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Results of a retrospective study suggest that well-managed warfarin therapy confers a low risk of complications in patients with non-valvular atrial fibrillation (NVAF).
However, certain patients require close monitoring, including those with renal failure, those taking aspirin concomitantly, and those with an individual time in therapeutic range (iTTR) less than 70% or high international normalized ratio (INR) variability.
Fredrik Björck, MD, of Umea University in Umea, Sweden, and his colleagues conducted this research and reported the results in JAMA Cardiology.
The researchers noted that warfarin has been compared to non-vitamin K antagonist oral anticoagulants for stroke prevention in NVAF, but these studies were based on comparisons with warfarin arms that had TTRs of 55.2% to 64.9%, which makes the results less credible in healthcare systems with higher TTRs.
So the team wanted to evaluate the efficacy and safety of well-managed warfarin therapy in patients with NVAF. They analyzed data from Swedish registries to identify 40,449 patients who were starting warfarin due to NVAF.
The patients’ mean age was 72.5, 40% (n=16,201) were women, and their mean CHA2DS2-VASc score at baseline was 3.3. They were monitored until they stopped treatment, died, or the study ended.
Overall results
The annual incidence of all-cause mortality was 2.19%. The annual incidence of any major bleeding was 2.23%—0.76% gastrointestinal, 0.44% intracranial, and 1.23% other bleeding.
The annual incidence of any thromboembolism was 2.95%—1.73% arterial thromboembolism, 1.23% myocardial infarction, and 0.13% venous thromboembolism.
Aspirin and intracranial bleeding
When compared to patients who were only taking warfarin, those who were also taking aspirin had significantly higher rates of any major bleeding (2.04% vs 3.07%), gastrointestinal bleeding (0.67% vs 1.18%), and other major bleeding (1.13% vs 1.67%).
But there was no significant difference in intracranial bleeding (0.41% vs 0.62%).
Overall, patients had an increased risk of intracranial bleeding if they had renal failure (hazard ratio [HR]=2.25, P=0.003), stroke (HR=1.58, P=0.002), or hypertension (HR=1.37, P=0.03).
In addition, the risk of intracranial bleeding increased significantly with age (HR=1.03, P=0.002), and women had a lower risk than men (HR=0.71, P=0.01).
INR and iTTR
Patients with an iTTR of less than 70% had a significantly higher incidence of treatment complications than patients with an iTTR of 70% or greater.
This includes all-cause mortality (4.35% vs 1.29%), any major bleeding (3.81% vs 1.61%), intracranial bleeding (0.72% vs 0.34%), gastrointestinal bleeding (1.26% vs 0.56%), other bleeding (2.17% vs 0.84), any thromboembolism (4.41% vs 2.37%), arterial thromboembolism (2.52% vs 1.41%), myocardial infarction (1.90% vs 0.98%), and venous thromboembolism (0.24% vs 0.09%).
Similarly, patients with high INR variability had a significantly higher incidence of nearly all events when compared to patients with low INR variability (below the mean value of 0.83).
This includes all-cause mortality (2.94% vs 1.50%), any major bleeding (3.04% vs 1.47%), gastrointestinal bleeding (1.05% vs 0.50%), other bleeding (1.79% vs 0.71), any thromboembolism (3.48% vs 2.46%), arterial thromboembolism (1.98% vs 1.51%), and myocardial infarction (1.53% vs 0.96%).
The exceptions were intracranial bleeding (0.51% vs 0.38%) and venous thromboembolism (0.16% vs 0.11%).
For patients with an iTTR of 70% or greater, there was no significant difference in the cumulative incidence of complications when comparing groups according to INR variability. 
Photo courtesy of NIGMS
Results of a retrospective study suggest that well-managed warfarin therapy confers a low risk of complications in patients with non-valvular atrial fibrillation (NVAF).
However, certain patients require close monitoring, including those with renal failure, those taking aspirin concomitantly, and those with an individual time in therapeutic range (iTTR) less than 70% or high international normalized ratio (INR) variability.
Fredrik Björck, MD, of Umea University in Umea, Sweden, and his colleagues conducted this research and reported the results in JAMA Cardiology.
The researchers noted that warfarin has been compared to non-vitamin K antagonist oral anticoagulants for stroke prevention in NVAF, but these studies were based on comparisons with warfarin arms that had TTRs of 55.2% to 64.9%, which makes the results less credible in healthcare systems with higher TTRs.
So the team wanted to evaluate the efficacy and safety of well-managed warfarin therapy in patients with NVAF. They analyzed data from Swedish registries to identify 40,449 patients who were starting warfarin due to NVAF.
The patients’ mean age was 72.5, 40% (n=16,201) were women, and their mean CHA2DS2-VASc score at baseline was 3.3. They were monitored until they stopped treatment, died, or the study ended.
Overall results
The annual incidence of all-cause mortality was 2.19%. The annual incidence of any major bleeding was 2.23%—0.76% gastrointestinal, 0.44% intracranial, and 1.23% other bleeding.
The annual incidence of any thromboembolism was 2.95%—1.73% arterial thromboembolism, 1.23% myocardial infarction, and 0.13% venous thromboembolism.
Aspirin and intracranial bleeding
When compared to patients who were only taking warfarin, those who were also taking aspirin had significantly higher rates of any major bleeding (2.04% vs 3.07%), gastrointestinal bleeding (0.67% vs 1.18%), and other major bleeding (1.13% vs 1.67%).
But there was no significant difference in intracranial bleeding (0.41% vs 0.62%).
Overall, patients had an increased risk of intracranial bleeding if they had renal failure (hazard ratio [HR]=2.25, P=0.003), stroke (HR=1.58, P=0.002), or hypertension (HR=1.37, P=0.03).
In addition, the risk of intracranial bleeding increased significantly with age (HR=1.03, P=0.002), and women had a lower risk than men (HR=0.71, P=0.01).
INR and iTTR
Patients with an iTTR of less than 70% had a significantly higher incidence of treatment complications than patients with an iTTR of 70% or greater.
This includes all-cause mortality (4.35% vs 1.29%), any major bleeding (3.81% vs 1.61%), intracranial bleeding (0.72% vs 0.34%), gastrointestinal bleeding (1.26% vs 0.56%), other bleeding (2.17% vs 0.84), any thromboembolism (4.41% vs 2.37%), arterial thromboembolism (2.52% vs 1.41%), myocardial infarction (1.90% vs 0.98%), and venous thromboembolism (0.24% vs 0.09%).
Similarly, patients with high INR variability had a significantly higher incidence of nearly all events when compared to patients with low INR variability (below the mean value of 0.83).
This includes all-cause mortality (2.94% vs 1.50%), any major bleeding (3.04% vs 1.47%), gastrointestinal bleeding (1.05% vs 0.50%), other bleeding (1.79% vs 0.71), any thromboembolism (3.48% vs 2.46%), arterial thromboembolism (1.98% vs 1.51%), and myocardial infarction (1.53% vs 0.96%).
The exceptions were intracranial bleeding (0.51% vs 0.38%) and venous thromboembolism (0.16% vs 0.11%).
For patients with an iTTR of 70% or greater, there was no significant difference in the cumulative incidence of complications when comparing groups according to INR variability.
Photo courtesy of NIGMS
Results of a retrospective study suggest that well-managed warfarin therapy confers a low risk of complications in patients with non-valvular atrial fibrillation (NVAF).
However, certain patients require close monitoring, including those with renal failure, those taking aspirin concomitantly, and those with an individual time in therapeutic range (iTTR) less than 70% or high international normalized ratio (INR) variability.
Fredrik Björck, MD, of Umea University in Umea, Sweden, and his colleagues conducted this research and reported the results in JAMA Cardiology.
The researchers noted that warfarin has been compared to non-vitamin K antagonist oral anticoagulants for stroke prevention in NVAF, but these studies were based on comparisons with warfarin arms that had TTRs of 55.2% to 64.9%, which makes the results less credible in healthcare systems with higher TTRs.
So the team wanted to evaluate the efficacy and safety of well-managed warfarin therapy in patients with NVAF. They analyzed data from Swedish registries to identify 40,449 patients who were starting warfarin due to NVAF.
The patients’ mean age was 72.5, 40% (n=16,201) were women, and their mean CHA2DS2-VASc score at baseline was 3.3. They were monitored until they stopped treatment, died, or the study ended.
Overall results
The annual incidence of all-cause mortality was 2.19%. The annual incidence of any major bleeding was 2.23%—0.76% gastrointestinal, 0.44% intracranial, and 1.23% other bleeding.
The annual incidence of any thromboembolism was 2.95%—1.73% arterial thromboembolism, 1.23% myocardial infarction, and 0.13% venous thromboembolism.
Aspirin and intracranial bleeding
When compared to patients who were only taking warfarin, those who were also taking aspirin had significantly higher rates of any major bleeding (2.04% vs 3.07%), gastrointestinal bleeding (0.67% vs 1.18%), and other major bleeding (1.13% vs 1.67%).
But there was no significant difference in intracranial bleeding (0.41% vs 0.62%).
Overall, patients had an increased risk of intracranial bleeding if they had renal failure (hazard ratio [HR]=2.25, P=0.003), stroke (HR=1.58, P=0.002), or hypertension (HR=1.37, P=0.03).
In addition, the risk of intracranial bleeding increased significantly with age (HR=1.03, P=0.002), and women had a lower risk than men (HR=0.71, P=0.01).
INR and iTTR
Patients with an iTTR of less than 70% had a significantly higher incidence of treatment complications than patients with an iTTR of 70% or greater.
This includes all-cause mortality (4.35% vs 1.29%), any major bleeding (3.81% vs 1.61%), intracranial bleeding (0.72% vs 0.34%), gastrointestinal bleeding (1.26% vs 0.56%), other bleeding (2.17% vs 0.84), any thromboembolism (4.41% vs 2.37%), arterial thromboembolism (2.52% vs 1.41%), myocardial infarction (1.90% vs 0.98%), and venous thromboembolism (0.24% vs 0.09%).
Similarly, patients with high INR variability had a significantly higher incidence of nearly all events when compared to patients with low INR variability (below the mean value of 0.83).
This includes all-cause mortality (2.94% vs 1.50%), any major bleeding (3.04% vs 1.47%), gastrointestinal bleeding (1.05% vs 0.50%), other bleeding (1.79% vs 0.71), any thromboembolism (3.48% vs 2.46%), arterial thromboembolism (1.98% vs 1.51%), and myocardial infarction (1.53% vs 0.96%).
The exceptions were intracranial bleeding (0.51% vs 0.38%) and venous thromboembolism (0.16% vs 0.11%).
For patients with an iTTR of 70% or greater, there was no significant difference in the cumulative incidence of complications when comparing groups according to INR variability.