Extracranial internal carotid arterial disease in children with sickle cell anemia.

BACKGROUND: Sickle cell anemia is one of the commonest causes of stroke in children. It is usually, but not always, associated with intracranial vasculopathy. We have assessed the value of ultrasound screening for extracranial internal carotid artery disease. DESIGN AND METHODS: Using Doppler ultrasound scanning, we assessed peak systolic blood velocity, tortuosity and stenosis in the extracranial internal carotid arteries of 236 children with sickle cell anemia. Seventeen of the children had previously had a stroke. All measurements were performed as part of routine clinical care. RESULTS: The median extracranial internal carotid artery velocity was 148cm/s (5(th) centile 84, 95(th) centile 236). Higher velocities were significantly correlated with younger age, higher white blood cell counts and higher rates of hemolysis. Fourteen (5.9%) had tortuous extracranial internal carotid arteries and 13 (5.4%) had stenosis or occlusion. None of the children with tortuous vessels but 8 of those with stenosis had previously had a stroke; the presence of stenosis was strongly associated with overt clinical stroke (OR 35.9, 95% C.I. 9.77-132, P<0.001). In 6 children, extracranial stenosis was part of extensive intracranial vasculopathy, but in 2 there was no evidence of intracranial disease. Stenosis seemed to be more common in older children. CONCLUSIONS: Extracranial internal carotid artery stenosis is strongly associated with stroke in children with sickle cell anemia, and may explain some cases of stroke without overt intracranial vasculopathy. Doppler ultrasound scanning of extracranial internal carotid arteries is non-invasive and fairly quick to perform and may identify children at increased risk of stroke who would otherwise be missed. The value of extracranial internal carotid artery scanning should be studied prospectively.

Stroke prevention in the young child with sickle cell anaemia.

Cerebrovascular disease resulting in stroke is a serious and preventable complication of sickle cell anaemia (SCA). Children at high risk of preventable stroke can be identified by transcranial Doppler ultrasound (TCD). Current guidelines in the UK recommend annual TCD screening from 3 years, although studies suggest an earlier peak incidence, between 2 and 5 years. A single centre retrospective review was undertaken to identify the prevalence of stroke and success of TCD screening in young children. We report five episodes of stroke in under 3s and outcome of TCD screening in children under 3, compared to over 3. TCD analysis was as successful in the 2-3-year age group as in the 3-4-year group. We therefore propose that all children with SCA should be offered TCD screening from the age of 2 years. Furthermore, infants with high risk features of SCA should undergo a first attempt at TCD screening even earlier.

Arteriovenous access ischemic steal (AVAIS) in haemodialysis: a consensus from the Charing Cross Vascular Access Masterclass 2016.

Arteriovenous access ischaemic steal (AVAIS) is a serious and not infrequent complication of vascular access. Pathophysiology is key to diagnosis, investigation and management. Ischaemia distal to an AV access is due to multiple factors. Clinical steal is not simply blood diversion but pressure changes within the adapted vasculature with distal hypoperfusion and resultant poor perfusion pressures in the distal extremity. Reversal of flow within the artery distal to the AV access may be seen but this is not associated with ischaemia in most cases.Terminology is varied and it is suggested that arteriovenous access ischemic steal (AVAIS) is the preferred term. In all cases AVAIS should be carefully classified on clinical symptoms as these determine management options and allow standardisation for studies.Diabetes and peripheral arterial occlusive disease are risk factors but a 'high risk patient' profile is not clear and definitive vascular access should not be automatically avoided in these patient groups.Multiple treatment modalities have been described and their use should be directed by appropriate assessment, investigation and treatment of the underlying pathophysiology. Comparison of treatment options is difficult as published studies are heavily biased. Whilst no single technique is suitable for all cases of AVAIS there are some that suit particular scenarios and mild AVAIS may benefit from observation whilst more severe steal mandates surgical intervention.

The significance of inadequate transcranial Doppler studies in children with sickle cell disease.

Sickle cell disease (SCD) is a common cause of cerebrovascular disease in childhood. Primary stroke prevention is effective using transcranial Doppler (TCD) scans to measure intracranial blood velocities, and regular blood transfusions or hydroxycarbamide when these are abnormal. Inadequate TCD scans occur when it is not possible to measure velocities in all the main arteries. We have investigated the prevalence and significance of this in a retrospective audit of 3915 TCD scans in 1191 children, performed between 2008 and 2015. 79% scans were normal, 6.4% conditional, 2.8% abnormal and 12% inadequate. 21.6% of 1191 patients had an inadequate scan at least once. The median age of first inadequate scan was 3.3 years (0.7-19.4), with a U-shaped frequency distribution with age: 28% aged 2-3 years, 3.5% age 10 years, 25% age 16 years. In young children reduced compliance was the main reason for inadequate TCDs, whereas in older children it was due to a poor temporal ultrasound window. The prevalence of inadequate TCD was 8% in the main Vascular Laboratory at King's College Hospital and significantly higher at 16% in the outreach clinics (P<0.0001), probably due to the use of a portable ultrasound machine. Inadequate TCD scans were not associated with underlying cerebrovascular disease.

Aneurysms in vascular access: state of the art and future developments.

A master class was held at the Vascular Access at Charing Cross (VA@CX2017) conference in April 2017 with invited experts and active audience participation to discuss arteriovenous (AV) vascular access aneurysms, a serious and common complication of vascular access (VA). The natural history of aneurysms in VA is poorly defined, and although classifications exist they are not uniformly applied in studies or clinical practice. True and pseudo aneurysms of AV access occur. Whilst an AV fistula by definition is an abnormal dilatation of a blood vessel, an agreed definition of 18 mm, or 3 times accepted maturation diameter, is proposed. The mechanism of aneurysmal dilatation is unknown but appears to be a combination of excessive external remodeling, wall changes due to injury, and obstruction of outflow. Diagnosis of AV aneurysms is based on physical examination and ultrasound. Venography and cross-sectional imaging may assist and be required for the investigation of outflow stenosis. Treatment of pseudo aneurysms and true aneurysms of VA (AVA) is not evidence-based, but relies on clinical experience and available facilities. In many AVA, a conservative approach with surveillance is suitable, although intervals and modalities are unclear. Avoidance of rupture is imperative and preemptive treatment should aim for access preservation, ideally with avoidance of prosthetic materials. Different techniques of aneurysmorrhaphy are described with good results in published series. Although endovascular approaches and stenting are described with good short-term results, issues with cannulation of stented areas occur and, while possible, this is not recommended, and long-term access revision is recommended.

Extracranial internal carotid artery stenosis in children with sickle cell disease - Which transducer, what measurement?

BACKGROUND: Transcranial Doppler ultrasound is used to screen and assess the intracranial arteries of children with sickle cell disease. Recent findings suggest that extracranial internal carotid artery (eICA) stenosis is also a contributing factor to silent cerebral infarction. Stenosis has been measured using phased array transducers with no beam/flow angle correction and linear arrays with angle correction. METHODS: A total of 124 children undergoing TCD assessment were investigated for eICA velocities. Manual measurements of peak systolic velocity and TCD mean velocity were made with phased and linear array transducers. RESULTS: Peak systolic velocities ranged from 60 to 534 cm/s (median 126 cm/s) using the linear array and 53 to 394 cm/s (median 115 cm/s) using the phased array transducers. TCD mean ranged from 39 to 419 cm/s (median 81 cm/s) using the linear array and 34 to 295 cm/s (median 72 cm/s) using the phased array transducers. CONCLUSIONS: There are advantages and disadvantages of each method, but stenoses were readily identified as focal velocity increases. We suggest thresholds for each transducer and recommend that imaging of the eICA forms part of screening for this group of children.

The diabetic foot: the importance of coordinated care.

Because of the severe morbidity and mortality associated with diabetes, diabetic foot care is an essential component of a peripheral vascular service. The goal of this article is to describe the vascular diabetic foot care pathway and how the coordinated foot care service for diabetic patients is delivered at King's College Hospital, London.

Transformation of the multidisciplinary diabetic foot clinic into a multidisciplinary diabetic foot day unit: results from a service evaluation.

The natural history of the diabetic foot is aggressive and complex. To counteract this, we describe the transformation of a Multidisciplinary Diabetic Foot Clinic into a Multidisciplinary Diabetic Foot Day Unit, which delivers an emergency open access system for patients, with a "one-stop," same day service in which investigations are performed, results reviewed and treatment implemented. It also provides joint clinics with vascular, orthopaedic, and plastic surgeons and specialized clinics for casting of complex neuropathic feet and for the administration of intravenous or intramuscular antibiotics on the same day. The aim was to document these increasingly wide-ranging facilities by undertaking a retrospective evaluation over a 6-week period, with analysis of notes, investigations, and an anonymous patient satisfaction survey. The clinic was visited by 597 patients who attended in 1076 appointments, of which 112 (10.4%) were emergency visits; these patients attended the clinic without a booked appointment but via an open access policy, 93 of whom were known to the clinic, but 19 were new self-referred patients to the service. Furthermore, 197 (18%) were seen in a Joint Vascular Diabetic Foot Clinic and 98 (9%) were seen in a Joint Orthopaedic Plastic Diabetic Foot Clinic, 570 (53%) were seen in an Active Ulcer Clinic and 97 (9%) in a Total Contact Casting Clinic. Forty-five percent of patients were prescribed antibiotics, including 188 (76%) as oral and 45(18%) as intravenous antibiotics and 15(6%) as intramuscular injections. Of the 1076 appointments, 150 (14%) patients were in the foot clinic for more than 4 hours. Sixty (10%) patients were reviewed 4 or more times over the 6-week period. Only 22 (2%) were admitted to hospital. Of the 125 survey responders, 98% were satisfied with this service, which has evolved from a Diabetic Foot Clinic into a Multidisciplinary Diabetic Foot Day Unit.

Duplex ultrasound volumetric flow analysis before and after hemodialysis in patients with brachio-cephalic fistulae.

PURPOSE: The United Kingdom Renal Association recommends duplex ultrasound to monitor arteriovenous fistula (AVF) flow rates during surveillance. Significant flow rate changes should prompt further investigation or treatment to avoid a failing fistula. Hemodialysis is known to alter the hemorrheologic and physiologic factors with a potential impact on measured flow rates. The aim of this study was to determine the difference in flow rate measured with duplex ultrasound before and after a single hemodialysis session in patients with brachial-cephalic fistulae. METHODS: Patients with brachial-cephalic AVFs in our dialysis populations who were undergoing regular hemodialysis without recent intervention (less than six weeks) were invited to participate. Flow measurements were made pre-and post-hemodialysis using a Zonare ultrasound machine. The vascular scientist was always blinded to the pre-hemodialysis flow. RESULTS: A total of 157 patients were identified with brachial-cephalic fistulae. Following exclusions, 119 patients were eligible. However, a further 58 were excluded because they declined or did not attend leaving 61 patients in the study. Paired t test showed a statistically significant reduction in flow rate of 105 mL/min (P=0.026) post-hemodialysis which equates to a -6.9% change in flow (95% C.I. -12.7 to -0.8%). Bland-Altman analysis showed limits of flow rate agreement between -599 mL/min and +810 mL/min (+/-1.96 s.d.). CONCLUSIONS: Whilst we have shown a statistically significant change in flow rate post-hemodialysis, this is small and should be taken in the context of previously accepted interobserver variability. Therefore, the practical and financial considerations of implementing an AVF surveillance programme are likely to outweigh the minimal benefit of consistency that would be enabled by strict protocol of pre-hemodialysis flow measurements.

Occult carotid artery disease in patients who have undergone coronary angioplasty.

OBJECTIVES: The aim was to evaluate the prevalence of asymptomatic mild (30-49%), moderate (50-69%) and severe (70-99%) ICA stenosis in patients who underwent previous coronary angioplasty (PTA). METHODS: After obtaining ethics committee approval, 144 consecutive patients aged between 65 and 75 years were invited for carotid Duplex evaluation with a linear 6 MHz array transducer by trained vascular sonographers within a single unit. A peak systolic velocity >230 cm/s in the ICA was considered as significant (>70% stenosis). RESULTS: Of the 144 patients approached, 117 (81%) attended (male:female ratio 3.2:1, age range 65-75 years, median age 71 years). Duplex ultrasound revealed one occlusion, 70% or more ICA stenosis in three patients (2.6%), 50-69% stenosis in 12 patients (10.3%) and 30-49% stenosis in 29 patients (24.8%). CONCLUSIONS: Carotid artery disease with a luminal stenosis of 30% or more is common in patients who underwent previous PTA. The yield of significant ICA stenosis (70% or more), which would benefit from carotid endarterectomy according to the Asymptomatic Carotid Surgery Trial is low. Recommendation for initial screening and subsequent follow-up Duplex examination for evaluation of disease progression of such cohorts remains debatable.

Transcranial Doppler scanning and the assessment of stroke risk in children with HbSC [corrected] disease.

OBJECTIVE: To assess the role of transcranial Doppler (TCD) scanning in assessing the risk of stroke in children with haemoglobin SC (HbSC) disease. TCD scanning has an established role in primary stroke prevention in sickle cell anaemia but its value in HbSC is unknown. DESIGN: A retrospective audit of routinely performed TCD scans and routinely collected clinical data. SETTING: A paediatric sickle cell clinic in a teaching hospital in south London, UK. PATIENTS: 46 children with HbSC disease who have undergone routinely performed TCD scans and steady-state blood tests. MAIN OUTCOME MEASURES: The time-averaged mean of the maximum velocity (TAMMV) in the middle cerebral artery circulation correlated with clinical and laboratory data. RESULTS: The mean TAMMV was 94 cm/s, with a 98(th) centile of 128 cm/s. This is significantly less than the published ranges for HbSS, with a mean reading of 129 cm/s. One child had a stroke at the age of 5 years, when her TAMMV was measured at 146 cm/s. CONCLUSIONS: Further studies are needed to assess stroke risk in HbSC disease, but we suggest that TCD measurements are potentially useful in this condition, and that readings greater than 128 cm/s are abnormally high and warrant further investigation.

A simple index using age, hemoglobin, and aspartate transaminase predicts increased intracerebral blood velocity as measured by transcranial Doppler scanning in children with sickle cell anemia.

OBJECTIVE: Increased intracerebral blood velocity measured by transcranial Doppler scanning identifies children with sickle cell anemia who are at increased risk of stroke. We have tried to develop an index based on routine clinical measurements that also predicts increased intracerebral blood flow. METHOD: Routinely collected clinical and laboratory data were correlated with transcranial Doppler measurements on children with sickle cell anemia seen in a single institution in 2006. The index produced was validated on a second independent data set from children with sickle cell anemia. RESULTS: The time-averaged mean of the maximum velocity in centimeters per second in the middle cerebral artery circulation correlated significantly with age, hemoglobin, lactate dehydrogenase, and aspartate transaminase levels, white blood cell count, and creatinine level. On multiple regression, hemoglobin and aspartate transaminase levels maintained their significance, whereas age had borderline significance, and an index was developed linked to a time-averaged mean of the maximum velocity of 220 - (8 x hemoglobin) - (1.4 x age) + (0.4 x aspartate transaminase). This detected a time-averaged mean of the maximum velocity of >170 cm/second with 100% sensitivity and 58% specificity. The index was validated on the second data set and again showed 100% sensitivity with 73% specificity. CONCLUSION: This simple index has the potential to identify children who are at higher risk of cerebrovascular disease to allow them to be prioritized for transcranial Doppler scanning and other intracerebral imaging.