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Dive into the research topics where Umar Sadat is active.

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Featured researches published by Umar Sadat.


Journal of Vascular Surgery | 2008

Endovascular stenting versus open surgery for thoracic aortic disease : Systematic review and meta-analysis of perioperative results

Stewart R. Walsh; Tjun Y. Tang; Umar Sadat; Jag Naik; Michael E. Gaunt; R. Boyle Jonathan; Paul D. Hayes; Kevin Varty

BACKGROUND Endovascular stenting has emerged as an alternative to open repair in patients requiring surgery for thoracic aortic pathology. A number of comparative series have been published but, to date, there has been no meta-analysis comparing outcomes following stenting as opposed to open surgery. METHODS Electronic abstract databases and conference proceedings were searched to identify relevant series. Pooled odds ratios were calculated using random effects models for perioperative mortality, neurological injury, and major reintervention. RESULTS The search identified 17 eligible series, totaling 1109 patients (538 stenting). Stenting was associated with a significant reduction in mortality (pooled odds ratio 0.36; 95% CI 0.228-0.578; P < .0001) and major neurological injury (pooled odds ratio 0.39; 95% CI 0.25-0.62; P = .0001). There was no difference in the major reintervention rate (pooled odds ratio 0.91; 95% CI 0.610-1.619). There was a reduction in hospital and critical care stay although there was evidence of heterogeneity and bias with respect to these outcomes. Subgroup analyses suggested that endovascular repair reduced mortality (pooled odds ratio 0.25; 95% CI 0.09-0.66) and neurological morbidity (pooled odds ratio 0.28; 95% CI 0.13-0.61) in stable patients undergoing repair of thoracic aortic aneurysms. There was no effect on mortality in patients with thoracic aortic trauma but neurological injury was reduced (pooled odds ratio 0.17; 95% CI 0.03-1.03). Endovascular repair did not confer any apparent benefit over open surgery in patients with thoracic aortic rupture. CONCLUSION Endovascular thoracic aortic repair reduces perioperative mortality and neurological morbidity in patients with descending thoracic aortic aneurysms. There may be less benefit in other thoracic aortic conditions.


Journal of Vascular Surgery | 2009

Neurological complications after left subclavian artery coverage during thoracic endovascular aortic repair: a systematic review and meta-analysis.

David G. Cooper; Stewart R. Walsh; Umar Sadat; Ayesha Noorani; Paul D. Hayes; Jonathan R. Boyle

INTRODUCTION Recent studies suggest an increased risk of neurologic complications after coverage of the left subclavian artery (LSA) during thoracic endovascular aortic repair (TEVAR). The preventative role of preoperative revascularization of the LSA using carotid-subclavian bypass or transposition remains controversial. We assessed this increased risk and the role of revascularization by undertaking a systematic review and meta-analysis of the literature. METHODS In the absence of any randomized controlled trials, the Pubmed and Embase databases were searched to identify all series reporting TEVAR without LSA coverage compared with LSA coverage with and without revascularization. The incidence of neurologic complications, namely cerebrovascular accident (CVA) and spinal cord ischemia (SCI), were recorded for each group. Pooled odds ratios (POR) were then calculated for postoperative CVA and SCI. RESULTS Compared with patients without LSA coverage, the risk of CVA was increased both in patients with LSA coverage alone (4.7% vs 2.7%; POR, 2.28; 95% confidence interval [CI], 1.28-4.09; P = .005) and in those with LSA coverage after revascularization (4.1% vs 2.6%; POR, 3.18; 95% CI, 1.17-8.65; P = .02). The risk of SCI was also increased in patients requiring LSA coverage (2.8% vs 2.3%; POR, 2.39; 95% CI, 1.30-4.39; P = .005) but not for LSA coverage after revascularization (0.8% vs 2.7%; POR, 1.69; 95% CI, 0.56-5.15; P = .35). CONCLUSION The risk of neurologic complications is increased after coverage of the LSA during TEVAR. Preemptive revascularization offers no protection against CVA, perhaps indicating a heterogeneous etiology. Revascularization may reduce the risk of SCI, although limited data tempers this conclusion. Improved or perhaps compulsory reporting to registries of a minimum data set may help further assess the exact etiology of these complications and identify a higher-risk subset of patients in whom revascularization might prove protective.


Arteriosclerosis, Thrombosis, and Vascular Biology | 2009

Iron Oxide Particles for Atheroma Imaging

Tjun Y. Tang; Karin H. Müller; Martin J. Graves; Zhi Y. Li; Stewart R. Walsh; Victoria E. Young; Umar Sadat; Simon P.S. Howarth; Jonathan H. Gillard

The selection of patients for vascular interventions has been solely based on luminal stenosis and symptomatology. However, histological data from both the coronary and carotid vasculature suggest that other plaque features such as inflammation may be more important in predicting future thromboembolic events. Ultrasmall superparamagnetic iron oxide (USPIO) contrast agents have been used for noninvasive MRI assessment of atherosclerotic plaque inflammation in humans. It has reached the stage of development to have been recently used in an interventional drug study to not only assess inflammatory progression but also select patients at high risk. This article reviews the basic science behind the use of USPIO contrast agents in atheroma MR imaging, experimental work in animals, and how this has led to the emergence of this promising targeted imaging platform for assessment of high risk carotid atherosclerosis in humans.


Journal of Endovascular Therapy | 2009

Remote Ischemic Preconditioning for Renal and Cardiac Protection during Endovascular Aneurysm Repair: A Randomized Controlled Trial

Stewart R. Walsh; Jonathan R. Boyle; Tjun Y. Tang; Umar Sadat; David G. Cooper; Marta Lapsley; Anthony G.W. Norden; Kevin Varty; Paul D. Hayes; Michael E. Gaunt

Purpose: To report a randomized clinical trial designed to determine if remote ischemic preconditioning (IP) has the ability to reduce renal and cardiac damage following endovascular aneurysm repair (EVAR). Methods: Forty patients (all men; mean age 76±7 years) with abdominal aortic aneurysms averaging 6.3±0.8 cm in diameter were enrolled in the trial from November 2006 to January 2008. Eighteen patients (mean age 74 years, range 72–81) were randomized to preconditioning and completed the full remote IP protocol; there were no withdrawals. Twenty-two patients (mean age 76 years, range 66–80) were assigned to the control group. Remote IP was induced using sequential lower limb ischemia. Serum and urinary markers of renal and cardiac injury were compared between the groups. Results: Urinary retinol binding protein (RBP) levels increased 10-fold from a median of 235 µmol/L to 2356 µmol/L at 24 hours (p=0.0001). There was a lower increase in the preconditioned group, from 167 µmol/L to 413 µmol/L at 24 hours (p=0.04). The median urinary albumin:creatinine ratio was significantly lower in the preconditioned group at 24 hours (5 versus 8.8, p=0.06). There were no differences in the rates of renal impairment or major adverse cardiac events. Conclusion: Remote preconditioning reduces urinary biomarkers of renal injury in patients undergoing elective EVAR. This small pilot trial was unable to detect an effect on clinical endpoints; further trials are warranted.


Journal of Vascular Surgery | 2008

Endovascular vs open repair of acute abdominal aortic aneurysms--a systematic review and meta-analysis.

Umar Sadat; Jonathan R. Boyle; Stewart R. Walsh; Tjun Y. Tang; Kevin Varty; Paul D. Hayes

OBJECTIVE To compare the results of emergency open repair of acute (ruptured or symptomatic intact) abdominal aortic aneurysms with that of endovascular repair. METHODS A systematic literature search was performed to identify series that reported comparative outcomes. PubMed, Embase, the randomized controlled trial (RCT) register, and all relevant major journals were searched independently by two researchers. The outcome measures were 30-day mortality, intensive care unit (ICU) stay, hospital stay, blood loss, and operative time. RESULTS Twenty-three studies were identified. Of these, only one was a randomized controlled trial, which is now halted. The total number of patients in the pooled data was 7040 (730 emergency endovascular aneurysm repair [eEVAR]). Emergency EVAR was associated with a significant reduction in mortality (pooled odds ratio 0.624; 95% confidence interval [CI] 0.518 to 0.752; P < .0001). The eEVAR groups ICU stay was reduced by 4 days (pooled effect size estimate -0.70; 95% CI -1.05 to -0.35; P < .0001) and hospital stay with eEVAR was reduced by 8.6 days (pooled effect size estimate -0.33; 95% CI -0.50 to -0.16; P = .0001). In addition, eEVAR was also associated with a significant reduction in blood loss (pooled effect size estimate -1.88 liters; 95% CI -2.49 to -1.27; P < .0001) and reduced procedure time (pooled effect size estimate -0.65; 95% CI -0.95 to -0.36; P < .0001). CONCLUSION This meta-analysis suggests benefits to the selected group of patients undergoing this minimally invasive procedure. There is a reduction in the high mortality, prolonged intensive care requirement and total hospital stay, which are historically associated with open repair. It also indicates that most patients are fit enough to undergo computerized tomography (CT) scanning in acute settings. However, because of heterogeneity and bias in the outcomes these results should be interpreted with caution.


Vascular and Endovascular Surgery | 2010

Remote Ischemic Preconditioning for Cerebral and Cardiac Protection During Carotid Endarterectomy: Results From a Pilot Randomized Clinical Trial

Stewart R. Walsh; S.A.R. Nouraei; Tjun Y. Tang; Umar Sadat; R. H. S. Carpenter; Michael E. Gaunt

Remote ischemic preconditioning (RIPC) is a physiological mechanism whereby brief ischemia—reperfusion episodes attenuate damage by subsequent prolonged ischemic insults. It reduces myocardial injury following cardiac and aortic aneurysm surgery. We aimed to determine whether RIPC affects neurological or cardiac injury following carotid endarterectomy (CEA). Patients were preconditioned using 10 minutes of lower limb ischemia—reperfusion. The primary neurological outcome was saccadic latency deterioration. The primary cardiac outcome measure was increased in serum troponin I >0.15 mg/dL. In all, 70 patients were randomized, of whom 55 completed the neurological surveillance protocol. Although there were fewer saccadic latency deteriorations in the RIPC arm, this did not reach statistical significance (32% versus 53%; P = .11). The primary cardiac outcome occurred in 1 patient in each arm (P = .97). There were no adverse events related to the preconditioning protocol. Remote ischemic preconditioning appears safe in patients with CEA. Large-scale trials are required to determine whether RIPC confers clinical benefits.


Vascular and Endovascular Surgery | 2010

Remote Ischemic Preconditioning for Renal Protection During Elective Open Infrarenal Abdominal Aortic Aneurysm Repair: Randomized Controlled Trial

Stewart R. Walsh; Umar Sadat; Jonathan R. Boyle; Tjun Y. Tang; Marta Lapsley; Anthony G.W. Norden; Michael E. Gaunt

We aimed to determine whether remote ischemic preconditioning (IP) reduces renal damage following elective open infrarenal abdominal aortic aneurysm (AAA) repair. Sequential common iliac clamping was used to induce remote IP in randomized patients. Urinary retinol binding protein (RBP) and albumin-creatinine ratio (ACR) were measured following induction and 3, 24, and 48 hours postoperatively. In controls (n = 22), median urinary RBP increased from 112 µg/mL (interquartile range [IQR] 96-173 µg/mL) preoperatively to 5919 µg/mL (IQR 283-17 788 µg/mL) at 3 hours. Preoperative urinary RBP in preconditioned patients was 96 µg/mL (IQR 50 to 229 µg/mL) preoperatively, rising to 1243 µg/mL (IQR 540 to 15400 µg/mL) at 3 hours. Although control patients’ median urinary RBP level was 5 times greater at 3 hours, there were no statistically significant differences in renal outcome indices. This trial could not confirm that remote IP reduces renal injury following elective open aneurysm surgery.


Journal of the American College of Cardiology | 2013

Does Ascorbic Acid Protect Against Contrast-Induced Acute Kidney Injury in Patients Undergoing Coronary Angiography: A Systematic Review With Meta-Analysis of Randomized, Controlled Trials

Umar Sadat; Ammara Usman; Jonathan H. Gillard; Jonathan R. Boyle

OBJECTIVES This study sought to perform a systematic review with meta-analysis of randomized controlled trials comparing the use of ascorbic acid with placebo or other treatment options for the treatment of contrast induced-acute kidney injury (CI-AKI) in patients undergoing coronary angiography. BACKGROUND CI-AKI remains the most widely discussed and debated topic in cardiovascular medicine, with its incidence increasing due to an increasing number of contrast media-enhanced radiological procedures being performed. METHODS MEDLINE, Embase, and Cochrane central databases were searched from inception to May 2013, without language restrictions. For a study to be selected, it had to report the incidence of CI-AKI as an outcome measure. Studies were excluded if at least 1 study arm did not have ascorbic acid administered alone or with saline solution hydration. Data were extracted by 1 author, and random checks were made by another author. RESULTS Nine randomized, controlled trials reported data on the incidence of CI-AKI in 1,536 patients who had completed the trial and were included in the final analysis. Patients receiving ascorbic acid had 33% less risk of CI-AKI compared with patients receiving placebo or an alternate pharmacological treatment (risk ratio by random-effects model: 0.672; 95% confidence interval, 0.466 to 0.969; p = 0.034). CONCLUSIONS Ascorbic acid provides effective nephroprotection against CI-AKI and may form a part of effective prophylactic pharmacological regimens.


Atherosclerosis | 2009

Utility of high resolution MR imaging to assess carotid plaque morphology: A comparison of acute symptomatic, recently symptomatic and asymptomatic patients with carotid artery disease

Umar Sadat; R. Weerakkody; David J. Bowden; Victoria E. Young; Martin J. Graves; Zhi-Yong Li; Tjun Y. Tang; Michael E. Gaunt; Paul D. Hayes; Jonathan H. Gillard

OBJECTIVES Compare carotid plaque morphology of acute symptomatic, recently symptomatic and asymptomatic patients (groups 1, 2 and 3 respectively) with carotid artery disease using high resolution magnetic resonance imaging (MRI), to identify high-risk plaque characteristics best associated with risk of recurrent thrombo-embolic events. METHODS 60 patients underwent multi-contrast imaging of their internal carotid arteries. Different plaque components were manually delineated on acquired axial images to assess the difference in prevalence of plaque hemorrhage, fibrous cap (FC) rupture and FC thickness among the three groups. RESULTS 55% acute symptomatic patients had plaque hemorrhage vs. 35% for recently symptomatic group and 5% for asymptomatic group (p-value: group 1 vs. 3: 0.001, group 2 vs. 3: 0.04). Type 1 hemorrhage was more common in acute symptomatic patients than recently symptomatic patients (40% vs. 5%, p=0.01). Type 2 hemorrhage was more common in recently symptomatic vs. acute symptomatic patients (15% vs. 30%). FC rupture was observed in 50% of patients in group 1 vs. 35% of group 2 patients (p=0.02) but none in group 3. The mean minimum FC thickness was same in acute and recently symptomatic groups (600+/-200microm), compared to 800+/-200microm for asymptomatic patients (p-value: 0.03 and 0.007 respectively). Good correlation was present among the three MR readers (intra-class correlation coefficient=0.71). CONCLUSION High resolution MRI can differentiate plaque components associated with increased risk of thrombo-embolic events.


European Journal of Vascular and Endovascular Surgery | 2010

Association between Biomechanical Structural Stresses of Atherosclerotic Carotid Plaques and Subsequent Ischaemic Cerebrovascular Events – A Longitudinal in Vivo Magnetic Resonance Imaging-based Finite element Study

Umar Sadat; Zhongzhao Teng; Victoria E. Young; Stewart R. Walsh; Zhi-Yong Li; Martin J. Graves; Kevin Varty; Jonathan H. Gillard

BACKGROUND High-resolution magnetic resonance (MR) imaging has been used for MR imaging-based structural stress analysis of atherosclerotic plaques. The biomechanical stress profile of stable plaques has been observed to differ from that of unstable plaques; however, the role that structural stresses play in determining plaque vulnerability remains speculative. METHODS A total of 61 patients with previous history of symptomatic carotid artery disease underwent carotid plaque MR imaging. Plaque components of the index artery such as fibrous tissue, lipid content and plaque haemorrhage (PH) were delineated and used for finite element analysis-based maximum structural stress (M-C Stress) quantification. These patients were followed up for 2 years. The clinical end point was occurrence of an ischaemic cerebrovascular event. The association of the time to the clinical end point with plaque morphology and M-C Stress was analysed. RESULTS During a median follow-up duration of 514 days, 20% of patients (n = 12) experienced an ischaemic event in the territory of the index carotid artery. Cox regression analysis indicated that M-C Stress (hazard ratio (HR): 12.98 (95% confidence interval (CI): 1.32-26.67, p = 0.02), fibrous cap (FC) disruption (HR: 7.39 (95% CI: 1.61-33.82), p = 0.009) and PH (HR: 5.85 (95% CI: 1.27-26.77), p = 0.02) are associated with the development of subsequent cerebrovascular events. Plaques associated with future events had higher M-C Stress than those which had remained asymptomatic (median (interquartile range, IQR): 330 kPa (229-494) vs. 254 kPa (166-290), p = 0.04). CONCLUSIONS High biomechanical structural stresses, in addition to FC rupture and PH, are associated with subsequent cerebrovascular events.

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Tjun Y. Tang

Changi General Hospital

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Kevin Varty

Cambridge University Hospitals NHS Foundation Trust

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Stewart R. Walsh

National University of Ireland

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Paul D. Hayes

Cambridge University Hospitals NHS Foundation Trust

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