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PVSS5. Simultaneous Pre- and Post-Filter Transcranial Doppler Monitoring During Carotid Artery Stenting

Zsolt Garami, Kristofer Charlton-Ouw, Jean Bismuth, Mark G. Davies, Eric K. Peden, Alan B. Lumsden.
Baylor College of Medicine, Houston, Texas.;The Methodist Hospital; Houston, Texas. 

OBJECTIVES: Carotid artery stenting (CAS) is emerging as an acceptable treatment alternative to surgery for patients with carotid artery stenosis. The major risk of CAS is cerebral embolization of plaque and thrombus causing stroke or asymptomatic brain infarction. Use of embolic protection devices (EPD) to catch emboli before they reach the brain is now standard practice in CAS. The pore size of the currently available filters is >100 microns and emboli smaller than the EPD pores can still reach the brain. While the use of EPD is widespread, little evidence exists of their in vivo hemodynamic effects or their efficacy in preventing distal embolization. Our aim was to determine the hemodynamic effects of EPD and to quantify the number of emboli reaching the brain with the device in place.

METHODS: Patients were monitored with ipsalateral simultaneous dual probe transcranial Doppler (TCD) during CAS. By placing TCD probes both proximal and distal to the EPD, we quantify the microembolic signals before the EPD and how many reach the intracranial circulation after the EPD. One probe is placed submandibularly to monitor the internal carotid artery and another probe is placed transtemporally to monitor the middle cerebral artery. We compare the number of extracranial emboli prior to the EPD with the number of intracranial emboli after the EPD.

RESULTS: Dual probe monitoring was successful. Significantly more microembolic events were recorded proximal to the EPD in the internal carotid artery than were recorded distal to the EPD in the middle cerebral artery. Movement of the deployed filter caused distal microembolization not seen in the proximal internal carotid artery. Additionally, emboli were noted to emanate from the filter.

CONCLUSIONS: EPD significantly reduces but does not eliminate the number of microemboli reaching the brain during carotid artery angioplasty and stenting. We propose to monitor all cases of CAS with submandibular and transtemporal TCD probes to further evaluate the practice of distal embolization protection. Such information is vital in assessing the various devices and the techniques of utilization.