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

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.

Allopurinol and the risk of incident peripheral arterial disease in the elderly: a US Medicare claims data study

Objective

The aim was to examine whether allopurinol use is independently associated with a reduction in the risk of incident peripheral arterial disease (PAD) in the US elderly.

Methods

We used the 5% random Medicare sample from 2006 to 2012 to examine the association of allopurinol use and duration of use with the risk or hazard of incident PAD in a retrospective cohort study using a new user design. Multivariable Cox regression models adjusted for demographics, co-morbidity, cardiac medications and cardiac conditions. Hazard ratios (HRs) and 95% CIs were calculated.

Results

We identified 26 985 episodes of incident allopurinol use in 25 282 beneficiaries; 3167 allopurinol use episodes (12%) ended in incident PAD. In multivariable-adjusted analyses, allopurinol use was associated with an HR of 0.88 (95% CI: 0.81, 0.95) for incident PAD, as was female gender, HR 0.84 (95% CI: 0.78, 0.90). In a separate multivariable-adjusted model, compared with no allopurinol use, longer durations of allopurinol use were associated with lower HR of PAD: 181 days to 2 years, 0.88 (95% CI: 0.79, 0.97); and >2 years, 0.75 (95% CI: 0.63, 0.89). Other factors significantly associated with a higher HR of PAD were age 75 to < 85 and ⩾85 years, higher Charlson index score and black race. Sensitivity analyses that adjusted for cardiac conditions and medications confirmed these findings, with minimal to no attenuation of HRs.

Conclusion

New allopurinol use was independently associated with a lower risk of PAD in the elderly. Longer allopurinol use durations seemed more protective. Mechanisms of the protective effect need to be investigated in future studies.

Allopurinol reduces the risk of myocardial infarction (MI) in the elderly: a study of Medicare claims

BACKGROUND

Previous observational studies that have examined the association of allopurinol with myocardial infarction (MI) have provided contradictory results. One study showed that allopurinol reduced the risk, while another study showed an increased risk with allopurinol. Therefore, our objective was to assess whether allopurinol use is associated with a reduction in the risk of MI in the elderly.

METHOD

We used the 2006-2012 5 % random sample of Medicare beneficiaries to study the association of new allopurinol initiation and the risk of incident MI in a cohort study. Multivariable-adjusted Cox regression models adjusted for age, gender, race, and Charlson index, in addition to various cardio-protective medications (beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, diuretics, statins). We calculated hazard ratios (HRs) with 95 % confidence intervals (CIs). Sensitivity analyses adjusted for coronary artery disease (CAD) risk factors, including hypertension, hyperlipidemia, diabetes, and smoking.

RESULTS

Of the 29,298 episodes of incident allopurinol use, 1544 were associated with incident MI (5.3 % episodes). Allopurinol use was associated with reduced hazards of MI, with a HR of 0.85 (95 % CI, 0.77 to 0.95). Compared to no allopurinol use, longer durations of allopurinol use were associated with a lower HR of MI: 1-180 days, 0.98 (95 % CI, 0.84 to 1.14); 181 days to 2 years, 0.83 (95 % CI, 0.72 to 0.95); and >2 years, 0.70 (95 % CI, 0.56 to 0.88). Other factors associated with a higher hazard of MI were: age 75 to <85 years and ≥85 years, male gender, higher Charlson index score, and the use of an ACE inhibitor. Adjustment for CAD risk factors confirmed these findings.

CONCLUSION

Incident allopurinol use was associated with a reduction in the risk of incident MI in the elderly. Longer durations of allopurinol use reduced the risk of incident MI incrementally. Future studies should assess the underlying mechanisms for MI prevention and assess the risk-benefit ratio for allopurinol use.

Admission hyperuricemia increases the risk of acute kidney injury in hospitalized patients(.)

Background

The association between elevated admission serum uric acid (SUA) and risk of in-hospital acute kidney injury (AKI) is limited. The aim of this study was to assess the risk of developing AKI in all hospitalized patients with various admission SUA levels.

Methods

This is a single-center retrospective study conducted at a tertiary referral hospital. All hospitalized adult patients who had admission SUA available from January 2011 through December 2013 were analyzed in this study. Admission SUA was categorized based on its distribution into six groups (<3.4, 3.4–4.5, 4.5–5.8, 5.8–7.6, 7.6–9.4 and >9.4 mg/dL). The primary outcome was in-hospital AKI occurring after hospital admission. Logistic regression analysis was performed to obtain the odds ratio (OR) of AKI of various admission SUA levels using the most common SUA level range (5.8–7.6 mg/dL) as the reference group.

Results

Of 1435 patients enrolled, AKI occurred in 263 patients (18%). The incidence of AKI and need for dialysis was increased in patients with higher admission SUA levels. After adjusting for potential confounders, SUA >9.4 mg/dL was associated with an increased risk of developing AKI, with ORs of 1.79 [95% confidence interval (CI) 1.13–2.82]. Conversely, admission SUA <3.4 and 3.4–4.5 mg/dL were associated with a decreased risk of developing AKI, with ORs of 0.38 (95% CI 0.17–0.75) and 0.50 (95% CI 0.28–0.87), respectively.

Conclusions

Elevated admission SUA was associated with an increased risk for in-hospital AKI.

Elevated uric acid increases the risk for acute kidney injury

BACKGROUND

Uric acid has been proposed to play a role in acute kidney injury. We therefore investigated the potential influence of preoperative serum uric acid (SUA) on acute kidney injury in patients undergoing cardiovascular (CV) surgery. The primary aims were to investigate the incidence of acute kidney injury, peak serum creatinine (SCr) concentrations, hospital length of stay, and days on mechanical ventilation.

METHODS

Retrospective study included patients who underwent CV surgery and had preoperative SUA available. Acute kidney injury was defined as an absolute increase in SCr ≥0.3 mg/dL from baseline within 48 hours after surgery. Univariate and multivariate logistic regression analysis was performed to determine the odds ratio for acute kidney injury.

RESULTS

There were 190 patients included for analysis. SUA were divided into deciles. The incidences of acute kidney injury were higher with higher deciles of SUA. When the incidences of acute kidney injury were plotted against all available values of SUA at increments of 0.5 mg/dL, a J-shaped curve emerged demonstrating higher incidences of acute kidney injury associated with both hypo- and hyperuricemia. In the univariate analysis, SUA ≥5.5 mg/dL was associated with a 4-fold (odds ratio [OR] 4.4; 95% confidence interval [CI], 2.4-8.2), SUA ≥6 mg/dL with a 6-fold (OR 5.9; 95% CI, 3.2-11.3), SUA ≥6.5 mg/dL with an 8-fold (OR 7.9; 95% CI, 3.9-15.8), and SUA ≥7 mg/dL with a 40-fold (OR 39.1; 95% CI, 11.6-131.8) increased risk for acute kidney injury. In the multivariate analysis, SUA ≥7 mg/dL also was associated with a 35-fold (OR 35.4; 95% CI, 9.7-128.7) increased risk for acute kidney injury. The 48-hour postoperative and hospital-stay mean peak SCr levels also were higher in the SUA ≥5.5 mg/dL group compared with the SUA <5 mg/dL group. SUA ≥7 mg/dL was associated with increased length of hospital stay (SUA <7 mg/dL, 18.5 ± 1.8 days vs SUA ≥7 mg/dL, 32.0 ± 6.8 days, P = 0.058) and a longer duration of mechanical ventilation support (SUA <7 mg/dL, 2.4 ± 0.4 days vs SUA ≥7 mg/dL, 20.4 ± 4.5 days, P = 0.001).

CONCLUSION

Preoperative SUA was associated with increased incidence and risk for acute kidney injury, higher postoperative SCr values, and longer hospital length of stay and duration of mechanical ventilation support in patients undergoing cardiac surgery. A J-shaped relationship appears to exist between SUA and acute kidney injury.

Hyperuricemia and untreated gout are poor prognostic markers among those with a recent acute myocardial infarction

Introduction

Patients with a history of myocardial infarction (MI) are often at risk for complications, including subsequent MI and death. Use of prognostic markers may aid in preventing these poor outcomes. Hyperuricemia is associated with increased risk for coronary heart disease (CHD) and/or mortality; however, it is unknown if serum urate (sUA) levels predict outcomes in patients with previous MI. The purpose of this study was to assess hyperuricemia as a biomarker of CHD outcomes in such patients.

Methods

These were post hoc analyses of datasets from the Aspirin Myocardial Infarction Study, a 1:1 randomized, double-blind clinical trial, conducted from 1975 to 1979, that examined mortality rates following daily aspirin administration over three years in individuals with documented MI. The primary outcome measures were all-cause death, CHD mortality, coronary incidence, and stroke by quartile of baseline sUA. A sub-analysis of all outcome measures in the presence or absence of gouty arthritis was also performed.

Results

Of 4,524 enrolled participants, data on 4,352 were analyzed here. All outcomes were greatest for patients in the fourth sUA quartile. In multivariate regression models, the hazard ratios (HR) for patients in the highest quartile were 1.88 for all-cause mortality (95% confidence interval (CI), 1.45 to 2.46), 1.99 for CHD mortality (95% CI, 1.49 to 2.66), and 1.36 for coronary incidence (95% CI, 1.08 to 1.70). Participants with untreated gout had an adjusted hazard ratio ranging from 1.5 to 2.0 (all P < 0.01) for these outcomes. Participants with gout who were receiving treatment did not exhibit this additional risk.

Conclusions

sUA and untreated gout may be independent prognostic markers for poor all-cause and CHD mortality in patients with recent acute MI.

Use of electron paramagnetic resonance spectroscopy to evaluate the redox state in vivo

The aim of this article is to provide an overview of how electron paramagnetic resonance (EPR) can be used to measure redox-related parameters in vivo. The values of this approach include that the measurements are made under fully physiological conditions, and some of the measurements cannot be made by other means. Three complementary approaches are used with in vivo EPR: the rate of reduction or reactions of nitroxides, spin trapping of free radicals, and measurements of thiols. All three approaches already have produced unique and useful information. The measurement of the rate of decrease of nitroxides technically is the simplest, but difficult to interpret because the measured parameter, reduction in the intensity of the nitroxide signal, can occur by several different mechanisms. In vivo spin trapping can provide direct evidence for the occurrence of specific free radicals in vivo and reflect relative changes, but accurate absolute quantification remains challenging. The measurement of thiols in vivo also appears likely to be useful, but its development as an in vivo technique is at an early stage. It seems likely that the use of in vivo EPR to measure redox processes will become an increasingly utilized and valuable tool.

Relationship between oxidative stress, lipid peroxidation, and ultrastructural damage in patients with coronary artery disease undergoing cardioplegic arrest/reperfusion

OBJECTIVE

In animal models, formation of oxidants during postischemic reperfusion may exert deleterious effects ("oxidative stress"). Cardioplegic arrest/reperfusion during cardiac surgery might similarly induce oxidative stress. However, the phenomenon has not been precisely characterized in patients, and therefore the role of antioxidant therapy at cardiac surgery is a matter of debate. Thus, we wanted to ascertain whether the relationship between oxidant formation and development of myocardial injury also translates to the situation of patients subjected to cardioplegic arrest.

METHODS

In 24 patients undergoing coronary artery bypass, trans-cardiac blood samples and myocardial biopsies were taken before cardioplegic arrest and again following reperfusion.

RESULTS

Cardiac glutathione release (marker of oxidant production) was negligible at baseline (0.02+/-0.04 micromol/L), but it increased 15 min into reperfusion (1.10+/-0.40 micromol/L; p<0.05); concomitantly, myocardial concentration of the antioxidant ubiquinol decreased from 144.5+/-52.0 to 97.6+/-82.0 nmol/g (p<0.05). Although these changes document cardiac exposure to oxidants, they were not accompanied by evidence of injury. Neither coronary sinus blood nor cardiac biopsies showed increased lipid peroxide concentrations. Furthermore, electron microscopy showed no major ultrastructural alterations. Finally, full recovery of left ventricular systolic and diastolic function was observed.

CONCLUSIONS

Careful investigation reveals that while oxidant production does occur during cardiac surgery in patients with chronic ischemic heart disease, cardiac oxidative stress may not progress through membrane damage and irreversible injury.

Measuring reactive species and oxidative damage in vivo and in cell culture: how should you do it and what do the results mean?

Free radicals and other reactive species (RS) are thought to play an important role in many human diseases. Establishing their precise role requires the ability to measure them and the oxidative damage that they cause. This article first reviews what is meant by the terms free radical, RS, antioxidant, oxidative damage and oxidative stress. It then critically examines methods used to trap RS, including spin trapping and aromatic hydroxylation, with a particular emphasis on those methods applicable to human studies. Methods used to measure oxidative damage to DNA, lipids and proteins and methods used to detect RS in cell culture, especially the various fluorescent "probes" of RS, are also critically reviewed. The emphasis throughout is on the caution that is needed in applying these methods in view of possible errors and artifacts in interpreting the results.

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.

Uric acid and survival in chronic heart failure: validation and application in metabolic, functional, and hemodynamic staging

BACKGROUND

Serum uric acid (UA) could be a valid prognostic marker and useful for metabolic, hemodynamic, and functional (MFH) staging in chronic heart failure (CHF).

METHODS AND RESULTS

For the derivation study, 112 patients with CHF (age 59+/-12 years, peak oxygen consumption [Vo2] 17+/-7 mL/kg per minute) were recruited. In separate studies, we validated the prognostic value of UA (n=182) and investigated the relationship between MFH score and the decision to list patients for heart transplantation (n=120). In the derivation study, the best mortality predicting UA cutoff (at 12 months) was 565 micromol/L (9.50 mg/dL) (independently of age, peak Vo2, left ventricular ejection fraction, diuretic dose, sodium, creatinine, and urea; P<0.0001). In the validation study, UA >or=565 micromol/L predicted mortality (hazard ratio, 7.14; P<0.0001). In 16 patients (from both studies) with UA >or=565 micromol/L, left ventricular ejection fraction <or=25% and peak Vo2 <or=14 mL/kg per min (MFH score 3), 12-month survival was lowest (31%) compared with patients with 2 (64%), 1 (77%), or no (98%, P<0.0001) risk factor. In an independent study, 51% of patients with MFH score 2 and 81% of patients with MFH score 3 were listed for transplantation. The positive predictive value of not being listed for heart transplantation with an MFH score of 0 or 1 was 100%.

CONCLUSIONS

High serum UA levels are a strong, independent marker of impaired prognosis in patients with moderate to severe CHF. The relationship between serum UA and survival in CHF is graded. MFH staging of patients with CHF is feasible.