Saroj Das

Continuing controversy in the management of concomitant coronary and carotid disease: an overview

OBJECTIVES To perform an analytical overview of the risk factors, pathogenesis of stroke and the strategies for the management of concomitant coronary artery disease and carotid artery stenosis (CAS). Four strategies were analysed; CABG in the presence of CAS, combined (CE+CABG), reverse (CABG+CE<3 months) and prior staged (CE+CABG<3 months). METHODS A literature search formed the basis of a reference database. Outcome was assessed by the 30-day permanent stroke and mortality rate for the different approaches. Accrued rates of permanent stroke and mortality rate were expressed in terms of mean stroke and mortality rate (MSR, MMR). Data was analysed comparatively and expressed in terms of P value, odds ratio and confidence limits. RESULTS 33 different risk factors for stroke at CABG were identified. Significant factors included: ascending aortic atheroma, emergency procedures, impaired left ventricular function, cardioplegia and peripheral vascular disease. Risk of stroke at CABG increased with higher grade CAS (50 vs. 80%, P=0.009). Pathogenesis of stroke at CABG is multifactorial; the role of flow limiting CAS is controversial and other mechanisms are implicated. Analysis of the four strategies revealed that in the Prior Stage (n=573) the MSR was 1.5% and MMR 5.9%, in the Unprotected CABG+CAS series the MSR was 3.8% (n=840) and MMR (n=596) 4.4%, in the Reverse stage series (n=83) the MSR was 2.4%, and MMR 4.8%. For Combined procedures (n=3,295) the MSR was 3.9% and MMR 4.5%. Comparative analysis indicated a significant reduction in stroke for Prior vs. Combined (1.5 vs. 3.9%, P=0.007, odds 0.39, CI 0.2-0.77) with a higher mortality (5.9 vs. 4.5%, P=0.1, odds 1.41, Cl 0.96-2.06, NS). The stroke rate in the Prior stage also remained significantly lower compared to the Unprotected CABG group both mixed (P=0.015) and asymptomatic CAS (P=0.047). When total risks (MSR+MMR), were analysed, similar results were found between the groups; Prior 7.4%, Reverse stage 7.2%, Combined 8.4%, Unprotected CABG+ >50% CAS 11.5%. CONCLUSIONS Stroke at CABG is due to multiple risk factors, one of which is high-grade carotid stenosis. Pathophysiology of stroke, although multifactorial, supports embolism rather than flow limitation as the primary mechanism. Lack of randomised trials has made it impossible to draw firm conclusions regarding the best management strategy. There was no significant difference in the overall stroke and mortality risk between the various strategies, however, subgroup analysis suggests that, when carefully selected, patients do better by staging the operations. In our opinion patients without severe cardiac disease should be considered for Prior staging and the rest for Combined procedure. The role of reverse staging needs further evaluation.

Diagnosis and management of cellulitis

#### Summary points Cellulitis is an acute, spreading, pyogenic inflammation of the lower dermis and associated subcutaneous tissue. It is a skin and soft tissue infection that results in high morbidity and severe financial costs to healthcare providers worldwide. Cellulitis is managed by several clinical specialists including primary care physicians, surgeons, general medics, and dermatologists. We assess the most recent evidence in the diagnosis and management of cellulitis. #### Sources and selection criteria We searched PubMed and the Cochrane library for recent and clinically relevant cohort studies and randomised controlled trials on cellulitis, using the search terms “cellulitis”, “erysipelas”, “diagnosis”, “investigation”, “recurrence”, “complications” and “management”. For position statements and guidelines we consulted the British Lymphology Society (BLS), National Health Service Clinical Knowledge Summaries (CKS), Clinical Resource Efficiency Support Team (CREST), and Infectious Disease Society of America (IDSA). In 2008-9 there were 82 113 hospital admissions in England and Wales lasting a mean length of 7.2 days1; an estimated £133m (€170m;

Study of the collateral capacity of the circle of Willis of patients with severe carotid artery stenosis by 3D computational modeling.

209m) was spent on bed stay alone.2 Cellulitis accounted for 1.6% of emergency hospital admissions during 2008-9.3 In Australia, hospital admissions for cellulitis have risen to 11.5 people …

Geriatric surgery is about disease, not age.

This numerical study aims to investigate the capacity of the circle of Wills (CoW) to provide collateral blood supply for patients with unilateral carotid arterial stenosis. The basic 3D geometry of the CoW was reconstructed based on a magnetic resonance angiogram of a normal human subject. A total of 52 computational fluid dynamics simulations were performed for four geometry configurations of the CoW with an artificially inserted axisymmetric stenosis of different luminal area reductions in an internal carotid artery (ICA) under a variety of boundary conditions. The CoW geometric configurations included (a) a normal CoW with all communicating arteries; (b) as model (a) but with enlarged communicating arterial diameters; (c) as (a) but with the ipsilateral posterior communicating artery missing, and (d) as (c) but with enlarged communicating arteries. It is found that the blood perfusion pressure drop between the ipsilateral ICA and the middle cerebral artery (MCA) only becomes significant when the degree of stenosis is greater than 86%. The cerebral autoregulation range varied significantly between the different CoW configurations for the severe stenosis cases. Without causing the flow rates to decrease at the efferent arterial ends, the mean perfusion pressure in the ipsilateral ICA can drop from 100 to 73, 67, 92 and 84 mmHg for the CoW models (a)-(d) with 96% luminal area reduction stenosis, respectively. The additional pathways are able to raise the ipsilateral MCA pressure significantly without reducing the total flow perfusion. Cerebral autoregulation effects were not directly included in the study. Therefore, the findings in the study should be interpreted with cautions when comes to the biological and clinical significance.

Study of carotid arterial plaque stress for symptomatic and asymptomatic patients

Summary Maintaining life span and quality of life remains a valid aim of surgery in elderly people. Surgery can be an effective way of restoring both length and quality of life to older people. Minimally invasive techniques and surgery under local anaesthesia make fewer demands on geriatric physiology; given that co-morbidity is a stronger predictor of outcome from surgery than age, this is a significant consideration.

Stress Analysis of Carotid Atheroma in Transient Ischemic Attack Patients: Evidence for Extreme Stress-Induced Plaque Rupture

Stroke is one of the leading causes of death in the world, resulting mostly from the sudden ruptures of atherosclerosis carotid plaques. Until now, the exact plaque rupture mechanism has not been fully understood, and also the plaque rupture risk stratification. The advanced multi-spectral magnetic resonance imaging (MRI) has allowed the plaque components to be visualized in-vivo and reconstructed by computational modeling. In the study, plaque stress analysis using fully coupled fluid structure interaction was applied to 20 patients (12 symptomatic and 8 asymptomatic) reconstructed from in-vivo MRI, followed by a detailed biomechanics analysis, and morphological feature study. The locally extreme stress conditions can be found in the fibrous cap region, 85% at the plaque shoulder based on the present study cases. Local maximum stress values predicted in the plaque region were found to be significantly higher in symptomatic patients than that in asymptomatic patients (200 ± 43 kPa vs. 127 ± 37 kPa, p=0.001). Plaque stress level, defined by excluding 5% highest stress nodes in the fibrous cap region based on the accumulative histogram of stress experienced on the computational nodes in the fibrous cap, was also significantly higher in symptomatic patients than that in asymptomatic patients (154 ± 32 kPa vs. 111 ± 23 kPa, p<0.05). Although there was no significant difference in lipid core size between the two patient groups, symptomatic group normally had a larger lipid core and a significantly thinner fibrous cap based on the reconstructed plaques using 3D interpolation from stacks of 2D contours. Plaques with a higher stenosis were more likely to have extreme stress conditions upstream of plaque throat. The combined analyses of plaque MR image and plaque stress will advance our understanding of plaque rupture, and provide a useful tool on assessing plaque rupture risk.

Preoperative blood tests in elective general surgery: cost and clinical implications.

Plaque rupture has been considered to be the result of its structural failure. The aim of this study is to suggest a possible link between higher stresses and rupture sites observed from in vivo magnetic resonance imaging (MRI) of transient ischemic attack (TIA) patients, by using stress analysis methods. Three patients, who had recently suffered a TIA, underwent in vivo multi-spectral MR imaging. Based on plaque geometries reconstructed from the post-rupture status, six pre-rupture plaque models were generated for each patient dataset with different reconstructions of rupture sites to bridge the gap of fibrous cap from original MRI images. Stress analysis by fluid structure interaction simulation was performed on the models, followed by analysis of local stress concentration distribution and plaque rupture sites. Furthermore, the sensitivity of stress analysis to the pre-rupture plaque geometry reconstruction was examined. Local stress concentrations were found to be located at the plaque rupture sites for the three subjects studied. In the total of 18 models created, the locations of the stress concentration regions were similar in 17 models in which rupture sites were always associated with high stresses. The local stress concentration region moved from circumferential center to the shoulder region (slightly away from the rupture site) for a case with a thick fibrous cap. Plaque wall stress level in the rupture locations was found to be much higher than the value in non-rupture locations. The good correlation between local stress concentrations and plaque rupture sites, and generally higher plaque wall stress level in rupture locations in the subjects studied could provide indirect evidence for the extreme stress-induced plaque rupture hypothesis. Local stress concentration in the plaque region could be one of the factors contributing to plaque rupture.

Assessment of cardiac risk before peripheral vascular surgery: a comparison of myocardial perfusion imaging and long axis echocardiography at rest.

A retrospective observational study was performed in our trust in October 2010 that examined compliance, and the financial and clinical implications of performing inappropriate preoperative blood tests on adult patients prior to elective surgery, against the 2003 NICE guidelines. An unacceptable proportion of inappropriate tests (31.3%) were being performed. None were associated with adverse outcome or changes in management. Based on our results, we estimate that an extrapolated cost of £11.2 million is being spent on inappropriate blood tests in NHS England and Wales.

Circumferential Residual Stress Distribution and Its Influence in a Diseased Carotid Artery

OBJECTIVE To compare resting long axis echocardiography with adenosine thallium-201 emission tomography in detecting myocardial ischaemic abnormalities and surgical related risk in patients before peripheral vascular surgery. DESIGN A prospective and blinded pre-operative examination of resting left ventricular minor and long axes and myocardial perfusion during adenosine vasodilation using thallium-201 emission tomography. SETTING A tertiary referral centre for cardiac and vascular disease equipped with invasive, non-invasive and surgical facilities. SUBJECTS 65 patients (40 male) with significant peripheral vascular disease, mean age 63+/-10 (S.D.) years, and 21 normal subjects of similar age. RESULTS Thallium-201 myocardial perfusion tomography was abnormal in 50/65 patients; 27 had fixed, 23 reversible abnormalities (19 of whom had both). Long axis was considered abnormal if one or more of two systolic long axis disturbances, reduced extent of total excursion <1 cm at any of the three (left, septal and posterior left ventricular) sites or prolonged shortening >1 mm after A2, and two diastolic abnormalities, delayed onset of lengthening >80 ms after A2 or reduced peak lengthening velocity <4.5 cm/s, was present. Long axis score (maximum 12) was based on the presence or absence of these four disturbances at each of the three sites. Myocardial perfusion imaging with thallium-201 classified the patients into three different groups according to their liability to low, moderate or high surgical risk (summed stress perfusion score of 36). Thirteen of 50 patients were identified as subjects at high surgical risk, with a perfusion score of 22/36 and below. Twelve of these demonstrated significantly greater impairment of systolic and diastolic long axis function, compared to those at low surgical risk, with a total long axis echo score of 6/12 or more. Seventeen of 18 patients identified as being at low surgical risk, with a perfusion score of 32/36 and above, had total long axis score of less than 6/12. The remaining 19 moderate risk patients had a wide range of long axis scores. In the 65 patients studied there were two post-operative deaths, one post-discharge death due to cerebrovascular accident, and one due to renal failure. CONCLUSION The combination of both systolic and diastolic long axis disturbances in patients with peripheral vascular disease can be used to predict the thallium assessment of surgical risk. Long axis echocardiography may thus have value as a screening test before non-cardiac surgery as well as providing a means of monitoring myocardial perfusion.

Don't get in a flap!: A case report of progression through the spectrum of an acute aortic syndrome

Residual stresses are present in a variety of biological tissues, such as the arteries [1]. It is believed that residual stress tends to make stress distribution more uniform throughout normal arterial wall [2]. However, the influence of residual stress in a diseased artery remains unclear. The aim of this study is to investigate the circumferential residual stress in a diseased carotid artery (atherosclerotic plaque) and its influence on the stress distribution under normal blood pressure loading. To achieve a more realistic stress analysis, an anisotropic non-linear material properties based on ANSYS™ framework with parameter constants, obtained according to Gasser et al [3], was used for all simulations in the study.Copyright