Anticoagulation for Nonvalvular Atrial Fibrillation

Clinical Impact of Switching or Continuation of Apixaban or Rivaroxaban among Patients with Non-Valvular Atrial Fibrillation

BACKGROUND

Real-world evidence on direct oral anticoagulant outcomes among Non-Valvular Atrial Fibrillation (NVAF) patients is limited. We aimed to evaluate stroke/systemic embolism (SE) and major bleeding (MB) risks among NVAF patients continuing or switching to different oral anticoagulants.

METHODS

Using Optum's de-identified Clinformatics® Data Mart Database, we identified NVAF patients initiating apixaban or rivaroxaban between 1 January 2013 and 31 December 2021. Patients switching therapies within 30 days before or 90 days after discontinuing their initial DOAC and those who continued initial therapy were included. The index date was the switch date for switchers, while continuers were assigned a hypothetic index date. Switchers and continuers were propensity score matched based on pre-index characteristics.

RESULTS

Among 167,868 apixaban and 65,888 rivaroxaban initiators, 2900 apixaban-to-rivaroxaban switchers were matched with 14,500 apixaban continuers, and 2873 rivaroxaban-to-apixaban switchers were matched with 14,365 rivaroxaban continuers. Apixaban-to-rivaroxaban switching was associated with higher stroke/SE risk (HR: 1.99, 95% CI: 1.38-2.88) and MB risk (HR:1.80, 95% CI: 1.46-2.23) than continuing apixaban. Rivaroxaban-to-apixaban switching had similar stroke/SE risk (HR: 0.74, 95% CI: 0.45-1.22) but lower MB risk (HR: 0.49, 95% CI: 0.38-0.65) than continuing rivaroxaban.

CONCLUSIONS

These findings may aid physicians and patients in making informed decisions when considering a switch between apixaban and rivaroxaban.

Evaluation of the Risk of Stroke Without Anticoagulation Therapy in Men and Women With Atrial Fibrillation Aged 66 to 74 Years Without Other CHA2DS2-VASc Factors

Importance

There are limited clinical trial data and discrepant recommendations regarding use of anticoagulation therapy in patients with atrial fibrillation (AF) aged 65 to 74 years without other stroke risk factors.

Objectives

To evaluate the risk of stroke without anticoagulation therapy in men and women with AF aged 66 to 74 years without other CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, stroke, vascular disease, age 65-74 years, female sex) risk factors and examine the association of stroke incidence with patient age.

Design, Setting, and Participants

A population-based retrospective cohort study was conducted using linked administrative databases. The population included 16 351 individuals aged 66 to 74 years who were newly diagnosed with AF in Ontario, Canada, between April 1, 2007, and March 31, 2017. Exclusion criteria included long-term care residence, prior anticoagulation therapy, valvular disease, heart failure, hypertension, diabetes, stroke, and vascular disease. The cumulative incidence function was used to estimate the 1-year incidence of stroke in patients who did not receive anticoagulation therapy. Fine-Gray regression was used to study the association of patient characteristics with stroke incidence and derive estimates of stroke risk at each age. Death was treated as a competing risk and patients were censored if they initiated anticoagulation therapy. Inverse probability of censoring weights was used to account for patient censoring. Data analysis was performed from May 26, 2019, to December 9, 2020.

Exposures

Atrial fibrillation and age.

Main Outcomes and Measures

Hospitalizations for stroke.

Results

Of the 16 351 individuals with AF (median [interquartile range] age, 70 [68-72] years), 8352 (51.1%) were men; 6314 individuals (38.6%) started anticoagulation therapy during follow-up. The overall 1-year stroke incidence among patients who did not receive anticoagulation therapy was 1.1% (95% CI, 1.0%-1.3%) and the incidence of death without stroke was 8.1% (95% CI, 7.7%-8.5%). The incidence of stroke was not significantly associated with sex. The estimated 1-year stroke risk increased with patient age from 66 years (0.7%; 95% CI, 0.5%-0.9%) to 74 years (1.7%; 95% CI, 1.3%-2.1%).

Conclusions and Relevance

The risk of stroke more than doubled in this study as men and women with AF but no other CHA2DS2-VASc risk factors aged from 66 to 74 years. These data suggest that anticoagulation therapy is more likely to benefit older individuals within this group of patients, whereas younger individuals are less likely to gain net clinical benefit from anticoagulation therapy.

Importance of Considering Competing Risks in Time-to-Event Analyses: Application to Stroke Risk in a Retrospective Cohort Study of Elderly Patients With Atrial Fibrillation

Supplemental Digital Content is available in the text.

Background:

Ignoring competing risks in time-to-event analyses can lead to biased risk estimates, particularly for elderly patients with multimorbidity. We aimed to demonstrate the impact of considering competing risks when estimating the cumulative incidence and risk of stroke among elderly atrial fibrillation patients.

Methods and Results:

Using linked administrative databases, we identified patients with atrial fibrillation aged ≥66 years discharged from hospital in ON, Canada between January 1, 2007, and March 31, 2011. We estimated the cumulative incidence of stroke hospitalization using the complement of the Kaplan–Meier function and the cumulative incidence function. This was repeated after stratifying the cohort by presence of prespecified comorbidities: chronic kidney disease, chronic obstructive pulmonary disease, cancer, or dementia. The full cohort was used to regress components of the CHA₂DS₂VASc (congestive heart failure, hypertension, age, diabetes mellitus, stroke, vascular disease, sex) score on the hazard of stroke hospitalization using the Fine-Gray and Cox methods. These models were subsequently used to predict the 5-year risk of stroke hospitalization. Among 136 156 patients, the median CHA₂DS₂VASc score was 4 and 84 728 patients (62.2%) had ≥1 prespecified comorbidity. The 5-year cumulative incidence of stroke was 5.4% (95% confidence interval, 5.3%–5.5%), whereas that of death without stroke was 48.8% (95% confidence interval, 48.5%–49.1%). The incidence of both events was overestimated by the Kaplan–Meier method; stroke incidence was overestimated by a relative factor of 39%. The degree of overestimation was larger among patients with non-CHA₂DS₂VASc comorbidity because of higher incidence of death without stroke. The Fine-Gray model demonstrated better calibration than the Cox model, which consistently overpredicted stroke incidence.

Conclusions:

The incidence of death without stroke was 9-fold higher than that of stroke, leading to biased estimates of stroke risk with traditional time-to-event methods. Statistical methods that appropriately account for competing risks should be used to mitigate this bias.

Ischemic stroke risk estimation in patients without oral anticoagulation: an observational cohort study based on secondary data from Germany

BACKGROUND

Oral anticoagulants can cause potentially serious adverse events. Therefore, before prescribing oral anticoagulants for ischemic stroke prevention in patients with atrial fibrillation (AF), stroke risk assessment is required to identify patients that are likely to benefit from treatment. Current guidelines recommend the CHA2DS2-VASc-score for stroke risk assessment. The CHA2DS2-VASc-score is based on observational studies from different treatment settings and countries. As ischemic stroke risk differs by setting and region, the aim of this study is to estimate ischemic stroke risk (stratified by the CHA2DS2-VASc-score) for a broadly representative population with AF from southern Germany and compare them to results from previous studies.

METHODS

The study design is a retrospective cohort study on patients with atrial fibrillation based on secondary data. We calculated CHA2DS2-VASc-score based on patient's diagnoses recorded in the year 2014 and assessed outcomes in 2015-2016. The primary outcome is hospitalization for ischemic stroke. The secondary outome is hospitalizations for any thromboembolic event, including ischemic stroke, transient ischemic attack, peripheral arterial embolism, pulmonary embolism, and mesenterial embolism. We estimated the incidence rates of the outcomes (and corresponding 95%-confidence intervals) stratified by CHA2DS2-VASc-score.

RESULTS

The primary endpoint occurred in 961 of the 30,299 patients constituting the study population, resulting in a total incidence rate of 2.2 per 100 person-years. The secondary endpoint occurred in 1553 patients (3.6 per 100 person-years). Ischemic stroke rates stratified by the CHA2DS2-VASc-score tended to be lower than those reported previously. Thromboembolic event rates stratified tended to be similar to those reported previously.

CONCLUSIONS

Our results show that the performance of the CHA2DS2-VASc-score differs in the German population, as compared to internationally published data, with an overall trend towards lower risk of ischemic stroke in uncoagulated patients with AF. These results should not be practice changing, but they emphasize that stroke risk estimation in patients with atrial fibrillation should be further refined.