Stroke and Right-to-Left Shunt in ICU: Role of the Transcranial Doppler (TCD/TCCS)

The detection of right-to-left shunt and patent foramen ovale is a frequent medical question for several specialists, including neurologists, cardiologists, and anesthesiologists. Paradoxical embolism could be indeed responsible for stroke and for signs and symptoms of decompression sickness in divers and in high altitude pilots. The techniques aimed at this diagnosis are transcranial Doppler and echocardiography, with saline contrast agents. Transesophageal echocardiography, considered the gold standard for the morphological diagnosis, is invasive and cannot be performed as a routine screening method, while transcranial Doppler has a very high sensitivity for the shunt detection, even higher than trans-thoracic echocardiography, with the capability of easily given objective measures for the shunt quantification. Transcranial Doppler technique and protocols will be described in this review, with several methodological aspects and clinical considerations.