Background The benefit of blood transfusion in patients with myocardial infarction is controversial, and a possibility of harm exists.
Methods A systematic search of studies published between January 1, 1966, and March 31, 2012, was conducted using MEDLINE, EMBASE, CINAHL, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials databases. English-language studies comparing blood transfusion with no blood transfusion or a liberal vs restricted blood transfusion strategy were identified. Two study authors independently reviewed 729 originally identified titles and abstracts and selected 10 for analysis. Study title, follow-up period, blood transfusion strategy, and mortality outcomes were extracted manually from all selected studies, and the quality of each study was assessed using the strengthening Meta-analysis of Observational Studies in Epidemiology checklist.
Results Studies of blood transfusion strategy in anemia associated with myocardial infarction were abstracted, as well as all-cause mortality rates at the longest available follow-up periods for the individual studies. Pooled effect estimates were calculated with random-effects models. Analyses of blood transfusion in myocardial infarction revealed increased all-cause mortality associated with a strategy of blood transfusion vs no blood transfusion during myocardial infarction (18.2% vs 10.2%) (risk ratio, 2.91; 95% CI, 2.46-3.44; P < .001), with a weighted absolute risk increase of 12% and a number needed to harm of 8 (95% CI, 6-17). Multivariate meta-regression revealed that blood transfusion was associated with a higher risk for mortality independent of baseline hemoglobin level, nadir hemoglobin level, and change in hemoglobin level during the hospital stay. Blood transfusion was also significantly associated with a higher risk for subsequent myocardial infarction (risk ratio, 2.04; 95% CI, 1.06-3.93; P = .03).
Conclusions Blood transfusion or a liberal blood transfusion strategy compared with no blood transfusion or a restricted blood transfusion strategy is associated with higher all-cause mortality rates. A practice of routine or liberal blood transfusion in myocardial infarction should not be encouraged but requires investigation in a large trial with low risk for bias.
Thrombolysis, anticoagulation, and antiplatelet drugs have revolutionized the therapeutic approach to acute coronary syndrome, with significant improvements in clinical outcomes.1-7 However, such therapy may concomitantly increase the risk for bleeding, leading to the development of anemia during the hospital stay and to subsequent blood transfusion.8-10Quiz Ref IDDespite advancement in reperfusion therapy, patients with low hemoglobin levels continue to have more postoperative complication and higher mortality rates,11-14 and the presence of anemia in acute myocardial infarction has been associated with worse prognosis.15-19
In patients with significant coronary occlusion, low oxygen-carrying capacity secondary to anemia may further compromise the myocardial oxygen supply, worsening the ischemia. By increasing the oxygen-carrying capacity, blood transfusion might be beneficial, especially in anemia secondary to acute blood loss. However, inappropriate blood transfusion may lead to circulatory overload and increased thrombogenicity, which can worsen the clinical outcomes. Furthermore, elevated hemoglobin levels have been shown to be associated with increased mortality.11,19 In post hoc analyses of a multicenter randomized controlled trial, Hébert et al20 reported no mortality benefits of liberal blood transfusion in maintaining hemoglobin levels of at least 10 mg/mL in critically ill patients with cardiovascular disease. However, because patients receiving blood transfusion tend to be older and have advanced disease and more associated comorbid conditions, these variables may act as confounding factors when determining mortality and morbidity rates.21-23 Because of conflicting results reported in various investigations, the benefits and harm of blood transfusion in myocardial infarction remain controversial. In the present meta-analysis, we systematically evaluated the potential risk-benefit of blood transfusion in patients with myocardial infarction.
Data sources and searches
A systematic search of studies published between January 1, 1966, and March 31, 2012, was conducted using MEDLINE, EMBASE, CINAHL, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials databases. Studies were identified that evaluated mortality outcomes and compared blood transfusion with no blood transfusion or a liberal vs restricted blood transfusion strategy. The search terms used were transfusion, myocardial infarction, and mortality. Pertinent trials were also searched for in clinicaltrials.gov and in proceedings from major international cardiology meetings (American College of Cardiology, American Heart Association, European Society of Cardiology, and Transcatheter Cardiovascular Therapeutics). References of original and review articles were cross-checked. Study selection was performed by 2 of us independently (S.C. and A.S.), with disagreement resolved by consensus among all the authors. Citations were first reviewed at the title and abstract level. Studies that were short-listed were then retrieved in full text.
Studies were considered suitable for inclusion if they met the following criteria: (1) they reported the effect of blood transfusion or a liberal blood transfusion strategy (blood transfusion levels at which there was no blood transfusion in the comparator arm) on mortality, (2) they had a comparator group with no blood transfusion or a restricted blood transfusion strategy and identified a mean hemoglobin level for both groups, and (3) they used statistical methods to minimize confounding between the groups (matching, covariate adjustment, or propensity-based adjustment). Our search was restricted to studies in the English language. Full texts of 16 potentially relevant articles were independently reviewed by at least 2 of us (S.C. and A.S.) to establish eligibility according to the inclusion criteria. To avoid confounding, we excluded studies assessing the effect of transfusion of components other than whole blood or red blood cells.
Data extraction and quality assessment
Data abstraction and study appraisal were performed by 2 of us (S.C. and A.S.) independently, with disagreement resolved by consensus among all authors. Key study and patient characteristics were extracted, including the outcomes of all-cause mortality and myocardial infarction reported at the longest available follow-up periods. Prespecified subgroup analyses were planned for patients with ST-segment elevation myocardial infarction (STEMI) and for patients with a hematocrit of less than 30% (to convert hematocrit to a proportion of 1.0, multiply by 0.01).
Data analyses were performed using commercially available software (RevMan 5.1 [Cochran IMS], TSA version 0.9 [Copenhagen Trial Unit], and STATA version 11 [StataCorp LP]). Outcomes were assessed using random-effects models to exclude the presence of significant heterogeneity (evaluated and quantified with the I2 statistic), and then pooled random-effects risk ratios (RRs [95% CIs]) were calculated following the method by DerSimonian and Laird.
The quality of the studies was assessed on the basis of elements from the strengthening Meta-analysis Of Observational Studies in Epidemiology checklist for cohort studies. We did not assign a threshold for study inclusion. All the studies included in the analyses met at least 15 variables in the checklist.
Data synthesis and analysis
When available, odds ratios (ORs) reported in the articles were used to determine event rates, and unadjusted ORs (95% CIs) were used preferentially over adjusted ORs to avoid bias from different types of adjustments in the various studies.24 If ORs were not reported, we calculated them using the event and sample size frequencies. If frequencies were not given, ORs were estimated from percentages and were rounded to the nearest integer. If any cell had a 0 count, ORs were calculated by adding 0.5 to all cell counts from the study to avoid division by 0. The I2 statistic was used to examine the heterogeneity of effect sizes in the overall aggregations: I2 of less than 25% indicates low heterogeneity, and I2 exceeding 75% indicates high heterogeneity. Publication bias was evaluated using a combination of a funnel plot–based method, the regression test by Egger, and the trim-and-fill method to estimate the number of missing studies and to calculate a corrected OR as if these studies were present. The effect of potential outliers was examined by comparing the pooled estimate with estimates obtained after iterations using k minus 1 findings (each study is left out, and the effect is reestimated), where k is the number of studies. Studies were treated as statistical outliers if the k minus 1 estimate produced a 95% CI that did not overlap with the 95% CI of the aggregated estimate. P < .05 was considered statistically significant.
Study sequential analysis
In a single study, interim analyses increase the risk for type I error. To avoid an increase of overall type I error, monitoring boundaries can be applied to decide whether a single study could be terminated early because the P value is sufficiently small. Because no reason exists why the standards for a meta-analysis should be less rigorous than those for a single study, analogous study sequential monitoring boundaries can be applied to meta-analysis as study sequential analysis.25,26 Cumulative meta-analyses of studies are at risk for producing random errors because of few data27 and repetitive testing of accumulating data and because the requirement for the amount of information analogous to the sample size of a single optimally powered clinical study might not be met.25,26
The underlying assumption for study sequential analysis is that significance testing and calculation of the 95% CIs are performed each time a new study is published. Study sequential analysis depends on the quantification of the required amount of information. In this context, the smaller the required amount is, the more lenient is the trial sequential analysis and the more lenient are the criteria for significance.25,26 A required diversity (D2)–adjusted information size was calculated, with D2 being the relative variance reduction when the meta-analysis model is changed from a random-effects model to a fixed-effects model.28D2 is the percentage of the variability between trials to the within-trial variance and constitutes the percentage of the variability between trials to the total variance in the meta-analysis. D2 is different from the intuitively obvious adjusting factor based on the common quantification of heterogeneity, the inconsistency (I2 statistic), which might underestimate the required information size.28
Study sequential analysis was performed with an intent to maintain an overall 5% risk for type I error, which is the standard in most meta-analyses and systematic reviews, and we calculated the required information size (ie, the meta-analysis information size needed to detect or reject an intervention effect of a 20% relative risk increase for harm, with a risk for type II error of 10%, at a power of 90%).25,26 Study monitoring boundaries were constructed with the conventional test boundary and using methods by O’Brien and Fleming.29
Our MEDLINE search returned 720 studies. After elimination of duplicate results, EMBASE, Cochrane Central Register of Controlled Trials, and the other registries returned 9 additional studies, leaving 729 studies for evaluation. Through a review of titles and abstracts, 705 studies were rejected for relevance. The remaining 24 articles were reviewed and assessed for satisfaction of the inclusion and exclusion criteria. Ten studies that met all criteria were included in this analysis (Figure 1).
Studies were fairly homogeneous for inclusion and exclusion criteria, with a few key differences. These results are summarized in Table 1.
We used the published strengthening Meta-analysis Of Observational Studies in Epidemiology40 checklist to select the studies for this review (Figure 1). The included studies reported statistically adjusted effect estimates for the outcome of mortality. Quiz Ref IDAmong 10 studies included, all except one (low-bias risk) were intermediate-bias risk studies as assessed by the Newcastle-Ottawa Scale41 for quality assessment risk evaluation of adequacy of selection, comparability, and outcomes assessment for individual studies (Table 2).
We identified 10 studies,30-39 including 203 665 study participants, that met our inclusion and exclusion criteria. Only one study31 was a randomized trial; the others were observational studies.Quiz Ref IDAnalyses of blood transfusion in myocardial infarction revealed increased all-cause mortality associated with a strategy of blood transfusion vs no blood transfusion during myocardial infarction (18.2% vs 10.2%) (RR, 2.91; 95% CI, 2.46-3.44; P < .001), with a weighted absolute risk increase of 12% (P < .001) and a number needed to harm of 8 (95% CI, 6-17). The risk remained unchanged even on exclusion of the only randomized study.31 Pooled analysis using adjusted rates of mortality instead of the actual number of events yielded an effect largely similar to that of the primary analysis (eFigure 1). However, the mortality risk with blood transfusion was found to be mitigated when restricted to studies that included patients with STEMI (RR, 2.89; 95% CI, 0.54-15.58; P = .22) and patients with a baseline hematocrit of less than 30% (RR, 1.72; 95% CI, 0.39-7.63; P = .47) (eFigure 2 and eFigure 3). Multivariate meta-regression were performed using the log of the RR as the dependent variable and adjusting for the following variables as covariates: follow-up period, history of bleeding, baseline creatinine level, baseline hemoglobin level, nadir of hemoglobin level, and change in hemoglobin level during the hospital stay, as well as the use of glycoprotein IIb or IIIa, thrombolytics, or antiplatelets. The meta-regression showed that blood transfusion is associated with higher mortality after adjustment for all these variables. However, we could not adjust for demographic variables in the multivariate model because we did not have patient-level data. Significant heterogeneity was noted among the outcomes (I2 = 93%) (Figure 2). A sensitivity analysis performed by sequentially excluding one study at a time and performing a cumulative evaluation identified no single study as the source of heterogeneity. No significant publication bias was noted among the outcomes with visual inspection of the funnel plot, the regression test by Egger (P = .40), or with trim-and-fill adjustment (Figure 3).
Study sequential analysis
The required diversity-adjusted information size (D2 = 97%) for the outcome of all-cause mortality was calculated based on analyzing a 10.2% proportion of events in the no blood transfusion or a restricted blood transfusion strategy group and evaluating for a 20% relative risk increase with blood transfusion or a liberal blood transfusion strategy at α = .05 and β = .10 (90% power). The cumulative z curves (calculated with both the conventional test boundary and the methods by O’Brien and Fleming)29 crossed the study sequential monitoring boundary of harm, suggesting firm evidence for a 20% relative risk increase with blood transfusion or a liberal blood transfusion strategy compared with no blood transfusion or a restricted blood transfusion strategy (Figure 4). We also constructed a L’Abbé plot42 and a small study regression graph to avoid a possible error with the effect of inclusion of small studies on the composite outcome.
Blood transfusion was also significantly associated with a higher risk for subsequent myocardial infarction (RR, 2.04; 95% CI, 1.06-3.93; P = .03). Significant heterogeneity was present for this outcome (I2 = 98%) as well. No significant publication bias was detected (Figure 5).
Several important clinical findings emerged from our systematic review and meta-analysis. First and foremost, a significant mortality risk is demonstrated with a policy of liberal blood transfusion in patients with myocardial infarction, especially in those patients without STEMI or with a hematocrit of less than 30%, bringing to light a real possibility of harm with the practice of routine blood transfusion in patients with myocardial infarction. The mortality outcome was associated with statistically significant heterogeneity, likely associated with concomitant therapies, heterogeneity in the patient population, and clinical settings (which could not be adjusted for in our analysis because of the unavailability of patient-level data) , but might also be due to the precision of the large observational studies, conferring an artificially high I2 statistic. Also notable was the fact that the results remained unchanged with meta-regression adjusting for certain variables, including the follow-up period, a history of bleeding, baseline hemoglobin level, nadir of hemoglobin level, and change in hemoglobin level during the hospital stay, indicating a significant risk for blood transfusion over and above that associated with bleeding (and anemia) in myocardial infarction.43 The single randomized trial included in our analysis, the Conservative Versus Liberal Red Cell Transfusion in Acute Myocardial Infarction Trial,31 had a small sample size and was underpowered to make any relevant conclusions regarding clinically important intervention effects. We attempted to overcome the risk for increased random error due to sparse data and repetitive testing in our analysis by constructing study sequential monitoring boundaries, and our results indicated that random error was not the greatest risk in our meta-analysis. However, confounding by indication may be an important problem because the patients liberally transfused may also be the patients with the most serious disease and at the greatest risk for mortality as estimated by prognostic factors at baseline independent of the interventions subsequently used. We also drew a regression plot to avoid overestimating the effects of small studies on the overall outcomes. Our 95% CIs were narrow, with a large sample size, indicating at least a possibility of real harm with liberal and indiscriminate blood transfusion practices.
Quiz Ref IDOf even greater concern was our finding of a significantly greater risk for myocardial reinfarction with blood transfusion. This finding seems to conform to recent findings of detrimental effects on platelet aggregation with blood transfusion.44 Overall, our findings are consistent with recent recommendations by the AABB (formerly the American Association of Blood Banks)45 and in a prior Cochrane review46 for a restrictive blood transfusion policy in critically ill patients. Our analysis attempts to address the lacuna in the knowledge about blood transfusion practices among patients with acute coronary syndromes as expressed in the aforementioned guidelines by providing an updated meta-analysis on the topic in the absence of an adequately powered randomized trial.
We also found that the risks for blood transfusion became mitigated during our subgroup analyses in patients with STEMI and in patients with a baseline hematocrit of less than 30%. This suggests a future direction of further research in identifying specific subgroups that may accrue a real benefit from blood transfusion, overcoming its detrimental influence.47,48
Our study had several methodological limitations. Quiz Ref IDAll the studies but one in our meta-analysis were observational, diverse study designs and patient characteristics made interpretation of aggregated estimates challenging, and causality could not be inferred. In addition, despite our efforts at adjusting for different variables, the relevance and reliability of the results were limited. For more definitive conclusions, randomized designs by blood transfusion at different hemoglobin levels and hematocrits and relevant outcomes are needed. For these analyses, we had only summary estimates and were unable to adjust for important patient-level covariates. Red blood cell transfusion may be a surrogate for other variables that could have favorable or adverse effects on outcomes (eg, baseline risk, infection, adenosine diphosphate, and soluble CD40 ligand).49,50 However, these variables were not reported in the studies used for this analysis and could not be considered. We also restricted our search to English-language sources.
Our study method also had several strengths. The magnitude and consistency of the observed effects for blood transfusion in myocardial infarction make the likelihood of random error affecting this observation unlikely. Moreover, we rigorously controlled for publication bias and used random-effects models, which are generally better suited when studies are gathered only from the published literature. We also evaluated for the validity of our mortality findings by constructing study sequential monitoring boundaries and inferred that our results indicated a firm evidence of harm with a practice of liberal blood transfusion in myocardial infarction.
In conclusion, this meta-analysis provides evidence that rates of all-cause mortality and subsequent myocardial infarction are significantly higher in patients with acute myocardial infarction receiving blood transfusion. Additional outcomes data are needed from randomized clinical trials that investigate important outcomes with adequate sample size and with low risk for bias.
Correspondence: Saurav Chatterjee, MD, Division of Cardiology, Department of Medicine, Brown University, and Providence Veterans Affairs Medical Center, 40 Roger Williams Green, Providence, RI 02904 (firstname.lastname@example.org).
Accepted for Publication: August 20, 2012.
Published Online: December 24, 2012. doi:10.1001/2013.jamainternmed.1001
Author Contributions: Dr Chatterjee had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Chatterjee, Wetterslev, and Lichstein. Acquisition of data: Chatterjee and Sharma. Analysis and interpretation of data: Chatterjee, Wetterslev, Lichstein, and Mukherjee. Drafting of the manuscript: Chatterjee, Wetterslev, and Sharma. Critical revision of the manuscript for important intellectual content: Chatterjee, Wetterslev, Lichstein, and Mukherjee. Statistical analysis: Chatterjee and Wetterslev. Administrative, technical, and material support: Chatterjee and Lichstein. Study supervision: Wetterslev, Lichstein, and Mukherjee.
Conflict of Interest Disclosures: None reported.
Anderson JL, Adams CD, Antman EM,
et al; American College of Cardiology; American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines for the Management of Patients With Unstable Angina/Non ST-Elevation Myocardial Infarction); American College of Emergency Physicians; Society for Cardiovascular Angiography and Interventions; Society of Thoracic Surgeons; American Association of Cardiovascular and Pulmonary Rehabilitation; Society for Academic Emergency Medicine. ACC/AHA 2007 guidelines for the management of patients with unstable angina/non ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines for the Management of Patients With Unstable Angina/Non ST-Elevation Myocardial Infarction): developed in collaboration with the American College of Emergency Physicians, the Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons: endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation and the Society for Academic Emergency Medicine. Circulation
. 2007;116(7):e148-e304http://circ.ahajournals.org/content/116/7/e148.long. Accessed October 5, 2012
Wright RS, Anderson JL, Adams CD,
et al. 2011 ACCF/AHA focused update of the Guidelines for the Management of Patients with Unstable Angina/Non-ST-Elevation Myocardial Infarction (updating the 2007 guideline): a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines developed in collaboration with the American College of Emergency Physicians, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons [published correction appears in Lancet
. 2002;359(9323):2120]. J Am Coll Cardiol
. 2011;57(19):1920-195921450428PubMedGoogle ScholarCrossref
Eikelboom JW, Anand SS, Malmberg K, Weitz JI, Ginsberg JS, Yusuf S. Unfractionated heparin and low-molecular-weight heparin in acute coronary syndrome without ST elevation: a meta-analysis. Lancet
. 2000;355(9219):1936-194210859038PubMedGoogle ScholarCrossref
Boersma E, Harrington RA, Moliterno DJ,
et al. Platelet glycoprotein IIb/IIIa inhibitors in acute coronary syndromes: a meta-analysis of all major randomised clinical trials. Lancet
. 2002;359(9302):189-19811812552PubMedGoogle ScholarCrossref
Steinhubl SR, Berger PB, Mann JT III,
et al; CREDO Investigators. Early and sustained dual oral antiplatelet therapy following percutaneous coronary intervention: a randomized controlled trial [published correction appears in JAMA
. 2003;289(8):987]. JAMA
. 2002;288(19):2411-242012435254PubMedGoogle ScholarCrossref
Antithrombotic Trialists' Collaboration. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. BMJ
. 2002;324(7329):71-8611786451PubMedGoogle ScholarCrossref
Yusuf S, Zhao F, Mehta SR, Chrolavicius S, Tognoni G, Fox KK.Clopidogrel in Unstable Angina to Prevent Recurrent Events Trial Investigators. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation. N Engl J Med
. 2001;345(7):494-50211519503PubMedGoogle ScholarCrossref
Moscucci M, Fox KA, Cannon CP,
et al. Predictors of major bleeding in acute coronary syndromes: the Global Registry of Acute Coronary Events (GRACE). Eur Heart J
. 2003;24(20):1815-182314563340PubMedGoogle ScholarCrossref
Alexander KP, Newby LK, Cannon CP,
et al; American Heart Association Council on Clinical Cardiology; Society of Geriatric Cardiology. Acute coronary care in the elderly, part I: non-ST-segment-elevation acute coronary syndromes: a scientific statement for healthcare professionals from the American Heart Association Council on Clinical Cardiology: in collaboration with the Society of Geriatric Cardiology. Circulation
. 2007;115(19):2549-256917502590PubMedGoogle ScholarCrossref
Segev A, Strauss BH, Tan M, Constance C, Langer A, Goodman SG.Canadian Acute Coronary Syndromes Registries Investigators. Predictors and 1-year outcome of major bleeding in patients with non-ST-elevation acute coronary syndromes: insights from the Canadian Acute Coronary Syndrome Registries. Am Heart J
. 2005;150(4):690-69416209967PubMedGoogle ScholarCrossref
Reinecke H, Trey T, Wellmann J,
et al. Haemoglobin-related mortality in patients undergoing percutaneous coronary interventions. Eur Heart J
. 2003;24(23):2142-215014643275PubMedGoogle ScholarCrossref
McKechnie RS, Smith D, Montoye C,
et al; Blue Cross Blue Shield of Michigan Cardiovascular Consortium (BMC2). Prognostic implication of anemia on in-hospital outcomes after percutaneous coronary intervention. Circulation
. 2004;110(3):271-27715226214PubMedGoogle ScholarCrossref
Lee PC, Kini AS, Ahsan C, Fisher E, Sharma SK. Anemia is an independent predictor of mortality after percutaneous coronary intervention. J Am Coll Cardiol
. 2004;44(3):541-54615358017PubMedGoogle ScholarCrossref
Carson JL, Duff A, Poses RM,
et al. Effect of anaemia and cardiovascular disease on surgical mortality and morbidity. Lancet
. 1996;348(9034):1055-10608874456PubMedGoogle ScholarCrossref
Arant CB, Wessel TR, Olson MB,
et al; National Heart, Lung, and Blood Institute Women's Ischemia Syndrome Evaluation Study. Hemoglobin level is an independent predictor for adverse cardiovascular outcomes in women undergoing evaluation for chest pain: results from the National Heart, Lung, and Blood Institute Women's Ischemia Syndrome Evaluation Study. J Am Coll Cardiol
. 2004;43(11):2009-201415172405PubMedGoogle ScholarCrossref
Nikolsky E, Mehran R, Aymong ED,
et al. Impact of anemia on outcomes of patients undergoing percutaneous coronary interventions. Am J Cardiol
. 2004;94(8):1023-102715476616PubMedGoogle ScholarCrossref
Vis MM, Sjauw KD, van der Schaaf RJ,
et al. Prognostic value of admission hemoglobin levels in ST-segment elevation myocardial infarction patients presenting with cardiogenic shock. Am J Cardiol
. 2007;99(9):1201-120217478141PubMedGoogle ScholarCrossref
Eikelboom JW, Mehta SR, Anand SS, Xie C, Fox KA, Yusuf S. Adverse impact of bleeding on prognosis in patients with acute coronary syndromes. Circulation
. 2006;114(8):774-78216908769PubMedGoogle ScholarCrossref
Sabatine MS, Morrow DA, Giugliano RP,
et al. Association of hemoglobin levels with clinical outcomes in acute coronary syndromes. Circulation
. 2005;111(16):2042-204915824203PubMedGoogle ScholarCrossref
Hébert PC, Yetisir E, Martin C,
et al; Transfusion Requirements in Critical Care Investigators for the Canadian Critical Care Trials Group. Is a low transfusion threshold safe in critically ill patients with cardiovascular diseases? Crit Care Med
. 2001;29(2):227-23411246298PubMedGoogle ScholarCrossref
Engoren MC, Habib RH, Zacharias A, Schwann TA, Riordan CJ, Durham SJ. Effect of blood transfusion on long-term survival after cardiac operation. Ann Thorac Surg
. 2002;74(4):1180-118612400765PubMedGoogle ScholarCrossref
Koch CG, Li L, Duncan AI,
et al. Morbidity and mortality risk associated with red blood cell and blood-component transfusion in isolated coronary artery bypass grafting. Crit Care Med
. 2006;34(6):1608-161616607235PubMedGoogle ScholarCrossref
Koch CG, Khandwala F, Li L, Estafanous FG, Loop FD, Blackstone EH. Persistent effect of red cell transfusion on health-related quality of life after cardiac surgery. Ann Thorac Surg
. 2006;82(1):13-2016798179PubMedGoogle ScholarCrossref
Deeks JJ, Dinnes J, D’Amico R,
et al; International Stroke Trial Collaborative Group; European Carotid Surgery Trial Collaborative Group. Evaluating non-randomised intervention studies. Health Technol Assess
. 2003;7(27):iii-x, 1-17314499048PubMedGoogle Scholar
Brok J, Thorlund K, Gluud C, Wetterslev J. Trial sequential analysis reveals insufficient information size and potentially false positive results in many meta-analyses. J Clin Epidemiol
. 2008;61(8):763-76918411040PubMedGoogle ScholarCrossref
Wetterslev J, Thorlund K, Brok J, Gluud C. Trial sequential analysis may establish when firm evidence is reached in cumulative meta-analysis. J Clin Epidemiol
. 2008;61(1):64-7518083463PubMedGoogle ScholarCrossref
Aronson D, Dann EJ, Bonstein L,
et al. Impact of red blood cell transfusion on clinical outcomes in patients with acute myocardial infarction. Am J Cardiol
. 2008;102(2):115-11918602505PubMedGoogle ScholarCrossref
Cooper HA, Rao SV, Greenberg MD,
et al. Conservative versus liberal red cell transfusion in acute myocardial infarction (the CRIT Randomized Pilot Study). Am J Cardiol
. 2011;108(8):1108-111121791325PubMedGoogle ScholarCrossref
Jani SM, Smith DE, Share D,
et al. Blood transfusion and in-hospital outcomes in anemic patients with myocardial infarction undergoing percutaneous coronary intervention. Clin Cardiol
. 2007;30(10):(suppl 2)
Jolicoeur EM, O’Neill WW, Hellkamp A,
et al; APEX-AMI Investigators. Transfusion and mortality in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention. Eur Heart J
. 2009;30(21):2575-258319596659PubMedGoogle ScholarCrossref
Nikolsky E, Mehran R, Sadeghi HM,
et al. Prognostic impact of blood transfusion after primary angioplasty for acute myocardial infarction: analysis from the CADILLAC (Controlled Abciximab and Device Investigation to Lower Late Angioplasty Complications) Trial. JACC Cardiovasc Interv
. 2009;2(7):624-63219628185PubMedGoogle ScholarCrossref
Rao SV, Jollis JG, Harrington RA,
et al. Relationship of blood transfusion and clinical outcomes in patients with acute coronary syndromes. JAMA
. 2004;292(13):1555-156215467057PubMedGoogle ScholarCrossref
Shishehbor MH, Filby SJ, Chhatriwalla AK,
et al. Impact of drug-eluting versus bare-metal stents on mortality in patients with anemia. JACC Cardiovasc Interv
. 2009;2(4):329-33619463445PubMedGoogle ScholarCrossref
Singla I, Zahid M, Good CB, Macioce A, Sonel AF. Impact of blood transfusions in patients presenting with anemia and suspected acute coronary syndrome. Am J Cardiol
. 2007;99(8):1119-112117437739PubMedGoogle ScholarCrossref
Wu WC, Rathore SS, Wang Y, Radford MJ, Krumholz HM. Blood transfusion in elderly patients with acute myocardial infarction. N Engl J Med
. 2001;345(17):1230-123611680442PubMedGoogle ScholarCrossref
Yang X, Alexander KP, Chen AY,
et al; CRUSADE Investigators. The implications of blood transfusions for patients with non-ST-segment elevation acute coronary syndromes: results from the CRUSADE National Quality Improvement Initiative. J Am Coll Cardiol
. 2005;46(8):1490-149516226173PubMedGoogle ScholarCrossref
Stroup DF, Berlin JA, Morton SC,
et al; Meta-analysis of Observational Studies in Epidemiology (MOOSE) Group. Meta-analysis of observational studies in epidemiology: a proposal for reporting: Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group. JAMA
. 2000;283(15):2008-201210789670PubMedGoogle ScholarCrossref
Kumbhani DJ, Bhatt DL. Platelet activation: yet another strike against routine TRANSFUSION. Eur Heart J
. 2010;31(22):2712-271420736242PubMedGoogle ScholarCrossref
Silvain J, Pena A, Cayla G,
et al. Impact of red blood cell transfusion on platelet activation and aggregation in healthy volunteers: results of the TRANSFUSION study. Eur Heart J
. 2010;31(22):2816-282120591842PubMedGoogle ScholarCrossref
Carson JL, Grossman BJ, Kleinman S,
et al; Clinical Transfusion Medicine Committee of the AABB. Red blood cell transfusion: a clinical practice guideline from the AABB. Ann Intern Med
. 2012;157(1):49-58Google Scholar
Carson JL, Carless PA, Hebert PC. Transfusion thresholds and other strategies for guiding allogeneic red blood cell transfusion. Cochrane Database Syst Rev
. 2012;4:CD00204222513904PubMedGoogle Scholar
Valente S, Lazzeri C, Chiostri M,
et al. The impact of blood transfusion on short and long term prognosis in STEMI patients treated with primary percutaneous coronary intervention: a single center–experience. Int J Cardiol
. 2012;157(2):281-283Google ScholarCrossref
Alexander KP, Chen AY, Wang TY,
et al; CRUSADE Investigators. Transfusion practice and outcomes in non-ST-segment elevation acute coronary syndromes. Am Heart J
. 2008;155(6):1047-105318513518PubMedGoogle ScholarCrossref
Twomley KM, Rao SV, Becker RC. Proinflammatory, immunomodulating, and prothrombotic properties of anemia and red blood cell transfusions. J Thromb Thrombolysis
. 2006;21(2):167-17416622613PubMedGoogle ScholarCrossref
Urbich C, Dernbach E, Aicher A, Zeiher AM, Dimmeler S. CD40 ligand inhibits endothelial cell migration by increasing production of endothelial reactive oxygen species. Circulation
. 2002;106(8):981-98612186804PubMedGoogle ScholarCrossref