Tjun Y. Tang

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

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.

How Critical Is Fibrous Cap Thickness to Carotid Plaque Stability?: A Flow–Plaque Interaction Model

Background and Purpose— Acute cerebral ischemic events are associated with rupture of vulnerable carotid atheroma and subsequent thrombosis. Factors such as luminal stenosis and fibrous cap thickness have been thought to be important risk factors for plaque rupture. We used a flow–structure interaction model to simulate the interaction between blood flow and atheromatous plaque to evaluate the effect of the degree of luminal stenosis and fibrous cap thickness on plaque vulnerability. Methods— A coupled nonlinear time-dependent model with a flow–plaque interaction simulation was used to perform flow and stress/strain analysis in a stenotic carotid artery model. The stress distribution within the plaque and the flow conditions within the vessel were calculated for every case when varying the fibrous cap thickness from 0.1 to 2 mm and the degree of luminal stenosis from 10% to 95%. A rupture stress of 300 kPa was chosen to indicate a high risk of plaque rupture. A 1-sample t test was used to compare plaque stresses with the rupture stress. Results— High stress concentrations were found in the plaques in arteries with >70% degree of stenosis. Plaque stresses in arteries with 30% to 70% stenosis increased exponentially as fibrous cap thickness decreased. A decrease of fibrous cap thickness from 0.4 to 0.2 mm resulted in an increase of plaque stress from 141 to 409 kPa in a 40% degree stenotic artery. Conclusions— There is an increase in plaque stress in arteries with a thin fibrous cap. The presence of a moderate carotid stenosis (30% to 70%) with a thin fibrous cap indicates a high risk for plaque rupture. Patients in the future may be risk stratified by measuring both fibrous cap thickness and luminal stenosis.

Impact of calcification and intraluminal thrombus on the computed wall stresses of abdominal aortic aneurysm

BACKGROUND Increased biomechanical stresses within the abdominal aortic aneurysm (AAA) wall contribute to its rupture. Calcification and intraluminal thrombus can be commonly found in AAAs, but the relationship between calcification/intraluminal thrombus and AAA wall stress is not completely described. METHODS Patient-specific three-dimensional AAA geometries were reconstructed from computed tomographic images of 20 patients. Structural analysis was performed to calculate the wall stresses of the 20 AAA models and their altered models when calcification or intraluminal thrombus was not considered. A nonlinear large-strain finite element method was used to compute the wall stress distribution. The relationships between wall stresses and volumes of calcification and intraluminal thrombus were sought. RESULTS Maximum stress was not correlated with the percentage of calcification, and was negatively correlated with the percentage of intraluminal thrombus (r = -0.56; P = .011). Exclusion of calcification from analysis led to a significant decrease in maximum stress by a median of 14% (range, 2%-27%; P < .01). When intraluminal thrombus was eliminated, maximum stress increased significantly by a median of 24% (range, 5%-43%; P < .01). CONCLUSION The presence of calcification increases AAA peak wall stress, suggesting that calcification decrease the biomechanical stability of AAA. In contrast, intraluminal thrombus reduces the maximum stress in AAA. Calcification and intraluminal thrombus should both be considered in the evaluation of wall stress for risk assessment of AAA rupture.

Assessment of Inflammatory Burden Contralateral to the Symptomatic Carotid Stenosis Using High-Resolution Ultrasmall, Superparamagnetic Iron Oxide–Enhanced MRI

Background and Purpose— It is well known that the vulnerable atheromatous plaque has a thin, fibrous cap and large lipid core with associated inflammation. This inflammation can be detected on MRI with use of a contrast medium, Sinerem, an ultrasmall superparamagnetic iron oxide (USPIO). Although the incidence of macrophage activity in asymptomatic disease appears low, we aimed to explore the incidence of MRI-defined inflammation in asymptomatic plaques in patients with known contralateral symptomatic disease. Methods— Twenty symptomatic patients underwent multisequence MRI before and 36 hours after USPIO infusion. Images were manually segmented into quadrants, and the signal change in each quadrant was calculated after USPIO administration. A mixed mathematical model was developed to compare the mean signal change across all quadrants in the 2 groups. Patients had a mean symptomatic stenosis of 77% compared with 46% on their asymptomatic side, as measured by conventional angiography. Results— There were 11 (55%) men, and the median age was 72 years (range, 53 to 84 years). All patients had risk factors consistent with severe atherosclerotic disease. All symptomatic carotid stenoses had inflammation, as evaluated by USPIO-enhanced imaging. On the contralateral sides, inflammatory activity was found in 19 (95%) patients. Contralaterally, there were 163 quadrants (57%) with a signal loss after USPIO when compared with 217 quadrants (71%) on the symptomatic side (P=0.007). Conclusions— This study adds weight to the argument that atherosclerosis is a truly systemic disease. It suggests that investigation of the contralateral side in patients with symptomatic carotid stenosis can demonstrate inflammation in 95% of plaques, despite a mean stenosis of only 46%. Thus, inflammatory activity may be a significant risk factor in asymptomatic disease in patients who have known contralateral symptomatic disease. Patients with symptomatic carotid disease should have their contralateral carotid artery followed up.

Iron Oxide Particles for Atheroma Imaging

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.

Renal Consequences of Endovascular Abdominal Aortic Aneurysm Repair

Endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm (AAA) is less invasive and has a lower operative mortality than conventional surgery. The relationship between renal function and outcome following open AAA repair has been extensively investigated, but less work has been undertaken with respect to renal function and outcome after EVAR. We reviewed the literature (Medline and PubMed databases) between 1991 and 2007 to investigate the relationship between EVAR and renal dysfunction. Our review found that perioperative renal dysfunction is attenuated by EVAR. However, dialysis rates after EVAR are similar to those after open surgery. EVAR patients develop progressive deterioration in renal function over time. The etiology is unclear and probably multifactorial, involving embolization, contrast media, and graft misplacement. The effect of transrenal endograft fixation on long-term renal function is unknown, but the technique may be associated with a significantly increased risk of renal infarction. The etiology of the renal injury during and after EVAR needs further evaluation, and techniques aimed at renal preservation should be pursued.

Ischaemic preconditioning during cardiac surgery: systematic review and meta-analysis of perioperative outcomes in randomised clinical trials

Numerous small trials have been conducted to confirm the existence of the ischaemic preconditioning (IP) mechanism in the human heart and to clarify whether it can be induced in a clinical situation. The effect on clinical end-points remains unclear. Most of the available trials reported some clinical outcomes. We performed a systematic review and meta-analysis in order to determine whether IP produces any clinical benefit in cardiac surgery. The systematic review identified 22 eligible trials containing 933 patients. All patients undergoing on-pump surgery also received cardioplegia or intermittent cross-clamp fibrillation (ICCF) with or without adjunctive cooling. IP was mainly performed after initiation of cardiopulmonary bypass, before any additional myocardial protection was initiated. Overall, IP was associated with significant reductions in ventricular arrhythmias (pooled odds ratio 0.11; 95% CI 0.04-0.29; p=0.001), inotrope requirements (pooled odds ratio 0.34; 95% CI 0.17-0.68; p=0.002) and intensive care unit stay (weighted mean difference -3h; 95% CI -4.6 to -1.5h; p=0.001). These effects persisted when the analyses were restricted to those patients receiving cardioplegia. The effect disappeared when the analyses were restricted to patients receiving ICCF. IP may provide additional myocardial protection over cardioplegia alone, but a large-scale clinical trial may be required to determine the role of IP with any certainty.

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

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.

Total abdominal hysterectomy versus total laparoscopic hysterectomy for benign disease: a meta-analysis.

Hysterectomy is a very common gynaecological procedure. The vaginal route is considered preferable for hysterectomy, although the ideal route for women unsuitable for the vaginal approach remains unclear. We performed a meta-analysis of published randomised controlled trials to compare outcomes in total abdominal hysterectomy (TAH) and total laparoscopic hysterectomy (TLH) for benign disease. Pooled odds ratios (OR) were calculated for categorical variables using random effects models as per Der Simonian and Laird. Continuous variables were compared by means of weighted mean differences (WMD). TLH is associated with reduced overall peri-operative complications (pooled OR 0.19; 95% CI 0.07-0.50) and reduced estimated blood loss (WMD -183ml; 95% CI -346ml to -21ml; p=0.03). Additionally, there are trends towards shorter hospital stay (WMD -2.5 days; 95% CI -5.1 days to 0.01 days; p=0.05) and post-operative haematoma formation (pooled OR 0.17; 95% CI 0.03-1.01) compared to TAH. The only trade-off appears to be a longer operating time in the TLH group (WMD 22min; 95% CI 5-39min; p=0.01). Rates of major complication were not statistically different (pooled OR 1.35; 95% CI 0.32-5.73) though this analysis is likely underpowered to detect many major complications. As such, TLH appears to offer benefits to women requiring total hysterectomy for benign indications compared to TAH, particularly regarding minor complications, blood loss and hospital stay. However, larger studies are needed to assess the impact on major intra-operative complications and long-term clinical outcomes, particularly pelvic organ prolapse.

Role of ultrasonography in the diagnosis of temporal arteritis

Temporal artery (TA) biopsy is the current standard for diagnosing temporal arteritis, but has limited sensitivity. Colour duplex ultrasonography is a newer, non‐invasive method of diagnosing temporal arteritis.