Safety of embolic protection device-assisted and unprotected intravascular ultrasound in evaluating carotid artery atherosclerotic lesions

Abstract

Background: Significant atherosclerotic stenosis of internal carotid artery (ICA) origin is common (5-10% at ≥ 60 years). Intravascular ultrasound (IVUS) enables high-resolution (120 µm) plaque imaging, and IVUS-elucidated features of the coronary plaque were recently shown to be associated with its symptomatic rupture/thrombosis risk. Safety of the significant carotid plaque IVUS imaging in a large unselected population is unknown.

Material/methods: We prospectively evaluated the safety of embolic protection device (EPD)-assisted vs. unprotected ICA-IVUS in a series of consecutive subjects with ≥ 50% ICA stenosis referred for carotid artery stenting (CAS), including 104 asymptomatic (aS) and 187 symptomatic (S) subjects (age 47-83 y, 187 men). EPD use was optional for IVUS, but mandatory for CAS.

Results: Evaluation was performed of 107 ICAs (36.8%) without EPD and 184 with EPD. Lesions imaged under EPD were overall more severe (peak-systolic velocity 2.97 ± 0.08 vs. 2.20 ± 0.08 m/s, end-diastolic velocity 1.0 ± 0.04 vs. 0.7 ± 0.03 m/s, stenosis severity of 85.7 ± 0.5% vs. 77.7 ± 0.6% by catheter angiography; mean ± SEM; p<0.01 for all comparisons) and more frequently S (50.0% vs. 34.6%, p=0.01). No ICA perforation or dissection, and no major stroke or death occurred. There was no IVUS-triggered cerebral embolization. In the procedures of (i) unprotected IVUS and no CAS, (ii) unprotected IVUS followed by CAS (filters - 39, flow reversal/blockade - 3), (iii) EPD-protected (filters - 135, flow reversal/blockade - 48) IVUS + CAS, TIA occurred in 1.5% vs. 4.8% vs. 2.7%, respectively, and minor stroke in 0% vs. 2.4% vs. 2.1%, respectively. EPD intolerance (on-filter ICA spasm or flow reversal/blockade intolerance) occurred in 9/225 (4.0%). IVUS increased the procedure duration by 7.27 ± 0.19 min.

Conclusions: Carotid IVUS is safe and, for the less severe lesions in particular, it may not require mandatory EPD use. High-risk lesions can be safely evaluated with IVUS under flow reversal/blockade.

Figure 1

Schematic presentation of the study flow.

Figure 2

Examples of IVUS acquisition with different types of EPD. (2-I) shows IVUS acquisition with a distal EPD in a 51-year-old female patient who presented without neurological symptoms, but with a family history of stroke at young age. RICA DUS velocities were 2.7/1.2 m/s and selective carotid artery angiography (A,B) indicated a significant RICA stenosis. Right hemispheric cerebral angiography (C) showed a normal flow to the right hemisphere. A distal EPD (FilterWire EZ, red arrow) was placed in a straight segment of the vessel distal to the lesion (D), and IVUS imaging was performed (E, imaging scanner indicated with white arrow). Index ICA spasm on the protective filter was noted (F) but the flow to the right hemispheric vessels was initially maintained (G) and there was no evidence of IVUS-related cerebral embolization. The ICA spasm, however, was progressive, and after a carotid self-expanding stent (Precise 8.0×40 mm) placement and post-dilatation, the spasm became ICA-occlusive, and this was symptomatic. The symptoms resolved after removal of the filter (whose macroscopic inspection showed limited debris), but a residual spasm was still seen (I); this was treated (J) with intra-arterial injection of nimodipine (200 μg). Post-procedural cerebral angiography showed normal flow to the right hemispheric vessels (K). IVUS mages of the distal reference segment (lumen reference area 17.1 mm²) and MLA (4.6 mm²) are shown in (L). Comparison of pre- and post-procedural MRI showed no evidence of brain injury, and a spasm-related intolerance of the distal EPD was diagnosed. (2-II) illustrates IVUS acquisition under proximal neuroprotection by flow reversal (tight stenosis of RICA in a 64-year-old man with recurrent transient right eye blindness). Consistent with DUS (RICA flow velocities of 4.5/1.4 m/s), angiography of the right carotid artery showed a tight lesion at the bifurcation (A). There was poor flow to the right hemispheric vessels from RICA (B), and the right anterior cerebral artery did not show (red arrow for the ‘missing’ vessel) from the contrast injection to RICA. In (C), there is contrast medium stagnation following an injection while the low-pressure balloons in the common carotid artery (CCA) and the external carotid artery (ECA) balloons are inflated, causing an intended occlusion of CCA and ECA. When the communication between the guiding catheter lumen and right femoral vein is opened, the flow in the index artery is reversed (green arrow indicates direction of the reversed ICA flow, (D); ‘back’ pressure was 62/48 mmHg and there was optimal tolerance of the temporary flow reversal). The index lesion was crossed under flow reversal (E, F), and IVUS imaging was performed (G). The tight lesion was predilated (H) prior to placing a stent (Xact 8–10×30 mm; in (I) the stent edges indicated with white dots, the stent post-dilatation is shown in (I and J). The final result of the procedure is shown in (K), with normalization of the flow from RICA to the right hemispheric vessels ((L), note that the right anterior cerebral artery, red arrow, is now visible from contrast injection to RICA). IVUS images of the RICA distal reference (lumen area of 28.5 mm²) and the MLA site (4.2 mm²) are shown in (M and N), respectively.

Figure 2

Examples of IVUS acquisition with different types of EPD. (2-I) shows IVUS acquisition with a distal EPD in a 51-year-old female patient who presented without neurological symptoms, but with a family history of stroke at young age. RICA DUS velocities were 2.7/1.2 m/s and selective carotid artery angiography (A,B) indicated a significant RICA stenosis. Right hemispheric cerebral angiography (C) showed a normal flow to the right hemisphere. A distal EPD (FilterWire EZ, red arrow) was placed in a straight segment of the vessel distal to the lesion (D), and IVUS imaging was performed (E, imaging scanner indicated with white arrow). Index ICA spasm on the protective filter was noted (F) but the flow to the right hemispheric vessels was initially maintained (G) and there was no evidence of IVUS-related cerebral embolization. The ICA spasm, however, was progressive, and after a carotid self-expanding stent (Precise 8.0×40 mm) placement and post-dilatation, the spasm became ICA-occlusive, and this was symptomatic. The symptoms resolved after removal of the filter (whose macroscopic inspection showed limited debris), but a residual spasm was still seen (I); this was treated (J) with intra-arterial injection of nimodipine (200 μg). Post-procedural cerebral angiography showed normal flow to the right hemispheric vessels (K). IVUS mages of the distal reference segment (lumen reference area 17.1 mm²) and MLA (4.6 mm²) are shown in (L). Comparison of pre- and post-procedural MRI showed no evidence of brain injury, and a spasm-related intolerance of the distal EPD was diagnosed. (2-II) illustrates IVUS acquisition under proximal neuroprotection by flow reversal (tight stenosis of RICA in a 64-year-old man with recurrent transient right eye blindness). Consistent with DUS (RICA flow velocities of 4.5/1.4 m/s), angiography of the right carotid artery showed a tight lesion at the bifurcation (A). There was poor flow to the right hemispheric vessels from RICA (B), and the right anterior cerebral artery did not show (red arrow for the ‘missing’ vessel) from the contrast injection to RICA. In (C), there is contrast medium stagnation following an injection while the low-pressure balloons in the common carotid artery (CCA) and the external carotid artery (ECA) balloons are inflated, causing an intended occlusion of CCA and ECA. When the communication between the guiding catheter lumen and right femoral vein is opened, the flow in the index artery is reversed (green arrow indicates direction of the reversed ICA flow, (D); ‘back’ pressure was 62/48 mmHg and there was optimal tolerance of the temporary flow reversal). The index lesion was crossed under flow reversal (E, F), and IVUS imaging was performed (G). The tight lesion was predilated (H) prior to placing a stent (Xact 8–10×30 mm; in (I) the stent edges indicated with white dots, the stent post-dilatation is shown in (I and J). The final result of the procedure is shown in (K), with normalization of the flow from RICA to the right hemispheric vessels ((L), note that the right anterior cerebral artery, red arrow, is now visible from contrast injection to RICA). IVUS images of the RICA distal reference (lumen area of 28.5 mm²) and the MLA site (4.2 mm²) are shown in (M and N), respectively.

Figure 3

Distribution of asymptomatic and symptomatic lesions in the unprotected IVUS and EPD-protected IVUS group.