The degree of right-to-left shunt in a patient with a patent foramen ovale can be graded by monitoring the flow of contrast microbubbles during transesophageal echocardiography.
(1) Insert a transesophageal Doppler echocardiography transducer.
(2) Release of contrast microbubbles in the right atrium.
(3) The number of microbubbles are counted.
Webster et al
Torti et al
1 to 5 bubbles (small)
few single bubbles
6 to 20 bubbles (medium)
between a few and a cloud
>= 21 bubbles (large)
The higher the grade the greater the shunt and the greater the risk of complications.
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