Carotid angioplasty and stenting in anatomically high-risk patients: Safe and durable except for radiation-induced stenosis

Article Outline

• Abstract
• Methods
  • Patients
  • End points and follow-up
  • Statistical analysis
• Results
  • Outcomes
  • Radiation-induced stenosis
• Discussion
• Conclusion
• Author contributions
• References
• Copyright

Objective

Carotid angioplasty and stenting (CAS) is used in patients considered high-risk for carotid endarterectomy (CEA). Patients qualify as high-risk because of medical comorbid conditions or for anatomic considerations (previous CEA, radical neck dissection, radiation). We compared the technical feasibility and durability of CAS in medically high-risk patients (MED) vs anatomically high-risk patients (ANAT).

Methods

A retrospective review was performed of all consecutive patients undergoing CAS by a single vascular surgery group. All patients were high risk and evaluated with duplex ultrasound imaging and angiography. Primary end points were technical success, 30-day stroke, myocardial infarction (MI), death, and in-stent restenosis. Standard statistical analysis included Kaplan-Meier life tables.

Results

From January 2003 to December 2007, 230 CAS (98 ANAT, 132 MED) procedures were attempted. The ANAT cohort comprised 84 patients with a single anatomic risk factor: 71 with a previous ipsilateral CEA, 6 high lesions, 6 history of neck radiation, and 1 with a tracheostomy. Ten patients had two or three anatomic risk factors: nine with radical neck dissection and radiation and one with neck radiation and ipsilateral CEA. The mean age was 71.1 years for ANAT vs 73.9 years for MED (P = .021). Technical success rates were 98% in ANAT and 98.5% in MED (P = .76). Thirty-day stroke rate was 1.0% in ANAT and 5.3% in MED (P = .14); the mortality rate was 2.0% in ANAT and 0.8% in MED (P = .79). The 2-year survival free from stroke was MED, 93.6% and ANAT, 98.9% (P = .118); and from restenosis was MED, 91.9%; and ANAT, 91.0% (P = .98). Two-year overall survival was significantly better in ANAT (84.6%) vs MED (70.1%; P = .026). Four of the seven restenoses in the ANAT group occurred in patients with previous neck radiation. The restenosis rate for radiation-induced (RAD) stenosis treated with CAS was significantly higher at 22.2% (4 of 18) compared with 3.8% (3 of 78) in ANAT group patients without a history of radiation (non-RAD; P = .028). The 2-year restenosis-free survival was 72.7% in the RAD group vs 95.9% in the non-RAD group (P = .017).

Conclusion

CAS is as technically feasible, safe, and durable in anatomically high-risk patients as in medically high-risk patients, with similar rates of periprocedural stroke and death and late restenosis. However, patients with radiation-induced stenosis appear to be at an increased risk for restenosis.

Carotid endarterectomy (CEA) is the gold standard for the treatment of carotid artery stenosis in patients with good operative risk. However, restenosis after CEA and de novo stenosis in patients with a history of neck irradiation or radical dissection presents a more difficult treatment dilemma. CEA in an anatomically complex or scarred neck increases the risk for adverse local sequelae, including cranial nerve injury, recurrent nerve palsy, cervical hematoma, and wound dehiscence.¹, ², ³, ⁴ Carotid angioplasty and stenting (CAS) presents a potential alternative for those patients deemed too high risk for operative intervention.

CAS has been increasingly performed in patients considered high risk for CEA since its introduction in the mid-1990s.⁵, ⁶, ⁷ Most commonly, the high-risk indication for CAS is a medical condition making the patient a poor surgical candidate. Less commonly, CAS is indicated in anatomically high-risk patients who have a history of neck irradiation or surgery (radical neck dissection or CEA) or some other anatomic reason, such as tracheostomy, that would make CEA particularly hazardous.

The Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial investigators demonstrated that CAS could be performed with similar rates of complications as CEA in patients considered high risk for surgery.⁸ However, most of the participants in this trial were medically high-risk patients. Only a small proportion of the study population was considered high risk by anatomic considerations, and those anatomically high-risk patients were not specifically described in the trial, making few conclusions possible for the use of CAS in these patients based on their data.

In this study, we sought to compare the technical feasibility and the success and durability of CAS in medically high-risk patients (MED) vs anatomically high risk patients (ANAT) and identify if there is a subset of patients at higher risk for restenosis.

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Methods 

After approval by the Institutional Review Board of Eastern Virginia Medical School, a retrospective medical record review was performed of all consecutive patients who underwent CAS by a single vascular surgery group.

Patients 

All patients were considered high risk for CEA, and operative intervention had been deferred. Criteria for high risk were based on SAPPHIRE criteria⁸ and included medical conditions such as clinically significant cardiac disease, severe chronic obstructive pulmonary disease, contralateral carotid occlusion, and age >80 years, and anatomic considerations including previous neck surgery or irradiation therapy to the neck, recurrent stenosis after CEA, and tracheostomy. Symptomatic patients were defined as those with a stroke or transient ischemic attack (TIA) in the distribution of the ipsilateral carotid artery ≤6 months of the procedure. Asymptomatic patients underwent intervention when internal carotid artery stenosis >80%.

The preprocedural workup included evaluation with duplex ultrasound (DUS) imaging, with the addition of computed tomography angiogram (CTA) or diagnostic carotid angiography, or both, in select patients. Angiography was performed before the procedure or at the time of intervention. Data collected included age, gender, high-risk criteria, comorbid risk factors, side, procedural data, preprocedural and follow-up DUS imaging, and clinical outcomes.

DUS data collected included internal carotid artery (ICA) and common carotid artery (CCA) peak systolic (PSV) and end diastolic velocities (EDV) and ICA/CCA ratios. Standard DUS velocity criteria were used with an ICA EDV ≥140 cm/s or an ICA/CCA PSV ratio ≥4 defining a >80% stenosis.

End points and follow-up 

Primary end points included technical success, in-stent restenosis >50% at any point during follow-up, stroke (cerebrovascular accident), or death at 30 days or at any point during follow-up. In-stent restenosis was defined as >50% stenosis using DUS with an ICA PSV ≥220 cm/s and an ICA/CCA PSV ratio ≥2.7. We defined an in-stent restenosis >80% by DUS imaging with an ICA EDV ≥140 cm/s and an ICA/CCA PSV ratio ≥4. Completion carotid DUS imaging was performed ≤24 hours of CAS in all patients. All patients were discharged the day after CAS on a clopidogrel regimen.

Follow-up protocol included a clinical assessment with DUS imaging at 1 month, 6 to 12 months, then annually thereafter. CAS was performed in an angiography suite by 1 of 3 vascular surgeons (R. J. D., R. M. S., J. M. P.) alone or occasionally in conjunction with a vascular surgery fellow or another vascular surgeon for training or proctoring purposes. Carotid angiography was performed at the start of each procedure to confirm DUS findings and delineate anatomy.

Most CAS procedures were performed as part of a clinical trial (62.6%) or as a postmarketing surveillance study, and the type of stent was mandated by the trial. The number of stents was chosen at the discretion of the surgeon. The stents used were all self-expanding, nitinol stents: Precise or Smart (Cordis, Miami Lakes, Fla), Acculink (Guidant, Indianapolis, Ind) or Xact (Abbott, Abbott Park, Ill). Embolic protection devices (EPDs), including PercuSurge Guardwire (Medtronic AVE, Santa Rosa, Calif), Accunet (Guidant Corp), Angioguard (Cordis), Emboshield (Abbott), and Spider (ev3 Endovascular Inc, Plymouth, Minn) were used whenever technically feasible.

Statistical analysis 

Data analysis was performed using the t test, Fisher exact test, χ², Kaplan-Meier life tables, and log-rank test. A value of P < .05 was used to determine statistical significance.

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Results 

During the 5-year period from January 2003 to December 2007, 230 CAS (ANAT, 98; MED, 132) were attempted in 212 patients (ANAT, 94; MED, 118), with 18 patients undergoing bilateral procedures. The ANAT cohort (mean age, 71.1 years) was significantly younger than the MED cohort (mean age, 73.9 years; P = .021). The ANAT cohort consisted of 84 patients with a single anatomic risk factor: 71 patients with a previous ipsilateral CEA (2 patients with bilateral ipsilateral CEA), 6 with high lesions, 6 with a history of neck irradiation, and 1 with a tracheostomy. Ten patients in the ANAT cohort had more than one anatomic risk factor: nine had a history of a radical neck dissection and irradiation, and 1 had neck irradiation, dissection, and a unilateral CEA with bilateral stenosis. A total of 18 CAS procedures were performed in 16 patients who presented with a history of neck irradiation.

The ANAT and MED cohorts were similar in gender distribution and proportion of patients aged >80 years. The two groups were also similar in rates of several cardiovascular risk factors, including hypertension, hyperlipidemia, current tobacco use, and a history of stroke, chronic obstructive pulmonary disease, and congestive heart failure (Table I). The MED cohort had a significantly higher number of patients with symptomatic ipsilateral stenosis, diabetes mellitus, end-stage renal disease, coronary artery disease, and contralateral carotid artery occlusion.

Table I. Patient characteristics

ANAT, Anatomically high-risk cohort; MED, medically high-risk cohort; SD, standard deviation.

Outcomes 

Technical success was achieved in 96 of 98 ANAT patients (98.0%) and in 130 of 132 MED patients (98.5%; P = .76). In the MED cohort, CAS was aborted in a patient with a tortuous ICA that could not be crossed safely and in another patient with a highly calcified ICA that could not be cannulated. In the ANAT cohort, one case was aborted because the ICA branched off the CCA at a right angle, which required a significant amount of manipulation, and it was determined to be unsafe to continue. A second aborted case in the ANAT cohort involved a tortuous ICA restenosis after CEA with an excessively redundant artery.

An EPD was used in 129 of 130 patients in the MED cohort (99.2%) compared with 89 of 96 in the ANAT cohort (92.7%; P = .011). A single stent was in used most CAS procedures (MED, 122; ANAT, 89), with the remaining procedures requiring two stents (MED, 8; ANAT, 7; P = .79). Two of these procedures requiring two stents were in patients with a history of previous neck irradiation.

Mean follow-up was 21.5 months in the ANAT group compared with 10.5 months in MED patients (P < .0001). The number of strokes at 30 days was not significantly different between the two cohorts (ANAT, 1 of 98 [1.0%], MED, 7 of 132 [5.3%], P = .14). Of the eight strokes that occurred, seven were in patients who were symptomatic at the time of CAS (MED, 6 of 7; ANAT 1 of 1). In the medically high-risk cohort, strokes occurred in 9.7% of the symptomatic patients (6 of 62) and in only 1.4% of the asymptomatic patients (1 of 70; P = .051). The stroke-free survival, using Kaplan-Meier method, was not statistically different between the two cohorts at 1 year (MED, 93.6%; ANAT, 98.9%) or at 2 years (MED, 93.6%; ANAT, 98.9%; P = .118; Fig 1).

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• Fig 1. 

  Kaplan-Meier stroke-free survival curves for the medical high-risk (MED) cohort (black line) and anatomic high-risk (ANAT) cohort (gray line) were similar at 1 year (MED, 93.6%; ANAT, 98.9%) and 2 years (MED, 93.6%; ANAT, 98.9%; P = .118). Abbreviated life-table data are included along the horizontal axis.

The 30-day mortality rate was similar and low between the two cohorts, at 2.0% for and 0.8% for MED (P = .79; Table II). The 30-day combined event rate of stroke and death was 2.0% for ANAT and 5.3% for MED (P = .31). Overall survival after CAS was significantly better in the ANAT group than the MED group at 1 year (ANAT, 89.5%, MED, 85.1%) and at 2 years (ANAT, 84.6%, MED, 70.1%; P = .026; Fig 2).

Table II. Outcomes at 30 days

Outcome	MED	ANAT	P
	(n = 132)	(n = 98)
Rate at 30-days, No. (%)
Stroke	7(5.3)	1(1.0)	.14
Mortality	1(0.8)	2(2.0)	.79
Stroke and mortality	7(5.3)	2(2.0)	.31

ANAT, Anatomically high-risk cohort; MED, medically high-risk cohort.

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• Fig 2. 

  Kaplan-Meier overall survival curves were better for the anatomic high-risk (ANAT) cohort (gray line) than for the medical high-risk (MED) cohort (black line) at 1 year (ANAT, 89.5%; MED, 85.1%) and 2 years (ANAT, 84.6%; MED, 70.1%; P = .026). Abbreviated life-table data are included along the horizontal axis.

During follow-up, there were 12 cases of restenosis, seven in the ANAT cohort (7.3%) and five in the MED cohort (3.8%; P = .36). There was no statistical difference in the survival free of restenosis between the two groups at 1 year (MED, 91.9%; ANAT, 95.2%) or at 2 years (MED, 91.9%; ANAT, 91.0%; P = .98; Fig 3).

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• Fig 3. 

  Kaplan-Meier curves show restenosis-free survival for the medical high-risk (MED) cohort (black line) and anatomic high-risk (ANAT) cohort (gray line) were similar at 1 year (MED, 91.9%; ANAT, 95.2%) and 2 years (MED, 91.9%; ANAT, 91.0%; P = .98). Abbreviated life-table data are included along the horizontal axis.

Radiation-induced stenosis 

Four of the seven cases of restenosis in the ANAT group occurred in patients with previous neck irradiation (Table III). Three of those patients underwent reintervention. Restenosis developed at 9.1 and 58.8 months in two patients with a history of radiotherapy and radical neck dissection. The restenosis in the first patient was treated with cutting balloon angioplasty and an EPD, leaving <10% residual stenosis. The second patient underwent redo CAS with similar results. In the third patient, restenosis developed after 13.4 months. The patient underwent redo CAS and the outcome was favorable, with no residual stenosis.

Table III. Restenosis in the anatomically high-risk cohort

Patient	High-risk criteria	Patency, mon		Reintervention
		Primary	Assisted primary
1	XRT,RND	7.5	7.5	None
2	CEA	9.9	9.9	None
3	XRT,RND	9.1	12.8	Angioplasty
4	XRT,CEA	13.4	14.1	CAS
5	CEA	16.6	16.6	None
6	CEA	25.4	25.4	None
7	XRT,RND	58.8	59.3	CAS

CAS, Carotid angioplasty and stenting; CEA, ipsilateral carotid endarterectomy; RND, radical neck dissection; XRT, neck irradiation.

The restenosis rate for radiation-induced stenosis (RAD) treated with CAS was significantly higher at 22.2% (4 of 18) compared with 3.8% (3 of 78; P = .028) for all other CAS performed in the ANAT group (non-RAD). The restenosis-free survival at 1 year (RAD, 83.1%; non-RAD, 98.3%) and at 2 years (RAD, 72.7%; non-RAD, 95.9%; P = .017; Fig 4) was significantly better in those ANAT patients who had no history of neck irradiation.

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• Fig 4. 

  Kaplan-Meier curves show restenosis-free survival was significantly better for the patients in the anatomic high risk cohort without a history of radiation (non-RAD, gray line) than for those patients in the anatomic high risk cohort with a history of radiation (RAD, black line) at 1 year (non-RAD, 98.3%; RAD, 83.1%) and 2 years (non-RAD, 95.9%; RAD, 72.7%; P = .017). Restenosis-free survival for patients without a history of radiation at 3 years was 92.8%. The standard error of the mean was >10% past 2 years (dotted line). Abbreviated life-table data are included along the horizontal axis.

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Discussion 

CAS is increasingly being performed for ICA stenosis in patients who are high risk for CEA for anatomic reasons. Previous neck surgery (ipsilateral CEA and radical neck dissection) and radiotherapy are the most common reasons CAS is chosen rather than CEA. For a surgeon, these indications for CAS are amongst the most desirable intuitively because of the difficulties encountered in a reoperative or irradiated neck. The “hostile neck” from a history of a neck dissection or radiotherapy places the patient at a higher risk for local complications and restenosis. These are the patients who would appear to benefit the most surgically by remaining outside of the area of most concern. This is in contrast to those patients who are at a higher risk medically for cardiac events from the anesthesia and other complications and death.

Contralateral occlusion has not been shown to increase the risk associated with CEA in multiple studies.⁹, ¹⁰ However, we believe that it is, rather, an indicator of carotid disease and increases the patient's medical risk for complications. For these reasons, although contralateral carotid occlusion is traditionally included in the anatomically high-risk cohort, we believed these patients fit more appropriately in the medical high-risk cohort. However, although these situations are not rare, they are certainly not common, and lesion-specific CAS outcome data have been lacking. In our study, 98 patients with anatomically difficult necks underwent attempted CAS with similar technical success, safety, and durability as in the medically high-risk group.

Treating radiation-induced arteritis has been challenging in the past, with a high rate of complications with CEA. CEA in a cervical field that has undergone an operation or has been irradiated has historically increased the risk of local complications compared with primary CEA in a nonirradiated cervical field.¹, ³, ⁴, ¹¹, ¹², ¹³, ¹⁴, ¹⁵ Previously, the rates of cranial nerve injury, hematoma, and restenosis have been increased in this population, although the data is somewhat conflicted.

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) investigators demonstrated an 8.6% cranial nerve injury rate, with a 9.1% wound complication rate in primary CEAs.¹⁶ In comparison, in 1993 Gagne et al¹ published their series of 47 redo carotid artery reconstructions with a 4.3% cranial nerve injury rate. Similarly, in 1997 Mansour et al⁴ demonstrated a 7.3% cranial nerve injury rate and a 2.4% wound hematoma rate.⁴ These are in contrast to the series published by AbuRahma et al³ in 2001, where the cranial nerve injury was 17% in their redo CEA compared with 5.3% in the primary CEAs.³ With this increased risk of local complications with CEA in an anatomically high-risk patient, CAS was postulated to provide a suitable, less risky alternative to CEA.

Early attempts at CAS in radiation-induced stenosis were largely unsuccessful. Melliere et al¹⁷ attempted CAS in a single patient with radiation-induced stenosis. The procedure was aborted because the patient lost consciousness when the balloon was inflated.¹⁷ Teitelbaum et al¹⁸ reported their series of CAS in high-risk patients with one case of radiation-induced stenosis. Initially, this was technically successful but was occluded ≤6 months. Cheng et al¹⁹ performed four CAS procedures in radiation-induced stenosis and achieved technical success, but one postoperative stroke occurred after stent migration that thrombosed and later led to a fatal cerebral hemorrhage.

As time has passed, experience with CAS has improved and yielded better results. In 2007 Eskandari et al²⁰ published a series of 269 CAS with 66 successful procedures in hostile necks, which included patients with previous CEA or irradiation. At 30 days, the stroke rate was 2.2% (1.1% minor stroke rate and 1.1% major stroke rate), and the myocardial death rate was 0.4%; however, none of these adverse events occurred in the hostile neck group.

EPDs have been proven to be safe and shown to decrease neurologic events.²¹, ²², ²³ CAS should be performed routinely with an EPD. This was the goal in all of our patients, but EPDs were used significantly less in our ANAT cohort. Most of these patients who did not have an EPD were early in our experience with CAS (2003), when few options were available for their use. Almost all of these patients were in the anatomically high-risk cohort, so the rate of EPD usage was significantly lower. Therefore, it was not a failure to deploy the EPD, but that EPDs were not used routinely in our early experience. Later, when studies demonstrated the benefits of EPDs, their use became routine.

Interestingly, the less frequent use of EPD in the anatomically high-risk cohort was not associated with an increased periprocedural stroke rate. In fact, the stroke rate in the hostile neck group was low, with only one stroke occurring in the 30 days after CAS. The 30-day stroke rate in the medically high-risk group was 5.3%, however, which was higher than expected considering more than half the patients were asymptomatic at the time of CAS. In the medically high-risk group, 85.7% of the strokes were in symptomatic patients. The stroke rate was lower in the anatomically high-risk group, although this difference was not statistically significant. A significantly greater proportion of the anatomically high-risk cohort was asymptomatic, however, and this may explain the lower incidence of strokes.

In this series, CAS was attempted in 98 high-risk patients with carotid artery stenosis considered high risk for CEA for anatomic reasons. This included 18 patients with radiation-induced arteritis, for which CAS was 100% technically successful.

A recent study by Eskandari et al²⁰ demonstrated an overall restenosis or occlusion rate of 2.6%, which was statistically the same between the hostile neck and the de novo lesions (4.5% vs 2.0%). This is not a completely comparable group, however, because the hostile neck group included 40 patients with restenosis after CEA and 26 with radiation-induced arteritis. The authors were able to successfully treat all restenosis with repeat CAS in some cases, with no periprocedural stroke, death, or restenosis.

Protack et al,²⁴ published a similar series to ours with fewer patients overall (N = 150), but a greater proportion of their patients had radiation-induced stenosis (n = 23). Asymptomatic occlusions only occurred in the radiation group, and the restenosis-free survival at 3 years was significantly worse in the radiation group (20%) compared with all other patients undergoing CAS (74%).

Radiation-induced arteritis is considered one of the strongest and most appealing indications for CAS, making these poor long-term results for CAS in these patients troublesome. CAS was successful initially in our patients, but during the long-term follow-up, the restenosis rate in this subgroup was significantly higher. Our ANAT cohort had longer follow-up. In our practice, patients with a hostile neck were amongst the first to be offered CAS. CAS was not performed in medically high-risk patients until later within the trials. This is likely the explanation for the longer follow-up in the anatomically high-risk patients.

Our experience and the series published by Protack et al²⁴ prompts the question of whether radiation-induced arteritis should not be treated with CAS. Despite advances and improvement in the stents used in CAS, the results with radiation-induced arteritis continue to be disappointing. This study has described the clinical question of CAS in radiation-induced arteritis but is limited by the retrospective design and the small numbers due to the rarity of the condition. The small numbers of the study may contribute to the lack of a significant difference in the 30-day stroke rate between the medically and anatomically high-risk cohorts. Our data show a trend toward more strokes in the medically high-risk cohort, but the value of P does not reach statistical significance and may be due to the lack of power. With a larger sample size it is possible that this may or may not reach statistical significance.

Future possible options for the treatment of radiation-induced arteritis will include covered or drug-eluting stents to improve long-term patency in these difficult patients. However, although CAS for radiation-induced arteritis does have a higher rate of restenosis, we still believe it is a better therapeutic option for these patients than CEA. Currently, we continue to use CAS in these patients and until a better option is found, we will continue to do so.

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Conclusion 

CAS is as technically feasible, safe, and durable in anatomically high-risk patients as in medically high-risk patients, with similar rates of periprocedural stroke, death, and late restenosis. However, patients with radiation-induced stenosis appear to be at an increased risk for restenosis.

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Author contributions 

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