Carotid Artery Imaging in the United Kingdom: A Postal Questionnaire of Current Practice

Temporal Trends in Eversion Carotid Endarterectomy for Carotid Atherosclerosis: Single-Center Experience with 5,034 Patients

The aim of this article is to review our experience in surgical treatment of carotid atherosclerosis using eversion carotid endarterectomy (ECEA) in 5,034 patients, with particular attention to temporal changes in patients' characteristics, diagnostic approach, surgical technique, medical therapy, and outcome in the early (group A, 1991–1997) versus late (group B 1998–2004) period of ECEA. From January 1991 to December 2004, 5,034 primary ECEAs were performed for high-grade carotid stenosis. Patients treated for restenosis after previous carotid surgery were excluded from the analysis. Group A consisted of 1,714 patients who underwent surgery between 1991 and 1997, and group B consisted of 3,320 patients who underwent surgery between 1998 and 2004. Follow-up included routine clinical evaluation and noninvasive surveillance, with duplex scanning at 1 month after surgery, after 6 months, and annually afterward. Only 3% of patients in group A and 0.6% in group B were asymptomatic, with 23% and 47% of them having preoperative stroke, respectively. In group A, angiography was used for the final diagnosis in 78% of patients. In group B, duplex scanning was performed in 82% of patients and angiography in only 18% ( p < .001). Clamping time was shorter in the latter group (12.4 ± 3.1 vs 14.5 ± 4.1 min, p < .01). Introperative shunting and regional anesthesia were rarely performed in both groups (1.4% vs. 0.4%, p < .01, and 2% vs 0.3%, p < .001). Total and neurologic morbidity was significantly higher in group A than in group B (6.41% ± 0.47% vs 4.81% ± 0.53%, p < .001, and 2.14% ± 0.31% vs 1.23% ± 0.29%, p < .001, respectively). Total mortality was also higher in group A than in group B (1.92% ± 0.24% vs 1.36% ± 0.50%, p < .05), but although there was a trend toward lower neurologic mortality, it did not reach statistical significance (1.04% ± 0.5% vs 0.57% ± 0.25%, p = .074). There was a lower rate of nonsignificant restenosis (< 50%) in group B (2% vs 5%, p < .01), but the incidence of restenosis ≥ 50% was identical between the groups (5.5% for both). Our data show that ECEA is a reliable surgical technique for the treatment of atherosclerotic carotid disease. Temporal trends in our patients demonstrated a decline in periopertive mortality and morbidity, despite a higher incidence of preoperative stroke.

Eversion carotid endarterectomy--our experience after 20 years of carotid surgery and 9897 carotid endarterectomy procedures

BACKGROUND

The aim of this article is to review our experience in surgical treatment of carotid atherosclerosis using eversion carotid endarterectomy (eCEA) in 9,897 patients performed in the last 20 years, with particular attention to diagnostic approach, surgical technique, medical therapy, and final outcome.

METHODS

From January 1991 to December 2010, 9,897 primary eCEAs were performed for high-grade carotid stenosis. Patients treated for restenosis after previous carotid surgery were excluded from the analysis. Follow-up included routine clinical evaluation and noninvasive surveillance, with duplex scanning, 1 and 6 months after surgery, and annually afterward.

RESULTS

The majority of the patients were symptomatic (stroke, 42.8%; transient ischemic attack, 55.1% [focal cerebral and retinal ischemia]), whereas only 2.1% of the patients were asymptomatic. For the final diagnosis, duplex scanning was performed in 83.4% of patients and angiography in only 16.3% (P < 0.001). Average carotid artery clamping time was 11.9 ± 3.2 minutes, and the majority of the patients were operated under general anesthesia (99.4%). Intraoperative shunting and local anesthesia were rarely performed; 0.6% of the patients were operated under local anesthesia, and in 0.5% of the patients, intraluminal shunt was used. Neurological and total morbidity showed a steady decline over time, with rate of neurological morbidity of 1.1% and total morbidity of 3.9% at the end of 2010. Neurological mortality and total mortality also showed a steady decline over time, with rate of neurological mortality of 0.3% and total mortality of 0.8% at the end of 2010. There was a low rate of both, nonsignificant restenosis (<50%), which was verified in 2.1% of the patients, and significant restenosis (>50%), which was observed in 4.3% of the patients.

CONCLUSION

Our data show that eCEA is a reliable surgical technique for the treatment of atherosclerotic carotid disease, with low morbidity and mortality. The specificity of our experience is the significant number of patients with preoperative stroke, but despite this fact, results are comparable with previously published series. It also highlights the importance of comprehensive surgical training in reducing complications.

In vivo Doppler ultrasound quantification of turbulence intensity using a high-pass frequency filter method

The objective of this investigation was to implement a high-pass frequency filter method to analyze Doppler ultrasound velocity waveforms and quantify turbulence intensity (TI) in vivo. Doppler velocity data were analyzed using two techniques, based on either ensemble averaging or high-pass frequency domain filtering of the periodic waveforms. The accuracy and precision of TI measurements were determined with controlled in vitro experiments, using a pulsatile-flow model of a stenosed carotid bifurcation. The high-pass filter technique was also applied in vivo to determine whether this technique could successfully distinguish between pertinent hemodynamic sites within the carotid artery bifurcation. Twenty-five seconds of Doppler audio data were acquired at three sites (common carotid artery [CCA], internal carotid artery [ICA] stenosis and distal ICA) within 10 human carotid arteries, and repeated three times. Doppler velocity data were analyzed using a ninth-order high-pass Butterworth filter with a 12-Hz inflection point. TI measured within the CCA and distal ICA was found to be significantly different (p < 0.0001) for moderate to nearly occluded carotid artery classifications. Also, TI measured within the distal ICA increased with stenosis severity, with the ability to distinguish between each stenosis class (p < 0.05). This investigation demonstrated the ability to precisely quantify TI using a conventional Doppler ultrasound machine in human subjects, without interfering with normal clinical protocols.

Carotid Artery Imaging for Secondary Stroke Prevention

Background and Purpose— Patients with transient ischemic attack require carotid imaging to diagnose carotid stenosis. The differing sensitivity/specificity and availability of carotid imaging methods have created uncertainty over which noninvasive method is best and whether intra-arterial angiography is still required. We evaluated the influence of carotid imaging methods on secondary stroke prevention.

Methods— We modeled the effect of different carotid imaging strategies and timing on endarterectomy workload, stroke, and death at 1 and 5 years. We used all available data on stroke prevention after transient ischemic attack from systematic reviews (carotid imaging, medical and surgical interventions), population-based transient ischemic attack/stroke studies, government statistics, and stroke prevention clinics.

Results— Choice of imaging strategy affected speed of assessment, strokes prevented, and endarterectomy workload. The number of strokes prevented at 5 years varied by up to 22 per 1000 patients between imaging strategies for a given time to assessment. Delaying endarterectomy from 14 to approximately 30 days would fail to prevent up to 11 strokes per 1000 patients depending on the imaging strategy. Sensitive fast imaging (eg, ultrasound) was best for patients seen early; specific imaging (eg, CT angiography or contrast-enhanced MR angiography) was best for patients seen late after transient ischemic attack. Intra-arterial angiography conferred no advantage over noninvasive imaging.

Conclusions— Rapid access to sensitive noninvasive carotid imaging prevents most strokes. However, imaging strategies differ in their effect on stroke prevention by as much as 22 per 1000 patients and optimal imaging varies with time after transient ischemic attack TIA. Routine intra-arterial angiography should be avoided.

Carotid Imaging for Secondary Stroke Prevention in Routine Practice

Carotid imaging is key to effective secondary stroke prevention. It is commonly performed, but is a rather specialist procedure requiring regular practice to maintain acceptable accuracy. Previously the domain of the neuroradiologist, noninvasive carotid imaging is now widely practiced in general departments where specialist knowledge of anatomy and intracranial disorders may be less available. Noninvasive imaging is largely replacing intraarterial angiography in the assessment of carotid stenosis in most centres because the accuracy is perceived to be sufficient. However, effective stroke prevention needs to be delivered rapidly, guided by imaging tests that are used with an understanding of their limitations and accuracy. This review will discuss currently available imaging methods, their advantages and disadvantages, difficulties in determining their accuracy, current estimates of accuracy and gaps in knowledge.

Introduction: Stroke is common, has a poor outcome, and treatment must be delivered quickly. Many pharmacological acute stroke treatments have failed, reinforcing the need for effective prevention. There has been extensive testing of many pharmacological secondary prevention treatments and most of the ‘positive’ stroke trials have been in secondary prevention of ischaemic stroke. The surgical procedures for stroke prevention, carotid endarterectomy and angioplasty, have also been subjected to far closer scrutiny in large randomised-controlled trials than almost any other surgical or interventional radiological procedures. However, it is unfortunate that much of the focus of secondary stroke prevention has been on drug mechanisms, or surgery vs. endovascular methods, rather than on how to identify accurately and quickly the right patients for each intervention. Thus, until fairly recently ( 1 , 2 ), the need for very rapid initiation of medical and surgical interventions in patients whose carotid stenosis has been accurately diagnosed by imaging ( 3 ), and the service modifications required to deliver this ( 4 ), have largely been overlooked.

Non-invasive imaging compared with intra-arterial angiography in the diagnosis of symptomatic carotid stenosis: a meta-analysis

BACKGROUND

Accurate carotid imaging is important for effective secondary stroke prevention. Non-invasive imaging, now widely available, is replacing intra-arterial angiography for carotid stenosis, but the accuracy remains uncertain despite an extensive literature. We systematically reviewed the accuracy of non-invasive imaging compared with intra-arterial angiography for diagnosing carotid stenosis in patients with carotid territory ischaemic symptoms.

METHODS

We searched for articles published between 1980 and April 2004; included studies comparing non-invasive imaging with intra-arterial angiography that met Standards for Reporting of Diagnostic Accuracy (STARD) criteria; extracted data to calculate sensitivity and specificity of non-invasive imaging, to test for heterogeneity and to perform sensitivity analyses; and categorised percent stenosis by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method.

RESULTS

In 41 included studies (2541 patients, 4876 arteries), contrast-enhanced MR angiography was more sensitive (0.94, 95% CI 0.88-0.97) and specific (0.93, 95% CI 0.89-0.96) for 70-99% stenosis than Doppler ultrasound, MR angiography, and CT angiography (sensitivities 0.89, 0.88, 0.76; specificities 0.84, 0.84, 0.94, respectively). Data for 50-69% stenoses and combinations of non-invasive tests were sparse and unreliable. There was heterogeneity between studies and evidence of publication bias.

INTERPRETATION

Non-invasive tests, used cautiously, could replace intra-arterial carotid angiography for 70-99% stenosis. However, more data are required to determine their accuracy, especially at 50-69% stenoses where the balance of risk and benefit for carotid endarterectomy is particularly narrow, and to explore and overcome heterogeneity. Methodology for evaluating imaging tests should be improved; blinded, prospective studies in clinically relevant patients are essential basic characteristics.