Non-Vitamin K Antagonist Oral Anticoagulant Use in Patients With Atrial Fibrillation and Associated Intracranial Hemorrhage: A Focused Review

Comparing Major Bleeding Risk in Outpatients With Atrial Fibrillation or Flutter by Oral Anticoagulant Type (from the National Cardiovascular Disease Registry's Practice Innovation and Clinical Excellence Registry)

Direct oral anticoagulants (DOACs) have a favorable bleeding risk profile in patients with atrial fibrillation (AF). However, the safety of individual DOACs relative to warfarin for specific bleeding outcomes is less certain. We identified 423,450 patients with AF between 2013 to 2015 in the NCDR PINNACLE national ambulatory registry matched to the Centers for Medicare and Medicaid Services database. Outcomes included time to first major bleed, intracranial hemorrhage (ICH), major gastrointestinal bleed (GIB), or other major bleed. We estimated the association of OAC with bleeding using Cox proportional hazard models. The median duration of follow-up was 1.4 years. OACs were used in 64% of AF patients (66% warfarin, 15% rivaroxaban, 12% dabigatran, and 7% apixaban). A major bleeding event occurred in 6.9% of patients. Compared with warfarin users, fewer patients experienced ICH with the use of rivaroxaban (HR 0.73; 95% CI 0.64 to 0.84), dabigatran (HR 0.56; 95% CI 0.48 to 0.65), and apixaban (HR 0.70; 95% CI 0.55 to 0.90). The risk of major GIB was higher in rivaroxaban users (HR 1.20; 95% CI 1.12 to 1.27), and lower in dabigatran (HR 0.88; 95% CI 0.82 to 0.95) and apixaban (HR 0.84; 95% CI 0.74 to 0.95) users. For any DOAC versus warfarin, age (≥75 or <75 years) interacted with major bleeding (HR 0.93 vs 0.78; p <0.001), GIB (HR 1.10 vs 0.82; p <0.001), and other major bleeding (HR 0.93 vs 0.80; p <0.001). In conclusion, our results suggest that the safety of DOACs is superior to warfarin in AF patients, except with rivaroxaban and GIB. Age ≥75 years attenuated the relative safety benefits of DOACs.

Efficacy and safety of dabigatran, rivaroxaban, and warfarin for stroke prevention in Chinese patients with atrial fibrillation: the Hong Kong Atrial Fibrillation Project

BACKGROUND

Little is known about the comparative effectiveness and safety of non-vitamin K antagonist oral anticoagulants (NOAC) compared to warfarin in Chinese atrial fibrillation (AF) patients. Our aim was to compare the ischemic stroke risk reduction and incidence of intracranial hemorrhage (ICH) of warfarin in relation to quality of anticoagulation control (as reflected by time in therapeutic range [TTR]), and to dabigatran and rivaroxaban in a real-world cohort of Chinese AF patients.

HYPOTHESIS

NOAC, rather than warfarin, is preferred in Chinese AF patients.

METHODS

Of 2099 patients studied (73.1 ± 12.3 years, female: 44.6%, CHA₂ DS₂ -VASc 3.7 ± 1.9 and HAS-BLED 2.0 ± 1.0) with nonvalvular AF, 963 patients (45.9%) were on warfarin (only 16.3% had TTR ≥65%), 669 patients were on rivaroxaban, and 467 patients were on dabigatran.

RESULTS

After a mean follow-up of 21.7 ± 13.4 months, there were 156 ischemic strokes (annual incidence of 4.10%/year), with the incidence of ischemic stroke being highest in patients on warfarin with TTR <65% (5.24%/year), followed by those on rivaroxaban (3.74%/year), and those on warfarin with TTR ≥65% (3.35%/year), whereas patients on dabigatran had the lowest incidence of ischemic stroke (1.89%/year). The incidence of ICH was lowest in patients on dabigatran (0.39%/year) compared with those on rivaroxaban (0.52%/year) and warfarin, with TTR <65% (0.95%/year) and TTR ≥65% (0.58%/year). Patients on rivaroxaban 20 mg daily had similar ischemic stroke risk (1.93%/year) and ICH risk (0.21%/year) compared to dabigatran.

CONCLUSIONS

In Chinese AF patients, the benefits of warfarin therapy for stroke prevention and ICH reduction depend on TTR. Of the treatments compared, dabigatran, as well as rivaroxaban 20 mg daily, was associated with lowest ischemic stroke and ICH rates.

Improved persistence with non-vitamin-K oral anticoagulants compared with warfarin in patients with atrial fibrillation: recent Australian experience

OBJECTIVE

Long-term anticoagulant therapy in patients with non-valvular atrial fibrillation (AF) is essential to prevent thromboembolic complications, especially ischemic stroke, but treatment persistence with warfarin is poor. This study examines Australian nationwide persistence in AF patients using a non-vitamin-K oral anticoagulant (NOAC) drug.

RESEARCH DESIGN AND METHODS

We assessed national Pharmaceutical Benefit Scheme records November-December 2013 through March 2015 for prescription of NOAC drugs in a 10% random sample of long-term concession card holders. An historical comparison was made with patients prescribed warfarin in 2008. Key outcome measures were (i) the proportion not filling first repeat prescription and (ii) discontinuation within 12 months.

RESULTS

A total of 1471 patients with AF were new users of a NOAC drug (228 apixaban, 645 dabigatran, 598 rivaroxaban) and 1348 were new users of warfarin. Mean age on a NOAC was 76 years (58% male), on warfarin 74 years (54% male). Only 9% (95% CI 7-10) failed to collect the first repeat prescription on a NOAC, 30% (27-32) discontinued within 12 months; corresponding proportions on warfarin were 14% (12-16) and 62% (60-65). In a regression model adjusted for age, gender, heart failure, hypertension and diabetes, warfarin-treated patients were 2.5 times more likely to discontinue over 12 months than those who were NOAC treated (hazard ratio =2.47 [95% CI 2.19-2.79]).

CONCLUSIONS

Persistence with NOAC drugs in patients with AF appears to be superior to warfarin. If continued long-term, this alone will be of clinical importance in the prevention of stroke and death.

Reversal agents for direct oral anticoagulants: A focused review

For several decades the vitamin K antagonist oral anticoagulants were the only outpatient therapy that existed to reduce the risk of stroke and thromboembolism. When the new direct oral anticoagulants were approved for use and addressed many of the issues associated with oral vitamin K antagonists, a new concern arose-the lack of rapid ability to reverse these agents. Physicians and patients were concerned that in cases of life-threatening bleeding or need for emergent surgery, an antidote to reverse the anticoagulation effect of these agents did not exist. Contemporary research has aimed to produce reversal agents that can be administered to safely neutralize the anticoagulant effect. In this focused review we describe the clinical development as well as mechanisms of action of three agents (idarucizumab, andexanet alpha, and ciraparantag). We review the pharmacokinetics, animal and human study data of these reversal agents and outline the evidence supporting their use. Although questions of safety and appropriate use remain, these reversal agents offer a significant step forward in the widespread use of direct oral anticoagulants and overall management of the anticoagulant effect.

Anticoagulation therapy among patients presenting to the emergency department with symptomatic atrial fibrillation - the FinFib2 study

OBJECTIVES

Atrial fibrillation (AF) causes numerous visits to emergency departments (EDs). We evaluated the thromboembolic and bleeding risk profile and use of oral anticoagulation (OAC) therapy among patients presenting with symptomatic AF to ED.

METHODS

Within a 2-week period, all patients whose primary reason for the ED visit was AF were enrolled into this prospective study in 35 EDs around Finland. The risk of thromboembolic and bleeding events was assessed by the CHA2DS2VASc and the HAS-BLED score, respectively. Thereafter, we evaluated whether OAC was used according to the contemporary management guidelines.

RESULTS

The study population included 1013 patients (mean age 70±13 years, 52.4% men) with newly or previously diagnosed symptomatic AF. The mean CHA2DS2VASc and HAS-BLED score was 3.1±2.1 and 1.9±1.2, respectively. At admission, 76.3% of the patients with previously diagnosed AF and CHA2DS2VASc score of at least 2 were using OAC (warfarin 92.3%). However, the international normalized ratio was not at the therapeutic level in 41.9% of them. At discharge, 84.1% of the high-risk patients (85.5% of previously diagnosed and 79.6% of newly diagnosed) and 57.0 and 37.0% of the moderate-risk and low-risk patients were on OAC, respectively. Of the high-risk patients, 5.4% were treated with aspirin.

CONCLUSION

These data showed that OAC was prescribed frequently to patients with symptomatic AF and risk factors for stroke. However, in patients using warfarin, international normalized ratio was not at the therapeutic level in a large proportion of the patients with previously diagnosed AF.

Discovery and characterization of an antibody directed against exosite I of thrombin

ESSENTIALS: An IgA paraprotein with anti-thrombin activity was not associated with a severe bleeding phenotype. This observation challenges the paradigm that anticoagulant therapy necessarily increases bleeding risk. Characterization of the antibody showed that it specifically binds to thrombin exosite I. A therapeutic drug with the properties of this antibody might be an antithrombotic that doesn't cause bleeding.

BACKGROUND

We report the case of a 54-year-old female who presented with a traumatic subdural hemorrhage. Coagulation tests were markedly prolonged due to the presence of an anti-thrombin IgA paraprotein at 3 g L(-1) . The patient made a complete recovery and has had no abnormal bleeding during a 7-year follow-up, despite the persistence of the paraprotein.

OBJECTIVES

To determine how the paraprotein prolonged clotting tests by defining its target and its epitope.

METHODS

The paraprotein was purified and added to normal pooled plasma for in vitro clotting assays. Binding studies were conducted to determine the affinity of the IgA for thrombin. The Fab was isolated and crystallized with thrombin.

RESULTS

The purified IgA was sufficient to confer the patient's in vitro coagulation profile in normal pooled plasma, and was found to bind specifically and with high affinity to thrombin. A crystal structure of the Fab fragment in complex with thrombin revealed an exosite I interaction involving CDRH3 of the antibody.

CONCLUSIONS

Although the patient originally presented with a subdural bleed, the hematoma resolved without intervention, and no other bleeding event occurred during the subsequent 7 years. During this period, the patient's IgA paraprotein levels have remained constant at 3 g L(-1) , suggesting that the presence of a high-affinity, exosite I-directed antibody is consistent with normal hemostasis. A therapeutic derivative of this antibody might therefore permit antithrombotic dose escalation without an associated increase in the risk of bleeding.