Measurement and impact of proximal and distal tortuosity in carotid stenting procedures

Background: Proximal and distal carotid tortuosity is considered of paramount importance in carotid artery stenting (CAS) procedures. Specifically, distal internal carotid coiling or kinking is thought to interfere with proper distal protection devices, thus contraindicating CAS. The type of the aortic arch is also considered a key factor in CAS success; however, no standardized method of evaluation of these indicators is available in the literature. We have evaluated the impact of arch angulation and proximal and distal tortuosity in a series of CAS procedures. Methods: In patients undergoing CAS, arch angulation and tortuosity of both common and distal internal carotid arteries were evaluated prospectively by calculating the sum of all angles diverging from the ideal straight axis, considering a 90° ideal angle for the origin from the arch (tortuosity index, TI). All procedures were through a transfemoral approach and with distal protection. Results were correlated with technical procedural success (residual stenosis<30%) and neurologic complication by Student t test. Multivariate logistic regression analysis was conducted to identify independent predictors of results. Results: In a group of 298 CAS procedures, the mean proximal TI was 111.9° 96.77° and the mean distal TI was 123.4° 117.47°. Technical success was obtained in 272 patients (91.2%). Causes for the 26 technical failures were incapacity to obtain stable proximal access in 25 (96.1%), and uncrossable stenosis in one (3.9%). Neurologic protection was achieved with distal filters in all cases. Neurologic complications occurred in 23 patients (7.7%), consisting of 16 transient ischemic attacks and seven minor strokes. The proximal TI was significantly greater in the 26 cases of technical failure (158.4° 102.2° vs 107.6° 95.3°, P .01). The distal TI was not different in the two groups (89° 99.1° vs 126.5° 118.6°, P .11). Similarly, the proximal TI was significantly greater in neurologic complications (162.8° 111.8° vs 107.6° 18.2°, P .03); the distal TI was not different in the two groups (112.6° 110.1° vs 124.3° 96.1°, P .5) By logistic regression analysis, a proximal TI >150 was an independent predictor of both neurologic complications and technical failure. Age was also independently associated with technical failure. Appropriate distal filter placement was possible in all cases with a crossable stenosis, irrespective of the internal carotid TI. Conclusions: The proximal TI is significantly associated with both technical success and neurologic complications after CAS, whereas the distal TI did not influence either outcome. The presence of distal kinking or coiling should not be considered a contraindication to CAS