Allopurinol pretreatment improves postoperative recovery and reduces lipid peroxidation in patients undergoing coronary artery bypass grafting

Allopurinol for Secondary Prevention in Patients with Cardiovascular Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

The effects of allopurinol in patients with cardiovascular disease are not well defined; therefore, the latest evidence is summarized in this study.

METHODS

PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases were searched for randomized controlled trials (RCTs) of allopurinol in patients with cardiovascular disease published up to 11 February 2023. The primary outcome was cardiovascular death.

RESULTS

We combined the results of 21 RCTs that included 22,806 patients. Compared to placebo/usual care, allopurinol treatment was not associated with a significant reduction in cardiovascular death (RR 0.60; 95% CI 0.33-1.11) or all-cause death (RR 0.90; 95% CI 0.72-1.12). However, evidence from earlier trials and studies with small sample sizes indicated that allopurinol might confer a protective effect in decreasing cardiovascular death (RR 0.34; 95% CI 0.15-0.76) across patients undergoing coronary artery bypass grafting (CABG) or having acute coronary syndrome (ACS). In comparisons between allopurinol and febuxostat, we observed no difference in cardiovascular death (RR 0.92; 95% CI 0.69-1.24) or all-cause death (RR 1.02; 95% CI 0.75-1.38).

CONCLUSION

Allopurinol could not reduce cardiovascular (CV) death or major adverse CV outcomes significantly in patients with existing cardiovascular diseases. Given the limitations of the original studies, the potential advantages of allopurinol observed in patients undergoing CABG or presenting with ACS necessitate further confirmation through subsequent RCTs. In the comparisons between allopurinol and febuxostat, our analysis failed to uncover any marked superiority of allopurinol in reducing the risk of adverse cardiovascular incidents.

Do reactive oxygen species damage or protect the heart in ischemia and reperfusion? Analysis on experimental and clinical data

The role of reactive oxygen species (ROS) in ischemic and reperfusion (I/R) injury of the heart has been discussed for more than 40 years. It has been demonstrated that reperfusion triggers a multiple increase in free radical generation in the isolated heart. Antioxidants were found to have the ability to mitigate I/R injury of the heart. However, it is unclear whether their cardioprotective effect truly depends on the decrease of ROS levels in myocardial tissues. Since high doses and high concentrations of antioxidants were experimentally used, it is highly likely that the cardioprotective effect of antioxidants depends on their interaction not only with free radicals but also with other molecules. It has been demonstrated that the antioxidant N-2-mercaptopropionyl glycine or NDPH oxidase knockout abolished the cardioprotective effect of ischemic preconditioning. Consequently, there is evidence that ROS protect the heart against the I/R injury.

Time-varying serum uric acid predicts new-onset atrial fibrillation in treated hypertensive patients. The LIFE Study

Aim: The Losartan Intervention For Endpoint reduction in hypertension (LIFE) Study showed less new-onset atrial fibrillation (AF) in hypertensive patients receiving losartan- vs. atenolol-based treatment. Because losartan reduces serum uric acid (SUA) levels, the aim of the present study was to investigate relations of SUA with new-onset AF in the study. Methods: Hypertensive patients with electrocardiographic (ECG) left ventricular hypertrophy (LVH) and no prior AF (n = 8,243) were treated for 5.0 ± 0.4 years with losartan- or atenolol-based therapy. Associations of SUA with new-onset AF documented by Minnesota coding were assessed by Cox models using SUA and systolic blood pressure as time-varying covariates to take into account changes of SUA related to losartan or diuretic treatment, changes in renal function, and aging. Results: Time-varying SUA was associated with new AF defined by Minnesota code [hazard ratio (HR) = 1.19 per 16.8 μmol/L (1 mg/dL), (95% confidence intervals (CIs), 1.12–1.26), P < 0.0001], independent of losartan treatment [HR = 0.75 (95% CIs, 0.61–0.93), P = 0.007], older age [HR = 1.95 per 7.0 years (95% CIs, 1.73–2.20), P < 0.0001], male sex [HR = 1.46 (95% CIs, 1.09–1.94), P = 0.010] and higher Cornell voltage-duration product [HR = 1.10 per 1,023 ms·mm (95% CIs, 1.01–1.21), P = 0.034]. Similar results were obtained in Cox models with SUA levels partitioned according to baseline quartiles and in which AF was defined by physician reports or by both Minnesota coding and physician reports. Conclusions: In-treatment SUA is a strong predictor for new-onset AF in hypertensive patients, independent of effects of antihypertensive treatment, age, sex, and ECG-LVH. Further research is needed to clarify how uric acid may provoke AF (ClinicalTrials.gov identifier: NCT00338260).

Allopurinol attenuates oxidative injury in rat hearts suffered ischemia/reperfusion via suppressing the xanthine oxidase/vascular peroxidase 1 pathway

Allopurinol, a xanthine oxidase (XO) inhibitor, is reported to alleviate myocardial ischemia/reperfusion (I/R) injury by reducing the production of reactive oxygen species (ROS). As an XO-derived product, H2O2 can act as a substrate of vascular peroxidase 1 (VPO1) to induce the generation of hypochlorous acid (HOCl), a potent oxidant. This study aims to explore whether the XO/VPO1 pathway is involved in the anti-oxidative effects of allopurinol on the myocardial I/R injury. In a rat heart model of I/R, allopurinol alleviated I/R oxidative injury accompanied by decreased XO activity, XO-derived products (H2O2 and uric acid), and VPO1 expression (mRNA and protein). In a cardiac cell model of hypoxia/reoxygenation (H/R), allopurinol or XO siRNA reduced H/R injury concomitant with decreased XO activity, VPO1 expression as well as the XO and VPO1-derived products (H2O2, uric acid, and HOCl). Although knockdown of VPO1 could also exert a beneficial effect on H/R injury, it did not affect XO activity, XO expression, and XO-derived products. Based on these observations, we conclude that the novel pathway of XO/VPO1 is responsible for, at least partly, myocardial I/R-induced oxidative injury, and allopurinol exerted the cardioprotective effects on myocardial I/R injury via inhibiting the XO/VPO1 pathway.

A meta-analysis of the efficacy of allopurinol in reducing the incidence of myocardial infarction following coronary artery bypass grafting

Background

The xanthine oxidase inhibitor allopurinol that is commonly used to treat gout, has been suggested to have pleiotropic effects that are likely to reduce the incidence of myocardial infarction (MI) in at risk individuals. The aim of this meta-analysis was to assess the efficacy of allopurinol treatment in reducing the incidence of MI.

Method

MEDLINE, Scopus, Web of Science, and Cochrane Library databases were searched for randomised controlled trials examining the efficacy of allopurinol in reducing the incidence of MI. The quality of study methodology was assessed by two independent reviewers using the Cochrane Collaboration’s tool for assessing risk of bias. This meta-analysis was conducted using a fixed-effects model, and heterogeneity was assessed with the I² index.

Results

One thousand one hundred twenty-three citations were screened and only six studies satisfied the inclusion criterion. Published between 1988 and 1995, all studies examined the cardioprotective efficacy of allopurinol in the setting of coronary artery bypass graft (CABG). From a total pooled sample size of 229, MI was reported in 2 (1.77%) allopurinol and 14 (12.07%) control patients. A fixed-effects meta-analysis (I² = 0%) identified a statistically significant reduced incidence of myocardial infarction (RR 0.21, 95% CI: 0.06, 0.70, p = 0.01) in patients allocated to allopurinol. However, in the leave-one-out sensitivity analyses, the treatment effect became non-significant with the removal of one of the studies.

Conclusion

Based on the limited evidence available, allopurinol appears to reduce the incidence of perioperative MI following CABG. Further research is required to confirm these findings.

Electronic supplementary material

The online version of this article (10.1186/s12872-018-0881-6) contains supplementary material, which is available to authorized users.

Protective Effects of Topiroxostat on an Ischemia-Reperfusion Model of Rat Hearts

BACKGROUND

Ischemia/reperfusion (I/R) injury triggers cardiac dysfunctions via creating reactive oxygen species (ROS). Because xanthine oxidase (XO) is one of the major enzymes that generate ROS, inhibition of XO is expected to suppress ROS-induced I/R injury. However, it remains unclear whether XO inhibition really yields cardioprotection during I/R. The protective effects of the XO inhibitors, topiroxostat and allopurinol, on cardiac I/R injury were evaluated.

METHODS AND RESULTS

Using isolated rat hearts, ventricular functions, occurrence of arrhythmias, XO activities and thiobarbituric acid reactive substances (TBARS) productions and myocardial levels of adenine nucleotides before and after I/R, and cardiomyocyte death markers during reperfusion, were evaluated. Topiroxostat prevented left ventricular dysfunctions and facilitated recovery from arrhythmias during I/R. Allopurinol and the antioxidant, N-acetylcysteine (NAC), exhibited similar effects at higher concentrations. Topiroxostat inhibited myocardial XO activities and TBARS productions after I/R. I/R decreased myocardial levels of ATP, ADP and AMP, but increased that of xanthine. While topiroxostat, allopurinol or NAC did not change myocardial levels of ATP, ADP or AMP after I/R, all of the agents decreased the level of xanthine. They also decreased releases of CPK and LDH during reperfusion.

CONCLUSIONS

Topiroxostat showed protective effects against I/R injury with higher potency than allopurinol or NAC. It dramatically inhibited XO activity and TBARS production, suggesting suppression of ROS generation.

Xanthine oxidase inhibition for the treatment of cardiovascular disease: an updated systematic review and meta-analysis

Background

Previous studies have shown that xanthine oxidase inhibitors (XOI) might improve outcome for patients with cardiovascular disease. However, more evidence is required.

Methods and results

We published a meta‐analysis of trials conducted before 2014 examining the effects of XOI on mortality in patients with cardiovascular disease. At least two further trials (N = 323 patients) have since been published. Accordingly, we repeated our analysis after a further search for randomized controlled trials of XOI in PubMed/MEDLINE, EMBASE, and Cochrane Databases. We identified eight relevant trials with 1031 patients. The average age of the patients was 61 years and 68% were men (one study did not report gender). There were 57 deaths in these eight trials, 26 in those assigned to XOI, and 31 in those assigned to the control. The updated meta‐analysis could not confirm a reduction in mortality for patients assigned to XOI compared with placebo (odds ratio 0.84) but 95% confidence intervals were wide (0.48–1.47).

Conclusions

This updated meta‐analysis does not suggest that XOI exert a large reduction in mortality but also cannot exclude the possibility of substantial harm or benefit.

Xanthine oxidase and the fetal cardiovascular defence to hypoxia in late gestation ovine pregnancy

Hypoxia is a common challenge to the fetus, promoting a physiological defence to redistribute blood flow towards the brain and away from peripheral circulations. During acute hypoxia, reactive oxygen species (ROS) interact with nitric oxide (NO) to provide an oxidant tone. This contributes to the mechanisms redistributing the fetal cardiac output, although the source of ROS is unknown. Here, we investigated whether ROS derived from xanthine oxidase (XO) contribute to the fetal peripheral vasoconstrictor response to hypoxia via interaction with NO-dependent mechanisms. Pregnant ewes and their fetuses were surgically prepared for long-term recording at 118 days of gestation (term approximately 145 days). After 5 days of recovery, mothers were infused i.v. for 30 min with either vehicle (n = 11), low dose (30 mg kg(-1), n = 5) or high dose (150 mg kg(-1), n = 9) allopurinol, or high dose allopurinol with fetal NO blockade (n = 6). Following allopurinol treatment, fetal hypoxia was induced by reducing maternal inspired O2 such that fetal basal P aO 2 decreased approximately by 50% for 30 min. Allopurinol inhibited the increase in fetal plasma uric acid and suppressed the fetal femoral vasoconstrictor, glycaemic and lactate acidaemic responses during hypoxia (all P < 0.05), effects that were restored to control levels with fetal NO blockade. The data provide evidence for the activation of fetal XO in vivo during hypoxia and for XO-derived ROS in contributing to the fetal peripheral vasoconstriction, part of the fetal defence to hypoxia. The data are of significance to the understanding of the physiological control of the fetal cardiovascular system during hypoxic stress. The findings are also of clinical relevance in the context of obstetric trials in which allopurinol is being administered to pregnant women when the fetus shows signs of hypoxic distress.

Beyond gout: uric acid and cardiovascular diseases

OBJECTIVES

This article discusses the results of clinical and experimental studies that examine the association of hyperuricemia and gout with cardiovascular (CV) disease.

METHODS

Key papers for inclusion were identified by a PubMed search, and articles were selected for their relevance to the topic, according to the authors' judgment.

RESULTS AND CONCLUSIONS

Significant progress has been made in confirming an association, possibly causal, between hyperuricemia and CV outcomes. Xantine-oxidase (XO) inhibitors appear to be the most promising agents for prevention and treatment of CV consequences associated with hyperuricemia. Several small and medium sized studies have examined the effect of these agents on CV function in a variety of patient populations. Improvements in measures of endothelial function, oxidative stress, cardiac function, hemodynamics, and certain inflammatory indices have been demonstrated. Compounds for XO inhibition with more specific clinical effects and fewer side effects than allopurinol may be promising options to further explore the therapeutic potential in patients with CV disease. It is too early to make clinical recommendations with regard to the benefits of using XO inhibitor allopurinol or the novel febuxostat in patients with asymptomatic increased UA levels and high CV risk because only a small number of studies have shown that they may be beneficial in terms of CV outcomes. More studies are therefore needed to determine the potential of these drugs for reducing the risk of developing CV disease.

Serum uric acid and metabolic risk

OBJECTIVES

This review presents the information available on the role of uric acid (UA) on metabolic risk and on the link between hyperuricemia and metabolic syndrome.

METHODS

Key papers for inclusion were identified by a PubMed search and articles were selected according to their relevance for the topic, according to the authors' judgment.

RESULTS AND CONCLUSIONS

An elevated UA is both strongly associated and predictive of the metabolic syndrome, and increasing evidence suggests that UA may have a causal role. The classical viewpoint that UA is simply an innocuous marker of metabolic syndrome that should not even be measured will likely have to be modified. Lowering UA may be a novel treatment target for preventing diabetes and justify prospective clinical trials on the possible benefits of the measurement and lowering of serum UA on multiple chronic disease end points.

Xanthine oxidase and uric acid in cardiovascular disease: clinical impact and therapeutic options

The association between increased uric acid (UA) levels and cardiovascular disease (CVD) has been observed and studied for many decades. The value of UA as an independent factor within the metabolic risk profile for prediction of CVD in the normal population remains an issue of ongoing discussion. In turn, increasing evidence suggests that among patients with established CVD such as heart failure UA is an independent marker of disease state and prognosis. Increased UA levels may be an indicator of up-regulated activity of xanthine oxidase, a powerful oxygen radical-generating system in human physiology. Increased reactive oxygen species (ROS) accumulation contributes to endothelial dysfunction, metabolic and functional impairment, inflammatory activation, and other features of cardiovascular pathophysiology. Accordingly, inhibition of xanthine oxidase activity has been shown to improve a range of surrogate markers in patients with CVD, but this effect seems to be confined to hyperuricemic patients because disappointing results were reported in studies with normouricemic patients. In this review we summarize current evidence on hyperuricemia in CVD. The value of UA as a biomarker and as a potential therapeutic target for tailored metabolic treatment in CVD is discussed.

The cellular and molecular origin of reactive oxygen species generation during myocardial ischemia and reperfusion

Myocardial ischemia-reperfusion injury is an important cause of impaired heart function in the early postoperative period subsequent to cardiac surgery. Reactive oxygen species (ROS) generation increases during both ischemia and reperfusion and it plays a central role in the pathophysiology of intraoperative myocardial injury. Unfortunately, the cellular source of these ROS during ischemia and reperfusion is often poorly defined. Similarly, individual ROS members tend to be grouped together as free radicals with a uniform reactivity towards biomolecules and with deleterious effects collectively ascribed under the vague umbrella of oxidative stress. This review aims to clarify the identity, origin, and progression of ROS during myocardial ischemia and reperfusion. Additionally, this review aims to describe the biochemical reactions and cellular processes that are initiated by specific ROS that work in concert to ultimately yield the clinical manifestations of myocardial ischemia-reperfusion. Lastly, this review provides an overview of several key cardioprotective strategies that target myocardial ischemia-reperfusion injury from the perspective of ROS generation. This overview is illustrated with example clinical studies that have attempted to translate these strategies to reduce the severity of ischemia-reperfusion injury during coronary artery bypass grafting surgery.

Role of oxidative stress in disease progression in Stage B, a pre-cursor of heart failure

Oxidative stress represents a persistent imbalance between the production and the compensation of reactive oxygen species. Though predominantly found in advanced heart failure, the most frequent "at-risk" condition has been associated with underlying oxidative stress. It is therefore conceivable that timely detection and early intervention to reduce oxidative stress processes provide an opportunity to prevent disease progression to overt heart failure. This article reviews the current understanding of the current evidence of oxidative stress involvement in the pathophysiology of human heart failure and its potential therapeutic interventions in patients with Stage A and B heart failure.

Free radical reaction products and antioxidant capacity in beating heart coronary artery surgery compared to conventional bypass

Oxygen-derived free radicals are important agents of tissue injury during ischemia and reperfusion. The aim of this study was to investigate changes in protein and lipid oxidation and antioxidant status in beating heart coronary artery surgery and conventional bypass and to compare oxidative stress parameters between the two bypass methods. Serum lipid hydroperoxide, nitric oxide, protein carbonyl, nitrotyrosine, vitamin E, and β-carotene levels and total antioxidant capacity were measured in blood of 30 patients undergoing beating heart coronary artery surgery (OPCAB, off-pump coronary artery bypass grafting) and 12 patients undergoing conventional bypass (CABG, on-pump coronary artery bypass grafting). In the OPCAB group, nitric oxide and nitrotyrosine levels decreased after reperfusion. Similarly, β-carotene level and total antioxidant capacity also decreased after anesthesia and reperfusion. In the CABG group, nitric oxide and nitrotyrosine levels decreased after ischemia and reperfusion. However, protein carbonyl levels elevated after ischemia and reperfusion. Vitamin E, β-carotene, and total antioxidant capacity decreased after ischemia and reperfusion. Significantly decreased nitration and impaired antioxidant status were seen after reperfusion in both groups. Moreover, elevated protein carbonyls were found in the CABG group. The off-pump procedure is associated with lower degree of oxidative stress than on-pump coronary surgery.

Uric acid in heart disease: a new C-reactive protein?

PURPOSE OF REVIEW

To review and interpret the recently published data on hyperuricemia and cardiovascular disease to present an opinion on the nature of link between serum uric acid concentration and the risk for cardiovascular outcomes, and to comment on its implications for clinical practice.

RECENT FINDINGS

Evidence has accumulated in prospective observational studies that link hyperuricemia among younger adults with the risk of subsequent hypertension. Such associations have been observed with respect to insulin resistance, diabetes, and other cardiovascular risk factors. Newer data confirm the link between hyperuricemia and cardiovascular mortality. The use of allopurinol has been shown to be associated with reduced mortality risk in longer term observational studies and with reduced blood pressure in short-term randomized controlled trials. None of these findings is confounded by traditional risk factors.

SUMMARY

The available evidence has established a link between hyperuricemia and cardiovascular disease and this may be causal. Without waiting for the resolution of causality arguments, one can start using serum uric acid concentration as an inexpensive cardiovascular risk marker.

Inflammation, oxidative stress and lipids: the risk triad for atherosclerosis in gout

For many years, the relationship between cardiovascular disease risk and gout, though strong and consistent, was suspected of being coincidental rather than causative. In recent years, compelling epidemiological and clinical data have increasingly favoured an aetiological connection. However, that connection is notably complex, involving a multifaceted model that includes interactions between inflammatory processes, oxidative stress and potential genetic influences, as well as cardiovascular and renal components that remain only partly explained. Urate appears to be able to activate the immune response, and in that context has a mediating role in the inflammatory process via the inflammasome. This interaction of urate and inflammation is central to the inflammatory cascade associated with gout flares. In the arena of oxidative stress, urate has both antioxidant and pro-oxidant properties, and while potentially beneficial in scavenging free radicals, it can also impair endothelial function and thereby give rise to atherosclerotic risk. Human and animal studies have revealed associations between hyperuricaemia and a host of atherosclerotic risk factors, whereas a reduction in urate levels is frequently associated with improvement or even resolution of such risk factors. The degree to which reduction of serum urate can reliably improve cardiovascular risk remains uncertain. It is hoped that the introduction of newer urate-lowering agents may help to clarify this picture and improve treatment options for both gout and atherosclerosis.

Allopurinol for preventing mortality and morbidity in newborn infants with suspected hypoxic-ischaemic encephalopathy

BACKGROUND

Delayed neuronal death following a perinatal hypoxic insult is due partly to xanthine oxidase-mediated production of cytotoxic free radicals. Evidence exists that allopurinol, a xanthine-oxidase inhibitor, reduces delayed cell death in animal models of perinatal asphyxia and in human patients with other forms of organ reperfusion injury.

OBJECTIVES

To determine the effect of allopurinol on mortality and morbidity in newborn infants with suspected hypoxic-ischaemic encephalopathy.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2007), MEDLINE (1966 - December 2007), EMBASE (1980 - December 2007), conference proceedings, and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared allopurinol administration vs. placebo or no drug in newborn infants with suspected hypoxic-ischaemic encephalopathy.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Neonatal Review Group were used, with separate evaluation of trial quality and data extraction by two authors. Data were synthesised using a fixed effects model and reported using typical relative risk, typical risk difference and weighted mean difference.

MAIN RESULTS

Three trials in which a total of 114 infants participated were identified. In one trial, participants were exclusively infants with severe encephalopathy. The other trials also included infants with mild and moderately-severe encephalopathy. These studies were generally of good methodological quality, but were underpowered to detect clinically important effects of allopurinol on mortality and morbidity. Meta-analysis did not reveal a statistically significant difference in the risk of death during infancy [typical relative risk 0.92 (95% confidence interval 0.59 to 1.45); typical risk difference -0.03 (95% confidence interval -0.16 to 0.11)], nor in the incidence of neonatal seizures [typical relative risk 0.93 (95% confidence interval 0.75 to 1.16); typical risk difference -0.05 (95% confidence interval -0.21 to 0.11)]. Only one trial assessed neurodevelopment in surviving children and did not find a statistically significant effect.

AUTHORS' CONCLUSIONS

The available data are not sufficient to determine whether allopurinol has clinically important benefits for newborn infants with hypoxic-ischaemic encephalopathy and, therefore, larger trials are needed. Such trials could assess allopurinol as an adjunct to therapeutic hypothermia in infants with moderate and severe encephalopathy and should be designed to exclude clinically important effects on mortality and adverse long-term neurodevelopmental outcomes.

Effect of intravenous N-acetylcysteine on outcomes after coronary artery bypass surgery: A randomized, double-blind, placebo-controlled clinical trial

OBJECTIVE

N-acetylcysteine, a potent anti-inflammatory and antioxidant agent, is known to decrease the production of reactive oxygen species after cardiac surgery. The objective of this study was to evaluate the effects of intravenous N-acetylcysteine on clinical and biochemical outcomes after coronary artery bypass surgery with cardiopulmonary bypass.

METHODS

One hundred patients (mean age 60.5 years, range 43-78 years, 89% male) undergoing coronary artery bypass grafting at the Montreal Heart Institute were randomized to receive either N-acetylcysteine (600 mg orally the day before and the morning of the operation, a bolus of 150 mg/kg of intravenous N-acetylcysteine before skin incision, followed by perfusion at 12.5 mg x kg(-1) x h(-1) over 24 hours; n = 50) or placebo (n = 50). The patients and clinical team were blinded to group assignments. Preoperative characteristics were similar between the two groups. Postoperative clinical data (death, myocardial infarction, low-output syndromes, arrhythmias, bleeding, transfusion requirements, and intensive care unit and hospital lengths of stay) and biochemical markers (creatine kinase MB, troponin T, creatinine, hemoglobin, and platelet levels) were evaluated serially over 4 days.

RESULTS

Clinical outcomes were not significantly different between the two groups with regard to the incidence of death, myocardial infarction, bleeding, transfusion requirements, intubation time, and hospital length of stay. No differences were found in postoperative biochemical markers (troponin T, creatine kinase MB, creatinine, hemoglobin, and platelets) between the groups. No differences were observed between the groups in interleukin-6 production (P = not significant).

CONCLUSIONS

Prophylactic use of N-acetylcysteine in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass does not lead to improvement in clinical results or biochemical markers. Further strategies to decrease reperfusion injury should be devised.

Could uric acid have a role in acute renal failure?

Acute renal failure (ARF), induced by either toxins or ischemia, is associated with significant morbidity. The pathogenesis of ARF is complex and is characterized by renal vasoconstriction and oxidative stress in association with tubular and microvascular injury and interstitial inflammation. In many situations, ARF is associated with a rise in serum uric acid as a result of both increased generation and decreased excretion. Although it is widely recognized that markedly elevated levels of uric acid can cause ARF via supersaturation within the tubules with crystallization and intrarenal obstruction ("acute urate nephropathy"), the possibility that uric acid may affect renal outcomes at concentrations that do not lead to tubular obstruction have not been considered. This article reviews both the salutary and the adverse effects of uric acid on biologic processes and presents the hypothesis that hyperuricemia, particularly if chronic and marked, likely represents a true risk factor for ARF. Hyperuricemia also may account for the paradoxic lack of benefit of diuretics in the management of ARF. It is suggested that studies are needed to investigate the role of chronic hyperuricemia on renal outcomes after acute tubular injury.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Cell culture modeling to test therapies against hyperglycemia-mediated oxidative stress and injury

The concept that oxidative stress is a key mediator of nerve injury in diabetes has led us to design therapies that target oxidative stress mechanisms. Using an in vitro model of glucose-treated dorsal root ganglion (DRG) neurons in culture, we can examine both free radical generation, using fluorimetric probes for reactive oxygen species, and cell death via the TUNEL assay. The cell culture system is scaled down to a 96-well plate format, and so is well suited to high-throughput screening. In the present study, we test the ability of three drugs, nicotinamide, allopurinol, and alpha-lipoic acid, alone and in combination to prevent DRG neuron oxidative stress and cell death. This combination of drugs is currently in clinical trial in type 1 diabetic patients. We demonstrate independent effects on oxidative stress and neuronal survival for the three drugs, and neuronal protection using the three drugs in combination. The data strengthen the rationale for the current clinical trial. In addition, we describe an effective tool for rapid preclinical testing of novel therapies against diabetic neuropathy.

Uric acid in chronic heart failure

The pathophysiologic understanding of chronic heart failure (CHF) has shifted from a mere hemodynamic disorder to a much more complex approach including changes and imbalances in neurohormonal, immune, and metabolic functions. Among metabolic abnormalities, hyperuricemia is a constant finding in CHF. The xanthine oxidase metabolic pathway increasingly is appreciated as an important contributor to both symptoms of CHF as well as progression of the disease. Recent data suggest hyperuricemia to be an independent marker of impaired prognosis in CHF. In this article, the significance of the xanthine oxidase metabolic pathway in CHF is discussed. Data on xanthine oxidase inhibition are reviewed, which suggest a beneficial effect of therapeutically targeting this enzymatic pathway.

Uric acid as a mediator of endothelial dysfunction, inflammation, and vascular disease

Recent experimental findings have led to renewed interest in the possible role of uric acid in the pathogenesis of both hypertension and vascular disease. Often considered an antioxidant, biochemical and in vitro data indicate that noncrystalline, soluble uric acid also can react to form radicals, increase lipid oxidation, and induce various pro-oxidant effects in vascular cells. In vitro and in vivo findings suggest that uric acid may contribute to endothelial dysfunction by inducing antiproliferative effects on endothelium and impairing nitric oxide production. Proinflammatory and proliferative effects of soluble uric acid have been described on vascular smooth muscle cells (VSMCs), and in animal models of mild hyperuricemia, hypertension develops in association with intrarenal vascular disease. Possible adverse effects of uric acid on the vasculature have been linked to increased chemokine and cytokine expression, induction of the renin-angiotensin system, and to increased vascular C-reactive protein (CRP) expression. Experimental evidence suggests a complex but potentially direct causal role for uric acid in the pathogenesis of hypertension and atherosclerosis.

Allopurinol as a cardioprotectant during coronary artery bypass graft surgery

OBJECTIVE

To examine the role of allopurinol as a cardioprotectant during coronary artery bypass graft (CABG) surgery.

DATA SOURCES

A search of MEDLINE (1966-October 2002) was performed using the following terms: allopurinol, xanthine oxidase, oxygen free radical, and coronary artery bypass. References evaluated were limited to English-language and human studies, yielding 41 citations, 13 of which were found suitable. The 5 largest studies are discussed.

DATA SYNTHESIS

Multiple studies with various doses have evaluated the effects of allopurinol on outcomes in CABG patients. These studies found that allopurinol can reduce in hospital mortality, improve cardiac performance, reduce incidence of arrhythmias, reduce markers of ischemia and free-radical generation, and reduce the need for inotropic support. However, these findings were not consistent between all studies.

CONCLUSIONS

Allopurinol may reduce the incidence of CABG complications. Although the optimal dose has not been determined, reviewed literature suggests that patients should receive at least 600 mg one day prior to surgery, as well as at least 600 mg on the day of surgery.

Antioxidants in myocardial ischemia-reperfusion injury: therapeutic potential and basic mechanisms

Oxidative stress is a constant threat to all living organisms and an immense repertoire of cellular defense systems is being employed by most pro- and eukaryotic systems to eliminate or to attenuate oxidative stress. Ischemia and reperfusion is characterized by both a significant oxidative stress and characteristic changes in the antioxidant defense. By focusing on this antioxidant response of the cardiovascular system in the setting of ischemia-reperfusion injury, the aim of this review was threefold. First, based on recent animal experiments and clinical studies we shall discuss how endogenous antioxidants respond to oxidative stress during ischemia-reperfusion injury and highlight the results of recent trials on the ability of antioxidants to modulate ischemia-reperfusion injury. In this aspect, we will particularly focus on the emerging concept that various lines of antioxidant defenses do not act individually but are linked to each other in a systematic relationship as part of an antioxidant network. It is well known that enzymatic mechanisms are important components of the endogenous antioxidant repertoire; however, the relative importance of the different enzyme systems and isoforms has been much debated. The second part will focus on recent suggestions attributing a potentially key role of mitochondrial MnSOD in cardiac ischemia-reperfusion injury. Finally, the third part of the review will critically examine how endogenous antioxidants might regulate the complex signal transduction pathways of cellular activation with particular attention to the NF-kappaB and MAPK systems that appears to determine outcome of injury, survival, and adaptation.

N-acetylcysteine prevents reactive oxygen species-mediated myocardial stress in patients undergoing cardiac surgery: results of a randomized, double-blind, placebo-controlled clinical trial

OBJECTIVE

Reactive oxygen species have been shown to contribute to myocardial stress in patients undergoing cardiac surgery, as demonstrated by myocardial 8-iso-prostaglandin-F(2)alpha and nitrotyrosine formation. We hypothesized that the reactive oxygen species scavenger N-acetylcysteine attenuates reactive oxygen species-mediated myocardial stress in patients undergoing cardiac surgery.

METHODS

Forty patients undergoing coronary artery surgery (mean age +/- SD, 66 +/- 9 years; 9 women and 31 men) were randomized to receive either N-acetylcysteine (100 mg/kg into cardiopulmonary bypass prime followed by infusion at 20 mg.kg(-1).h(-1), n = 20) or placebo (n = 20). Patients and clinical staff were blinded to group assignment. Transmural left ventricular biopsy specimens collected before and at the end of cardiopulmonary bypass were subjected to immunocytochemical staining against 8-iso-prostaglandin-F(2)alpha (primary measure) as an indicator for reactive oxygen species-mediated lipid peroxidation and nitrotyrosine (coprimary measure) as a marker for peroxynitrite-mediated tissue injury. Cardiomyocyte staining was quantitatively determined by using densitometry (in gray units). Global left ventricular function was measured on the basis of fractional area of contraction by using transesophageal echocardiography.

RESULTS

Patient characteristics in both groups were comparable. The change in left ventricular cardiomyocyte staining (end of cardiopulmonary bypass--before cardiopulmonary bypass) differed significantly between groups for both primary measures: 8-iso-prostaglandin-F(2)alpha, -1.8 +/- 7.5 gray units (mean +/- SD, N-acetylcysteine group) versus 5.0 +/- 4.1 gray units (placebo group; 95% confidence interval, 2.6-11.0, P =.003); nitrotyrosine, -6.4 +/- 10.0 gray units (N-acetylcysteine group) versus 9.2 +/- 8.4 gray units (placebo group; 95% confidence interval, 9.4-21.7, P <.001). Hemodynamics and clinical outcomes were comparable in both groups.

CONCLUSIONS

Reactive oxygen species scavenging with N-acetylcysteine attenuates myocardial oxidative stress in the hearts of patients subjected to cardiopulmonary bypass and cardioplegic arrest.

Allopurinol improves cardiac dysfunction after ischemia-reperfusion via reduction of oxidative stress in isolated perfused rat hearts

It has been reported that the xanthine oxidase inhibitor, allopurinol, has a protective effect on ischemia - reperfusion injury, but the precise mechanism of its action is still unclear. Therefore, in the present study the mechanisms of the myocardial protection of allopurinol were evaluated in isolated perfused rat hearts. Allopurinol significantly inhibited myocardial xanthine oxidase activity, and improved left ventricular dysfunction after ischemia - reperfusion. In addition, the lactate dehydrogenase content in the coronary effluent obtained after reperfusion was significantly decreased. ATP, ADP, AMP and IMP significantly decreased, whereas inosine, hypoxanthine and xanthine significantly increased after ischemia in both the control and allopurinol groups. The concentration of xanthine was significantly decreased after ischemia - reperfusion in the allopurinol group; however, allopurinol did not affect the other purine metabolites. To evaluate the accumulation of oxidative stress, thiobarbituric acid reactive substances (TBARS) production in myocardial tissue was measured and allopurinol significantly decreased TBARS formation after ischemia - reperfusion. Finally, myocardial hydroxyl radicals were directly measured by electron spin resonance spectroscopy with the nitroxide radical 4-hydroxy-2, 2,6,6-tetramethyl-piperidine-N-oxyl. Hydroxyl radicals significantly increased immediately after reperfusion, but were significantly decreased in the allopurinol group. In conclusion, allopurinol reduced myocardial injury after ischemia-reperfusion by suppressing oxidative stress, but not by salvage of ATP. These findings may lead to the development of new therapeutic strategies for myocardial ischemia - reperfusion injury.

Nitrotyrosine and 8-isoprostane formation indicate free radical-mediated injury in hearts of patients subjected to cardioplegia

OBJECTIVE

Myocardial ischemia and reperfusion induced by cardioplegic arrest subjects the heart to free radical-mediated stress. The purpose of our study was to investigate the effect of cardioplegia-induced ischemia and reperfusion on myocardial formation and distribution of (1) nitrotyrosine as an indicator for peroxynitrite-mediated tissue injury resulting from increased nitric oxide release and (2) 8-isoprostane as an indicator for oxygen-derived free radical-mediated lipid peroxidation.

METHODS

In 10 patients undergoing coronary artery operations (64 +/- 6 [mean +/- SD] years, 3 women and 7 men) subjected to cardiopulmonary bypass and intermittent cold blood cardioplegia, we collected transmural left ventricular biopsy specimens before and at the end of cardiopulmonary bypass. Specimens were cut at 10 micro m and subjected to immunocytochemical staining against the nitric oxide-producing enzyme constitutive nitric oxide synthase, cyclic guanosine monophosphate (intracellular second messenger of nitric oxide), nitrotyrosine, and 8-isoprostane by using polyclonal antibodies. For global left ventricular function determination, we measured the fractional area of contraction using transesophageal echocardiography.

RESULTS

Nitric oxide synthase activity in cardiac myocytes increased from 34 +/- 10 gray units before cardiopulmonary bypass to 47 +/- 12 gray units at the end of bypass (P =.015), and all hearts showed increased cyclic guanosine monophosphate content in both myocytes and endothelial cells at the end of bypass. The number of nitrotyrosine-positive capillaries increased from 36 +/- 29/mm(2) before bypass to 82 +/- 47/mm(2) at the end of bypass (P =.012), and 8-isoprostane-positive capillaries increased from 92 +/- 72/mm(2) before bypass to 209 +/- 108/mm(2) at the end of bypass (P =.005). The fractional area of contraction was 53% +/- 12% before bypass and 56% +/- 12% after bypass (P =.47) but was slightly decreased to 45% +/- 14% at 4 hours after bypass (P =.121).

CONCLUSIONS

Our data show that cardioplegia-induced myocardial ischemia and reperfusion is associated with nitrotyrosine and 8-isoprostane formation mainly in the coronary endothelium, indicating injury mediated by both peroxynitrite and oxygen-derived free radicals. Because nitric oxide synthase activation was accompanied with increased cyclic guanosine monophosphate, these data suggest that direct effects of nitric oxide on cardiac myocytes, as well as nitric oxide-mediated coronary endothelial injury, might contribute to injury associated with cardioplegia and cardiopulmonary bypass.

Effects of xanthine oxidase inhibition with allopurinol on endothelial function and peripheral blood flow in hyperuricemic patients with chronic heart failure: results from 2 placebo-controlled studies

BACKGROUND

In patients with chronic heart failure (CHF), hyperuricemia is a common finding and is associated with reduced vasodilator capacity and impaired peripheral blood flow. It has been suggested that the causal link of this association is increased xanthine oxidase (XO)-derived oxygen free radical production and endothelial dysfunction. We therefore studied the effects of XO inhibition with allopurinol on endothelial function and peripheral blood flow in CHF patients after intra-arterial infusion and after oral administration in 2 independent placebo-controlled studies.

METHODS AND RESULTS

In 10 CHF patients with normal serum uric acid (UA) levels (315+/-42 micromol/L) and 9 patients with elevated UA (535+/-54 micromol/L), endothelium-dependent (acetylcholine infusion) and endothelium-independent (nitroglycerin infusion) vasodilation of the radial artery was determined. Coinfusion of allopurinol (600 microg/min) improved endothelium-dependent but not endothelium-independent vasodilation in hyperuricemic patients (P<0.05). In a double-blind, crossover design, hyperuricemic CHF patients were randomly allocated to allopurinol 300 mg/d or placebo for 1 week. In 14 patients (UA 558+/-21 micromol/L, range 455 to 743 micromol/L), treatment reduced UA by >120 micromol/L in all patients (mean reduction 217+/-15 micromol/L, P<0.0001). Compared with placebo, allopurinol improved peak blood flow (venous occlusion plethysmography) in arms (+24%, P=0.027) and legs (+23%, P=0.029). Flow-dependent flow improved by 58% in arms (P=0.011). Allantoin, a marker of oxygen free radical generation, decreased by 20% after allopurinol treatment (P<0.001). There was a direct relation between change of UA and improvement of flow-dependent flow after allopurinol treatment (r=0.63, P<0.05).

CONCLUSIONS

In hyperuricemic CHF patients, XO inhibition with allopurinol improves peripheral vasodilator capacity and blood flow both locally and systemically.

Allopurinol neurocardiac protection trial in infants undergoing heart surgery using deep hypothermic circulatory arrest

OBJECTIVE

This pharmacologic protection trial was conducted to test the hypothesis that allopurinol, a scavenger and inhibitor of oxygen free radical production, could reduce death, seizures, coma, and cardiac events in infants who underwent heart surgery using deep hypothermic circulatory arrest (DHCA).

DESIGN

This was a single center, randomized, placebo-controlled, blinded trial of allopurinol in infant heart surgery using DHCA. Enrolled infants were stratified as having hypoplastic left heart syndrome (HLHS) and all other forms of congenital heart disease (non-HLHS). Drug was administered before, during, and after surgery. Adverse events and the clinical efficacy endpoints death, seizures, coma, and cardiac events were monitored until infants were discharged from the intensive care unit or 6 weeks, whichever came first.

RESULTS

Between July 1992 and September 1997, 350 infants were enrolled and 348 subsequently randomized. A total of 318 infants (131 HLHS and 187 non-HLHS) underwent heart surgery using DHCA. There was a nonsignificant treatment effect for the primary efficacy endpoint analysis (death, seizures, and coma), which was consistent over the 2 strata. The addition of cardiac events to the primary endpoint resulted in a lack of consistency of treatment effect over strata, with the allopurinol treatment group experiencing fewer events (38% vs 60%) in the entire HLHS stratum, compared with the non-HLHS stratum (30% vs 27%). In HLHS surgical survivors, 40 of 47 (85%) allopurinol-treated infants did not experience any endpoint event, compared with 27 of 49 (55%) controls. There were fewer seizures-only and cardiac-only events in the allopurinol versus placebo groups. Allopurinol did not reduce efficacy endpoint events in non-HLHS infants. Treated and control infants did not differ in adverse events.

CONCLUSIONS

Allopurinol provided significant neurocardiac protection in higher-risk HLHS infants who underwent cardiac surgery using DHCA. No benefits were demonstrated in lower risk, non-HLHS infants, and no significant adverse events were associated with allopurinol treatment.congenital heart defects, hypoplastic left heart syndrome, induced hypothermia, ischemia-reperfusion injury, neuroprotective agents, allopurinol, xanthine oxidase, free radicals, seizures, coma.

A placebo-controlled study examining the effect of allopurinol on heart rate variability and dysrhythmia counts in chronic heart failure

AIMS

Allopurinol improves endothelial function in chronic heart failure by reducing oxidative stress. We wished to explore if such an effect would attenuate autonomic dysfunction in CHF in line with many other effective therapies in CHF.

METHODS

We performed a prospective, randomized, double-blind cross-over study in 16 patients with NYHA Class II-IV chronic heart failure (mean age 67 +/- 10 years, 13 male, comparing allopurinol (2 months) at a daily dose of 300 mg (if creatinine < 150 micromol l-1) or 100 mg (if creatinine > 150 micromol l-1) with matched placebo. Mean heart rate and dysrhythmia counts were recorded from 24 h Holter tapes at monthly intervals for 6 months. We assessed autonomic function using standard time domain heart rate variability parameters (HRV): SDNN, SDANN, SDNN index, rMSSD and TI.

RESULTS

Allopurinol had no significant effect on heart rate variability compared with placebo; the results are expressed as a difference in means +/- s.d. with 95% confidence interval (CI) between allopurinol and placebo: SDNN mean = 6.5 +/- 4.8 ms, P = 0.18 and 95% CI (-3.7, 17); TI mean = -2.1 +/- 1.4, P = 0.16 and 95% CI (-5.2, 0.8); SDANN mean = -2.8 +/- 7 ms, P = 0.68 and 95% CI (-18, 12); SDNNi mean = 2 +/- 6.6, P = 0.7 and 95% CI (-12, 16); RMSSD mean = -0.9 +/- 2, P = 0.68 and 95% CI (-5.6, 3.7). For mean heart rate the corresponding results were 0.9 +/- 1.4, P = 0.5 and 95% CI (-2, 3.8). Log 24 h ventricular ectopic counts (VEC) were 0.032 +/- 0.37, P = 0.7 and 95% CI (-0.1, 0.2). Patient compliance with study medication was good since allopurinol showed its expected effect of reducing plasma uric acid (P < 0.001).

CONCLUSIONS

Allopurinol at doses, which are known to reduce oxidative stress appear to have no significant effect on resting autonomic tone, as indicated by time domain heart rate variability or on dysrhythmia count in stable heart failure patients.

Changes in brain natriuretic peptide concentrations following open cardiac surgery with cardioplegic cardiac arrest

Elevated brain natriuretic peptide (BNP) concentration in peripheral blood reflects impaired cardiac ventricular function. We investigated the release pattern of BNP following cardioplegic cardiac arrest during heart surgery. In particular, we sought to discover whether there is an increase in peripheral BNP concentrations following reperfusion of the ischaemic heart. A secondary aim of the study was to investigate whether allopurinol, an anti-oxidant, has any effect on BNP release. A total of 29 patients scheduled for elective coronary artery bypass grafting were recruited, of whom 12 were randomly allocated to receive allopurinol with their pre-medication. Blood specimens were taken at six time points from the indwelling arterial catheter, the first before surgery and the last 2 h following the termination of cardiopulmonary bypass (CPB). BNP was found to decrease markedly when the aortic cross clamp was applied and the heart was isolated from circulation (P=0.0001). There was a slight increase in BNP following cross clamp release and myocardial reperfusion (P=0.04). A more substantial increase occurred with weaning from CPB when ventricular filling occurred (P=0.0015). Only the final BNP value, 2 h after CPB, was elevated compared with baseline (P=0.0013). Allopurinol had no demonstrable effect on changes in BNP.

Antioxidant vitamins and enzymatic and synthetic oxygen-derived free radical scavengers in the prevention and treatment of cardiovascular disease

Oxygen-derived free radical formation can lead to cellular injury and death. Under normal situations, the human body has a free radical scavenger system (catalase, superoxide dismutase) that can detoxify free radicals. Antioxidant vitamins and enzymatic and synthetic oxygen-derived free radical scavengers have been used clinically to prevent the formation of oxidized LDL and to prevent reperfusion injury, which is often caused by free radicals. In this article, the pathogenesis of free radical production and cell injury are discussed, and therapeutic approaches for disease prevention are presented.

Effect of allopurinol on myocardial oxygen free radical production in coronary bypass surgery

OBJECTIVES

Allopurinol protects the heart from reperfusion injury. The aim of this study was to investigate myocardial free radical production during reperfusion with and without allopurinol treatment in coronary artery bypass grafting patients randomized into allopurinol (n = 14) or placebo (n = 13) groups.

DESIGN

Allopurinol (1 g) was given blind prior to cardiopulmonary bypass and prior to opening the aorta. Oxygen free radicals were measured before anesthesia in arterial blood, before cross-clamping and 1 and 10 min after reperfusion in arterial and coronary sinus blood. Levels were measured as relative concentrations by the electron spin resonance method.

RESULTS

One minute after reperfusion the level of spin-trapped radicals in arterial blood was elevated significantly (p = 0.016) in the allopurinol group, from 7.7 (SE: 0.8) to 8.6 (1.4) and non-significantly (p = 0.074) in the placebo group, from 7.3 (0.7) to 8.3 (0.8). Ten minutes after reperfusion the arterial values were 8.6 (1.5) in the allopurinol and 7.6 (0.7) in the placebo group, the sinus values being 7.6 (1.3) and 8.3 (0.8), respectively. Myocardial free radical production was -0.94 (1.21) in the allopurinol and +0.79 (0.96) in the placebo group after 10 min reperfusion, the difference being significant (p = 0.043).

CONCLUSIONS

All patients in both groups had an increasing tendency to free radical production during early reperfusion. Patients treated with allopurinol showed less myocardial production of free radicals, indicating that its protective effect may be due to its antioxidative properties.

Excellence and low case volume: an example of the inapplicability of volume-based credentialing

BACKGROUND

Health care reform, public disclosure of hospital and surgeon-specific results, plus changes in reimbursement patterns have raised the specter of volume-based credentialing.

METHODS

Using The Society of Thoracic Surgeons Cardiac Database, we examined the data for all coronary artery bypass graft-only patients (n = 615) operated on by us from July 1991 to June 1997.

RESULTS

The observed mortality was 0.33% and the observed-to-expected ratio was 0.12 (p<0.005). Morbidity was low as well.

CONCLUSIONS

Excellent results can be obtained for patients undergoing coronary artery bypass grafting in the presence of both low surgeon and low hospital case volume.

Pathobiology and Clinical Impact of Reperfusion Injury

Reperfusion injury refers to cellular death or dysfunction caused by restoration of blood flow to previously ischemic tissue. This should be differentiated from the normal reparative processes that follow an ischemic insult. Four types of reperfusion injury have been described in the literature: (1) lethal reperfusion injury, (2) nonlethal reperfusion injury (myocardial stunning), (3) reperfusion arrhythmias, and (4) vascular injury (including the "no-reflow" phenomenon). There is continued debate whether reperfusion itself is capable of killing viable myocytes, which otherwise would have survived the ischemic insult. However, there is firm evidence for the existence of myocardial stunning following various ischemic syndromes, including reperfusion therapy for acute myocardial infarction, unstable angina pectoris, vasospastic angina, effort-induced ischemia, coronary artery bypass surgery, and cardiac transplantation. Reperfusion arrhythmia is more common after short ischemic episodes than after long ischemic periods. Thus, while reperfusion arrhythmias in the setting of acute myocardial infarction are relatively rare, reperfusion arrhythmias may be an important cause of sudden death. The "no-reflow" phenomenon has been described following reperfusion in patients with acute myocardial infarction. Three major components have been proposed as mediators of reperfusion injury: (1) oxygen free radicals, (2) the complement system, and (3) neutrophils. Numerous experimental studies have shown short-term benefit by blocking various stages of the postischemic inflammatory response. Oxygen free radicals scavangers, complement inhibition, leukocyte depletion, and the use of antibodies against various adhesion molecules have shown a reduction of infarct size in many ischemic/reperfusion experimental models. However, many of these agents failed to show a benefit in the clinical setting. Moreover, the long-term benefit of such intervention is still unknown.

Novel Insights Into the Pathogenesis and Therapy of Circulatory Shock

Several lines of evidence suggest central roles for nitric oxide, oxygen free radicals, cytokines, and adhesion molecules in circulatory shock. Lipid peroxidation fre quently accompanies ischemia-reperfusion injury; re cruitment of leukocytes exposed to ischemia-reperfu sion injury is largely dependent on leukocytes and endothelial cell adhesion interaction, enhanced nitric oxide stimulation by proinflammatory cytokines contrib utes to increased gut mucosal permeability in sepsis, and tumor necrosis factor (TNF) administration mimics the hemodynamic changes characteristic of circulatory shock. Recent advances in molecular and cellular biol ogy have paved the way for innovative approaches to the treatment of circulatory shock. Novel pharmaco logic approaches are being directed at three distinct levels of the inflammatory cascade: the inciting insult (ie, endotoxin), the mediators (ie, TNF, interleukin-1, oxygen free radicals), and the effector cells (ie, neutro phils). The intent of this review is to discuss the biology of mediators in circulatory shock as well as the experi mental and clinical evidence implicating their role in development and pathogenesis of the injury. Current status of novel adjunctive therapies for circulatory shock is reviewed.

Increased formation of the isoprostanes IPF2alpha-I and 8-epi-prostaglandin F2alpha in acute coronary angioplasty: evidence for oxidant stress during coronary reperfusion in humans

BACKGROUND

The role of oxidant stress in cardiac ischemia/reperfusion injury in humans remains controversial. This is due, in part, to the limitations of available indices of oxidant stress in vivo. Isoprostanes are stable, free radical-catalyzed products of arachidonic acid. We assessed their formation in patients undergoing coronary reperfusion via percutaneous transluminal coronary angioplasty (PTCA).

METHODS AND RESULTS

We developed specific, mass spectrometry assays for two structurally distinct F2 isoprostanes, 8-epi-PGF2alpha and IPF2alpha-I. Urine samples for isoprostane determination were collected in patients undergoing coronary arteriography (n=11), elective PTCA (n=15), and angiography after thrombolysis for acute myocardial infarction (MI) (n=10). Urinary levels (pmol/mmol creatinine) of both isoprostanes were markedly increased from baseline in the first 6 hours after PTCA for acute MI (105+/-17.8 versus 230+/-66 for 8-epi-PGF2alpha [P=.009] and 466+/-91 versus 833+/-153 for IPF2alpha-I [P=.001]) and returned toward preprocedural values by 24 hours (122+/-18 for 8-epi-PGF2alpha and 457+/-102 for IPF2alpha-I). There was a slight increase in urinary 8-epi-PGF2alpha levels (64.7+/-9.5 versus 84.9+/-10.6; P=.02) after diagnostic coronary arteriography and elective PTCA (88.7+/-7.5 versus 114.3+/-16.1; P=.01). A striking correlation was observed (r=.68, P<.0001; n=33) between urinary 8-epi-PGF2alpha and IPF2alpha-I levels in patients receiving thrombolytic agents for acute MI.

CONCLUSIONS

Urinary F2 isoprostane levels are elevated in patients after treatments resulting in reperfusion for acute MI. These findings provide evidence consistent with increased oxidant stress in vivo in this setting. Measurement of urinary isoprostanes may offer a noninvasive approach to the assessment of oxidant stress and the efficacy of antioxidant therapies in these syndromes.

[Reperfusion arrhythmias in valvular patients undergoing extracorporeal surgery and pretreated with captopril]

INTRODUCTION AND OBJECTIVES

After the ischemia-reperfusion process in extracorporeal cardiac surgery there are, among several phenomena, some reperfusion arrhythmias which are influenced by a varied series of mechanisms. These arrhythmias have been related to the release of oxygen-derived free radicals during the first moments of reperfusion. Thus, a previous administration of free-radical scavengers might be beneficial, among which captopril has been included with good results in human studies in vitro and in animals in vivo. The aim of this study was to evaluate the influence of pretreatment with captopril on the prevention of reperfusion arrhythmias in patients undergoing valvular cardiac surgery.

METHODS

30 patients were randomly allocated to pretreatment with either captopril (CTP group, n = 15) or without captopril (CON group, n = 15). Exclusion criteria (left ventricular ejection fraction < 40%, evidence of angiographic coronary disease, prior myocardial infarction and preoperatory myocardial infarction). The dose of captopril administered was 12.5 mg every 8 hours orally, from 24 hours before surgery. A Holter register was used to analyze the ventricular arrhythmias (extrasystoles, salvos, tachycardia and fibrillation) during the first hour of reperfusion. The need for cardioversion was examined and the number of shocks needed. These events were related to changes in blood analyses from coronary sinus samples to determine creatine phosphokinase, activity of the angiotensin converting enzyme and cyclic adenosine monophosphate, before aortic clamping and after the heart was rewarmed.

RESULTS

No significant differences were found in the number of ventricular arrhythmias. 60% of the patients with captopril and only 40% of the patients without it (non significant) had spontaneous defibrillation without electric shock; in those cases in which it was necessary, the number of shocks was less in the captopril group (p < 0.05). Excepting the significant correlation (p < 0.01) that we have found between ventricular fibrillation and the cyclic adenosine monophosphate increase, there is no significant correlation between the other arrhythmias and the analytical data studied.

CONCLUSIONS

These data suggest that captopril, given before cardiac surgery, has little or no protector effect on reperfusion ventricular arrhythmias in extracorporeal cardiac surgery, though in patients treated with captopril there is a greater possibility of spontaneous defibrillation and fewer shocks necessary for defibrillation, without negative effects.

Failure of allopurinol to improve left ventricular stroke work after cardiopulmonary bypass surgery

OBJECTIVE

This study examined the effects of allopurinol on global left ventricular function after coronary artery bypass surgery.

DESIGN

A randomized prospective partially blinded study in 52 patients undergoing elective coronary artery bypass surgery.

SETTING

Conducted in a university-affiliated tertiary care facility.

INTERVENTIONS

Participants received 400 mg of allopurinol 18 hours and 400 mg of allopurinol orally 3 hours before surgery or no allopurinol. Patients then received a standard anesthetic technique consisting of target-controlled opiate infusion and inhalation anesthesia. Coronary artery bypass was performed using moderate hypothermia and oxygenated crystalloid cardioplegia.

MEASUREMENTS AND MAIN RESULTS

Global left ventricular function was assessed by means of left ventricular stroke work index (LVSWI) calculated before and after induction of anesthesia and after cardiopulmonary bypass at 15 minutes, 6, 12 and 24 hours. There was no difference in the LVSWI before or after surgery when the two groups were compared.

CONCLUSIONS

In this population sample, the use of preoperative allopurinol did not result in improved left ventricular stroke work after coronary artery bypass surgery.