Response to Letter by Vatankhah et al
We read with great interest Dr Vatankhah et al’s considerations on a possible alternative approach for right-to-left shunt diagnosis by means of common carotid duplex recording. In fact there are some reports on this technique, suggesting this possibility.1,2 Nevertheless, we think that there are at least 3 reasons to prefer a transoccipital approach in case of insufficient temporal window: neurologists are interested in the amount of contrast medium reaching the brain, both on anterior or posterior circulation; moreover, as the test has to be done during Valsava maneuver, it is very difficult to obtain a correct maneuver without moving the probe on the neck. Finally, there is no study comparing the test on middle cerebral artery with the test on common carotid artery; thus, it is impossible to quantify the amount of shunt that is of crucial importance for the stratification of embolic risk.
It would be interesting to plan a study comparing the test monitoring middle cerebral and common carotid arteries, in terms of sensitivity, specificity and possibility to give a quantification of the shunt.
Teague SM, Sharma MK. Detection of paradoxical cerebral echo cointrast embolization by transcranial Doppler ultrasound. Stroke. 1991; 22: 740–745.
Draganski B, Blersch W, Holmer S, Koch H, May A, Bogdahn U, Hölscher T, Schlachetzki F. Detection of cardiac right-to-left shunts by contrast-enhanced harmonic carotid duplex sonography. J Ultrasound Med. 2005; 24: 1071–1076.