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Original research
Understanding risk factors for perioperative ischemic events with carotid stenting: is patient age over 80 years or is unfavorable arch anatomy to blame?
  1. Travis M Dumont1,2,
  2. Maxim Mokin1,2,
  3. Michael M Wach1,2,
  4. Patrick S Drummond1,2,
  5. Adnan H Siddiqui1,2,3,4,
  6. Elad I Levy1,2,3,4,
  7. L Nelson Hopkins1,2,3,4,5
  1. 1Department of Neurosurgery, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA
  2. 2Department of Neurosurgery, Kaleida Health, Gates Vascular Institute, Buffalo, New York, USA
  3. 3Department of Radiology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA
  4. 4Toshiba Stroke and Vascular Research Center, University at Buffalo, State University of New York, Buffalo, New York, USA
  5. 5Jacobs Institute, Buffalo, New York, USA
  1. Correspondence to Dr L N Hopkins, Jacobs Institute, 875 Ellicott Street, 5th Floor, Buffalo, NY 14203, USA; lnhbuffns{at}aol.com

Abstract

Objective Several studies have reported increased perioperative risk after carotid artery stenting (CAS) for patients ≥80 years of age; however, most have not considered unfavorable anatomic features noted more frequently in this population as a confounding variable. The purpose of this study was to show a correlation between poor aortic arch anatomy and perioperative ischemic complications after CAS.

Methods Our prospectively maintained database was queried for all CAS procedures performed on symptomatic patients between 2009 and 2011. Retrospective analysis of consecutive CAS procedures was performed. The primary endpoint was perioperative (within 30 days) ischemic events (stroke, transient ischemic attack (TIA)). Event incidence was compared between groups dichotomized by age and anatomical features. Incidence of unfavorable arch (acute angle between aortic arch and treated common carotid artery) was compared between age groups.

Results Perioperative ischemic events included four ischemic strokes and three TIAs (all events ipsilateral to the treated vessel). Event incidence was more frequent in patients with unfavorable arch anatomy (7.9%) than in those with favorable aortic arch features (0.7%) (p=0.0073). Event incidence in patients ≥80 years of age (4.5%) was not statistically different than that in patients <80 years (2.3%) (p=0.428). Unfavorable aortic arch anatomy was increased in frequency in patients aged 80 years and over (<80 years, 29%; ≥80 years, 52%; p<0.001).

Conclusions In the present series, the incidence of perioperative complications was increased in patients with unfavorable aortic arch anatomy but not in patients ≥80 years. CAS represents a revascularization option for patients of all ages; however, patients with unfavorable aortic arch anatomy may represent a group at relatively high risk for periprocedural ischemic events.

  • Artery
  • Stent
  • Stroke
  • Complication

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Introduction

The role of carotid artery stenting (CAS) for elderly patients remains unclear. Several studies have reported an increased perioperative risk after CAS for patients aged 80 years and older1–7; however, most of these have not shown specific reasons for this finding. Excellent outcomes have been reported in carefully selected octogenarians undergoing CAS,8 and experience suggests that unfavorable anatomy and premorbid medical problems, not patient age, account for perioperative complications in these patients.9–11 An understanding of the true risk factors for perioperative stroke associated with CAS will limit morbidity by improving patient selection for CAS.

The purpose of this study was to show a relationship between unfavorable vascular anatomy and perioperative ischemic complications. Concurrently, we attempted to dispel age in years as a risk factor for CAS and display it as a surrogate for unfavorable vascular anatomy.

Methods

After obtaining approval from the local institutional review board, our prospectively maintained database of endovascular neurosurgical procedures was queried for all CAS procedures performed for symptomatic atherosclerotic disease between January 2009 and December 2011. Retrospective analysis of consecutive CAS procedures was performed. The primary endpoint was perioperative ischemic events, including stroke and transient ischemic attack (TIA). Ischemic stroke events were defined as any worsening of the preoperative baseline National Institutes of Health Stroke Scale (NIHSS) score by 1 or more points or within 48 h of the procedure not due to sedation from medication, medical complication or comorbidity, or intracranial hemorrhage without resolution of symptoms. TIAs were defined as any worsening of preoperative baseline NIHSS score by 1 or more points with resolution to baseline within 24 h. Each case was assessed for any perioperative ischemic events as well as relevant demographic characteristics, including age, gender, and premorbid medical comorbidities. Angiographic features thought to be potentially relevant for procedural difficulty were noted. This included laterality of stenting,12 aortic arch type13 (I, II, or III14), bovine configuration of great vessels,13 ,15 common carotid artery tortuosity13 ,16 (defined as two or more turns measuring ≤90°), complex lesion features3 ,17 (plaque ulceration or pseudo-occlusion), and internal carotid artery tortuosity13 (defined as two or more ≤90° turns or a loop noted on either the anteroposterior or lateral view). Anatomical analysis was performed in all cases; however, four patients in whom the procedure was aborted due to anatomical constraints were not included in the primary outcome analysis.

For statistical comparison, patients were dichotomized into age groupings (<80 years and ≥80 years) and anatomical groupings (favorable or unfavorable vascular anatomy) at each of the following levels: aortic arch, common carotid artery, lesion, and internal carotid artery. Unfavorable aortic arch anatomy was defined as those cases where an acute angle turn from the aortic arch into the common carotid artery treated must be navigated. This includes patients having type II or III arch for right CAS and type III arch or bovine configuration for left CAS—schematic examples are shown in figure 1. The incidence of perioperative complications was compared between groups, dichotomized based on age and anatomical features. The incidence of unfavorable arch was compared between age groups. Statistical comparisons between groups were performed with the t test, χ2, or Fisher's exact test, when appropriate, with a p value <0.05 considered statistically significant for all tests. All statistical tests were calculated with the assumption of heteroskedastic data, with two tailed p values reported. A multivariate analysis was performed to assess the association of various demographic and anatomical risk factors on perioperative ischemic events. Independent variables found to be associated with perioperative ischemic complications (p≤0.20) were included in a multivariate regression analysis. To ensure patient age ≥80 years was not a confounding variable, a second regression analysis was performed due to its potential clinical relevance. Both regression models are reported in full, including OR with 95% CIs. Statistical analysis was performed with SPSS (V.20.0.0; IBM Inc, Armonk, New York, USA) and GraphPad Prism (V.6.0; GraphPad Software Inc, La Jolla, California, USA).

Figure 1

Schematic examples of unfavorable aortic arch anatomy. (A) Type III arch for right carotid artery lesion. (B) Type II arch for right carotid artery lesion. (C) Type III arch for left carotid artery lesion. (D) Bovine configuration for left carotid artery lesion. In each case, an acute angle must be passed with the guide catheter (arrow) to access the lesion of interest.

Carotid stenting procedure

As this was a retrospective study, not all patients were treated with an identical intraoperative strategy. Generally, at our center, patients are treated with oral dual antiplatelet therapy prior to the carotid stenting procedure. Conscious sedation and local anesthesia are employed unless the patient is not able to be still for the procedure, at which point general anesthesia is considered. For each case, intravenous anticoagulant is administered (generally heparin in a weight based format) to a target activated coagulation time of 250–300 s after confirmation of arterial access. Guide catheter, embolic protection device, and stent implant choice was determined by the senior surgeon for each case.

Results

Clinical characteristics for the 221 patients undergoing CAS are summarized in table 1. Mean patient age was 71.6±11.9 years (range 34–94 years). Patients aged ≥80 years (n=65) were less likely to have hypercholesterolemia, less likely to be active cigarette smokers, and more likely to have unfavorable aortic arch anatomy, but otherwise were characteristically similar to patients aged <80 years. Patients with unfavorable aortic arch configuration (n=76) were, on average, older, more likely to be women, more likely to be ≥80 years, and less likely to have a history of coronary artery disease. Anatomically, patients with unfavorable arch configuration were more likely to have left-sided lesions and bovine configuration. Patients with unfavorable arch configuration were otherwise characteristically similar to patients with favorable arch anatomy.

Table 1

Clinical characteristics: comparison between age subgroups and anatomical subgroups

Perioperative ischemic events included four ischemic strokes and three TIAs, for a neurological complication incidence of 3.2%. All ischemic events were ipsilateral to the treated vessel. The incidence of ischemic events was more frequent in patients with unfavorable arch anatomy (six events in 76 patients, 7.9%) than in patients with favorable aortic arch features (one event in 145 patients, 0.7%), with a risk ratio for ischemic events of 2.6% (95% CI 1.8 to 3.7, p=0.0073, Fisher's exact) (figure 2). No correlation with laterality, unfavorable common carotid artery, lesion, or internal carotid artery anatomic features and perioperative ischemic events was noted (summarized in table 2). Unfavorable aortic arch anatomy was more frequent in the older group (present in 52% (35/67) of patients ≥80 years vs 29% (46/159) of patients <80 years; p=0.0013, Fisher's exact) (figure 3). The incidence of ischemic events in patients ≥80 years (three events in 67 patients, 4.5%) was no different than that in patients aged <80 years (four events in 172 patients, 2.3%; p=0.6896, Fisher's exact) (figure 4).

Table 2

Anatomic features versus perioperative ischemic events

Figure 2

Incidence of ischemic events was more frequent in patients with unfavorable arch anatomy (six events in 76 patients, 7.9%) compared with those with favorable aortic arch features (one event in 145 patients, 0.7%), with a risk ratio for ischemic events of 2.6 (95% CI 1.8 to 3.7, p=0.0073, Fisher's exact).

Figure 3

Unfavorable aortic arch anatomy was more frequent in patients aged 80 years and older (present in 35/67, 52%) than in those less than 80 years old (46/159, 29%) (p=0.0013, Fisher's exact).

Figure 4

Incidence of perioperative ischemic events in patients aged 80 years and older (three events in 67 patients, 4.5%) was not statistically different than in those aged less than 80 years (four events in 172 patients, 2.3%) (p=0.6896, Fisher's exact).

In univariate analysis, factors associated with perioperative ischemic events included contralateral carotid occlusion and unfavorable aortic arch configuration (table 3). In multivariate analysis in this series, unfavorable aortic arch (OR 12, p=0.028) was found to have the strongest association with perioperative ischemic events (table 4). No association between these events and age 80 years or older was noted. A second multivariate analysis was performed with age 80 years or older as a covariate to ensure it was not a confounding variable (table 5), with minimal change to the model.

Table 3

Univariate analysis of factors potentially associated with perioperative ischemic events

Table 4

Multivariate logistic regression analysis

Table 5

Multivariate logistic regression: including age ≥80 years as a variable

In four cases, CAS was aborted due to inability to access the lesion. This included three patients with unfavorable aortic arch features, including two with type III arch and one with type II arch and bovine configuration in a patient with a left-sided lesion. In these cases, a guiding catheter was not successfully navigated into the common carotid lesion. In another case, the aortic arch anatomy was not unfavorable but the lesion was unable to be crossed with a microwire due to a sharp angulation at the site of the lesion within the internal carotid artery. Three of these patients were aged 80 years or older, and two of the three had unfavorable aortic arch anatomy.

Discussion

Analyses of the effect of age on outcomes after CAS and carotid endarterectomy in the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST) suggested an increased incidence of primary endpoint complications with older patients after CAS but not after carotid endarterectomy.2 ,18 In CREST, complication incidence in patients aged 75 years and older (12.7%) was considerably higher than that in patients aged 65–74 years (6.3%) or patients aged 64 years or less (3.9%).18 However, this subset analysis failed to assess aortic arch anatomy as a potential confounding variable. This is a commonality in case series reporting an increased incidence of perioperative stroke events in patients aged 80 years and older,1 ,3–7 ,19 with the exception of three studies,9 ,13 ,20 all of which found a positive correlation between unfavorable arch anatomy and ischemic complications.

These three studies merit review. Faggioli et al9 described a consecutive series of 214 patients undergoing CAS. Perioperative morbidity included 14 (6.5%) neurological complications (10 TIAs and four minor ischemic strokes). In their series, 25 patients with aortic arch anomalies were found to have a higher incidence of perioperative stroke (20%) compared with patients with no arch anomalies (5.3%). No association between patient age and perioperative ischemic stroke was noted. Setacci et al20 reported a registry of 2124 successful CAS procedures. Perioperative morbidity included 60 TIAs and 71 ischemic strokes, for a total neurological complication incidence of 6.2%. In this report, logistic regression suggested type III arch (OR 2.5, p<0.001) and bovine arch configuration (OR 4.0, p<0.001) were associated with perioperative ischemic stroke, although age was not associated with perioperative stroke. Werner et al13 reported perioperative complications in 833 consecutive CAS procedures, including 618 patients in whom anatomic difficulty was able to be assessed. Stroke or TIA occurred in 46 patients (35 TIAs, 11 strokes), for a total neurological complication incidence of 7.4%. In multivariate regression analysis, anatomic difficulty was associated with perioperative TIA or stroke (HR 3.79, p=0.001) whereas age over 80 years was not (HR 2.00, p=0.079). Our study mirrors the findings of these studies and builds on the supposition that poor arch anatomy is a potential harbinger of stroke in patients undergoing CAS.

As the role for CAS in elderly patients remains uncertain, we feel that an understanding of the anatomic risk factors for perioperative ischemic events within this demographic is important. In this series, no correlation between unfavorable features of the common carotid artery, lesion, or distal carotid artery were noted although these characteristics have been reported previously to be associated with increased perioperative risk of ischemic events.3 ,13 ,16 ,17

The principal limitations of this study are its retrospective nature and small sample size. Because it is unlikely that a four arm study will be conducted in which patients with and without unfavorable aortic arch anatomy are compared with patients older and younger than 80 years of age, it is the hope of the authors that this series may serve as a guide for surgeons in planning CAS procedures. The seven-fold higher incidence of perioperative ischemic events in patients with unfavorable aortic arch anatomy serves as a warning that anatomical considerations may be the most relevant predictor of unwanted neurological complications in patients of all ages undergoing carotid revascularization via stenting.

Conclusion

In the present series, the incidence of perioperative complications was found to be increased in patients with unfavorable aortic arch anatomy but not in patients aged 80 years and older. It is our practice to match the best carotid revascularization procedure to the surgical anatomy, regardless of patient age. CAS represents a revascularization option for patients of all ages; however, patients with unfavorable aortic arch anatomy may represent a group at relatively high risk for periprocedural ischemic events.

References

Footnotes

  • Acknowledgements The authors thank Paul H Dressel, BFA, for assistance with the preparation of the illustrations, and Debra J Zimmer for editorial assistance.

  • Contributors Conception and design: TMD and LNH. Acquisition of the data: all authors. Analysis and interpretation of the data: TMD. Drafting the manuscript: TMD. Critically revising the manuscript: all authors. Final approval of the manuscript: all authors.

  • Competing interests LNH receives grant/research support from Toshiba; serves as a consultant to Abbott, Boston Scientific, Cordis, Micrus, and Silk Road; holds financial interests in AccessClosure, Augmenix, Boston Scientific, Claret Medical, Endomation, Micrus, and Valor Medical; holds a board/trustee/officer position with Access Closure and Claret Medical; serves on Abbott Vascular's speakers’ bureau; and has received honoraria from Bard, Boston Scientific, Cleveland Clinic, Complete Conference Management, Cordis, Memorial Health Care System, and the Society for Cardiovascular Angiography and Interventions (SCAI). EIL receives research grant support, other research support (devices), and honoraria from Boston Scientific, and research support from Codman and Shurtleff Inc and ev3/Covidien Vascular Therapies; has ownership interests in Intratech Medical Ltd and Mynx/Access Closure; serves as a consultant on the board of Scientific Advisors to Codman and Shurtleff Inc; serves as a consultant per project and/or per hour for Codman and Shurtleff Inc, ev3/Covidien Vascular Therapies, and TheraSyn Sensors Inc; and receives fees for carotid stent training from Abbott Vascular and ev3/Covidien Vascular Therapies. EIL receives no consulting salary arrangements. All consulting is per project and/or per hour. MM has received an educational grant from Toshiba. AHS has received research grants from the National Institutes of Health (co-investigator: NINDS 1R01NS064592-01A1, Hemodynamic induction of pathologic remodeling leading to intracranial aneurysms) and the University at Buffalo (Research Development Award) (neither is related to the present submission); holds financial interests in Hotspur, Intratech Medical, StimSox, Valor Medical and Blockade Medical; serves as a consultant to Codman and Shurtleff Inc, Concentric Medical, Covidien Vascular Therapies, GuidePoint Global Consulting, Penumbra Inc, Stryker Neurovascular, and Pulsar Vascular; belongs to the speakers’ bureaus of Codman and Shurtleff Inc and Genentech; serves on National Steering Committees for Penumbra Inc 3D Separator Trial and Covidien SWIFT PRIME Trial; serves on an advisory board for Codman and Shurtleff and Covidien Vascular Therapies; and has received honoraria from American Association of Neurological Surgeons’ courses, Annual Peripheral Angioplasty and All That Jazz Course, Penumbra Inc, and from Abbott Vascular and Codman and Shurtleff Inc for training other neurointerventionists in carotid stenting and for training physicians in endovascular stenting for aneurysms. AHS receives no consulting salary arrangements. All consulting is per project and/or per hour.

  • Ethics approval The study was approved by the University at Buffalo Health Sciences’ institutional review board, project No NSG2180712E.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Unpublished anonymised/de-identified data may be available. This would be on a per request basis.