Treatment and persistence with oral anticoagulants among newly diagnosed patients with non-valvular atrial fibrillation: a retrospective observational study in a US commercially insured and Medicare Advantage population

Comparing broad and narrow phenotype algorithms: differences in performance characteristics and immortal time incurred

Introduction: When developing phenotype algorithms for observational research, there is usually a trade-off between definitions that are sensitive or specific. The objective of this study was to estimate the performance characteristics of phenotype algorithms designed for increasing specificity and to estimate the immortal time associated with each algorithm. Materials and methods: We examined algorithms for 11 chronic health conditions. The analyses were from data from five databases. For each health condition, we created five algorithms to examine performance (sensitivity and positive predictive value (PPV)) differences: one broad algorithm using a single code for the health condition and four narrow algorithms where a second diagnosis code was required 1-30 days, 1-90 days, 1-365 days, or 1- all days in a subject's continuous observation period after the first code. We also examined the proportion of immortal time relative to time-at-risk (TAR) for four outcomes. The TAR's were: 0-30 days after the first condition occurrence (the index date), 0-90 days post-index, 0-365 days post-index, and 0-1,095 days post-index. Performance of algorithms for chronic health conditions was estimated using PheValuator (V2.1.4) from the OHDSI toolstack. Immortal time was calculated as the time from the index date until the first of the following: 1) the outcome; 2) the end of the outcome TAR; 3) the occurrence of the second code for the chronic health condition. Results: In the first analysis, the narrow phenotype algorithms, i.e., those requiring a second condition code, produced higher estimates for PPV and lower estimates for sensitivity compared to the single code algorithm. In all conditions, increasing the time to the required second code increased the sensitivity of the algorithm. In the second analysis, the amount of immortal time increased as the window used to identify the second diagnosis code increased. The proportion of TAR that was immortal was highest in the 30 days TAR analyses compared to the 1,095 days TAR analyses. Conclusion: Attempting to increase the specificity of a health condition algorithm by adding a second code is a potentially valid approach to increase specificity, albeit at the cost of incurring immortal time.

Risk of ischemic stroke associated with direct oral anticoagulants discontinuation on patients with non-valvular atrial fibrillation

INTRODUCTION

Although direct oral anticoagulants' (DOACs) prescriptions have experienced immense growth in the last decade, the proportion of discontinuers is still common yielding an increased risk of ischemic stroke (IS) onset.

AIMS

We aimed to estimate the association between DOACs discontinuation and risk of IS among patients with non-valvular atrial fibrillation (NVAF).

METHODS

We used data from a cohort of new DOACs users, followed patients from the first DOAC prescription date up to IS (index date) and conducted a nested case-control analysis using conditional logistic regression. Adjusted odds ratios, 95% confidence intervals were calculated for discontinuation of DOACs (current use compared with past use). The latter, subdivided among those stopping treatment 3 to 2 months and 6 and 3 months prior to index date. The effect of naïve current users against IS onset compared with non-naïve current users was also evaluated.

RESULTS

DOACs discontinuation showed an OR of IS of 1.47 (95% CI: 1.02-2.12); estimates were 2.51 (95% CI: 1.84-3.42) for whom discontinued treatment within months 3 and 2 and 1.43 (95% CI: 0.96-2.13) for those between months 6 and 3 prior to index date. Analyzing DOACs individually, risk of IS associated with past users compared with current users: 1.98 (95% CI: 1.25-3.12) for apixaban, 1.38 (95% CI: 0.40-4.72) for edoxaban, 1.98 (95% CI: 1.24-2.65) for dabigatran and 1.87 (95% CI: 1.26-2.76) for rivaroxaban. Similar results were found when stratified by naïve and non-naïve users.

CONCLUSIONS

DOACs' discontinuation is associated with higher risk of IS, especially in the second and third months following interruption.

Prognostic implications of adherence to oral anticoagulants among patients with atrial fibrillation: Insights from MISOAC-AF trial

OBJECTIVES

To explore the implications of adherence to oral anticoagulants (OACs) on all-cause mortality and cardiovascular outcomes in patients with atrial fibrillation (AF).

METHODS

This post-hoc analysis of the MISOAC-AF trial included recently hospitalized patients with AF. Adherence to OACs was assessed by the proportion of days covered (PDC). Good adherence was defined as PDC >80 %. Cox regression models were used to associate PDC with clinical outcomes of all-cause death, cardiovascular death (CVD), stroke, and bleeding. A sub-analysis was performed among adherent patients to compare outcomes between vitamin K antagonists (VKAs) and direct oral anticoagulants (DOACs).

RESULTS

During a median 31-month follow-up, 778 cardiac patients with comorbid AF who had been prescribed OACs upon hospital discharge were studied. The mean PDC was 0.78; 66 % of patients had good adherence (>80 %) which was associated with lower risk of all-cause death [adjusted hazard ratio (aHR): 0.64; 95 % confidence interval (CI): 0.46 to 0.84, p < 0.001] and CVD (aHR: 0.70; 95 % CI: 0.50 to 0.97, p = 0.03). The risk of stroke and major or non-major bleeding did not differ by adherence status. Among adherent patients to OACs, VKA use was associated with higher rates of all-cause death (p < 0.001), CVD (p < 0.001), and stroke (p = 0.01); no differences were found regarding major or non-major bleeding risk.

CONCLUSIONS

In recently hospitalized patients with AF, good adherence to OACs was associated with a reduced risk of all-cause death and CVD. The rates of stroke or bleeding events were not significantly different. VKAs were associated with more adverse events compared to DOACs.

Non-persistence to Oral Anticoagulation Treatment in Patients with Non-valvular Atrial Fibrillation in the USA

BACKGROUND

Studies have shown that patients with non-valvular atrial fibrillation (NVAF) who discontinue oral anticoagulants (OACs) are at higher risk of complications such as stroke.

OBJECTIVE

This analysis compared the risk of non-persistence with OACs among patients with NVAF.

METHODS

Adult patients with NVAF who initiated apixaban, dabigatran, rivaroxaban, or warfarin were identified using 01JAN2013-30JUN2019 data from Centers for Medicare and Medicaid Services and four US commercial claims databases. Non-persistence was defined as discontinuation (no evidence of index OAC use for ≥ 60 days from the last days' supply) or switch to another OAC. Kaplan-Meier curves were generated to illustrate time to non-persistence along with cumulative incidences of non-persistence. Baseline and time-varying covariates were evaluated, and adjusted Cox proportional hazards models were used to evaluate non-persistence risk.

RESULTS

In total, 363,823 patients receiving apixaban, 57,121 receiving dabigatran, 282,831 receiving rivaroxaban, and 317,337 receiving warfarin were included. Of these, 47-72% discontinued/switched OAC therapy within an average 9-month follow-up. Apixaban was associated with a lower risk of non-persistence than were dabigatran (hazard ratio [HR] 0.62; 95% confidence interval [CI] 0.61-0.62), rivaroxaban (HR 0.76; 95% CI 0.75-0.76), and warfarin (HR 0.74; 95% CI 0.74-0.75). Dabigatran was associated with a higher risk of non-persistence than were warfarin (HR 1.21; 95% CI 1.19-1.22) and rivaroxaban (HR 1.23; 95% CI 1.22-1.25), and rivaroxaban was associated with a lower risk of non-persistence than was warfarin (HR 0.98; 95% CI 0.97-0.98). Clinical events (stroke/systemic embolism and major bleeding [MB]) during follow-up were predictors of non-persistence (stroke HR 1.57; 95% CI 1.53-1.61; MB HR 2.96; 95% CI 2.92-3.00).

CONCLUSION

In over one million patients with NVAF, our results suggest differences in anticoagulation treatment persistence across OAC agents, even after accounting for clinical events after OAC initiation. It is important for clinicians and patients to take these differences into consideration, especially as non-persistence to OAC therapy is associated with thromboembolic complications.

Demonstration of proof-of-concept of StrokeShield system for complete closure and occlusion of the left atrial appendage for non-valvular atrial fibrillation therapy

In the US, the most significant morbidity and mortality associated with non-valvular atrial fibrillation (NVAF) is embolic stroke, with 90% of thrombus originating from the left atrial appendage (LAA). Anticoagulation is the preferred treatment for the prevention of stroke in NVAF patients, but clinical studies have demonstrated high levels of non-compliance and increased risk of bleeding or ineligibility for anticoagulation therapy, especially in the elderly population where the incidence of NVAF is highest. Alternatively, stroke may be preventing using clinically approved surgical and catheter-based devices to exclude or occlude the LAA, but these devices continue to be plagued by peri-device leaks and thrombus formation because of residual volume. To overcome these limitations, Cor Habere (Louisville, KY) and the University of Louisville are developing a LAA closure device (StrokeShield) that completely occludes and collapses the LAA to minimize the risk of stroke. The StrokeShield device is a collapsible occluder (nitinol reinforced membrane) that completely covers the LAA orifice with an expandable conical coil anchor that attaches to the myocardium. The device is designed for catheter-based delivery and expands to completely occlude the LAA orifice and collapse the LAA. The primary advantages of the StrokeShield system are a completely sealed LAA (no peri-device flow or residual space) and smooth endothelialized connection to the left atrial wall with minimal risk of cardiac bleeding and tamponade. We tested proof-of-concept of a prototype StrokeShield device in acute (n = 2) and chronic 60-day (n = 2) healthy canine models. Acute results demonstrated that the conical coil securely attached to the myocardium (5N pull-out force) and the Nitinol umbrella fully deployed and covered the LAA ostium. Results from the chronic implants demonstrated long-term feasibility of device placement with no procedural or device-related intra- or post-operative complications, secure placement and correct positioning of the device with no device migration. The device successfully occluded the LAA ostium and collapsed the LAA with no interference with the mitral valve, circumflex coronary artery, or pulmonary veins. Necropsy demonstrated no gross signs of thrombus or end-organ damage and the device was encapsulated in the LAA. Histology demonstrated mature neointima covering the device with expected foreign body inflammatory response. These early positive results will help to guide the iterative design process for the continued development of the StrokeShield system.

Real-world persistence to direct oral anticoagulants in patients with atrial fibrillation: a systematic review and network meta-analysis

OBJECTIVE

To conduct a systematic review and network meta-analysis of real-world evidence comparing adherence, persistence, cost, and utilization between oral anticoagulant (OAC) in non-valvular atrial fibrillation (NVAF) patients.

METHODS

A systematic search of MEDLINE and Embase (inception-July 2019) was conducted for published observational cohort studies comparing outcomes between ≥2 OACs. A network meta-analysis was performed to estimate odds ratios for non-persistence using a random-effects model.

RESULTS

There were 80 studies evaluating the outcomes of interest. However, due to a paucity in adherence studies and heterogeneity in adherence, cost, and utilization definitions, persistence was the focus of this network meta-analysis. There were 36 studies evaluating non-persistence in 395,593 participants, 24 of which used 3 gap definitions (30-, 60-, and 90-days); 18 unique studies evaluating non-persistence at 12 months were included in the network meta-analysis. Using 30- and 90-day gaps, all NOACs, when compared with VKAs, had lower odds of non-persistence (30-day OR (95%CI): apixaban: 0.63 (0.58, 0.69); rivaroxaban: 0.69 (0.62, 0.76); dabigatran: 0.89 (0.82, 0.97); 90-day OR (95%CI): apixaban: 0.33 (0.22, 0.47); rivaroxaban: 0.47 (0.36, 0.61); dabigatran 0.61 (0.44, 0.85)). When using a 60-day gap, dabigatran had higher odds of non-persistence vs VKAs (OR: 1.35; 95%CI: 1.12, 1.61), but there were no significant differences for apixaban and rivaroxaban. Apixaban had the lowest probability of non-persistence across the 3-gap definitions (95.7% with 30-day gap, 76.9% with 60-day gap, 98.4% with 90-day gap).

CONCLUSIONS

The current findings, despite multiple limitations, can raise awareness and understanding of real-world persistence associated with OAC therapy in NVAF patients.

Methodological considerations for investigating oral anticoagulation persistence in atrial fibrillation

AIMS

Reports of long-term oral anticoagulant (OAC) therapy for atrial fibrillation (AF) reveal highly variable, and generally suboptimal estimates of medication persistence. The objective of this review is to summarize current literature and highlight important methodological considerations for interpreting persistence research and designing studies of persistence on OAC treatment.

METHODS AND RESULTS

We summarize differences in study methodology, setting, timing, treatment, and other factors associated with reports of better or worse persistence. For example, prospective compared with retrospective study designs are associated with higher reported persistence. Similarly, patient factors such as permanent AF or high stroke risk, and treatment with non-vitamin K oral antagonists relative to vitamin K antagonists are associated with higher persistence. Persistence has also been reported to be higher in Europe compared with North America and higher when the treating physician is a general practitioner compared with a specialist. We propose a framework for assessing and designing persistence studies. This framework includes aspects of patient selection, reliability and validity of measures, persistence definitions, clinical utility of measurements, follow-up periods, and analytic approaches.

CONCLUSIONS

Differences in study design, patient selection, treatments, and factors such as the countries/regions where studies are conducted or the type of treating physician may help explain the variability in OAC persistence estimates. A framework is proposed to assess persistence studies. This may have utility to compare and interpret published studies as well as for planning of future studies.

Dose specific effectiveness and safety of DOACs in patients with non-valvular atrial fibrillation: A Canadian retrospective cohort study

BACKGROUND

Direct oral anticoagulants (DOACs) have been proven to be effective and safe for prevention of ischemic stroke and systemic embolism in patients with non-valvular atrial fibrillation (NVAF). However, suboptimal adherence, variable dosing and use in patient populations that otherwise would have been excluded from clinical trials may impact the efficacy and safety profile of DOACs in a routine care setting. We compared stroke, bleeding, and mortality rates on and off therapy for standard and low-dose DOACs (apixaban, rivaroxaban, dabigatran) versus warfarin in a Canadian cohort. We also assessed persistence of DOACs compared to warfarin.

METHODS

We conducted six 1-1 propensity-score matched retrospective cohort analyses using Quebec health administrative databases (2011-2017). NVAF patients (≥18 years) covered by the public medication insurance plan entered the cohort on the first OAC dispensation date. We excluded those with OAC use in the previous year or stroke or bleeding diagnoses in the previous two years. Follow-up ended at death, March 2017 or end of medication coverage by the public plan. Time-dependent Cox regression was applied.

RESULTS

We evaluated 10,893 patients initiated on apixaban (7206 standard, 3687 low-dose), 10,190 on rivaroxaban (7396 standard, 2794 low-dose), 5884 on dabigatran (2756 standard, 3128 low-dose), and propensity score-matched warfarin users. Across standard-dose DOACs, compared to warfarin, stroke risks were similar; bleeding risks were lower with apixaban (hazard ratio 0.63; 95% confidence interval 0.52-0.77) and dabigatran (0.47; 0.35-0.64) but not rivaroxaban (0.93; 0.79-1.10); death risks were lower with all DOACs. For low-dose DOACs, rivaroxaban demonstrated higher stroke (1.79; 1.21-2.64) and bleeding risks (1.37; 1.09-1.73); other agents had stroke risks similar to warfarin and bleeding risks lower than warfarin; only low-dose dabigatran had lower death risk (0.59; 0.52-0.68). Treatment discontinuation was lower with DOACs versus warfarin with the exception of low-dose rivaroxaban. The risks of stroke were 2-4 folds higher during time off any OAC versus time on warfarin. The risks of death were higher, while the risks of bleeding were generally lower during times off any OAC.

CONCLUSIONS

Standard-dose DOACs had similar stroke, better persistence and mortality profiles than warfarin. Only standard dose apixaban and dabigatran had better bleeding profiles than warfarin. Low-dose rivaroxaban had worse persistence, stroke and bleeding profiles than warfarin, while low-dose apixaban and dabigatran had similar stroke and better bleeding profiles. Real-world use of DOACs may explain some of the differences observed in Canadian routine care versus the phase III clinical trials.

Clinical Outcomes of Warfarin Initiation in Advanced Chronic Kidney Disease Patients With Incident Atrial Fibrillation

OBJECTIVES

The aim of this study was to examine the efficacy and safety of warfarin initiation following the diagnosis of atrial fibrillation (AF) in patients with late-stage chronic kidney disease (CKD) who transitioned to dialysis.

BACKGROUND

The clinical benefit of warfarin therapy for thromboprophylaxis after incident AF diagnosis in patients with late-stage CKD who are transitioning to dialysis is unknown.

METHODS

In this retrospective cohort analysis, the study population was a national cohort of 22,771 U.S. veterans with incident end-stage renal disease who developed incident AF before initiating renal replacement therapy. This study examined the association of warfarin therapy following the diagnosis of incident AF with ischemic cerebrovascular accidents (CVAs) (ischemic stroke or transient ischemic attack), ischemic CVA-related hospitalization, major bleeding events (gastrointestinal or intracranial bleeding), bleeding event-related hospitalizations, and post-dialysis, all-cause mortality in multivariable adjusted Cox regression analyses that adjusted for demographic characteristics and comorbidities.

RESULTS

The mean ± SD age of the cohort was 73.5 ± 8.8 years, 13% were African American, and the mean CHA₂DS₂-VASc score was 5.7 ± 2.1. Of the overall cohort, 6,682 (29.3%) patients were started on warfarin during the follow-up period. The hazard ratios (95% confidence intervals) for ischemic CVA, bleeding events, and death for those started on warfarin were 1.23 (1.16 to 1.30), 1.36 (1.29 to 1.44), and 0.94 (0.90 to 0.97), respectively, compared with those who received no anticoagulation. Warfarin exposure was associated with higher risk for ischemic CVA and bleeding event-related hospitalizations.

CONCLUSIONS

In patients with late-stage CKD who transitioned to dialysis, warfarin use was associated with higher risk of ischemic and bleeding events but a lower risk of mortality. Future studies such as those comparing warfarin with newer oral anticoagulant agents are needed to granularly define the net clinical benefit of anticoagulation therapy in patients with advanced CKD with incident AF.

Reducing Stroke Risk in Atrial Fibrillation: Adherence to Guidelines Has Improved, but Patient Persistence with Anticoagulant Therapy Remains Suboptimal

Atrial fibrillation (AF) is a significant risk factor for avoidable stroke. Among high-risk patients with AF, stroke risk can be mitigated using oral anticoagulants (OACs), however reduction is largely contingent on physician prescription and patient persistence with OAC therapy. Over the past decade significant advances have occurred, with revisions to clinical practice guidelines relating to management of stroke risk in AF in several countries, and the introduction of non-vitamin K antagonist OACs (NOACs). This paper summarises the evolving body of research examining guideline-based clinician prescription over the past decade, and patient-level factors associated with OAC persistence. The review shows clinicians' management over the past decade has increasingly reflected guideline recommendations, with an increasing proportion of high-risk patients receiving OACs, driven by an upswing in NOACs. However, a treatment gap remains, as 25–35% of high-risk patients still do not receive OAC treatment, with great variation between countries. Reduction in stroke risk directly relates to level of OAC prescription and therapy persistence. Persistence and adherence to OAC thromboprophylaxis remains an ongoing issue, with 2-year persistence as low as 50%, again with wide variation between countries and practice settings. Multiple patient-level factors contribute to poor persistence, in addition to concerns about bleeding. Considered review of individual patient's factors and circumstances will assist clinicians to implement appropriate strategies to address poor persistence. This review highlights the interplay of both clinician's awareness of guideline recommendations and understanding of individual patient-level factors which impact adherence and persistence, which are required to reduce the incidence of preventable stroke attributable to AF.

Geographic Disparities in the Incidence of Stroke among Patients with Atrial Fibrillation in the United States

AIM

To determine whether regional variation in stroke incidence exists among individuals with AF.

METHODS

Using healthcare utilization claims from 2 large US databases, MarketScan (2007-2014) and Optum Clinformatics (2009-2015), and the 2010 US population as the standard, we estimated age-, sex-, race- (only in Optum) standardized stroke incidence rates by the 9 US census divisions. We also used Poisson regression to examine incidence rate ratios (IRR) of stroke and the probability of anticoagulation prescription fills across divisions.

RESULTS

Both databases combined included 970,683 patients with AF who experienced 15,543 strokes, with a mean follow-up of 23 months. In MarketScan, the age- and sex-standardized stroke incidence rate was highest in the Middle Atlantic and East South Central divisions at 3.8/1000 person-years (PY) and lowest in the West North Central at 3.2/1000 PY. The IRR of stroke and the probability of anticoagulation fills were similar across divisions. In Optum Clinformatics, the age-, sex-, and race-standardized stroke incidence rate was highest in the East North Central division at 5.0/1000 PY and lowest in the New England division at 3.3/1000 PY. IRR of stroke and the probability of anticoagulation fills differed across divisions when compared to New England.

CONCLUSIONS

These findings suggest regional differences in stroke incidence among AF patients follow a pattern that differs from the hypothesized trend found in the general population and that other factors may be responsible for this new pattern. Cross-database differences provide a cautionary tale for the identification of regional variation using health claims data.