Krishnaraj S. Rathod

Nitrite-Derived Nitric Oxide Protects the Rat Kidney against Ischemia/Reperfusion Injury In Vivo: Role for Xanthine Oxidoreductase

In normal conditions, nitric oxide (NO) is oxidized to the anion nitrite, but in hypoxia, this nitrite may be reduced back to NO by the nitrite reductase action of deoxygenated hemoglobin, acidic disproportionation, or xanthine oxidoreductase (XOR). Herein, is investigated the effects of topical sodium nitrite administration in a rat model of renal ischemia/reperfusion (I/R) injury. Rats were subjected to 60 min of bilateral renal ischemia and 6 h of reperfusion in the absence or presence of sodium nitrite (30 nmol) administered topically 1 min before reperfusion. Serum creatinine, serum aspartate aminotransferase, creatinine clearance, fractional excretion of Na(+), and plasma nitrite/nitrate concentrations were measured. The nitrite-derived NO-generating capacity of renal tissue was determined under acidic and hypoxic conditions by ozone chemiluminescence in homogenates of kidneys that were subjected to sham, ischemia-only, and I/R conditions. Nitrite significantly attenuated renal dysfunction and injury, an effect that was abolished by previous treatment of rats with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl-3-oxide (2.5 mumol intravenously 5 min before ischemia and 50 nmol topically 6 min before reperfusion). Renal tissue homogenates produced significant amounts of NO from nitrite, an effect that was attenuated significantly by the xanthine oxidoreductase inhibitor allopurinol. Taken together, these findings demonstrate that topically administered sodium nitrite protects the rat kidney against I/R injury and dysfunction in vivo via the generation, in part, of xanthine oxidoreductase-catalyzed NO production. These observations suggest that nitrite therapy might prove beneficial in protecting kidney function and integrity during periods of I/R such as those encountered in renal transplantation.

Successful Recanalization of Chronic Total Occlusions Is Associated With Improved Long-Term Survival

OBJECTIVES This study investigated the impact of procedural success on mortality following chronic total occlusion (CTO) percutaneous coronary intervention (PCI) in a large cohort of patients in the drug-eluting stent era. BACKGROUND Despite advances in expertise and technologies, many patients with CTO are not offered PCI. METHODS A total of 6,996 patients underwent elective PCI for stable angina at a single center (2003 to 2010), 836 (11.9%) for CTO. All-cause mortality was obtained to 5 years (median: 3.8 years; interquartile range: 2.0 to 5.4 years) and stratified according to successful chronic total occlusion (sCTO) or unsuccessful chronic total occlusion (uCTO) recanalization. Major adverse cardiac events (MACE) included myocardial infarction (MI), urgent revascularization, stroke, or death. RESULTS A total of 582 (69.6%) procedures were successful. Stents were implanted in 97.0% of successful procedures (mean: 2.3 ± 0.1 stents per patient, 73% drug-eluting). Prior revascularization was more frequent among uCTO patients: coronary artery bypass grafting (CABG) (16.5% vs. 7.4%; p < 0.0001), PCI (36.0% vs. 21.2%; p < 0.0001). Baseline characteristics were otherwise similar. Intraprocedural complications, including coronary dissection, were more frequent in unsuccessful cases (20.5% vs. 4.9%; p < 0.0001), but did not affect in-hospital MACE (3% vs. 2.1%; p = NS). All-cause mortality was 17.2% for uCTO and 4.5% for sCTO at 5 years (p < 0.0001). The need for CABG was reduced following sCTO (3.1% vs. 22.1%; p < 0.0001). Multivariate analysis demonstrated that procedural success was independently predictive of mortality (hazard ratio [HR]: 0.32 [95% confidence interval (CI): 0.18 to 0.58]), which persisted when incorporating a propensity score (HR: 0.28 [95% CI: 0.15 to 0.52]). CONCLUSIONS Successful CTO PCI is associated with improved survival out to 5 years. Adoption of techniques and technologies to improve procedural success may have an impact on prognosis.

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.

Safety and feasibility of hospital discharge 2 days following primary percutaneous intervention for ST-segment elevation myocardial infarction

Aim Primary percutaneous coronary intervention (PPCI) produces more effective coronary reperfusion and allows immediate risk stratification compared with fibrinolysis. We investigated the safety and feasibility of very early discharge at 2 days following PPCI in selected low-risk cases. Methods This was a prospective observational cohort study of 2779 patients who underwent PPCI between 2004 and 2011. Patients meeting the following criteria were deemed suitable for very early discharge; TIMI III flow, left ventricle (LF) ejection fraction >40%, and rhythmic and haemodynamic stability out to 48 h. Higher-risk patients who did not fulfil these criteria were discharged later according to physician preference. All patients were offered outpatient review by a multidisciplinary team. Endpoints included 30 day readmission rates and major adverse cardiac events (MACE) out to a median of 2.8 years (IQR range: 1.3–4.4 years). Results 1309 (49.3%) PPCI patients met very early discharge criteria, of whom 1117 (85.3%) were actually discharged at 2 days. 620 (23.4%) were discharged at 3 days, and 916 (34.5%) >3 days after admission (median 5, IQR: 4–8) days). Patients discharged at 2 days were younger, and had lower rates of diabetes, renal dysfunction, multivessel coronary artery disease, previous myocardial infarction, and previous coronary artery bypass surgery, compared with patients discharged later. 30-day readmission rates for non-MACE events were 4.8%, 4.9% and 4.6% for patients discharged 2 days, 3 days and >3 days after admission, respectively. MACE rates were lowest in patients discharged at 2 days (9.6%, 95% CI 4.7% to 16.6%) compared with patients discharged at 3 days (12.3% 95% CI 6.0% to 19.2%) and >3 days (28.6% 95% CI 22.9% to 34.7%, p<0.0001) after admission. Conclusions Our data suggest that discharge of low-risk patients 2 days after successful PPCI is feasible and safe. Over 40% of all patients with ST-elevation myocardial infarction may be suitable for early discharge with important implications for healthcare costs.

Mortality in South Asians and Caucasians After Percutaneous Coronary Intervention in the United Kingdom: An Observational Cohort Study of 279,256 Patients From the BCIS (British Cardiovascular Intervention Society) National Database

OBJECTIVES The purpose of this study was to compare baseline characteristics and medium-term prognosis in South Asian and Caucasian patients undergoing percutaneous coronary intervention (PCI). BACKGROUND It is unclear whether South Asians undergoing PCI have worse outcomes than Caucasians. METHODS We performed a retrospective analysis of 279,256 patients undergoing PCI from 2004 to 2011 from the British Cardiovascular Intervention Society national database, of whom 259,318 (92.9%) were Caucasian and 19,938 (7.1%) were South Asian (South Asian includes patients of Pakistani, Indian, Bangladeshi, or Sri Lankan ethnic origin). The main outcome measures were in-hospital major adverse cardiac and cerebrovascular events and all-cause mortality during a median follow-up of 2.8 years (interquartile range: 1.5 to 4.5 years). RESULTS South Asians were younger (59.69 ± 0.27 years vs. 64.69 ± 0.13 years, p > 0.0001); more burdened by cardiovascular risk factors, particularly diabetes mellitus (42.1 ± 1.2% vs. 15.4 ± 0.4%, p > 0.0001); and more likely to have multivessel coronary disease than Caucasians. In-hospital rates of major adverse cardiac and cerebrovascular events were similar for South Asians and Caucasians (3.5% vs. 2.8%, p = 0.40). Unadjusted Kaplan-Meier estimates of all-cause mortality showed better survival for South Asians compared with Caucasians, after PCI for either acute myocardial infarction or angina. Age-adjusted analysis revealed increased mortality (hazard ratio: 1.24; 95% confidence interval: 1.18 to 1.30), but after adjustment for the substantial variation in baseline risk factors including diabetes, there was no significant difference between South Asians and Caucasians (hazard ratio: 0.99; 95% confidence interval: 0.94 to 1.05). CONCLUSIONS In this large, contemporary cohort of patients treated by PCI, South Asians were younger but had more extensive disease and major risk factors, particularly diabetes. However, after correcting for these differences, in-hospital and medium-term mortality of South Asians was no worse than that of Caucasians. This suggests that in South Asians, the high prevalence of diabetes exerts an adverse influence on mortality, but ethnicity itself is not an independent predictor of outcome.

Accelerated resolution of inflammation underlies sex differences in inflammatory responses in humans

BACKGROUND. Cardiovascular disease occurs at lower incidence in premenopausal females compared with age-matched males. This variation may be linked to sex differences in inflammation. We prospectively investigated whether inflammation and components of the inflammatory response are altered in females compared with males. METHODS. We performed 2 clinical studies in healthy volunteers. In 12 men and 12 women, we assessed systemic inflammatory markers and vascular function using brachial artery flow-mediated dilation (FMD). In a further 8 volunteers of each sex, we assessed FMD response to glyceryl trinitrate (GTN) at baseline and at 8 hours and 32 hours after typhoid vaccine. In a separate study in 16 men and 16 women, we measured inflammatory exudate mediators and cellular recruitment in cantharidin-induced skin blisters at 24 and 72 hours. RESULTS. Typhoid vaccine induced mild systemic inflammation at 8 hours, reflected by increased white cell count in both sexes. Although neutrophil numbers at baseline and 8 hours were greater in females, the neutrophils were less activated. Systemic inflammation caused a decrease in FMD in males, but an increase in females, at 8 hours. In contrast, GTN response was not altered in either sex after vaccine. At 24 hours, cantharidin formed blisters of similar volume in both sexes; however, at 72 hours, blisters had only resolved in females. Monocyte and leukocyte counts were reduced, and the activation state of all major leukocytes was lower, in blisters of females. This was associated with enhanced levels of the resolving lipids, particularly D-resolvin. CONCLUSIONS. Our findings suggest that female sex protects against systemic inflammation-induced endothelial dysfunction. This effect is likely due to accelerated resolution of inflammation compared with males, specifically via neutrophils, mediated by an elevation of the D-resolvin pathway. TRIAL REGISTRATION. ClinicalTrials.gov NCT01582321 and NRES: City Road and Hampstead Ethics Committee: 11/LO/2038. FUNDING. The authors were funded by multiple sources, including the National Institute for Health Research, the British Heart Foundation, and the European Research Council.

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.

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.

Atypical risk factor profile and excellent long-term outcomes of young patients treated with primary percutaneous coronary intervention for ST-elevation myocardial infarction

Introduction: Several studies have examined the relationship between age and clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (PPCI). The majority of studies have concentrated on describing elderly patients and there has been less focus on the profile and outcome of young patients suffering from STEMI. The aim of this study was to describe the clinical profile and outcomes of young patients compared with an older cohort and to establish what risk factors were associated with young patients having PPCI for STEMI. Methods: This was an observational cohort study of 3618 patients with STEMI treated by PPCI at a regional heart attack centre in London between January 2004 and September 2012. Clinical characteristics and outcomes in (young) patients aged ≤45 years were compared with those in (older) patients aged >45 years. The primary and main secondary outcomes were all-cause mortality and major adverse cardiovascular event rates, respectively, at a median follow-up of 3.0 (interquartile range 1.2–4.6) years. Results: Of the 3618 patients, 367 (10.1%) were aged ≤45 years and 3251 (89.9%) were aged >45 years. The proportion of patients aged ≤45 years increased from 8.5% to 11.5% (p=0.04) during the study period. Compared with older patients, those aged ≤45 years were more likely to be male, smokers, of South Asian ethnicity and to have a family history of premature coronary artery disease. Young patients were less likely to have a history of hypertension, hypercholesterolaemia, diabetes mellitus, previous myocardial infarction, myocardial revascularisation, or to have left ventricular systolic impairment or renal impairment. Over the follow-up period, mortality (2.7% vs. 7.6%; p<0.0001) and major adverse cardiovascular event rates (7.0% vs. 13.5%; p<0.0001) were significantly lower in patients aged ≤45 years compared with older patients. After adjustment for potential confounding factors, young age remained a predictor of reduced all cause mortality when compared with older patients (hazard ratio 0.12 (95% confidence interval 0.04–0.38)), including after incorporation of a propensity score (hazard ratio: 0.14 (95% confidence interval 0.04–0.36)). Conclusions: In this cohort of patients with STEMI treated by PPCI there was an increasing incidence of young patients aged ≤45 years throughout the study period. These patients were more often male, smokers and of South Asian ethnicity. Outcomes in younger patients was good. Focusing preventative strategies on smokers and high risk ethnic groups may help reduce the incidence of premature coronary artery disease.

A ‘green’ diet-based approach to cardiovascular health? Is inorganic nitrate the answer?

Ingestion of fruit and vegetables rich in inorganic nitrate (NO(3)(-)) has emerged as an effective method for acutely elevating vascular nitric oxide (NO) levels through formation of an NO(2)(-) intermediate. As such a number of beneficial effects of NO(3)(-) and NO(2)(-) ingestion have been demonstrated including reductions in blood pressure, measures of arterial stiffness and platelet activity. The pathway for NO generation from such dietary interventions involves the activity of facultative oral microflora that facilitate the reduction of inorganic NO(3)(-), ingested in the diet, to inorganic NO(2)(-). This NO(2)(-) then eventually enters the circulation where, through the activity of one or more of a range of distinct NO(2)(-) reductases, it is chemically reduced to NO. This pathway provides an alternative route for in vivo NO generation that could be utilized for therapeutic benefit in those cardiovascular disease states where reduced bioavailable NO is thought to contribute to pathogenesis. Indeed, the cardiovascular benefits of NO(2)(-) and NO(3)(-) are now starting to be translated in patients in several clinical trials. In this review, we discuss recent evidence supporting the potential utility of delivery of NO(3)(-) or NO(2)(-) for the treatment of cardiovascular diseases.