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Original Investigation |

Risk of Stroke at the Time of Carotid Occlusion

Catherine Yang, BHSc1; Chrysi Bogiatzi, MD2; J. David Spence, MD2
[+] Author Affiliations
1Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada
2Stroke Prevention & Atherosclerosis Research Centre, Robarts Research Institute, Western University, London, Ontario, Canada
JAMA Neurol. 2015;72(11):1261-1267. doi:10.1001/jamaneurol.2015.1843.
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Published online

Importance  Many patients with asymptomatic carotid stenosis are offered carotid stenting for the prevention of carotid occlusion. However, this treatment may be inappropriate if the risk of stroke is low at the time of occlusion and with intensive medical therapy.

Objectives  To determine the risk resulting from progression to occlusion among patients with asymptomatic carotid stenosis and to assess the role of severity of carotid stenosis or the presence of contralateral occlusion as factors that may predict the risk of stroke or death after occlusion of a previously asymptomatic carotid stenosis.

Design, Setting, and Participants  We conducted a retrospective analysis of data collected from patients at the Stroke Prevention Clinic of Victoria Hospital from January 1, 1990 (when annual surveillance with carotid ultrasonography first began), through December 31, 1995, or the Stroke Prevention at University Hospital from January 1, 1995, through December 31, 2012. The last date of follow-up was August 26, 2014.

Exposures  A new carotid occlusion during annual monitoring with carotid duplex ultrasonography (index occlusion).

Main Outcomes and Measures  Ipsilateral stroke or transient ischemic attack, death from ipsilateral stroke, or death from unknown cause.

Results  Among 3681 patients in our clinic database with data on sequential annual carotid ultrasonographic examinations during the study period, 316 (8.6%) were asymptomatic before an index occlusion that occurred during observation. Most of the new occlusions (254 of 316 [80.4%]) occurred before 2002, when medical therapy was less intensive; the frequency decreased by quartile of years (P < .001, χ2 test). Only 1 patient (0.3%) had a stroke at the time of the occlusion, and only 3 patients (0.9%) had an ipsilateral stroke during follow-up (all before 2005). In Kaplan-Meier survival analyses, neither severity of stenosis (P = .80, log-rank test) nor contralateral occlusion (P = .73) predicted the risk of ipsilateral stroke or transient ischemic attack, death from stroke, or death from unknown cause at a mean (SD) follow-up of 2.56 (3.64) years. In Cox proportional hazards regression analyses, only age (P = .02), sex (P = .01), and carotid plaque burden (P = .006) significantly predicted risk of those events.

Conclusions and Relevance  The risk of progression to carotid occlusion is well below the risk of carotid stenting or endarterectomy and has decreased markedly with more intensive medical therapy. Preventing carotid occlusion may not be a valid indication for stenting.

Figures in this Article

Figures

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Figure 1.
Percentage of Patients in the Clinic With New Index Occlusion by Year

Among 3681 patients in the database, the percentage of patients who progressed to occlusion was much higher before 2002; the frequency decreased markedly after implementation in 2002-2003 of more intensive therapy based on plaque measurements. Error bars indicate 95% CI.

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Figure 2.
Event-Free Survival by Groups of Percent Stenosis of the Index Carotid Artery

In Kaplan-Meier analysis, survival after the index carotid occlusion free of ipsilateral stroke or transient ischemic attack, death from ipsilateral stroke, or death from unknown cause was not predicted (P = .80, log-rank test) by severity of stenosis before the index occlusion by groups (<60%, 60%-80%, 81%-90%, and >90%). Plots were truncated at 2000 days because of low numbers surviving after that time, but the P values from log-rank tests are for the entire follow-up period.

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Figure 3.
Event-Free Survival by Quartile of Carotid Plaque Burden

In Kaplan-Meier analysis, survival free of ipsilateral stroke or transient ischemic attack, death from ipsilateral stroke, or death from unknown cause was significantly predicted (P = .006, log-rank test) by quartile of carotid plaque burden (total plaque area) at the time of the occlusion (<283 mm2, 283-377 mm2, 377-535 mm2, and ≥535 mm2). Plots were truncated at 2000 days because of low numbers surviving after that time, but the P values from log-rank tests are for the entire follow-up period.

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