Faculty Bibliography

AIMS/OBJECTIVE:Non-invasive risk stratification of low- and intermediate-risk non-ST-elevation acute coronary syndromes (NSTE ACS) patients has been recommended, but limited data exist about the variation in clinical practice of stress testing in these patients and the impact of such testing on their outcomes. METHODS AND RESULTS/RESULTS:Patients with NSTE ACS enrolled in the GUSTO IIb (Global Use of Strategies To Open occluded coronary arteries in acute coronary syndromes-IIb) trial (n = 8011) were analysed to evaluate patterns of stress testing in US and non-US patients and to further evaluate the clinical characteristics, procedure use, and outcomes of patients who underwent stress testing compared with those who did not. Stress testing was performed in 1878 (24%) patients. Compared with patients not undergoing stress testing, those undergoing stress testing had low-risk characteristics and significantly lower death (0.6% vs. 4.8%), and death or myocardial infarction (MI, 3.9% vs. 11%) rates at 30 days. Stress testing was performed as often after as before coronary angiography. Importantly, stress testing was helpful in stratifying patients into low (equivocal or negative test) or high (positive test) risk groups (30 day death 3.1% vs. 5%). Stress testing was performed more often in non-US than US patients, and US patients were 3.5 times more likely to undergo imaging as part of stress testing. However, the risks of 30-day death or MI; 6-month death, MI or revascularization; and 1-year death did not differ between US and non-US patients. CONCLUSION/CONCLUSIONS:Stress testing is commonly performed in low-risk NSTE ACS patients and provides modest additional prognostic information in this cohort. Significant geographical variation exists in the use of stress testing. Therefore, in the current practice environment where cardiac catheterization is often the first diagnostic modality used in patients with NSTE ACS, the role of non-invasive testing both before and after invasive procedure is in need of further study.

OBJECTIVES/OBJECTIVE:To describe the association between transfusion and outcomes as a function of nadir hematocrit (HCT) in patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS). BACKGROUND:The adverse outcomes associated with transfusion in NSTE ACS is uncertain and may vary by nadir HCT of the transfused. METHODS:Using data from 44242 patients with NSTE ACS in 400 US hospitals in the CRUSADE initiative (January 2004-December 2005), we describe blood transfusion as a function of nadir HCT and associated outcomes across nadir HCT groups (<or=24%, 24.1%-27%, 27.1%-30%, >30%). We further explore patient and process variation across hospital quartiles defined by transfusion use. RESULTS:Overall, 22.2% of patients with NSTE ACS are anemic and 10.4% receive a blood transfusion during their care. Likelihood of transfusion rose from 1% when nadir HCT was >30% to 70% when nadir HCT was <or=24%. The threshold for transfusion is a median nadir HCT of 25.7% (interquartile range 23.8%-27.5%). Although nadir HCT of transfused remains constant across quartiles of transfusion use, occurrence of bleeding increases. Inhospital mortality is higher in lower nadir HCT groups. In those with a nadir HCT of <or=24%, transfusion tended to have a beneficial impact on mortality (HCT <or=24% adjusted odds ratio [OR] 0.68 [0.45-1.02]). In the median range where transfusion occurs, transfusion had a neutral impact on mortality (HCT 24%-27% adjusted OR 1.01 [0.79-1.30]). Although rare, those transfused with nadir HCT of 27% to 30% (adjusted OR 1.18 [0.92-1.50]) or HCT of >30% (adjusted OR 3.47 [2.30-5.23]) had higher mortality. CONCLUSION/CONCLUSIONS:Anemia and transfusion are common in the care of NSTE ACS. The observed association between transfusion and adverse outcomes is neutral in the nadir HCT range where transfusions are most often given and trends strongly to benefit when nadir HCT is <or=24%. Although reassuring, randomized trials are needed to confirm the safety of transfusion in NSTE ACS. In the meantime, avoiding the need for transfusion is the best approach.

This paper, developed from the proceedings of the 2007 Platelet Colloquium, considers emerging constructs in platelet biology, preclinical models of thrombosis, and their potential application to the development of platelet-directed pharmacotherapies. Discussed first is the developmental biology of platelets, including megakaryocyte maturation, and the role of apoptotic and growth factors and other proteins in thrombopoiesis. A brief overview of current methods and observations from platelet proteomic analyses is also presented, illustrating the complex interplay of genes, gene expression, protein expression, and protein modification in various atherothrombotic phenotypes. The factor Xa-platelet interface is used as a working model for discussion of anticoagulants as platelet antagonists, highlighting the importance of receptor expression, substrate binding kinetics, platelet subpopulations, and cofactors in thrombosis. Finally, we discuss the use of emerging technologies--such as intravital microscopy and ex vivo perfusion chambers--as translatable platforms for investigating the role of platelets and their pharmacologic inhibition in human health and disease.

BACKGROUND:Guidelines for the management of high-risk non ST-segment elevation acute coronary syndrome (NSTE ACS) recommend antithrombotic and antiplatelet therapy combined with an early invasive strategy. While this strategy reduces ischemic complications, it places patients at risk for bleeding complications. OBJECTIVE:We sought to provide a narrative review of the risk factors for bleeding, risks associated with bleeding and strategies to prevent bleeding complications. METHODS:A comprehensive literature review was performed to identify relevant evidence. RESULTS/CONCLUSIONS/CONCLUSIONS:Bleeding complications in NSTE ACS are associated with adverse events and higher mortality. Prevention of bleeding complications can be achieved through judicious dosing of medications, the use of antithrombotic agents associated with a lower bleeding risk and use of the radial artery approach in patients requiring coronary intervention. Future work should focus on delineating the mechanisms underlying the bleeding-mortality relationship and developing a better understanding of the tradeoff between efficacy and safety.

BACKGROUND:Clinical trials of drug-eluting stents (DES) vs bare metal stents (BMS) report a reduced need for target lesion revascularization with no difference in death or myocardial infarction. However, these trials selectively enrolled patients with lower risk, single-vessel coronary artery disease (CAD) and limited the follow-up period to 1 year or less. Thus, it is not known how these short-term results apply to patients with higher risk, multivessel CAD seen in community practice settings. The objective of this study was to compare the long-term clinical outcomes of patients receiving DES vs BMS in a clinical practice setting. METHODS:Patients from the Duke Databank for Cardiovascular Disease undergoing their initial revascularization with DES or BMS from January 1, 2000, through July 31, 2005, were included in the study population. Propensity scores and inverse probability weighted estimators were used to adjust for treatment group imbalances. RESULTS:The study population included 1501 patients who received DES and 3165 who received BMS. After adjustment, DES reduced target vessel revascularization (TVR) rates at 6, 12, and 24 months compared with BMS (24-month rates: DES, 6.6%; BMS, 16.3%; difference, -9.7%; 95% confidence interval [CI], -11.7% to -7.7%; P < .001). The TVR benefit for DES increased among patients with multivessel CAD (1-vessel CAD: -8.3%; 95% CI, -10.9% to -5.8%; P < .001; 2-vessel CAD: -9.7%; 95% CI, -3.6% to -5.8%; P < .001; 3-vessel CAD: -16.2%; 95% CI, -25.2% to -7.2%; P < .001). However, in the overall cohort there were no statistically significant differences in the composite of death or myocardial infarction. CONCLUSIONS:Patients receiving DES vs BMS in a clinical practice setting have lower TVR rates, albeit with less absolute benefit than those observed in clinical trials. Patients with multivessel vs single-vessel disease experience a greater reduction in TVR.

The optimal duration of clopidogrel administration after percutaneous coronary intervention (PCI) remains unknown. Clopidogrel is currently recommended for minimums of 1 and 12 months after bare-metal stent and drug-eluting stent implantation, respectively. To determine the impact of clopidogrel discontinuation 1 year after PCI, the outcomes of 530 consecutive patients who underwent PCI from January 2004 to July 2006, were free of cardiovascular events for 6 months after PCI, and had follow-up available for >12 months were examined. The outcomes of patients who received clopidogrel for > or =1 year were compared with those of patients who received it for <1 year. The mean age was 65 +/- 9 years. Patients often presented with acute coronary syndromes (57%), and 85% received drug-eluting stents. Clopidogrel was used for > or =1 year and for <1 year in 341 and 189 patients, respectively. During a mean follow-up period of 2.4 +/- 0.8 years, 40 patients (8%) died, 21 (4%) had acute myocardial infarctions, and 89 (17%) underwent repeat coronary revascularization. Compared with patients with clopidogrel administration for <1 year after PCI, those who received clopidogrel for > or =1 year had lower mortality (14.8% vs 3.5%, p <0.001). On multivariate analysis, clopidogrel use for > or =1 year was associated with lower mortality (hazard ratio 0.28, 95% confidence interval 0.14 to 0.59), independent of traditional cardiovascular risk factors, clinical presentation, and the use of drug-eluting stents. In conclusion, the use of clopidogrel for > or =1 year after PCI was associated with lower mortality.

BACKGROUND:Bleeding among patients with acute myocardial infarction (AMI) is associated with worse long-term outcomes. Although the mechanism underlying this association is unclear, a potential explanation is that withholding antiplatelet therapies long beyond resolution of the bleeding event may contribute to recurrent events. METHODS AND RESULTS/RESULTS:We examined medication use at discharge, 1, 6, and 12 months after AMI among 2498 patients in the Prospective Registry Evaluating Myocardial Infarction: Events and Recovery (PREMIER) registry. Bleeding was defined as non-coronary artery bypass graft-related Thrombolysis of Myocardial Infarction major/minor bleeding or transfusion among patients with baseline hematocrit > or =28%. Logistic regression was used to evaluate the association between bleeding during the index AMI hospitalization and medication use. In-hospital bleeding occurred in 301 patients (12%) with AMI. Patients with in-hospital bleeding were less likely to be discharged on aspirin or thienopyridine (adjusted odds ratio=0.45; 95% CI, 0.31 to 0.64; and odds ratio=0.62; 95% CI, 0.42 to 0.91, respectively). At 1 month after discharge, although patients with in-hospital bleeding remained significantly less likely to receive aspirin (odds ratio=0.68; 95% CI, 0.50 to 0.92), use of thienopyridines in the 2 groups started to become similar. By 1 year, antiplatelet therapy use was similar among patients with and without bleeding. Postdischarge cardiology follow-up was associated with greater antiplatelet therapy use than either primary care or no clinical follow-up. CONCLUSIONS:Patients whose index AMI is complicated by bleeding are less likely to be treated with antiplatelet therapies during the first 6 months after discharge. Early reassessment of antiplatelet eligibility may represent an opportunity to reduce the long-term risk of adverse outcomes associated with bleeding.

BACKGROUND:Short-term use of clopidogrel plus aspirin among patients with acute coronary syndrome reduces ischemic events, but concerns about coronary artery bypass graft (CABG) surgery-related bleeding limit its early use. METHODS:Using data from 4,794 consecutive CABG procedures in the Duke Databank for Cardiovascular Disease (January 1999 to December 2003), we developed multivariable models for associations with CABG-related bleeding defined as reoperation for bleeding, red cell transfusion, and a composite of reoperation/transfusion/hematocrit drop>or=15%. We examined clopidogrel use<or=5 days versus no clopidogrel<or=5 days before CABG in each model. Models were adjusted for propensity for clopidogrel use<or=5 days. RESULTS:Of 4,794 CABG patients, 332 (6.9%) received clopidogrel<or=5 days before CABG, 127 (2.6%) had reoperation for bleeding, 3,277 (68.4%) received red cell transfusion, and 4,387 (91.5%) had the composite outcome. After adjustment, clopidogrel use<or=5 days was not significantly associated with reoperation (odds ratio [OR] 1.24, 95% CI 0.63-2.41) or the composite end point (OR 1.23, 95% CI 0.72-2.10). Clopidogrel<or=5 days was modestly associated with red cell transfusion (OR 1.40, 95% CI 1.04-1.89) but more weakly than other factors, including which surgeon performed the procedure. CONCLUSION/CONCLUSIONS:Clopidogrel administration<or=5 days before CABG was not significantly associated with reoperation for bleeding or a bleeding composite, and only weakly with red cell transfusion after surgery. The impact of withholding clopidogrel acutely in those for whom clopidogrel has proven benefits and the impact of delaying CABG to prevent bleeding among patients treated with clopidogrel should be viewed in the context of other stronger determinants of bleeding.