The impact of increasing age on anatomic factors affecting carotid angioplasty and stenting

Methods 

Patients 

From February 2003 to August 2005, 135 CAS procedures were performed in 133 patients. Data were compiled prospectively in a computerized vascular database and reviewed retrospectively. Preoperative imaging consisted of carotid duplex ultrasound or magnetic resonance angiography, or both. No patient was excluded from CAS based on anatomic characteristics noted on preoperative imaging. All but two patients in this cohort underwent successful CAS after initial diagnostic angiography.

Embolic protection devices were used in all but two cases: EPI Filterwire (Boston Scientific, Natick, Mass) in 19%, Guardwire (Medtronic, Minneapolis, Minn) in 19%, Accunet (Guidant, Minneapolis, Minn) in 47%, and Angioguard (Cordis, Sommerville, NJ) in 14%. All patients received a self-expanding stent: Wallstent (Boston Scientific) in 26%, NexStent (Endotex, Santa Rosa, Calif) in 10%, Acculink (Guidant) in 49%, and Precise (Cordis) in 14%. Most of the cases were performed under an investigational protocol. Indications for CAS included prior neck irradiation with or without neck surgery, restenosis after ipsilateral CEA, and significant comorbid medical conditions (Table I).

Table I. Patient characteristics by age <80 years old and age ≥80 years old

		<80, n = 96 (%)	≥80, n = 37 (%)
	Contralateral occlusion	13	14
	Previous ipsilateral CEA	18	11
	History of neck irradiation	7	0
	Goldman class II/III	66	57
	Symptomatic	28	37

CEA, Carotid endarterectomy.

Anatomic evaluation 

Digital subtraction angiograms of all 135 procedures were available for examination. Two vascular surgeons with very limited familiarity with the study population independently evaluated each angiogram blinded to patient identifiers. Because there was nonuniformity in the preoperative imaging, these studies were not used in this postprocedural analysis. Anatomic characteristics assessed were arch elongation, arch calcification, arch vessel origin stenosis, common and internal carotid artery tortuosity, treated lesion stenosis based on the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria, treated lesion calcification, and lesion length. These anatomic characteristics were defined as favorable or unfavorable for CAS. Interpretation of a favorable anatomy was based on anticipated difficulty with vessel cannulation, sheath placement, and passage and positioning of the devices. The criteria used to determine favorable and unfavorable characteristics were defined individually.

The aortic arch elongation classification was defined by the parallel planes perpendicular to the greater (outer) curvature and lesser (inner) curvature of the arch. If the arch vessels arose from the top of the arch or outer curvature, this was described as a type I arch, between the two planes was a type II arch, and proximal or caudal to the lesser curvature of the arch was a type III arch (Fig 1).

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Fig 1. Type III aortic arch with left common carotid and innominate originate caudal to the lesser curvature of the arch. Also note the significant irregularity visible along both luminal surfaces signifying unfavorable arch calcification.

Aortic arch calcification was assessed on left anterior oblique views and categorized as favorable if there was no or trace calcium shadowing and unfavorable if there was luminal irregularity or significant calcification.

Arch vessel origin stenosis was divided into <50% stenosis (favorable) and >50% stenosis (unfavorable). Both common and internal carotid tortuosity indices were designed to reflect increasing difficulty for wire and catheter passage. The grading was favorable if there was <30° angulation from the centerline flow of blood and unfavorable if there was >30°.

The internal carotid artery (ICA) was evaluated only for the extracranial portion beyond the carotid bulb, whereas the common carotid artery (CCA) was assessed in its entirety from the arch to the bifurcation (Fig 2 and Fig 3).

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Fig 2. Unfavorable common carotid shows significant tortuosity of bilateral common carotid arteries proximally with nearly 90° turns.

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Fig 3. Unfavorable internal carotid shows significant tortuosity of internal carotid artery with sinusoidal turns.

Index lesion stenoses were categorized into <85% (favorable) and >85% (unfavorable). Lesion calcification was examined on multiple magnified, oblique views and described as no or minimal calcium seen in the lesion (favorable) and calcium throughout the lesion (unfavorable).

Finally, lesion length was measured using a radiopaque ruler placed externally on the patient’s neck at the time of the procedure. The length of >50% diameter reduction that required treatment was divided into 0 to 5 mm (favorable) and >5mm (unfavorable).

Results 

There were 135 CAS procedures performed in 133 patients, of whom 87 (65%) were men and 46 (35%) were women, 37 (28%) were ≥80 years old (mean, 85 years), and 96 (72%) were <80 years old (mean, 65 years). The technical success rate in completing the CAS procedure was 99% in this study. The two cases in which CAS could not be completed occurred early in our experience. The anatomic factors that precluded completion of these procedures were bovine arch anatomy and ICA tortuosity.

Comparing patients <80 and ≥80 years old, there was an increased incidence of unfavorable anatomic characteristics in patients ≥80 years old for arch elongation (56% vs 82%, P = .008), arch calcification (30% vs 59%, P = .003), common carotid artery origin stenosis (22% vs 47%, P = .006), common carotid artery tortuosity (38% vs 70%, P = .0009), internal carotid artery tortuosity (50% vs 74%, P = .019), and treated lesion stenosis (56% vs 82%, P = .007). No statistically significant difference was found for the treated lesion degree of calcification (51% vs 56%. P = .62) or length (56% vs 62%, P = .59; Table II).

Table II. Anatomic evaluations by age <80 years old and age ≥80 years old

		<80, n = 96 (%)	≥80, n = 37 (%)	P
	Arch elongation	56	82	.008
	Arch calcification	30	59	.003
	Origin stenosis	22	47	.006
	CCA tortuosity	38	70	.0009
	Lesion stenosis	56	82	.007

Perioperative morbidity included three MIs (2.2%): two in the patients <80 years old and one in a patient ≥80 years old (2.1% vs 2.7%, P = NS). All three were detected by enzyme (troponin) elevation only and was not associated with any ECG changes. Comparing the incidence of comorbid medical conditions between patients <80 and ≥80 years old did not revealed any statistical significance for diabetes mellitus, hypertension, coronary artery disease, statin use, or duration of platelet therapy.

Four cerebrovascular accidents (CVAs) occurred, one in a patient <80 years old age and three in patients ≥80 years old (1.0% vs 8.1%, P = NS). Two of the three patients ≥80 years of age who experienced CVAs had unfavorable arch calcification and ICA tortuosity, and the remaining patient had only unfavorable ICA tortuosity. Three patients who experienced CVAs had no residual deficit >72 hours, and one had a persistent focal deficit. One patient ≥80 years old experienced both MI and CVA. The single death occurred in a 93-year-old man who sustained a hemorrhagic stroke after receiving periprocedural abciximab (0.8% overall, 2.7% in ≥80 group, P = NS). The composite complication rate consisting of stroke, MI, or death for the entire population was 3.7% (1.0% for patients <80 years old vs 10.8% for patients ≥80 years old, P = .012).

Discussion 

This study sought to examine the possibility that unfavorable arterial anatomic characteristics are associated with the reported increased incidence of perioperative complications when CAS is performed in elderly patients. Investigators in the Carotid Revascularization Endarterectomy vs Stent Trial (CREST) trial reported a 30-day stroke and death rate of 12% for octogenarians compared with 3.23% among nonoctogenarians.6 Kastrup et al7 also reported a combined stroke and death rate of 10% for symptomatic and 13% for asymptomatic patients >75 years old. This is compared with a rate of <3% stroke and death in patients <75 years old .7

Our hypothesis was that the higher rate of stroke associated with CAS in elderly patients was related to the more unfavorable anatomy that must be navigated in the course of performing the procedure. This includes not only ICA tortuosity as Hobson et al6 suggest but also aortic calcification, arch vessel origin stenosis, and aortic arch elongation and distortion.15, 16 Both aortic atherosclerosis and arch vessel tortuosity are associated with increased age.7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18

It is also likely that these factors make a CAS procedure technically more difficult and may contribute to an increase in technical errors leading to a higher risk of thromboembolic complications. Not only can emboli be dislodged during device manipulation within heavily calcified or angulated arch vessels, but dissections can occur and thrombus can form when significant force and repeated endothelial trauma is generated in crossing these lesions with the various catheters and wires required in complex CAS procedures.

There is a well-documented risk of neurologic events associated with cerebral angiography (<1%) as well as coronary angiography (0.3%).19, 20, 21 Coronary artery bypass grafting (CABG) is also associated with an estimated stroke risk of 2%.22 All of these complications have been attributed to emboli of atheromatous debris, thrombus, and even air bubbles.23, 24 It has also been shown that silent emboli are produced during these procedures and radiographically detected infarcts also occur.25, 26 Although not stratified for age, these data reflect the inherent risk of vascular procedures in patients with advanced atherosclerosis. In all of these studies, however, neither the volume of emboli nor the presence of defects on MRI has correlated directly with clinical neurologic changes.

As the demand for and comfort with CAS grows, it will be valuable to delineate those factors that may create a difficult, hazardous procedure and therefore warrant reconsideration of the use of this procedure. It is also likely that the additive effects of emboli, hypoperfusion, and susceptibility of elderly neuronal parenchyma produce the higher risk for a neurologic event in elderly patients undergoing CAS.27 The relatively small number of elderly patients and neurologic events limits our ability to determine how severe a particular anatomic factor must be to preclude CAS. However, the results do suggest that when there is a constellation of unfavorable anatomic characteristics are present, consideration of CEA or medical management alone should be considered, particularly in patients >80 years old (Table III).

Table III. Anatomic evaluation of favorable and unfavorable arterial characteristics

		Favorable	Unfavorable
	Arch elongation	Vessel origins off top of the arch (type I)	Origin from ascending or between greater and lesser curvatures (type II and III)
	Arch calcification	No or trace shadowing	Luminal irregularity or diffuse calcification
	Origin stenosis	<50%	>50%
	CCA or ICA tortuosity	<30° angularity	>30° angularity
	Lesion stenosis	<85%	>85%
	Lesion calcification	No or trace shadowing	Calcium in portions or throughout
	Lesion length	0-5 mm	>5 mm

CCA, Common carotid artery; ICA, internal carotid artery.

The finding of increased lesion stenosis in patients ≥80 years of age was unexpected. One explanation may be that the decision to operate was deferred in these elderly patients until the stenoses became severe. Moreover, atherosclerosis is generally a disease of advancing age, and it has been reported that the rate of plaque formation accelerates with age.28 Conversely, the lesions in the elderly were not necessarily more heavily calcified or of greater length, and to date, no known association has been found between plaque calcification and age.

Limitations of this study include the relatively small number of patients treated and the infrequency of neurologic events. This limits the ability to demonstrate statistically significant associations between unfavorable anatomic characteristics and neurologic complications. Additional limitations include the qualitative assessment of the arterial anatomic features and that patient selection for CAS was not randomized.

Conclusion 

This study aims to provide key decision points in assessing the suitability of patients for CAS. Arch elongation and calcification, origin and lesion stenosis, and vessel tortuosity are all features that increase the difficulty of CAS and may make it a high-risk procedure. Although more prevalent in the elderly, these characteristics may be found in patients of any age and may be considered as risk factors for perioperative stroke with CAS. In determining whether a patient should undergo CAS or CEA, evaluation of the relevant anatomy is important to minimize operative risk.

Author contributions