Asymptomatic Carotid Artery Stenosis: Past, Present and Future

Cognitive Functions in Patients after Carotid Artery Revascularization-A Narrative Review

Carotid revascularization may lead to improved cognitive function beyond stroke prevention. This article summarizes the conclusions from available studies on the effects of carotid reperfusion procedures on cognitive function. The papers cited used different neuropsychological tests for cognitive assessment, resulting in different methodologies and the results obtained were not always convergent. However, most studies reported an improvement in neurocognitive abilities after both vascular interventions, but a more precise assessment of the specific benefits is still awaited. Clinical determinants to predict the effects of these treatments on cognitive function are still being sought, but results are not yet satisfactory. In view of these studies, carotid stenosis seems to be an independent risk factor for cognitive deterioration, and the main mechanisms responsible are embolism and cerebral hypoperfusion. The aim of this study is to order the knowledge about the effects of carotid artery stenting (CAS) and endarterectomy (CEA) on neurocognitive functions and to verify the usefulness of using these treatments.

Functional posterior communicating artery of patients with posterior circulation ischemia using phase contrast magnetic resonance angiography

Posterior communicating artery (PCoA) in patients with posterior circulation ischemia (PCI) was quantitatively studied using phase contrast magnetic resonance angiography (PC-MRA). Fifty-one cases who received PC-MRA were included in the study, and divided into the research and control groups. The mean flow volume, mean flow velocity, minimum flow volume, maximum flow volume, minimum flow velocity and maximum flow velocity of the basal artery (BA), bilateral vertebral arteries, internal carotid arteries and functional posterior communicating artery (F-PCoA) were recorded, the peak heights of flow volume and flow velocity were calculated, and the typing of F-PCoA was analyzed, followed by statistical analysis. Fifty-two F-PCoAs were detected, and the median values of mean flow volume, mean flow velocity, cross-sectional area and lumen diameter were 20.31 ml/min, 4.01 cm/sec, 0.08 cm² and 0.16 cm, respectively. The blood flow curve of F-PCoA showed the sawtooth-like changes, and there could be either unidirectional blood flow or bidirectional blood flow in one cardiac cycle. F-PCoA was divided into the following 3 types: F-PCoA was consistent with anatomical PCoA (A-PCoA), F-PCoA was inconsistent with A-PCoA, and mixed type. In the presence of F-PCoA, both the diameter and cross-sectional area of BA were small, and the maximum flow velocity and peak height of flow volume were reduced, but there was no necessary correlation with the occurrence of PCI. Both flow volume and flow velocity of BA in the research group were reduced, and the forward posterior shunt flow of F-PCoA was increased. Hemodynamic characteristics of F-PCoA can be analyzed via PC-MRA. The forward posterior shunt flow of F-PCoA can provide references for the clinical auxiliary diagnosis.

Public health implications of overscreening for carotid artery stenosis, prediabetes, and thyroid cancer

Background

Overscreening occurs when people without symptoms undergo tests for diseases and the results will not improve their health. In this commentary, we examine three examples of how campaigns to screen and treat specific vascular, metabolic, and oncologic diseases in asymptomatic individuals have produced substantial overdiagnosis and may well have contributed to more harm than good. These conditions were chosen because they may not be as well known as other cases such as screening for breast or prostate cancer.

Main text

Screening for carotid artery stenosis can be a lucrative business using portable equipment and mobile vans. While this fatty buildup of plaque in the arteries of the neck is one risk factor for ischemic stroke, current evidence does not suggest that performing carotid dopplers to screen for CAS reduces the incidence of stroke or provide long-term benefits. After a positive screening, the follow-up procedures can lead to heart attacks, bleeding, strokes, and even death. Similarly, many organizations have launched campaigns for “prediabetes awareness.” Screening for prediabetes with a blood sugar test does not decrease mortality or cardiovascular events. Identifying people with prediabetes could lead to psychological stress and starting medication that may have significant side effects. Finally, palpating people’s necks or examining them with ultrasounds for thyroid cancer is common in many countries but ineffective in reducing mortality. Deadly forms of thyroid cancer are rare, and the overall 5-year survival rate is excellent. Interventions from treatment for more prevalent, less aggressive forms of thyroid cancer can lead to surgical complications, radiation side effects, or require lifelong thyroid replacement therapy.

Conclusions

Screening for carotid artery stenosis, prediabetes, and thyroid cancer in an asymptomatic population can result in unnecessary, harmful, and costly care. Systemic challenges to lowering overscreening include lack of clinician awareness, examination of conflicts of interests, perverse financial incentives, and communication with the general public.

Carotid artery stenosis screening: where are we now?

Stroke poses a significant burden on healthcare and is the second largest cause of death globally. Both medical and surgical interventions to reduce the risk of stroke in asymptomatic patients have been shown to be effective but identifying the target at risk population is more problematic. Screening for carotid artery stenosis offers one pathway for this, as there is some correlation between risk of stroke and extent of stenosis. Identification of patients who are at risk of cardiovascular disease as well as stroke, allows initiation of effective medical treatment of modifiable risk factors to address this risk. In addition, carotid intima-media thickness is a way of assessing systemic atherosclerosis and may be valuable in risk stratification of patients for cardiovascular disease. Given the low prevalence of stenosis in the general population and the risks associated with undergoing surgical intervention, population wide screening is not recommended. This recommendation has not changed over the last 15 years, since the last major studies evaluating management and outcomes were published. However, both medical and surgical/endovascular treatments have advanced over that time. Further studies are underway to compare current treatments for the appropriate management of both symptomatic and asymptomatic patients with stenosis. Two of these trials, ECST-2 and CREST-2, are expected to be completed in the next 2-4 years and the results may initiate changes in the recommendations. The use of carotid intima-media thickness alongside traditional risk scores is controversial and more research is required in this area.

[Asymptomatic atherosclerosis of the brachiocephalic arteries: Current approaches to diagnosis and treatment]

Acute cerebrovascular accident (ACVA) and transient ischemic attack are among the leading causes of morbidity, disability, and mortality in the Russian Federation and the world. Ischemic strokes account for 70-80% of all ACVAs, with 20-30% of them being associated with stenotic atherosclerosis of the brachiocephalic arteries (BCA). The paper describes modern views on the problem of asymptomatic BCA atherosclerosis and considers the possibilities of identifying risk groups among the patients with asymptomatic atherosclerosis of the BCA.

Dual energy computed tomography quantification of carotid plaques calcification: comparison between monochromatic and polychromatic energies with pathology correlation

PURPOSE

We compared carotid plaque calcification detection sensitivity and apparent cross-sectional area on CT as a function of CT beam energy using conventional CT techniques and virtual mono-energetic CT images generated from dual-energy acquisitions.

METHODS & MATERIALS

Five ex-vivo carotid endarterectomy (CEA) specimens were imaged with dual-energy computed tomography. Virtual monochromatic spectrum (VMS) CT images were reconstructed at energies between 40-140 keV. The same specimens were imaged using conventional polyenergetic spectrum (PS) CT with peak beam energies 80, 100, 120, and 140 kVp. The histological calcium areas on each corresponding CEA specimen were traced manually on digitized images of Toluidine-Blue/Basic-Fuchsin stained plastic sections.

RESULTS

40 keV VMS CT images provided high detection sensitivity (97 %) similar to conventional PS CT images (~96 %). The calcification size measured on CT decreased systematically with increasing CT beam energy; the rate of change was larger for the VMS images than for PS images.

CONCLUSION

From a single dual-energy CT, multiple VMS-CT images can be generated, yielding equivalent detection sensitivity and size correlations as conventional PS-CT in CEA calcification imaging. VMS-CT at 80-100 keV provided the most accurate estimates of calcification size, as compared to histology, but detection sensitivity was reduced for smaller calcifications on these images.

KEY POINTS

• Calcifications depicted at 80-100 keV were most similar to the histology standard. • Conventional polychromatic images demonstrated excellent correlation with plaque size at pathology. • Conventional polychromatic images systematically overestimate plaque size. • Plaque calcifications can be missed on high energy monochromatic images.

Clinical considerations in the management of asymptomatic carotid artery stenosis

Incidental findings pose considerable management dilemmas for the treating physician and psychological burden for the respective patient. With an aging population, more patients will be diagnosed with asymptomatic internal carotid artery stenosis. Patients will have to be counseled with regard to treatment options according to their individual risk profile and according to professionals' knowledge of evidence-based data derived from large randomized control trials. Treatment consensus has long been lacking for patients with asymptomatic carotid artery stenosis prior to any randomized controlled trials. Additionally, an individual's risk profile may be hard to assess according to knowledge gained from randomized controlled trials. Moreover, while earlier studies compared carotid endarterectomy and medical therapy, in the past years, a new therapeutic modality, carotid artery angioplasty and stenting, has emerged as a possible alternative. This has been evaluated in a recent randomized controlled trial, the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST), which compared carotid endarterectomy with angioplasty and stenting in both symptomatic and asymptomatic patients. The following review summarizes current knowledge of the natural history, diagnosis, and treatment strategies to counsel patients with asymptomatic carotid artery stenosis.

Strategies for asymptomatic carotid artery stenosis

The treatment of asymptomatic carotid artery stenosis (ACAS) has continued to evolve for the past 3 decades. With rapidly advancing technology, the results of old trials have become obsolete. While there has been little change in the efficacy of carotid endarterectomy, there have been vast improvements in both medical management and carotid angioplasty with stenting. Finding the best therapy for a given patient can therefore be difficult. In this article, the authors review the current literature regarding treatment options for ACAS and the methods available for stratifying patients who would benefit from surgical versus medical treatment.

Evaluation of inflammatory status of atherosclerotic carotid plaque before thromboendarterectomy using delayed contrast-enhanced subtracted images after magnetic resonance angiography

OBJECTIVE

To investigate the correlation among carotid plaque contrast enhancement (CPCE) at MRI, inflammatory cell infiltration (ICI) at histopathology, and carotid stenosis degree.

MATERIALS AND METHODS

Twenty-eight patients (19 males; mean age 67±9 years) scheduled for thromboendarterectomy prospectively underwent 1.5-T MR imaging using: (a) axial T1-weighted gradient-echo (T1wGRE) sequence centered on carotid bifurcations; (b) contrast-enhanced MR angiography (CE-MRA) with 0.1 mmol/kg of gadobenate dimeglumine; (c) enhanced axial T1wGRE sequence as in (a), 3 min after contrast injection. A three-point score system (absent, focal, wide) was used to assess CPCE on native and subtracted MRI images (c minus a) and ICI at histopathology. Carotid stenosis degree was determined on CE-MRA.

RESULTS

Six CPCE studies were discarded due to patient movement. In the remaining 22 studies, CPCE was absent, focal and wide in 13, 6 and 3 cases, respectively; ICI was absent, focal and wide in 13, 7 and 2 cases, respectively (k=0.57). On CE-MRA 21/28 stenoses were severe and 7/28 moderate. There was no correlation either with ICI (p=1.000, n=28) or CPCE (p=0.747, n=22).

CONCLUSION

The correlation between CPCE and ICI suggests a role for CPCE as an independent marker of plaque inflammation.

The effect of statin therapy on the progression of carotid artery stenosis in relation to stenosis severity

OBJECTIVES

To examine the effect of early statin treatment on progression of arteriosclerosis in internal carotid arteries (ICA); to compare the progression of arteriosclerosis in ICA of patients treated with a statin to the progression seen in drug-naïve patients.

PATIENTS AND METHODS

We performed repetitive Doppler scans of 363 carotid arteries with ICA stenosis > or =40% in 254 patients over time. Information on statin therapy and other risk factors for stroke were correlated with the annual change in degree of ICA stenosis.

RESULTS

In statin-treated patients, 19% of ICA stenosis showed a progression while 74% showed a regression of stenosis. In statin-naïve patients, 63% of stenotic arteries showed a progression, while a reduction could be observed in 28%. Decrease of ICA stenosis was most accentuated in patients with a mild stenosis and was independent of serum cholesterol levels.

CONCLUSION

Treatment with statins already in early stages of ICA stenosis might delay the progression and even reverse the degree of stenosis.

Medical (Nonsurgical) Intervention Alone Is Now Best for Prevention of Stroke Associated With Asymptomatic Severe Carotid Stenosis

Significant advances in vascular disease medical intervention since large randomized trials for asymptomatic severe carotid stenosis were conducted (1983–2003) have prompted doubt over current expectations of a surgical benefit. In this systematic review and analysis of published data it was found that rates of ipsilateral and any-territory stroke (+/−TIA), with medical intervention alone, have fallen significantly since the mid-1980s, with recent estimates overlapping those of operated patients in randomized trials. However, current medical intervention alone was estimated at least 3 to 8 times more cost-effective. In conclusion, current vascular disease medical intervention alone is now best for stroke prevention associated with asymptomatic severe carotid stenosis given this new evidence, other cardiovascular benefits, and because high-risk patients who benefit from additional carotid surgery or angioplasty/stenting cannot be identified.