Cerebral Microembolization: Open Versus Percutaneous Carotid Revascularization

BACKGROUND:
There is cumulative burden of data that suggests microembolization to the brain may result in long-term cognitive dysfunction despite the absence of immediate overt cerebrovascular events. We reviewed a series of patients treated electively with carotid endarterectomy (CEA), carotid stenting with filter (CAS), and carotid stenting with flow reversal (FRS) monitored continuously with transcranial doppler (TCD) during the procedure to detect microembolization rates.
METHODS:
TCD insonation of the M1 segment of the middle cerebral artery was conducted during 39 (14 CEA, 18 CAS and 7 FRS) procedures in 38 patients seen at an academic center. One patient had staged bilateral CEAs. Transcranial Doppler detects intra-procedural microemboli as high intensity transient signals (HITs). Cerebral blood flow dynamics and high intensity transient signals (HITs) were monitored ipsilaterally for CEA patients and bilaterally for CAS and FRS patients. Ipsilateral HITs were divided into 3 phases: pre-protection phase (PRE: till internal carotid artery cross clamped or shunted, filter deployed, or flow reversal established), protection phase (PROT: until clamp/shunt removed, filter removed, or antegrade flow re-established) and post-protection phase (POST: after clamp/shunt removed, filter removed, or antegrade flow re-established). Descriptive statistics are reported as mean +/- SE for continuous variables and N (%) for categorical variables. Differences in ipsilateral emboli counts based on cerebral protection strategy were assessed using nonparametric methods (Kruskal-Wallis test).
RESULTS:
TCD insonation and procedural success was obtained in 29 procedures (13 CEA, 11 CAS, and 5 FRS). Groups did not differ in baseline demographics. Total ipsilateral HITs were significantly different across all three groups (p< 0.001), as well as by separate two-group comparisons: CEA vs. CAS (p<0.001), CEA vs. FRS (p=0.002), FRS vs. CAS (p=0.027) (Table 1). Patients undergoing CEA had significantly less HITs than either FRS or CAS for all 3 phases (PRE, PROT, POST) (p<0.001).
CONCLUSIONS:
Carotid endarterectomy has the least microembolic potential and should remain the gold standard for carotid revascularization. Microembolization is decreased during carotid stenting with flow reversal as compared to stenting utilizing distal protection. Most of this benefit is due to a decrease during the protection phase of the procedure. These findings support flow reversal as a more effective manner of microembolic protection than distal filter protection in patients requiring percutaneous carotid revascularization. The clinical implications of this data needs further evaluation by post procedural long-term cognitive assessment and DW-MRI studies.