Risk of Chronic Oral Anticoagulation Therapy in Patients Undergoing Primary Percutaneous Coronary Intervention for ST Elevation Myocardial Infarction - Retrospective Cross-Sectional Study

Background: Although chronic oral anticoagulation therapy reduces mortality and morbidity from thromboembolic diseases, the risk of bleeding and mortality may increase when patients on anticoagulation presents with acute ST elevation myocardial infarction (STEMI) where aggressive antiplatelet and further anticoagulation therapies are warranted. Objective: To study the characteristics of patients who are on oral anticoagulation therapy (OAC) at the time of presentation with acute STEMI. Design: Retrospective, cross-sectional study. Setting: All patients who presented to Christiana Care Health System, Newark, DE with acute ST elevation myocardial infarction with intent of primary percutaneous angioplasty between January 2009 and December 2010. Outcome Measures: Composite end-point of major bleeding, in-hospital death, cardiogenic shock, and cardiac arrest. Subgroup analysis of major bleeding and in-hospital mortality. Results: A total of 637 patients were enrolled into the study, the average age of the study population was 61 years, 71% male and 84% Caucasian patients. Of 637 patients, 20 (3.1%) were on OAC at the time of presentation. Both OAC and non-OAC groups differed in baseline characteristics including hypertension, diabetes mellitus, dyslipidemia, peripheral vascular disease, previous coronary artery disease, and pre procedural laboratory data including hemoglobin and INR (all p < 0.05). The groups also differed in the treatment procedures. Patients who were on OAC were more likely to receive bare metal stents and clopidogrel and less likely to be treated with newer antiplatelet agents (prasugrel and ticagrelor) and drug eluting stents (all p <0.05). However, the composite endpoint (death, bleeding, and transfusion) was similar in both groups. On multivariable logistic regression analysis, use of anticoagulation and baseline INR were not significant independent predictors of study endpoints. Pre procedural hemoglobin (OR: 0.88, 95%CI: 0.77-0.98, p=0.012) and requirement of IABP (OR: 4.13, 95% CI: 2.25-7.59, p<0.001) were independent risk factors for study end points. Limitations: Overall sample size for patients who were on anticoagulation was limited due to the low (3%) observed prevalence in the study population, however it is similar to other published studies. The inclusion bias resulting from prehospitalization deaths may influence the results. Conclusions: The contemporary management of acute ST elevation myocardial infarction does not seem to raise the risk of bleeding, in-hospital death, or blood transfusion in patients who are on full anticoagulation