm H2O, respectively): V5-20, V10-20, V5-40, and V10-40. The ABG analysis was performed after pure oxygen breathing in 34 patients, and the shunt was calculated as percentage of cardiac output.


RESULTS
Among all VM conditions, V5-40 and V10-40 yielded the greatest median number of microbubbles (84 and 95, respectively; P<0.01). A significantly larger number of microbubbles were detected in V5-40 than in V5-20 (P<0.001) and in V10-40 than in V10-20 (P<0.01). ABG was not sensitive enough to detect a shunt in 31 patients.


CONCLUSIONS
The increase of VM expiratory pressure magnifies the number of microbubbles irrespective of the strain duration. Because the right-to-left shunt classification in PFO is based on the number of microbubbles, a controlled VM pressure is advised for a reproducible shunt assessment. The ABG measurement is not sensitive enough for shunt assessment in stroke patients with PFO.
Department of Neurology, CHUV, Avenue du Bugnon 46, 1011 Lausanne, Switzerland. gerald.devuyst@chuv.hospvd.ch
Gérald
G
Devuyst
Bartlomiej
B
Piechowski-Józwiak
Theodoros
T
Karapanayiotides
Jean-William
JW
Fitting
Vendel
V
Kémeny
Lorenz
L
Hirt
Luis A
LA
Urbano
Pierre
P
Arnold
Guy
G
van Melle
Paul-Andre
PA
Despland
Julien
J
Bogousslavsky
D000328:Adult; D000368:Aged; D001158:Arteries / Q000737:chemistry; D001784:Blood Gas Analysis; D002560:Cerebrovascular Circulation; D005260:Female; D006344:Heart Septal Defects, Atrial / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020521:Stroke / Q000209:etiology; D017585:Ultrasonography, Doppler, Transcranial; D014636:Valsalva Maneuver