Rakesh Uppal

Mechanisms Underlying Erythrocyte and Endothelial Nitrite Reduction to Nitric Oxide in Hypoxia: Role for Xanthine Oxidoreductase and Endothelial Nitric Oxide Synthase

Reduction of nitrite (NO2−) provides a major source of nitric oxide (NO) in the circulation, especially in hypoxemic conditions. Our previous studies suggest that xanthine oxidoreductase (XOR) is an important nitrite reductase in the heart and kidney. Herein, we have demonstrated that conversion of nitrite to NO by blood vessels and RBCs was enhanced in the presence of the XOR substrate xanthine (10 &mgr;mol/L) and attenuated by the XOR inhibitor allopurinol (100 &mgr;mol/L) in acidic and hypoxic conditions only. Whereas endothelial nitric oxide synthase (eNOS) inhibition had no effect on vascular nitrite reductase activity, in RBCs L-NAME, L-NMMA, and l-arginine inhibited nitrite-derived NO production by >50% (P<0.01) at pH 7.4 and 6.8 under hypoxic conditions. Western blot and immunohistochemical analysis of RBC membranes confirmed the presence of eNOS and abundant XOR on whole RBCs. Thus, XOR and eNOS are ideally situated on the membranes of RBCs and blood vessels to generate intravascular vasodilator NO from nitrite during ischemic episodes. In addition to the proposed role of deoxyhemoglobin, our findings suggest that the nitrite reductase activity within the circulation, under hypoxic conditions (at physiological pH), is mediated by eNOS; however, as acidosis develops, a substantial role for XOR becomes evident.

Remote ischemic preconditioning has a neutral effect on the incidence of kidney injury after coronary artery bypass graft surgery

Acute kidney injury (AKI) is a frequent complication of cardiac surgery and usually occurs in patients with preexisting chronic kidney disease (CKD). Remote ischemic preconditioning (RIPC) may mitigate the renal ischemia-reperfusion injury associated with cardiac surgery and may be a preventive strategy for postsurgical AKI. We undertook a randomized controlled trial of RIPC to prevent AKI in 86 patients with CKD (estimated glomerular filtration rate under 60 ml/min per 1.73 m(2)) undergoing coronary artery bypass graft (CABG) surgery. Forty-three patients each were randomized to receive standard care with or without RIPC consisting of three 5-minute cycles of forearm ischemia followed by reperfusion. The primary end point was the development of AKI defined as an increase in serum creatinine concentration over 0.3 mg/dl within 48 h of surgery. Secondary end points included a comparison between the study and control groups of several serum biomarkers of renal injury including cystatin-C, neutrophil gelatinase-associated lipocalin (NGAL), and interleukin-18 (IL-18), and urinary biomarkers including NGAL, IL-18, and kidney injury molecule-1 measured at 6, 12, and 24 h after CABG, and the 72-h serum troponin T concentration area under the curve as a marker of myocardial injury. Clinical and operative characteristics were similar between the preconditioned and control groups. AKI developed in 12 patients in both groups within 48 h of CABG. There were no significant differences between the two groups in the concentrations of any of the serum or urinary biomarkers of renal or cardiac injury after CABG. Thus, RIPC induced by forearm ischemia-reperfusion had no effect on the frequency of AKI after CABG in patients with CKD.

DNA Methylation Dynamics of Human Hematopoietic Stem Cell Differentiation

Summary Hematopoietic stem cells give rise to all blood cells in a differentiation process that involves widespread epigenome remodeling. Here we present genome-wide reference maps of the associated DNA methylation dynamics. We used a meta-epigenomic approach that combines DNA methylation profiles across many small pools of cells and performed single-cell methylome sequencing to assess cell-to-cell heterogeneity. The resulting dataset identified characteristic differences between HSCs derived from fetal liver, cord blood, bone marrow, and peripheral blood. We also observed lineage-specific DNA methylation between myeloid and lymphoid progenitors, characterized immature multi-lymphoid progenitors, and detected progressive DNA methylation differences in maturing megakaryocytes. We linked these patterns to gene expression, histone modifications, and chromatin accessibility, and we used machine learning to derive a model of human hematopoietic differentiation directly from DNA methylation data. Our results contribute to a better understanding of human hematopoietic stem cell differentiation and provide a framework for studying blood-linked diseases.

Performance of the EuroSCORE Models in Emergency Cardiac Surgery

Background—Accurate risk-adjustment models are useful for clinical decision making and are important for minimizing any tendency toward risk-averse clinical practice. In cardiac surgery, emergency patients are potentially at greatest risk of inappropriate risk-averse clinical decisions. UK cardiac surgery outcomes are currently risk-adjusted with EuroSCORE models. The objective of this study was to assess the performance of the EuroSCORE models in emergency cardiac surgery. Methods and Results—The National Institute for Cardiovascular Outcomes Research database was used to identify adult cardiac surgery procedures performed in the United Kingdom between April 2008 and March 2011. A subset of procedures (July 2010–March 2011) was used for EuroSCORE II validation. The outcome measure was in-hospital mortality. Model calibration (Hosmer–Lemeshow test, calibration plots, calculation of calibration intercept and slope) and discrimination (area under receiver-operating characteristic curve [area under the curve]) were assessed. In total, 109 988 cardiac procedures at 41 hospitals were included, of which 3342 were defined as emergency procedures. Compared with performance in all cardiac surgery and nonemergency cardiac surgery, the logistic EuroSCORE and EuroSCORE II models had poorer discrimination (area under the curve, 0.703 and 0.690, respectively) and poorer calibration for emergency surgery. The EuroSCORE risk factors of female sex, chronic pulmonary disease, neurological disease, active endocarditis, unstable angina, recent myocardial infarction, and pulmonary hypertension were not identified as important risk factors for emergency cardiac surgery. Conclusions—Both EuroSCORE models demonstrated poor calibration and comparatively poor discrimination for emergency cardiac surgery. This has important implications when these models are used for clinical decision making or to adjust governance analyses.

A surgical approach to coexistent coronary and carotid artery disease.

OBJECTIVE: To assess the early results of combined coronary artery bypass graft surgery and carotid endarterectomy. DESIGN: Retrospective and ongoing analysis of patients who underwent combined coronary artery bypass graft surgery and carotid endarterectomy. SETTING: Cardiothoracic unit in a London teaching hospital. PATIENTS: From June 1987 to March 1995, 64 patients were identified. They were patients who were scheduled to have coronary artery bypass graft surgery or required urgent coronary revascularisation and who were found to have significant coexistent carotid disease. (Unilateral carotid stenosis > 70%, bilateral carotid stenosis > 50%, or unilateral carotid stenosis > 50% with contralateral occlusion.) INTERVENTIONS: Both procedures were performed during one anaesthesia: the carotid endarterectomy was performed first without cardiopulmonary bypass. After completion of carotid endarterectomy, coronary artery bypass graft surgery was performed. MAIN OUTCOME MEASURES: The incidence of stroke, transient ischaemic attack, and myocardial infarction in the early postoperative period was analysed. RESULTS: Myocardial revascularisation was successful in all 64 patients. There were no perioperative infarcts. In three patients (4.7%) a new neurological deficit developed postoperatively: two recovered fully before hospital discharge. CONCLUSIONS: Combined coronary artery bypass graft surgery and carotid endarterectomy were performed safely and with good results.

The impact of acute kidney injury on midterm outcomes after coronary artery bypass graft surgery: a matched propensity score analysis.

BACKGROUND The development of acute kidney injury (AKI) after coronary artery bypass graft (CABG) surgery is associated with increased short- and long-term mortality. Whether AKI has a causal relationship with subsequent mortality or whether the development of AKI simply occurs in patients with more comorbidity undergoing more complex procedures remains unresolved. METHODS AND RESULTS This was an observational cohort study of prospectively collected data from 4694 patients discharged from the hospital after first-time CABG surgery at a tertiary cardiac center between 2003 and 2008. AKI was defined using the Risk, Injury, Failure, Loss, and End stage (RIFLE) criteria, which require at least a 50% increase in serum creatinine. The primary outcome measure was all-cause mortality determined via UK Office of National Statistics. A total of 562 (12.0%) of patients developed AKI after CABG surgery. Patients who developed AKI were older, more likely to be female, and had more comorbidity than patients who did not develop AKI. In a Cox multivariable analysis, the development of AKI was an independent predictor of midterm mortality (hazard ratio, 1.80; 95% confidence interval, 1.50-2.16). Subsequently, a comparison of 562 patients who sustained AKI with 562 propensity score-matched patients who did not sustain AKI was undertaken. After propensity matching, baseline clinical and operative characteristics were similar between both groups. After Cox multivariable analysis of the propensity-matched cohort, AKI remained an independent predictor of midterm mortality (hazard ratio, 1.52; 95% confidence interval, 1.19-1.93). CONCLUSIONS The development of AKI after CABG is a serious event associated with worse midterm survival. This excess mortality cannot be explained simply by coexisting comorbidity and surgical complexity.

Case fatality rates for South Asian and Caucasian patients show no difference 2.5 years after percutaneous coronary intervention

Objective To compare short and medium-term prognosis in South Asian and Caucasian patients undergoing percutaneous coronary intervention (PCI) to determine if there are ethnic differences in case death rates. Design Retrospective cohort study. Setting A cardiology referral centre in east London. Patients 9771 patients who underwent PCI from October 2003 to December 2007 of whom 7966 (81.5%) were Caucasian and 1805 (18.5%) were South Asian. Main outcome measures In-hospital major adverse cardiac events (MACE; death, myocardial infarction, stroke and target vessel revascularisation), subsequent revascularisation rates (PCI and coronary artery bypass grafting; CABG) and all-cause mortality during a median follow-up of 2.5 years (range 1.5–3.6 years). Results South Asian patients were younger than Caucasian patients (59.69±0.27 vs 64.69±0.13 years, p<0.0001), and more burdened by cardiovascular risk factors, particularly type II diabetes mellitus (45.9%±1.2% vs 15.7%±0.4%, p<0.0001). The in-hospital rates of MACE were similar for South Asians and Caucasians (3.5% vs 2.8%, p=0.40). South Asians had higher rates of clinically driven PCI for restenosis and subsequent CABG, although Kaplan–Meier estimates of all-cause mortality showed no significant differences; this was regardless of whether PCI was performed post-acute coronary syndrome or as an elective procedure. The adjusted hazard of death for South Asians compared with Caucasians was 1.00 (95% CI 0.81 to 1.23). Conclusion In this large PCI cohort, the in-hospital and longer-term mortality of South Asians appeared no worse than that of Caucasians. South Asians had higher rates of restenosis and CABG during follow-up. Data suggest that the excess coronary mortality for South Asians compared with Caucasians is not explained by differences in case-fatality rates.

Patients' views of the consent process for adult cardiac surgery: questionnaire survey

Objective—Consent for surgical procedures has assumed increasing importance in surgical practice in recent days especially following the public inquiry into paediatric cardiac surgery deaths at Bristol in the UK. This study examines patient perceptions and recollections following surgical consent as currently practised in a UK cardiac unit. Methods—One hundred consecutive patients who underwent cardiac surgery in a London teaching hospital from January to February 2003 were studied. Patients completed questionnaires a day before their discharge from the hospital. Results—The majority of patients (89/100) responded that the information given at consent had been adequate or more than adequate. The time spent on the consent process was thought to be adequate by 91 patients. Eleven patients felt the consent had been insensitive. Several patients (38/100) felt use of booklets in preference to verbal explanations would be less intimidating. For most patients (94/100) the operation and postoperative course met their expectations; although 12 patients experienced untold complications, only five felt that they should have been informed of the possibility of the complication. Although most patients were informed of the risk of death during consent, at time of discharge 43 had forgotten the figure that had been quoted. Regarding the influence of media and publicity, 19 patients said that media had influenced their expectations of the consent process, 59 would have liked to see hospital league tables while 26 would have liked to know the mortality figures for their surgeon prior to giving consent. Conclusions—Our study shows that patients undergoing cardiac surgery are largely satisfied with our improved consent procedures in the post‐Bristol era. Use of booklets may be a useful adjunct to verbal consent as currently practised.

Characteristics and Outcomes of Dialysis Patients with Infective Endocarditis

Background: The incidence of infective endocarditis (IE) in dialysis patients is higher than the general population. Dialysis patients who develop endocarditis are thought to have a poorer prognosis than other patients with IE. Aim: To examine the risk profiles, clinical features, and outcomes of patients on dialysis who developed IE in a large cohort. Design and Methods: A retrospective analysis of all patients developing IE on dialysis (using the modified Duke criteria) was undertaken between 1998 and 2011. Patients were identified from a prospectively collected clinical database. Results: 42 patients developed IE out of a total incident dialysis population of 1,500 over 13 years. 95% of the patients (40/42) were on long-term haemodialysis (HD) and 5% (2/42) on peritoneal dialysis. Mean patient age was 55.2 years (IQR: 43-69), and mean duration of HD prior to IE was 57.4 months. Primary HD access at the time of diagnosis was an arteriovenous fistula in 35% (14/40), a dual-lumen tunnelled catheter in 55% (22/40), and a dual-lumen non-tunnelled catheter in 10% (4/40). Staphylococcus aureus (including methicillin-resistant S. aureus) was present in 57.1% (24/42). The aortic valve was affected in 42.8% of the patients (18/42), the mitral valve in 30.9% (13/42), and both valves in 9.5% (4/42). 33.3% of the patients had an abnormal valve before the episode of IE. In 21.4% (9/42), valve surgery was performed and mortality was lower in the surgical group compared to the group managed medically during hospitalisation (11.1 vs. 15.2%, p = 0.892), at 3 months (13.1 vs. 19.6%, p = 0.501), and during follow-up (p = 0.207), but this difference did not reach statistical significance. Age >60 years, septic emboli, and methicillin-resistant S. aureus were all adverse prognostic factors. Patients receiving surgery were younger (mean 47.1 ± 14.4 years vs. 57.4 ± 14.3, p = 0.049) and less likely to be infected with S. aureus (surgery 33.3% vs. antibiotics 63.6%, p = 0.046). Conclusion: This is one of the largest reported series of IE in dialysis patients. The incidence of IE remains high and the prognosis poor in dialysis patients, although patients selected for early valve surgery have good 1-year survival.

Impact of diabetes mellitus and renal insufficiency on 5-year mortality following coronary artery bypass graft surgery: a cohort study of 4869 UK patients

OBJECTIVES Diabetes mellitus (DM) and renal impairment (RI) are both independent predictors of mortality after coronary artery bypass graft surgery (CABG). The two conditions often coexist, yet the impact on long-term prognosis after CABG of each factor relative to the other and the two in combination is uncertain. METHODS We undertook a prospective cohort study of 4869 patients who underwent CABG between 2003 and 2007. The cohort was divided into four groups according to preoperative diabetic status and renal function: patients without either DM or RI (reference group), patients with DM alone, patients with RI alone and patients with both DM and RI. Clinical outcomes were compared between groups. Patients receiving renal replacement therapy were excluded. The primary outcome was 5-year all-cause mortality. RESULTS The crude 5-year all-cause mortality rate was 9.0% for patients in the reference group, 11.1% for patients with DM alone, 20.3% for patients with RI alone and 28.5% for patients with both DM and RI (P < 0.0001). Five-year survival adjusted for potential confounding factors was significantly worse for patients with DM (hazard ratio (HR) 1.30; 95% confidence interval (CI) 1.06-1.59), patients with RI (HR 1.32; 95% CI 1.08-1.61) and patients with both DM and RI (HR 2.04; 95% CI 1.65-2.53) when compared with patients with neither condition. CONCLUSIONS Preoperative DM and RI were important predictors of 5-year mortality after CABG. Patients with RI alone had a higher mortality rate than patients with DM alone, but this difference was largely accounted for by age and other comorbidities. The combination of DM and RI doubled the 5-year mortality rate after CABG independently of potential confounding factors.