Response to letter to the editor: Microembolic Detection System

The benefit of carotid revascularization is hampered by strokes that occur due to the intervention itself. Recent analysis identified that thrombo-embolic events still comprise about half of procedural strokes, both in traditional carotid endarterectomy (CEA) and in carotid artery stenting [1]. Furthermore, the occurrence of white matter lesions in the brain identified on magnetic resonance diffusion-weighted imaging have now been accepted as a surrogate marker of procedural outcome. The use of transcranial Doppler (TCD) to detect emboli has been accepted as a tool to identify patients at risk for thrombo-embolic stroke and who have a high risk for new MR-DWI lesions. Moreover, in the recently published guideline for the treatment of atherosclerotic carotid artery disease and vertebral artery disease, the occurrence of emboli on TCD in asymptomatic patients with high-degree stenosis may serve as a marker of high risk in which case the guideline recommends considering carotid endarterectomy [2].

While the optimal periprocedural antiplatelet therapy is still a matter of debate, the authors of the letter to the editor indicate that EDS was developed as an assistive tool for human experts, mainly for the rapid identification of the presence of MES in TCD time series, and was therefore never intended to serve as a standalone classifier. Following the instructions for use, EDS would be useful for detailed post-intervention analysis of derived TCD data, especially for locating periods with high rates of embolization using the zoom function. EDS could be especially helpful for longer term monitoring, for example in three-hour monitoring of patients with asymptomatic carotid stenosis [3], or for research purposes in the identification of optimal antiplatelet therapy in carotid intervention using TCD emboli as a surrogate endpoint [4].

As such, the authors provided information to the reader that is relevant in the context of the Leunissen study [5]. The study assessed by Leunissen et al. did not intend to change the classification of the EDS system. However, although we agree with the comments of the authors, the conclusion of the Leunissen analysis remains the same: EDS cannot serve as a standalone monitor for emboli detection during carotid intervention. In the absence of any suitable alternatives, transcranial Doppler monitoring of embolization is still fully dependent on the dedicated human expert.

• References

• 1 Huibers A, Calvet D, Kennedy F. et al. Mechanism of procedural stroke following carotid endarterectomy or carotid artery stenting within the international carotid stenting study (ICSS) Randomised trial. Eur J Vasc Endovasc Surg 2015; 50: 281-288
• 2 Writing Group. Naylor AR, Ricco JB, de Borst GJ, Debus S. et al. Management of atherosclerotic carotid and vertebral artery disease: 2017 clinical practice guidelines of the European Society for Vascular Surgery (ESVS). Eur J Vasc Endovasc Surg 2018; 55: 3-81
• 3 Van Lammeren GW, den HartogAG, Pasterkamp G. et al. Asymptomatic carotid artery stenosis: identification of subgroups with different underlying plaque characteristics. EJVES 2012; 43: 632-636
• 4 De Borst GJ, Hilgevoord AA, de Vries JP. et al. Influence of antiplatelet therapy on cerebral micro-emboli after carotid endarterectomy using postoperative transcranial Doppler monitoring. EJVES 2007; 34: 135-142
• 5 Leunissen T, van vriesland D, den RuyterH. et al. Validation of the automated electronic microemboli detection system in patients undergoing carotid endarterectomy. Ultraschall Med 2017; DOI: 10.1055/s-0043-106737. [Epub ahead of print]