Diagnosis of Right-to-Left Shunt: Possible Alternative Approaches

To the Editor:

We read with great interest the recent article by Del Sette et al¹ about diagnosis of right-to-left shunt with vertebrobasilar doppler examination.

So far, neurologists used transtemporal recordings based on the manuscript by Teague and Sharma.² The emboli detection is in fact limited by insufficient temporal bone window in 10% to 20% of stroke patients.³ A probably even greater limitation is the lack of transcranial examination expertise in local hospitals treating stroke patients.⁴ Unfortunately, this issue cannot be solved by a transnuchal emboli detection technique.

Recordings at the common carotid artery should be considered as a possible alternative technique. This method was already described by Draganski et al in 2005⁵ but did not find its way into broad clinical practice. Performance and visualization of high-intensity transient signals using contrast-enhanced harmonic carotid duplex and Doppler sonography are simple. Findings in a patient with a patent foramen ovale can be seen in the Figure.

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Figure. Recording of high-intensity transient signals with extracranial doppler at the common carotid artery after injection of 5 mL contrast agent (Echovist, Bayer Vital, Leverkusen, Germany) and Vasalva maneuver. More than 10 high-intensity transient signals and a curtain effect could be seen. A comparable finding was seen at the middle cerebral artery.

It might turn into a feasible option for local hospitals and for patients without a sufficient acoustic bone window in stroke centers if sensitivity and specificity will turn out to be comparable to the established methods.