Persistent Microembolic Signals in the Cerebral Circulation on Transcranial Doppler after Intravenous Sulfur Hexafluoride Microbubble Infusion

ABSTRACT BACKGROUND AND PURPOSE Microembolic signals (MES) are detectable by transcranial Doppler monitoring and associated with increased risk of first or recurrent ischemic stroke. MES detection can also illuminate stroke etiology and the effect of prophylactic treatment. MES detection cannot accurately distinguish between stroke‐related microemboli and ultrasound contrast agents. These agents contain microbubbles and are frequently used in neuro‐ and cardiovascular diagnostics. We aimed to assess how long after contrast infusion microbubbles are detectable by transcranial Doppler monitoring. METHODS Ten healthy volunteers received an intravenous infusion of stabilized sulfur hexafluoride microbubbles (SonoVue®) for 30 minutes. The infusion was followed by continuous unilateral Doppler monitoring (TCD‐X, Atys Medical, Soucieu‐en‐Jarrest, France) for 3.5 hours. RESULTS MES persisted for 12 to 77 minutes (median 40.5 minutes), and the frequency tended to decrease gradually until cessation. CONCLUSIONS None of the subjects had detectable MES for more than 77 minutes after ultrasound contrast infusion. MES detection with the intent to detect stroke‐related microemboli should wait for at least this long after completed infusion.