Published Online
on February 26, 2004

A more recent version of this article appeared on April 1, 2004

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Submitted on November 24, 2003
Accepted on December 11, 2003

Controlled Contrast Transcranial Doppler and Arterial Blood Gas Analysis to Quantify Shunt Through Patent Foramen Ovale

Gérald Devuyst MD^*; Bartomiej Piechowski-Jówiak MD; Theodoros Karapanayiotides MD; Jean-William Fitting MD; Vendel Kémeny MD; Lorenz Hirt MD; Luis A. Urbano MD; Pierre Arnold MD; Guy van Melle PhD; Paul-Andre Despland MD; and Julien Bogousslavsky MD

From the Departments of Neurology (G.D., B.P-J., V.K., T.K., L.H., L.A.U., P.A., P-A.D., J.B.) and Pneumonology (J-W.F), CHUV, Lausanne, Switzerland; Department of Neurology, Medical University of Warsaw, Warsaw, Poland (B.P-J.); and University Institute of Social and Preventive Medicine, Lausanne, Switzerland (G. van M.).

^* To whom correspondence should be addressed. E-mail: gerald.devuyst{at}chuv.hospvd.ch.

Background and Purpose--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.

Key words: foramen ovale, patent • oxygen • ultrasonography, Doppler, transcranial • Valsalva maneuver

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