Diagnostic accuracy of carotid doppler ultrasound for the detection of right-to-left cardiac shunt

Background: Right-to-left cardiac shunt is a condition anatomically related to patent foramen ovale (PFO) and potentially related to cryptogenic cerebrovascular events. As recent studies demonstrated a reduction of recurrent stroke in patients undergoing percutaneous PFO closure after a cryptogenic cerebrovascular event, it is now of pivotal importance to screen these patients for Right-to-left shunt(RLS) presence. At this regard, transcranial color Doppler (TCCD) with contrast has a good sensitivity (97%) and specificity (93%) compared to transesophageal echocardiography and became the test of choice to assess RLS presence, thanks to its noninvasive nature. However, temporal bone window is not accessible in 6%-20% patients. Several approaches have been explored to overcome this limitation with encouraging but not definitive results for extracranial internal carotid artery (ICA) approach, proposed in previous pivotal studies. Aims of this study were to further assess the diagnostic accuracy of ICA Doppler ultrasound with contrast for RLS detection compared to TCCD, with the two tests performed simultaneously. Materials and Methods: Sixty-four patients underwent simultaneously to TCCD and ICA Doppler ultrasound, both performed at rest and after Valsalva maneuver. Diagnosis of RLS was made, both for TCCD and ICA ultrasound, if =1 microembolic signals (MES) were detected during the examination (either at rest or after Valsalva maneuver). Results: ICA Doppler ultrasound sensitivity and specificity resulted respectively of 97% (confidence interval [CI] 95%) and 100% ([CI] 95%), while negative likelihood ratio was 0.03 (CI 95%). Conclusions: ICA Doppler ultrasound represents a valid alternative to TCCD for RLS screening in patients without adequate transcranial acoustic window.