W arfarin, a vitamin K antagonist, is a commonly used anticoagulant in patients with atrial fibrillation (AF). Metaanalyses of randomized trials have shown that it reduces the risk of embolic stroke by 40% to 80% and of mortality by ≈30% but also doubles the risk of intracranial hemorrhage and increases the risk of extracranial bleeding by up to 66%. [1][2][3] It can be difficult to maintain patients in the therapeutic range (international normalized ratio of 2-3). A meta-analysis found that warfarintreated patients were in the therapeutic range 61% of the time. 4 In this study, an international normalized ratio <2 was associated with a 5-fold increase in stroke risk, and an international normalized ratio >3 was associated with a 3-fold increase in bleeding risk. Clinical Perspective on p 164Dabigatran is a competitive direct thrombin inhibitor approved in the United States to reduce the risk of stroke and systemic embolization in patients with nonvalvular AF. 5 In the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial, patients with AF were randomized to dabigatran doses of 110 or 150 mg twice daily or adjusted-dose warfarin. 6 At the dose subsequently approved in the United States (150 mg twice daily), dabigatran reduced the risk of stroke and intracranial hemorrhage and increased the risk of major gastrointestinal hemorrhage compared with warfarin. 6 Although dabigatranBackground-The comparative safety of dabigatran versus warfarin for treatment of nonvalvular atrial fibrillation in general practice settings has not been established. Methods and Results-We formed new-user cohorts of propensity score-matched elderly patients enrolled in Medicare who initiated dabigatran or warfarin for treatment of nonvalvular atrial fibrillation between October 2010 and December 2012. Among 134 414 patients with 37 587 person-years of follow-up, there were 2715 primary outcome events. The hazard ratios (95% confidence intervals) comparing dabigatran with warfarin (reference) were as follows: ischemic stroke, 0.80 (0.67-0.96); intracranial hemorrhage, 0.34 (0.26-0.46); major gastrointestinal bleeding, 1.28 (1.14-1.44); acute myocardial infarction, 0.92 (0.78-1.08) ; and death, 0.86 (0.77-0.96). In the subgroup treated with dabigatran 75 mg twice daily, there was no difference in risk compared with warfarin for any outcome except intracranial hemorrhage, in which case dabigatran risk was reduced. Most patients treated with dabigatran 75 mg twice daily appeared not to have severe renal impairment, the intended population for this dose. In the dabigatran 150-mg twice daily subgroup, the magnitude of effect for each outcome was greater than in the combined-dose analysis. Conclusions-In general practice settings, dabigatran was associated with reduced risk of ischemic stroke, intracranial hemorrhage, and death and increased risk of major gastrointestinal hemorrhage compared with warfarin in elderly patients with nonvalvular atrial fibrillation. These associations were most pronounced in patients treated...

Electronic health records (EHRs) provide opportunities to enhance patient care, embed performance measures in clinical practice, and facilitate clinical research. Concerns have been raised about the increasing recruitment challenges in trials, burdensome and obtrusive data collection, and uncertain generalizability of the results. Leveraging electronic health records to counterbalance these trends is an area of intense interest. The initial applications of electronic health records, as the primary data source is envisioned for observational studies, embedded pragmatic or post-marketing registry-based randomized studies, or comparative effectiveness studies. Advancing this approach to randomized clinical trials, electronic health records may potentially be used to assess study feasibility, to facilitate patient recruitment, and streamline data collection at baseline and follow-up.Ensuring data security and privacy, overcoming the challenges associated with linking diverse systems and maintaining infrastructure for repeat use of high quality data, are some of the challenges associated with using electronic health records in clinical research. Collaboration between academia, industry, regulatory bodies, policy makers, patients, and electronic health record vendors is critical for the greater use of electronic health records in clinical research. This manuscript identifies the key steps required to advance the role of electronic health records in cardiovascular clinical research.

IMPORTANCEDabigatran and rivaroxaban are non-vitamin K oral anticoagulants approved for stroke prevention in patients with nonvalvular atrial fibrillation (AF). There are no randomized head-to-head comparisons of these drugs for stroke, bleeding, or mortality outcomes. OBJECTIVE To compare risks of thromboembolic stroke, intracranial hemorrhage (ICH), major extracranial bleeding including major gastrointestinal bleeding, and mortality in patients with nonvalvular AF who initiated dabigatran or rivaroxaban treatment for stroke prevention. DESIGN, SETTING, AND PARTICIPANTSRetrospective new-user cohort study of 118 891 patients with nonvalvular AF who were 65 years or older, enrolled in fee-for-service Medicare, and who initiated treatment with dabigatran or rivaroxaban from November 4, 2011, through June 30, 2014. Differences in baseline characteristics were adjusted using stabilized inverse probability of treatment weights based on propensity scores. The data analysis was performed from May 7, 2015, through June 30, 2016.EXPOSURES Dabigatran, 150 mg, twice daily; rivaroxaban, 20 mg, once daily.MAIN OUTCOMES AND MEASURES Adjusted hazard ratios (HRs) for the primary outcomes of thromboembolic stroke, ICH, major extracranial bleeding including major gastrointestinal bleeding, and mortality, with dabigatran as reference. Adjusted incidence rate differences (AIRDs) were also estimated.RESULTS A total of 52 240 dabigatran-treated and 66 651 rivaroxaban-treated patients (47% female) contributed 15 524 and 20 199 person-years of on-treatment follow-up, respectively, during which 2537 primary outcome events occurred. Rivaroxaban use was associated with a statistically nonsignificant reduction in thromboembolic stroke (HR, 0.81; 95% CI, 0.65-1.01; P = .07; AIRD = 1.8 fewer cases/1000 person-years), statistically significant increases in ICH (HR, 1.65; 95% CI, 1.20-2.26; P = .002; AIRD = 2.3 excess cases/1000 person-years) and major extracranial bleeding (HR, 1.48; 95% CI, 1.32-1.67; P < .001; AIRD = 13.0 excess cases/1000 person-years), including major gastrointestinal bleeding (HR, 1.40; 95% CI, 1.23-1.59; P < .001; AIRD = 9.4 excess cases/1000 person-years), and with a statistically nonsignificant increase in mortality (HR, 1.15; 95% CI, 1.00-1.32; P = .051; AIRD = 3.1 excess cases/1000 person-years). In patients 75 years or older or with CHADS 2 score greater than 2, rivaroxaban use was associated with significantly increased mortality compared with dabigatran use. The excess rate of ICH with rivaroxaban use exceeded its reduced rate of thromboembolic stroke. CONCLUSIONS AND RELEVANCETreatment with rivaroxaban 20 mg once daily was associated with statistically significant increases in ICH and major extracranial bleeding, including major gastrointestinal bleeding, compared with dabigatran 150 mg twice daily.

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Women were well represented in trials of drugs for hypertension and atrial fibrillation, and overrepresented for pulmonary arterial hypertension. Representation of women fell below a PPR of 0.8 for trials in heart failure, coronary artery disease, and acute coronary syndrome. Minimal gender differences in drug efficacy and safety profiles were observed.