Assessment of Competence in EVAR Procedures: A Novel Rating Scale Developed by the Delphi Technique.

OBJECTIVE/BACKGROUND: To develop a procedure specific global rating scale for assessment of operator competence in endovascular aortic repair (EVAR). METHODS: A Delphi approach was used to achieve expert consensus. A panel of 32 international experts (median 300 EVAR procedures, range 200-3000) from vascular surgery (n = 21) and radiology (n = 11) was established. The first Delphi round was based on a review of endovascular skills assessment papers, stent graft instructions for use, and structured interviews. It led to a primary pool of 83 items that were formulated as global rating scale items with tentative anchors. Iterative Delphi rounds were executed. The panellists rated the importance of each item on a 5 point Likert scale. Consensus was defined as 80% of the panel rating an item 4 or 5 in the primary round and 90% in subsequent rounds. Consensus on the final assessment tool was defined as Cronbach's alpha > .8 after a minimum of three rounds. RESULTS: Thirty-two of 35 invited experts participated. Three rounds of surveys were completed with a completion rate of 100% in the first two rounds and 91% in round three. The 83 primary assessment items were supplemented with five items suggested by the panel and reduced to seven pivotal assessment items that reached consensus, Cronbach's alpha = 0.82. The seven item rating scale covers key elements of competence in EVAR stent placement and deployment. Each item has well defined grades with explicit anchors at unacceptable, acceptable, and superior performance on a 5 point Likert scale. CONCLUSION: The Delphi methodology allowed for international consensus on a new procedure specific global rating scale for assessment of competence in EVAR. The resulting scale, EndoVascular Aortic Repair Assessment of Technical Expertise (EVARATE), represents key elements in the procedure. EVARATE constitutes an assessment tool for providing structured feedback to endovascular operators in training.

Assessment of Competence in EVAR Stent Graft Sizing and Selection.

OBJECTIVES AND BACKGROUND: The aims of this study were to develop a test of competence in endovascular aortic repair (EVAR) stent graft sizing and selection; to examine the test for evidence of validity; and to explore the experience required for the task. METHODS: The test was developed based on a literature review resulting in 22 anatomical assessment points and a graft selection. Validity evidence was explored in an international cross sectional study. Twenty-two consultants with varying levels of experience in the field (novices, intermediates, and experts) were presented with computed tomography angiography of the aortic vessels from three patients. Test scores were based on summed z-scores using the anatomical measurements and graft choices of the experts as a reference. A proficiency score was established using the contrasting groups standard setting method. RESULTS: The assessment was shown to be reliable with an intraclass correlation coefficient of 0.83 (p<.001) and high internal consistency with a Cronbach's α of .91 (p<.001). Mann-Whitney U test showed that experts performed significantly better than novices and intermediates (p<.002 and p<.005, respectively). Regarding anatomical measurements, Mann-Whitney U test could discriminate between experts and novices (p=.002), between experts and intermediates (p=.010), and between novices and intermediates (p=.036). In stent selection the experts performed significantly better than both the novices and the intermediates (p=.002 and p=.007, respectively), while there was no significant difference between the two non-expert groups (p=1). A credible passing standard with appropriate consequences was established using the contrasting groups methods. CONCLUSION: This study presents a standardised and objective assessment tool of competence in vessel analysis and stent graft selection for endovascular aortic repair. This was supported by strong validity evidence with good internal consistency and discriminatory ability. The tool may be used to facilitate training and certification of future endovascular specialists.

A National Needs Assessment to Identify Technical Procedures in Vascular Surgery for Simulation Based Training.

OBJECTIVES AND BACKGROUND: Practical skills training in vascular surgery is facing challenges because of an increased number of endovascular procedures and fewer open procedures, as well as a move away from the traditional principle of "learning by doing." This change has established simulation as a cornerstone in providing trainees with the necessary skills and competences. However, the development of simulation based programs often evolves based on available resources and equipment, reflecting convenience rather than a systematic educational plan. The objective of the present study was to perform a national needs assessment to identify the technical procedures that should be integrated in a simulation based curriculum. DESIGN AND METHODS: A national needs assessment using a Delphi process was initiated by engaging 33 predefined key persons in vascular surgery. Round 1 was a brainstorming phase to identify technical procedures that vascular surgeons should learn. Round 2 was a survey that used a needs assessment formula to explore the frequency of procedures, the number of surgeons performing each procedure, risk and/or discomfort, and feasibility for simulation based training. Round 3 involved elimination and ranking of procedures. RESULTS: The response rate for round 1 was 70%, with 36 procedures identified. Round 2 had a 76% response rate and resulted in a preliminary prioritised list after exploring the need for simulation based training. Round 3 had an 85% response rate; 17 procedures were eliminated, resulting in a final prioritised list of 19 technical procedures. CONCLUSION: A national needs assessment using a standardised Delphi method identified a list of procedures that are highly suitable and may provide the basis for future simulation based training programs for vascular surgeons in training.

Red blood cell storage duration and long-term mortality in patients undergoing cardiac intervention: a Danish register study.

OBJECTIVES: To study the effect of red blood cell (RBC) storage duration on long-term mortality in patients undergoing cardiac intervention. BACKGROUND: RBCs undergo numerous structural and functional changes during storage. Observational studies have assessed the association between RBC storage duration and patient outcomes with conflicting results. METHODS: Between January 2006 and December 2014, 82 408 patients underwent coronary angiography. Of these, 1856 patients received one to four RBC units within 30 days after this procedure. Patients were allocated according to length of RBC storage duration: short-term (≤11 days), intermediate (IM)-term (12-23 days) and long-term (≥24 days). The study endpoints were 30-day and long-term all-cause mortality. RESULTS: A total of 4168 RBC units were given to 1856 patients. The mean RBC storage duration was 8.5 ± 2.1, 17.7 ± 3.4 and 29.9 ± 3.4 days in the short-term, IM-term and long-term storage groups, respectively. There was no difference in baseline characteristics between the groups. The long-term storage group received significantly more units (2.4 ± 1.0 units) as compared to the short-term (2.0 ± 1.0 units; P < 0.001) and IM-term storage group (2.2 ± 1.0 units; P < 0.01). In the survival analysis, there was no significant difference in all-cause mortality between the groups (log-rank: 0.509 for 30-days mortality; 0.493 for 5-year mortality). Additional stratified analysis demonstrated no association between RBC storage duration and long-term mortality. CONCLUSION: This study did not find an association between RBC storage duration and 30-days or long-term mortality in patients undergoing cardiac intervention.

Clinical and imaging features associated with an increased risk of early and late stroke in patients with symptomatic carotid disease.

OBJECTIVE: The aim of this review was to identify clinical and/or imaging parameters that are associated with an increased (decreased) risk of early/late stroke in patients with symptomatic carotid disease. IN THE FIRST 14 DAYS: Natural history studies suggest that 8-15% of patients with 50-99% stenoses will suffer a stroke within 72 hours of their index symptom. Currently, there are insufficient validated data to identify highest-risk patients for emergency carotid endarterectomy (CEA), but an increased risk of stroke appears to be predicted by (i) an ABCD(2) score of 4-7; (ii) the presence of acute cerebral injury on CT/MRI; (iii) Gray Scale Median (GSM) <15, (iv) spontaneous embolisation on Transcranial Doppler (TCD); and (v) increased fluorodeoxyglucose (FDG) uptake in the carotid plaque on positron emission tomography (PET). A future goal must be to develop predictive algorithms (based on accessible imaging strategies) for identifying acutely symptomatic patients with highly unstable plaques for emergency CEA. MEDIUM TO LONG TERM: In the randomised trials, about 70% of patients with symptomatic 70-99% stenoses were stroke-free on "best medical therapy" at 5 years. Clinical predictors of increased stroke risk include (i) male gender; (ii) age >75; (iii) hemispheric symptoms; and (iv) increasing comorbidity. Imaging features associated with increased stroke risk include (i) irregular stenoses; (ii) contralateral occlusion; (iii) increasing stenosis severity, but not subocclusion; (iv) tandem intracranial disease; (v) a failure to recruit intracranial collaterals; (vi) low GSM; (vii) MR diagnosis of intra-plaque haemorrhage; (vii) spontaneous embolisation on TCD; and (viii) increased FDG uptake in the carotid plaque on PET. Clinical/imaging parameters associated with a lower risk of stroke include (i) female gender, especially those with 50-99% stenoses; (ii) ocular symptoms/lacunar stroke; (iii) smooth stenoses; and (iv) chronic subocclusion.

Clinical and imaging features associated with an increased risk of late stroke in patients with asymptomatic carotid disease.

BACKGROUND: The 2011 American Heart Association Guidelines on the management of asymptomatic carotid disease recommends that carotid endarterectomy (CEA) (with carotid artery stenting (CAS) as an alternative) may be considered in highly selected patients with 70-99% stenoses. However, no guidance was provided as to what "highly selected" meant. This caveat is, however, important as up to 95% of asymptomatic individuals undergoing prophylactic CEA or CAS will ultimately undergo an unnecessary procedure. Even if the procedural risk following CEA or CAS could be reduced to 0%; 93% of patients would still undergo an unnecessary intervention. This, coupled with growing awareness that the risk of stroke in medically treated patients appears to be diminishing, has led to a renewed drive towards identifying patients with the highest risk of suffering a stroke whilst on medical therapy in whom to target CEA/CAS. METHODS: Review of clinical and/or imaging based scoring systems, predictive algorithms and imaging parameters that may be associated with an increased (or decreased) risk of stroke in patients with asymptomatic carotid disease. RESULTS: Parameters associated with an increased risk of late stroke include: (a) silent infarction on CT/MRI; (b) stenosis progression; (c) hypoechoic plaques or GSM <15; (d) irregular plaques; (e) evidence of spontaneous embolization on TCD; (f) AHA plaque types IV-V, VI; (g) MR diagnosed IPH; (h) plaque area >80 mm(2); (i) juxta-luminal black area >10 mm(2); and (j) tandem intracranial disease. CONCLUSIONS: A number of imaging parameters have been shown to be predictive of an increased risk of late stroke in previously asymptomatic patients. None have been independently validated, but many could easily be evaluated in natural history studies or randomized trials in order to identify a "high risk for stroke" cohort in whom CEA/CAS could be prioritized.

Endograft limb occlusion in EVAR: iliac tortuosity quantified by three different indices on the basis of preoperative CTA.

OBJECTIVE: To assess the incidence and outcome of graft limb occlusions after endovascular aortic repair (EVAR) of abdominal aortic aneurysm (AAA) in a high volume single centre. To quantify iliac artery tortuosity in patients with AAA and correlate this with limb occlusion. DESIGN: Data were collected consecutively and prospectively, and analyzed retrospectively. MATERIALS: Patients treated with Zenith bifurcated stent grafts from January 2000 to December 2010 at a tertiary referral vascular unit were analyzed. Routine regular office follow-up with computed tomography angiography (CTA) and, subsequently, duplex ultrasound imaging was performed. Patients with limb occlusions were identified. For each index patient, two controls were obtained, one immediately preceding and one following the index patient in the consecutive cohort of EVAR patients. METHODS: Demographics and CTA data on limb graft occlusions were recorded and compared with a defined control group. Three different indices were used to describe the tortuosity of the iliac vessels based on preoperative CTA: pelvic artery index of tortuosity (PAI), common iliac artery index of tortuosity (CAI), and a visual description of vessel tortuosity - the double iliac sign (DIS). Demographic data and indices were correlated for later occurring limb occlusion. RESULTS: 504 patients underwent EVAR and 18 patients experienced graft limb occlusion during a median follow-up of 28 months (range 0-133). Primary graft patency was 97% at 1 year and 96% at 3 years. Logistic regression showed that iliac artery tortuosity (DIS) (p = .001) and body mass index (p = .007) had a significant impact on graft patency. CONCLUSION: A tortuous vessel on the preoperative CTA is associated with an increased risk of limb occlusion after EVAR. Adjunctive stenting of iliac segments deemed at risk is suggested, which is achieved without compromise of the aneurysm repair.

Carotid endarterectomy after intravenous thrombolysis for acute cerebral ischaemic attack: is it safe?

OBJECTIVES: Intravenous thrombolysis (IVT) has proven effective in the treatment of acute cerebral ischaemic attack in selected cases. In the presence of a carotid artery stenosis, such patients may be candidates for carotid endarterectomy (CEA). Few studies have been made on the safety of CEA performed after IVT. DESIGN: This was a retrospective study. Data including 30 days' follow-up were obtained from medical records and from a vascular registry. MATERIALS: A consecutive series of 306 patients were operated on for symptomatic carotid artery stenosis during a 5-year period. Among these, 22 (7%) patients had been treated with IVT for an acute cerebral ischaemic attack prior to CEA and 284 (93%) patients had CEA only. METHODS: IVT as well as CEA was performed following established guidelines. CEA was performed in median 11 days (25 and 75% percentiles: 7-13 days) after the neurological index event in patients having undergone IVT and 12 days (25 and 75% percentiles: 8-21 days) in patients undergoing CEA only. RESULTS: The 30 days' stroke and death rate was 0% (95% confidence interval (CI): 0-15%) in patients who had IVT before CEA and 2.4% (95% CI: 0.9-4.7%) in patients who underwent CEA only. CONCLUSION: Our experience indicates that CEA performed after IVT for acute cerebral ischaemic attack is safe, confirming existing but sparse publications. However, our series is small and our study possesses a number of limitations. Thus, our results cannot necessarily be transferred to other units, who instead should perform similar studies, preferably together.

Outcomes after elective aortic aneurysm repair: a nationwide Danish cohort study 2007-2010.

OBJECTIVE: To assess outcomes after treatment for asymptomatic abdominal aortic aneurysm (AAA) in Denmark in a period when both open surgery (OR) and endoluminal repair (EVAR) have been routine procedures. METHODS: We performed a retrospective nationwide cohort study of patients treated for asymptomatic AAA between 2007 and 2010. Data on demographics, procedural data, perioperative complications, length of stay (LOS), 30-day reinterventions and readmissions, late aneurysm and procedure-related complications and mortality were obtained from the Danish Vascular Registry and the Danish National Patient Register. RESULTS: 525 EVAR and 1176 OR for asymptomatic AAA were identified. LOS was shorter after EVAR than OR (4 vs. 7 days, p < .001). During primary hospitalization procedure-related complications (12% vs. 6%) and general complications (21% vs. 8%) were more common after OR than EVAR (p < 0.001). The 30-day reintervention rate was higher for OR than EVAR (18% vs. 6%, p < 0.001), but there was no difference in readmissions within 30 days. During follow-up (mean 29 ± 15 months) aneurysm-related complications after EVAR were outweighed by procedure-related complications after OR. CONCLUSION: Elective AAA repair in Denmark is overall comparable with international results and both perioperative and late outcomes after EVAR of elective AAA are better than the results after OR.

Construct validity and reliability of structured assessment of endoVascular expertise in a simulated setting.

OBJECTIVES: To study the construct validity and reliability of a novel endovascular global rating scale, Structured Assessment of endoVascular Expertise (SAVE). DESIGN: A Clinical, experimental study. MATERIALS: Twenty physicians with endovascular experiences ranging from complete novices to highly experienced operators performed a video-recorded simulated contra-lateral iliac-artery-stenting procedure. The virtual-patient case was a novel technically challenging procedure presenting the distal arteries below the knee. METHODS: Three experts assessed the performances blinded to operator identity. Validity was analysed by correlating experience with performance results. Reliability was analysed according to generalisability theory. RESULTS: The mean score on the 29 items of the SAVE scale correlated well with clinical experience (R = 0.84, P < 0.01) and was found discriminative even among the more experienced participants having performed up to 500 endovascular procedures in total. Only the most experienced participants (>5000 procedures) obtained maximum scores. The inter-rater reliability was high (G = 0.94 and G = 0.95). The procedure time (median 69 min, range 32-86) correlated moderately with clinical experience (R = -0.53, P < 0.05), whereas the fluoroscopy time and amount of contrast fluid did not correlate. CONCLUSIONS: The construct validity and reliability of assessment with the SAVE scale was high when applied to performances in a simulation setting with advanced realism. No ceiling effect was present in the assessment situation.

Capturing the essence of developing endovascular expertise for the construction of a global assessment instrument.

OBJECTIVES: To explore what characterises the development of endovascular expertise and to construct a novel global assessment instrument. DESIGN: Literature review and an experimental study. MATERIALS AND METHODS: The literature was searched for information regarding available global rating scales (GRSs); scientific societies' official statements on endovascular competence; and task analyses of endovascular procedures. In the experimental study, clinicians performed a video-recorded simulated iliac-artery stenting procedure. Subsequently, by using the method of retrospective verbalisation, the clinicians were interviewed while watching their performance on video commenting on key issues of the construct. Data from all sources were analysed, categorised and synthesised into a novel rating scale. RESULTS: Available GRSs primarily included technical aspects of performance, whereas the competence statements, task analyses and clinicians' perceptions added a range of non-technical aspects. The novel rating scale SAVE (Structured Assessment of endoVascular Expertise) differs from prior scales by including issues of pre-planning; prediction of challenges; preparation of tools; management of imaging presentation; distinction of technical skills into external and internal control according to operator focus of visual attention; adaptation of strategy; clinical decision making; use of assistant; complications; inter-personal skills; and post-procedural planning. CONCLUSIONS: The essence of developing endovascular expertise goes far beyond mere technical aspects.

Duplex ultrasound scanning of peripheral arterial disease of the lower limb.

OBJECTIVES: To assess the reliability and applicability of duplex ultrasound scanning (DUS) of lower limb arteries, compared with digital subtraction angiography (DSA), in patients with peripheral arterial disease (PAD). DESIGN: A prospective, blinded, comparative study. MATERIALS AND METHODS: A total of 169 patients were examined by DUS and DSA. Intermittent claudication (IC) was present in 42 (25%) patients and critical limb ischaemia (CLI) in 127 (75%) patients. To allow segment-to-segment comparison, the arterial tree was divided into 15 segments. In total, 2535 segments were examined using kappa (κ) statistics to test the agreement. RESULTS: The agreement between DUS and DSA was very good (κ>0.8) or good (0.8 ≥ κ>0.6) in most segments, but moderate (0.6 ≥ κ>0.4) in the tibio-peroneal trunk and the peroneal artery. Agreement between the two techniques was significantly better in the supragenicular (κ=0.75 (95% confidence interval (CI): 0.70-0.80)) than in the infragenicular segments (κ=0.63 (0.59-0.67)) (p<0.001). Similarly, the technical success rate was significantly higher in the supragenicular segments (DUS: 100%; DSA: 99%) than in the infragenicular segments (both 93%) (p<0.001). DUS was the best technique for imaging of the distal crural arteries (92% vs. 97%; p<0.001) and DSA was the best technique for imaging of the proximal crural arteries (95% vs. 91%; p<0.01). Neither the agreement nor the technical success rate was influenced by the severity of PAD, that is, IC versus CLI. CONCLUSION: The agreement between DUS and DSA was generally good, irrespective of the severity of ischaemia. DUS performed better in the supragenicular arteries than in the infragenicular arteries. However, DUS compared favourably with DSA in both tibial vessels, particularly in the distal part, which makes DUS a useful non-invasive alternative to DSA.

A look into the endovascular crystal ball.

This paper summarizes the highlights of the 15th International Workshop of Endovascular Surgery, held in Ajaccio in June 2008. This is an annual event that attracts leading endovascular therapists from both sides of the Atlantic Ocean as well as a contingency from down-under. The layout of this meeting followed the previous events with sessions on carotid artery disease and abdominal and thoracic aortic aneurysms topped up with clinical cases, lower limb ischemia and venous disease. Generally the session takes off by summarising new evidence, followed by questions and discussion. This workshops gives the participants an excellent opportunity to get an updated perspective within these fast developing areas.

Minimum training requirement in ultrasound imaging of peripheral arterial disease.

OBJECTIVES: To demonstrate the minimum training requirement when performing ultrasound of peripheral arterial disease. DESIGN: Prospective and blinded comparative study. MATERIAL: 100 limbs in 100 consecutive patients suffering from peripheral arterial disease, 74% suffering critical limb ischemia, were enrolled during a 9 months period. METHODS: One physician with limited ultrasound experience performed all the ultrasound examinations of the arteries of the most symptomatic limb. Before enrolling any patients 15 duplex ultrasound examinations were performed supervised by an experienced vascular technologist. All patients had a digital subtraction arteriography performed by an experienced vascular radiologist, unaware of the ultrasound result. RESULTS: The number of insufficiently insonated segments (non-diagnostic segments) was significantly reduced during the study; from 9% among the initial 50 limbs to 2% among the last 50 limbs (P<0.0001). This improvement was evident only in the infragenicular segments, as the performance within the supragenicular segments was good from the beginning. There was no change in the agreement between ultrasound and arteriography from the initial 50 patients (overall Kappa=0.66, (95%-CI: 0.60-0.72); supragenicular Kappa=0.73 (95%-CI: 0.64-0.82); infragenicular Kappa=0.61 (95%-CI: 0.54-0.69)) to the last 50 patients (overall Kappa=0.66 (95%-CI: 0.60-0.72), supragenicular Kappa=0.67 (95%-CI: 0.57-0.76); infragenicular Kappa=0.66 (95%-CI: 0.58-0.73)). CONCLUSION: The minimum training requirement in ultrasound imaging of peripheral arterial disease appears to be less than 50 ultrasound examinations (probably only 15 examinations) for the supragenicular segments and 100 examinations for the infragenicular segments.

Evidence-based medicine in rapidly changing technologies.

Evidence-based medicine (EBM) is not a randomised controlled trial (RCT), but EBM seeks to apply evidence gained from scientific methods - which could be RCT - to daily medical practice. Any surgical treatment reflects a certain development technically as well as skills based. The procedure may be modified and refined and the device may be developed and inherent technical weaknesses may need to be corrected. Therefore the best time to conduct a trial may be discussed. The appropriate time to initiate a RCT is when all the participating surgeons or therapists have gone through their learning curve. Special considerations should be given in rapidly developing fields. If started too early the resulting comparison will likely turn out to be irrelevant because the new technology is not fully developed, not mastered or the device may have undergone major modifications rendering the results obsolete. On the other hand, if started too late there is a chance that data may be lost because the technology has already been introduced into the daily clinics and physicians may be unwilling to recruit patients. Or the opposite, that the technique may have been rejected without a proper trial. In this situation it has been suggested to perform a so called tracker trial. In such trials protocols are more flexible without prefixed sample size and will require repeated interim analyses. Often, it will be relevant to supplement the clinical trials with data from large clinical databases - in particular when long term results are needed.

Amputation-Free Survival after Crural Percutaneous Transluminal Angioplasty for Critical Limb Ischemia.

BACKGROUND AND AIM: To evaluate the amputation-free survival after below the knee percutaneous transluminal angioplasty in a consecutive group of patients with critical ischemia of the lower extremity. MATERIALS AND METHODS: A total of 70 consecutive patients with critical ischemia were treated with below the knee percutaneous transluminal angioplasty at the vascular center at Rigshospitalet with the purpose of limb salvage. All patients were deemed unfit for major surgery due to anatomical limitations or severe co-morbidity, and no prior attempts of revascularization were performed. Follow-up clinical examinations were performed within 6 weeks and after 1 year. All medical records were crosschecked with the national vascular registry ensuring a valid 1-year status in 97% of the patients. RESULTS: A total of 15 major amputations were performed during follow-up, with 11 amputations performed within the first year. Complications after percutaneous transluminal angioplasty were rare. Cumulative mortality after 1 and 2 years was 22% and 34%, respectively. Amputation-free survival at 1 and 2 years of follow-up was 68% and 58%, respectively. There were no association between known risk factors such as diabetes, ischemic ulcers, cardiac disease, history of smoking, major amputation, or overall amputation. CONCLUSION: Below the knee percutaneous transluminal angioplasty in patients with end-stage peripheral arterial disease and critical limb ischemia is a safe procedure in relieving critical ischemia, reducing the short-term rate of a major amputation as opposed to best medical treatment alone.

Ultrasonic echolucent carotid plaques predict future strokes.

BACKGROUND: We tested prospectively the hypothesis that stroke development can be predicted by echolucency of carotid atherosclerotic plaques in previously symptomatic and asymptomatic patients. METHODS AND RESULTS: We followed incidence of ipsilateral ischemic strokes for 4.4 years in 111 asymptomatic and 135 symptomatic patients with >/=50% relevant carotid artery stenosis. At inclusion, echogenicity of carotid plaques and degree of stenosis were evaluated with high-resolution B-mode ultrasound with computer-assisted image processing and Doppler ultrasound, respectively. We observed 44 ipsilateral ischemic strokes. In symptomatic patients, relative risk of ipsilateral ischemic stroke for echolucent versus echorich plaques was 3.1 (95% CI, 1.3 to 7.3), whereas for 80% to 99% versus 50% to 79% stenosis, the relative risk was 1.4 (95% CI, 0.7 to 3.0). Relative to symptomatic patients with echorich 50% to 79% stenotic plaques, those with echorich 80% to 99% stenotic plaques, echolucent 50% to 79% stenotic plaques, and echolucent 80% to 99% stenotic plaques had relative risks of ipsilateral ischemic strokes of 3.1 (95%CI, 0.7 to 14), 4.2 (95% CI, 1.2 to 15), and 7.9 (95% CI, 2.1 to 30), equivalent to absolute risk increases of 11%, 18%, and 28%. This was not observed in previously asymptomatic patients. CONCLUSIONS: Echolucent plaques causing >/=50% diameter stenosis by Doppler ultrasound are associated with risk of future stroke in symptomatic but not asymptomatic individuals. This suggests that measurement of echolucency, together with degree of stenosis, may improve selection of patients for carotid endarterectomy.

Middle cerebral artery flow velocity and blood flow during exercise and muscle ischemia in humans.

Changes in middle cerebral artery flow velocity (Vmean), measured by transcranial Doppler ultrasound, were used to determine whether increases in mean arterial pressure (MAP) or brain activation enhance cerebral perfusion during exercise. We also evaluated the role of "central command," mechanoreceptors, and/or muscle "metaboreceptors" on cerebral perfusion. Ten healthy subjects performed two levels of dynamic exercise corresponding to a heart rate of 110 (range 89-134) and 148 (129-170) beats/min, respectively, and exhaustive one-legged static knee extension. Measurements were continued during 2-2.5 min of muscle ischemia. MAP increased similarly during static [114 (102-133) mmHg] and heavy dynamic exercise [121 (104-136) mmHg] and increased during muscle ischemia after dynamic exercise. During heavy dynamic exercise, Vmean increased 24% (10-47%; P less than 0.01) over approximately 3 min despite constant arterial carbon dioxide tension. In contrast, static exercise with a higher rate of perceived exertion [18 (13-20) vs. 15 (12-18) units; P less than 0.01] was associated with no significant change in Vmean. Muscle ischemia after exercise was not associated with an elevation in Vmean, and it did not provoke an increase in Vmean after static exercise. Changes in Vmean during exercise were similar to those recorded with the initial slope index of the 133Xe clearance method. The data show that middle cerebral artery mean flow velocity reflects changes in cerebral perfusion during exercise. Furthermore, they support the hypothesis that cerebral perfusion during exercise reflects an increase in brain activation that is independent of MAP, central command, and muscle metaboreceptors but is likely to depend on influence of mechanoreceptors.