Immediate and long-term results of carotid endarterectomy

Neurovascular disease, diagnosis, and therapy: Cervical and intracranial atherosclerosis, vasculitis, and vasculopathy

Stroke is a leading cause of death, disability, and financial burden in the United States. Perhaps more than any other disease process, the rapidity with which the diagnosis and treatment of stroke are successfully achieved is paramount to the reduction of its associated morbidity and mortality. Steno-occlusive intracranial vascular disease, the most notorious culprit of cerebral ischemia and/or hemorrhage, traces its etiology to native and embolic atherosclerosis as well as various forms of vascular inflammation, insult, and dysfunction. Distinguishing between these causes is a critical first step in the diagnosis and treatment of a patient presenting with cerebrovascular compromise. In this chapter, we delineate the clinical and imaging features of cervical and intracranial atherosclerosis, vasculitis, and vasculopathy, along with the evidence behind the treatments which comprise their current-day standard of care. The modern imaging armamentarium is diverse and complex, with contrast-enhanced and non-contrast MR angiography, CT angiography, digital subtraction angiography, and ultrasound; each playing an important role in providing rapid insight into the patient's disease process. Understanding these imaging techniques and their application in the acute setting is critical for the provider caring for stroke patients.

[A role of carotid endarterectomy in prevention of cerebral ischemic damage]

Authors present a literature review on the prevalence, clinical presentations, diagnosis and outcome of surgical treatment of atherosclerotic stenosis of the internal carotid artery.

Decision analysis and carotid endarterectomy

A data base and a framework for clinical decision analysis are provided to enable the clinician to determine the value of carotid endarterectomy in patients with transient ischemic attacks. This approach permits optimal utilization of available data, maximizes the value of informed consent by clearly delineating areas of physician and patient expertise, and permits a quantitative assessment of the impact of uncertainty regarding underlying variables on decision outcome. The results of the analysis indicate that (a) the late nonstroke death rate has little effect on the value of endarterectomy, (b) the patient's relative valuation of stroke and immediate versus delayed death are among the most crucial variables underlying the value of endarterectomy, and (c) endarterectomy may be indicated in certain patients with transient ischemic attacks, but when its utility is measured in terms of value rendered to the patient, its relative cost may be greater than that of certain life-saving operations such as heart or liver transplant.

Frequency and management of recurrent stenosis after carotid artery stent implantation

Object. To determine the rate of hemodynamically significant recurrent carotid artery (CA) stenosis after stent-assisted angioplasty for CA occlusive disease, the authors analyzed Doppler ultrasonography data that had been prospectively collected between October 1998 and September 2002 for CA stent trials.

Methods. Patients included in the study participated in at least 6 months of follow-up review with serial Doppler studies or were found to have elevated in-stent velocities (> 300 cm/second) on postprocedure Doppler ultrasonograms. Hemodynamically significant (≥ 80%) recurrent stenosis was identified using the following Doppler criteria: peak in-stent systolic velocity at least 330 cm/second, peak in-stent diastolic velocity at least 130 cm/second, and peak internal carotid artery/common carotid artery velocity ratio at least 3.8. Follow-up studies were obtained at approximate fixed intervals of 1 day, 1 month, 6 months, and yearly. Angiography was performed in the event of recurrent symptoms, evidence of hemodynamically significant stenosis on Doppler ultrasonography, or both. Treatment was repeated because of symptoms, angiographic evidence of severe (≥ 80%) recurrent stenosis, or both of these.

Stents were implanted in 142 vessels in 138 patients (all but five patients were considered high-risk surgical candidates and 25 patients were lost to follow-up review). For the remaining 112 patients (117 vessels), the mean duration of Doppler ultrasonography follow up was 16.42 ± 10.58 months (range 4–54 months). Using one or more Doppler criteria, severe (≥ 80%) in-stent stenosis was detected in six patients (5%). Eight patients underwent repeated angiography. Six patients (three with symptoms) required repeated intervention (in four patients angioplasty alone; in one patient conventional angioplasty plus Cutting Balloon angioplasty; and in one patient stent-assisted angioplasty).

Conclusions. In a subset of primarily high-risk surgical candidates treated with stent-assisted angioplasty, the rates of hemodynamically significant restenosis were comparable to surgical restenosis rates cited in previously published works. Treatment for recurrent stenosis incurred no instance of periprocedure neurological morbidity.

Remodeling in peripheral vein graft revisions: serial study with three-dimensional ultrasound imaging

OBJECTIVE

Remodeling of vein grafts in the lower limb can lead to stenotic lesions that threaten long-term graft patency. Progressive changes in vein graft geometry were measured at sites of repaired stenoses with three-dimensional (3D) ultrasound imaging.

METHODS

Ten vein graft revisions with patch angioplasty were followed up for 31 to 47 weeks. Four revisions were at valve sites, and six were at sites of diffuse intimal hyperplasia. Sets of spatially registered two-dimensional (2D) cross-sectional ultrasound images were assembled to create 3D computer models of each vein graft. Cross-sectional area measurements in planes normal to the vessel center axis were calculated from the 3D surface reconstructions. Data sets from serial studies were registered in a common coordinate system, and cross-sectional area measurements were compared at matched sites.

RESULTS

Three of the four vein graft revisions at valve sites changed by less than 18%, and one decreased in cross-sectional area by 61%. Five of the six revisions at sites of diffuse intimal hyperplasia demonstrated significant decreases in lumen area ranging from 26% to 61%, and one revision exhibited no significant change in cross-sectional area. Reproducibility of the cross-sectional area measurements derived from the 3D imaging technique was 6.9%.

CONCLUSIONS

Sequential area measurements from 3D ultrasound scans demonstrated different remodeling patterns and rates of change among revision sites within the vein grafts. Lumen narrowing documented with 3D scanning was not associated with consistent flow velocity changes on conventional duplex graft surveillance scans.

Critical care of the vascular surgery patient

Providing effective critical care to vascular surgical patients is challenging to the intensivist. These patients often have multiple significant concurrent diseases that need to be adequately managed. A selective policy for identifying patients that need ICU is recommended. Early and smooth restoration to their preoperative physiological homeostasis is crucial. Optimal pain relief, return to normothermia, and adequate intravascular volume replacement are thus key interventions. Epidurals provide excellent analgesia. Vigilant monitoring and decisive therapy of the wide range of complications that may occur in the postoperative is of paramount importance. The level of monitoring should be an extension of that done intraoperatively. Hemorrhage and thrombosis are dreaded sequelae; cardiac morbidity and mortality is significant. Respiratory complications may necessitate prolonged postoperative mechanical ventilation. Careful clinical evaluation is necessary to detect the various neurological complications that may occur. Renal and gastrointestinal complications are potentially lethal. Graft sepsis may occur later. The development of new techniques, such as endovascular repairs of aneurysms, may minimize the need for ICU.

Outcome for patients with carotid stenosis undergoing carotid endarterectomy, the cerebral condition followed by extra/intracranial ultrasound examinations

Seventy-six patients undergoing carotid endarterectomy were studied to estimate the effect of operation, evaluate the accessible methods of examination and disclose the complications owing to the operation. In addition, the hypothesis that the pulsatility index in MCA measured by the Doppler method could disclose severe ischemia and risk of complications during endarterectomy was tested. The study was a prospective study of patients operated at the University Hospital in Odense in the years 1991-1996. Data collected included demographics, operative indications, complications, follow-up extra/transcranial Doppler examinations, cerebrovascular reactivity investigations, recurrent symptoms and deaths. Concerning the carotid stenosis, a fairly good correlation was found between the results of extracranial Doppler examinations, Duplex and carotid angiography. Serious complications after surgery were few. One patient, who had a coronary by-pass operation consecutive to the endarterectomy, died 3 weeks after the operation, owing to a hematothorax. Five patients (7%) suffered a stroke. Only 2 patients needed rehabilitation, and they came out with minor disturbances in the use of a hand. Recurrent stenosis in excess of 69% emerged in 3% of the patients. All were hemodynamically insignificant. One patient had a new TIA during the observation time of 3-60 months. After the operation she had a thrombosis in the operated carotid artery. Thus our results, a perioperative stroke rate of 7% and a mortality rate of 1%, are in line with the average results in multicenter trials. In addition a PI below 0.60 in the MCA seemed to be a warning of the risk of postoperative cerebral hyperemia.

Stent deformation and intimal hyperplasia complicating treatment of a post-carotid endarterectomy intimal flap with a Palmaz stent

We report a case of common carotid artery Palmaz stent placement for treatment of an intimal flap after surgical endarterectomy. Despite technical success with an excellent immediate result, a significant stenosis detected by duplex sonographic examination developed at 10 months. This stenosis, the result of stent compression and intimal hyperplasia, illustrates the previously theoretic risk associated with placement of the balloon-expandable stent in a compressible site such as the cervical carotid artery. In addition, we demonstrate that significant intimal hyperplasia may occur after carotid artery stent placement, potentially limiting long-term patency.

Cost-effectiveness of carotid endarterectomy in asymptomatic patients

PURPOSE

The purpose of this study was to determine the cost-effectiveness of carotid endarterectomy for treating asymptomatic patients with > or = 60% internal carotid stenosis, based on outcomes reported in the Asymptomatic Carotid Atherosclerosis Study (ACAS).

METHODS

A cost-effectiveness analysis was performed using a Markov decision model in which the probabilities for base-case analysis (average age, 67 years; 66% male; perioperative stroke plus death rate, 2.3%; ipsilateral stroke rate during medical management, 2.3% per year) were based on ACAS. The model assumed that patients who had TIAs or minor strokes during medical management crossed over to surgical treatment, and used the NASCET data to model the outcome of these now-symptomatic patients. Average cost of surgery ($8500), major stroke ($34,000 plus $18,000 per year), and other costs were based on local cost determinations plus a review of the published literature. Cost-effectiveness was calculated as the incremental cost of surgery per quality-adjusted life year (QALY) saved when compared with medical treatment, discounting at 5% per year. Sensitivity analysis was performed to determine the impact of key variables on cost-effectiveness.

RESULTS

In the base-case analysis, surgical treatment improved quality-adjusted life expectancy from 7.87 to 8.12 QALYs, at an incremental lifetime cost of $2041. This yielded an incremental cost-effectiveness ratio of $8,000 per QALY saved by surgical compared with medical treatment. The high cost of care after major stroke during medical management largely offset the initial cost of endarterectomy in the surgical group. Furthermore, 26% of medically managed patients eventually underwent endarterectomy because of symptom development, which also decreased the cost differential. Sensitivity analysis demonstrated that the relative cost of surgical treatment increased substantially with increasing age, increasing perioperative stroke rate, and decreasing stroke rate during medical management.

CONCLUSION

For the typical asymptomatic patient in ACAS with > or = 60% carotid stenosis, our results indicate that carotid endarterectomy is cost-effective when compared with other commonly accepted health care practices. Surgery does not appear cost-effective in very elderly patients, in settings where the operative stroke risk is high, or in patients with very low stroke risk without surgery.

Causes of the increased stroke rate after carotid endarterectomy in patients with previous strokes

Patients who have sustained a preoperative stroke are at increased risk for perioperative stroke after carotid endarterectomy. At our institution this risk was recently shown to be increased two-to threefold. The purpose of this study was to investigate the reasons for the increased surgical risk in these patients. Records of 606 patients undergoing 704 consecutive carotid endarterectomies from 1988 through 1993 were reviewed. Patients who suffered preoperative strokes (n = 183) were compared to those who were either asymptomatic or experienced only transient ischemic attacks (TIAs) preoperatively (n = 423). Of the 183 patients who had suffered preoperative strokes, eight patients who experienced perioperative strokes after endarterectomy were compared with 175 who successfully underwent surgery. Patients with a prior stroke had an increased perioperative stroke rate (4.4% versus 1.2%, p = 0.01). They had a significantly higher incidence of hypertension (62.6% versus 47.9%, p < 0.001), cardiac disease (54.7% versus 40.7%, p = 0.001), and positive smoking history (52% versus 40.6%, p = 0.01) than did the asymptomatic/TIA patients. The presence of contralateral total occlusion was also significantly increased (22% versus 10.3%, p < 0.001). Although not statistically significant due to the overall small number of patients who sustained perioperative strokes, the preoperative stroke patients who sustained perioperative strokes had a higher incidence of hypertension (87.5% versus 61.5%) and contralateral total occlusion (37.5% versus 21.3%) than did those who successfully underwent surgery. Patients with both a prior stroke and contralateral total occlusion had a 7.5% perioperative stroke rate. Patients with both a prior stroke and hypertension had a 6.1% perioperative stroke rate. The perioperative strokes in patients with prior strokes were not related to the severity of the prior stroke, the interval between the stroke and surgery, the use of a shunt, or the type of anesthesia employed. Patients who have sustained preoperative strokes have a higher incidence of significant medical illnesses and overall cerebrovascular disease. Hypertension and total occlusion of the contralateral carotid artery appear to be particularly poor prognostic indicators of outcome after endarterectomy in these patients. Patients who have sustained preoperative strokes may be more likely to display clinical neurologic symptoms in response to any form of cerebral ischemia. In this higher risk subgroup, intraoperative and surgeon-dependent factors appear to play less of a role.

A clinical marker for arterial wall healing: the double line

PURPOSE

B-mode imaging of a normal arterial wall shows two echo-dense lines separated by an echolucent zone. Immediately after carotid endarterectomy, this double-line pattern is no longer detectable, but it subsequently reappears in some patients. The objective of this study was to test the hypothesis that the postoperative double line is associated with a lower incidence of carotid restenosis.

METHODS

Carotid arteries were serially studied with B-mode ultrasound imaging at 2 weeks and 1, 2, 3, 6, 9, 12, 18, and 24 months after carotid endarterectomy. The wall of the common carotid artery 1 to 2 cm distal to the proximal endarterectomized shelf was analyzed for the presence, quality, and thickness of double lines. All hemodynamically significant stenoses (> or = 50% diameter reducing) were documented with standard duplex scanning criteria.

RESULTS

Twenty-four carotid arteries in 23 patients were studied for a mean of 14.7 months (range, 3 to 24 months). A double line developed in 21 common carotid arteries (87.5%) at a mean time of 3.2 months (range, 0.5 to 9.0 months) after surgery with a mean thickness of 0.65 mm (SD = 0.17 mm) at the time of initial detection. A single hemodynamically significant stenosis developed in this group. All three of the remaining arteries that did not form the double-line pattern developed hemodynamically significant stenoses. Carotid restenosis was more likely to occur in arteries that did not form double lines (p < 0.05, Fisher's exact test).

CONCLUSIONS

The majority of carotid arteries re-form a double line after endarterectomy. These arteries are less likely to develop restenotic lesions caused by myointimal hyperplasia.

Vein graft lesions: time of onset and rate of progression

PURPOSE

The objectives of this study were to determine the time of onset, location, severity, rate of progression, and subsequent fate of infrainguinal vein graft lesions.

METHODS

Sixty-one infrainguinal vein grafts were studied serially with duplex ultrasonography to document the location and severity of each lesion. Grafts were studied at 1, 2, 3, 4, 6, 9, 12, and 18 months and then annually.

RESULTS

The cumulative secondary graft patency rate at 3 years (life-table analysis) was 93.2%. A total of 158 lesions were detected in 55 of the 61 grafts studied. The degree of diameter reduction at the time of initial detection was as follows: 1% to 19% (29.6%), 20% to 49% (51.0%), 50% to 75% (17.3%), and greater than 75% (3.1%). Forty-eight percent were detected at the first examination, 59.2% within 2 months, and 85.7% within 6 months. Progression was detected in 31.2% of the lesions by 6 and in 39.1% of the lesions by 18 months (life-table analysis). Thrombosis, in the absence of significant changes in ankle-brachial index (> or = 0.15) or return of symptoms, was not observed in grafts that had lesions with less than 75% diameter reduction.

CONCLUSIONS

The data support the performance of a duplex scan either during surgery or before discharge from the hospital in addition to frequent surveillance for the first 6 months. Frequent surveillance is appropriate for lesions with less than 75% diameter reduction as long as they remain asymptomatic and without a significant reduction in the ankle-brachial index.

Short-stay carotid endarterectomy is safe and cost-effective

BACKGROUND

Carotid endarterectomy (CEA) is conventionally performed following a contrast arteriogram, under general anesthesia, and with postoperative admission to an intensive care unit (ICU). We investigated whether any of these traditional adjuncts to CEA is necessary.

PATIENTS AND METHODS

Eighteen consecutive patients had CEA performed according to a protocol of duplex scanning only, operation under regional anesthesia, and admission to the ICU only in cases of a proven need for services unique to the ICU (group I). Utilization of preoperative arteriography, admission to the ICU, postoperative complications, total hospital length of stay, and hospital charges were calculated for this group and results were compared with a group of 178 patients undergoing conventional CEA (arteriography, general anesthesia, routine ICU admission) during the same period (group II).

RESULTS

In group I, 1 patient (6%) underwent preoperative arteriography and 4 patients (22%) were admitted to the ICU after CEA. Most group II patients (114 of 178, or 64%) underwent preoperative arteriography and virtually all (175 of 178, or 98%) were admitted to the ICU. Compared with group II, the average hospital length of stay for group I was significantly shorter (1.3 +/- 0.1 versus 3.1 +/- 0.3 days, P = 0.03) and hospital charges were significantly reduced ($5,861 +/- 229 versus $11,140 +/- 729, P = 0.02).

CONCLUSIONS

This pilot study suggests that CEA can be safely performed without routine preoperative carotid arteriography; that routine ICU admission is unnecessary for the majority of cases; and that elimination of routine arteriography and ICU admission can reduce hospital charges for CEA by nearly one half.

The durability of bilateral carotid endarterectomy

To determine the natural history and durability of bilateral carotid endarterectomy (CEA), we studied 27 patients who participated in a randomized, prospective, consecutive entry trial comparing vein patch with primary CEA closure. This cohort represented 20% of the 136 patients who took part in the 4-year study. Bilateral CEAs were planned at the time of the original admission in 13 (48%), whereas 14 (52%) developed late indications for contralateral CEA a mean of 27 +/- 7 months after the initial procedure. Among the 27 patients, 15 underwent alternating methods of CEA closure. During a mean follow-up of 64 +/- 7 months, five patients had six recurrences (four unilateral, one bilateral). The type of closure did not affect the recurrence rate. All recurrences were asymptomatic and measured < 50% diameter loss by duplex criteria. There were no strokes. Two other patients had late transient ischemic attacks, but neither of them had arteriographic evidence of recurrent carotid disease. No patient underwent reoperative CEA. These data demonstrate that bilateral CEA is durable. Late recurrences are rare and clinically insignificant. The higher rate of unilateral recurrence suggests that local factors play a more important role than systemic factors in the etiology of recurrent disease.

Restenosis after vascular reconstruction

About 20-50% of vascular reconstructions used for restoration of circulation in atherosclerotic vessels fail because of restenosis. Despite progress in both experimental and clinical studies, the underlying mechanism of restenosis remains unclear. This has presented a problem for the targeting of pharmacological therapies, and so far the only effective cure for restenosis remains repetition of the operative treatment. However, the subsequent reconstructions are also subject to luminal narrowing. New approaches in preventing restenosis may involve identifying the patients most likely to be at risk, and treating them selectively with novel suppressive agents, or with combinations of already tested agents.

Stroke rates in patients with lacunar and large vessel cerebral infarctions

A stroke registry was developed to determine the value of various clinical data in distinguishing lacunar from large vessel infarctions. Adequate localization was achieved in 98% of 246 patients with brain infarcts. These and 30 transient ischemic attack patients were followed for a median of 1082 days (range 2-1657). Follow-up data on TIA patients were invalidated by evidence of serious underreporting of TIAs in our general population. Among 212 male patients with cerebral infarcts not due to cardiogenic embolism, syphilis, migraine, vasculitis, or other unusual etiologies, 1-, 12-, and 36-month recurrence rates were 23%, 31% and 39% among patients with large vessel anterior circulation infarcts; 15%, 20% and 28% among patients with large vessel posterior circulation infarcts; and 8%, 16% and 21% among patients with lacunar anterior circulation infarcts, respectively. Six patients with posterior circulation lacunes did not experience recurrence. Comparative case fatality data were also compiled. Large vessel infarcts tended to be followed by further large vessel infarcts, usually in the same vascular distribution, whereas lacunar infarcts were not predictive of the type or location of subsequent events.

Duplex sonography of the carotid arteries

Duplex sonography is the best noninvasive modality for investigation of possible carotid artery stenosis. By using the above described techniques, almost all significant stenoses can be detected and categorized correctly. Knowledge of common pitfalls in the performance and interpretation of the examination is essential to avoid misdiagnosis. Color imaging is a helpful addition to conventional duplex imaging, but is not essential to the performance of high-quality examinations.

Role of arteriography in the preoperative evaluation of carotid artery disease

This retrospective study was undertaken to determine the role of arteriography in the treatment of patients being considered for carotid endarterectomy. The results of preoperative classification of disease severity by duplex ultrasound and arteriography were compared, and the impact of arteriography on patient management was ascertained. We reviewed the records of 83 patients who had carotid surgery planned on the basis of their clinical history and duplex scan results and who then underwent arteriography. Duplex scan results agreed with the classification of stenosis by arteriography in 87% of evaluated sides and were within one category in 98%. In 87% of the cases reviewed, the clinical presentation and duplex scan findings were sufficient for appropriate patient management. In the instances that arteriography was useful (13%), the need for arteriography was evident when the duplex scan (1) was technically inadequate or equivocal; (2) showed an unusual distribution of disease, atypical anatomy, or a recurrent lesion; or (3) demonstrated an internal carotid artery with diameter-reducing stenosis of less than 50% in a patient with hemispheric neurologic symptoms despite antiplatelet therapy.

Perioperative stroke. Part I: General surgery, carotid artery disease, and carotid endarterectomy

Although stroke, defined as a focal neurological deficit lasting more than 24 hr, is uncommon in the perioperative period, its associated mortality and long-term disability are high. No large-scale data are available to identify the importance of recognized risk factors for stroke in the perioperative period. A review of the literature shows that the incidence and mechanism of its occurrence are influenced by the presence of cardiovascular disease and the type of surgery. The most common cause of perioperative stroke is embolism. In non-cardiac surgery, the incidence of perioperative stroke is higher among the elderly. Properly administered, controlled hypotension is associated with minimal risk of stroke. Cerebral vasospasm may be the cause of focal cerebral ischaemia in eclamptic patients, and the aggressive treatment of hypertension may exacerbate the neurological damage. The risk of stroke associated with carotid endarterectomy is closely related to the preoperative neurological presentation, and the experience of the surgical/anaesthetic team. Symptomatic cerebrovascular disease, acute stroke, asymptomatic carotid lesions, preoperative assessment of risk, local and general anaesthesia, cerebral protection and monitoring during carotid endarterectomy are discussed with reference to reducing the risk of perioperative stroke. Adequate monitoring and protection have minimized the risk of ischaemia from carotid clamping, and the major mechanism of stroke is embolization.