Is INR between 2.0 and 3.0 the optimal level for Chinese patients on warfarin therapy for moderate-intensity anticoagulation?

Comparative performance of pharmacogenetics-based warfarin dosing algorithms in Chinese population: use of a pharmacokinetic/pharmacodynamic model to explore dosing regimen through clinical trial simulation

OBJECTIVE

Warfarin has a narrow therapeutic window and large variability in dosing that are affected by clinical and genetic factors. To help guide the dosing of warfarin, the Clinical Pharmacogenetics Implementation Consortium has recommended the use of pharmacogenetic algorithms, such as the ones developed by the International Warfarin Pharmacogenetics Consortium (IWPC) and by Gage et al. when genotype information is available.

METHODS

In this study, simulations were performed in Chinese cohorts to explore how dosing differences between Western (by IWPC and Gage et al.) and Chinese algorithms (by Miao et al.) would mean in terms of anticoagulation effect in clinical trials. We first tried to replicate a published clinical trial comparing genotype-guided dosing to routine clinical dosing in Chinese patients. We then made simulations where Chinese cohorts received daily doses recommended by Gage, IWPC, and Miao algorithms.

RESULTS

We found that in simulation conditions where dosing specifications were strictly followed, genotype-guided dosing by IWPC and Lenzini formulae was more likely to overshoot the upper limit of the therapeutic window by day 15, and thus may have a lower % time in therapeutic range (%TTR) than that of clinical dosing group. Also, in comparing Gage, IWPC, and Miao algorithms, we found that the Miao dosing cohort has the highest %TTR and the lowest risk of over-anticoagulation by day 28.

CONCLUSION

In summary, our results confirmed that algorithms developed based on data from local patients may be more suitable for achieving therapeutic international normalized ratio window in Chinese population.

Warfarin and Polypharmacy Challenges in Sudan: Drug Interactions in Patient Cohort

Purpose

Warfarin plays an important role in anticoagulation therapy despite the availability of the newest oral anticoagulants, and achieving optimal anticoagulation is challenging due to its narrow therapeutic range and variable dose. This study aimed to highlight polypharmacy and drug interactions in patients receiving warfarin therapy at Medani Heart Centre, Sudan.

Methods

This retrospective hospital-based study was conducted from May 2017 to October 2018. Each concurrent medication prescribed for 104 patients was collected and checked for drug-drug interactions using Medscape Reference-Drug Interaction Checker. The data were analysed by using SPSS 20, and descriptive statistics were used.

Results

The results revealed that 95.2% of patients had more than three medications in their profile, (3-5), (6-9) and more than 10 medications were prescribed for 40.4%, 44.2% and 10.6% of patients, respectively. A total of 93.3% of patients had drug-drug interactions, as follows: (1-5), (6-10), (11-15), (16-20) and more than 20 drug-drug interactions were found in 31.7%, 32.7%, 19.2%, 5.8% and 3.8% of patients, respectively. A total of 178 warfarin-drug interactions were identified in 88.5% of the patients. The INR ranged between 2 and 2.99 in 13.4% of patients, and INR values below 2 and above 5 were found in 44.2% and 21.2% of patients, respectively. Analgesics (n=54; 30.3%), cardiovascular drugs (n=51; 28.6%), and anticoagulants (n=46; 25.8%) were the most common drug classes that interact with warfarin. Significant and serious types of interactions with warfarin were found in 51% and 37.5% of patients, respectively.

Conclusion

This study highlights the complexity of managing warfarin therapy amid prevalent polypharmacy. A substantial majority of patients experienced multiple drug interactions. The identification of significant and serious interactions emphasizes the need for vigilant management strategies, including improved communication among healthcare professionals and targeted education for both providers and patients, to enhance the safety and efficacy of warfarin therapy.

A Randomized Trial Comparing Standard of Care to Bayesian Warfarin Dose Individualization

The quality of warfarin treatment may be improved if management is guided by the use of models based upon pharmacokinetic-pharmacodynamic theory. A prospective, two-armed, single-blind, randomized controlled trial compared management aided by a web-based dose calculator (NextDose) with standard clinical care. Participants were 240 adults receiving warfarin therapy following cardiac surgery, followed up until the first outpatient appointment at least 3 months after warfarin initiation. We compared the percentage of time spent in the international normalized ratio acceptable range (%TIR) during the first 28 days following warfarin initiation, and %TIR and count of bleeding events over the entire follow-up period. Two hundred thirty-four participants were followed up to day 28 (NextDose: 116 and standard of care: 118), and 228 participants (114 per arm) were followed up to the final study visit. Median %TIR tended to be higher for participants receiving NextDose guided warfarin management during the first 28 days (63 vs. 56%, P = 0.13) and over the entire follow-up period (74 vs. 71%, P = 0.04). The hazard of clinically relevant minor bleeding events was lower for participants in the NextDose arm (hazard ratio: 0.21, P = 0.041). In NextDose, there were 89.3% of proposed doses accepted by prescribers. NextDose guided dose management in cardiac surgery patients requiring warfarin was associated with an increase in %TIR across the full follow-up period and fewer hemorrhagic events. A theory-based, pharmacologically guided approach facilitates higher quality warfarin anticoagulation. An important practical benefit is a reduced requirement for clinical experience of warfarin management.

Pregnancy outcomes in Chinese women with mechanical heart valves receiving warfarin treatment throughout pregnancy: 14-year experience

OBJECTIVE

The purpose was to evaluate pregnancy outcomes and risk factors associated with fetal complications in Chinese pregnant women with mechanical heart valves (MHVs) taking low-dose warfarin, aiming to fill in the research gap of this area.

METHODS

Between June 2010 and Aug 2023, 122 patients with MHVs who had 151 pregnancies and received warfarin throughout pregnancy were included. We compared them with 302 paired pregnancies without warfarin treatment. Binary logistic regression analyses were performed to explore risk predictors of fetal complications.

RESULTS

Pregnancy loss rate was 37.1 % in women taking warfarin, compared to only 4.6 % for those without warfarin exposure in pregnancy (RR = 8.00, 95 % CI: 4.61-13.90). In pregnant women with MHVs, there were 34 spontaneous abortions, 22 stillbirths and 1 neonatal malformation. In the first, second and third pregnant trimesters of women with MHVs, fetal complication incidences were 19.2 %, 9.9 % and 8.0 %, respectively. 86.0 % of fetal complications occurred in women taking a warfarin dose ≤5 mg/d, accounting for 94.0 % of the total population. The newborns' birth weight, gestational age and 1-minute Apgar score were significantly lower in pregnancies treated with warfarin compared to those without warfarin exposure. Only 2.0 % of postpartum hemorrhage and no thrombosis or maternal mortality data were collected in pregnant women on warfarin in this study.

CONCLUSION

Most Chinese pregnant women take a warfarin daily dose ≤5 mg and they might have only around 60 % chance of giving birth to a live baby without maternal complications.

Net clinical benefit of oral anticoagulants in Asian patients with atrial fibrillation based on a CHA2DS2-VASc score

BACKGROUND

This study was conducted to assess the net clinical benefit (NCB) for oral anticoagulant (OAC) in atrial fibrillation (AF) patients according to the CHA2DS2-VASc score.

METHODS

Patients with AF were prospectively recruited in the COOL AF Thailand registry from 2014 to 2017. The incidence rate of thromboembolic (TE) events and major bleeding (MB) was calculated. Cox proportional hazards model was used to compare the TE and MB rate in patients with and without OACs in CHA2DS2-VASc score of 0-1 and ≥ 2, respectively. The survival analysis was performed based on CHA2DS2-VASc score. The NCB of OACs was defined as the TE rate prevented minus the MB rate increased multiplied by a weighting factor.

RESULTS

A total of 3,402 AF patients were recruited. An average age of patients was 67.38 ± 11.27 years. Compared to non-anticoagulated patients, the Kaplan Meier curve showed anticoagulated patients with CHA2DS2-VASc score of 2 or more had the lower thromboembolic events with statistical significance (p = 0.043) and the higher MB events with statistical significance (p = 0.018). In overall AF patients, there were positive NCB in warfarin patients with CHA2DS2-VASc score of 3 or more while there were positive NCB in DOACs patients regardless of CHA2DS2-VASc score. Females with CHA2DS2-VASc score of 3 or more had a positive NCB regardless of OACs type. Good anticoagulation control (TTR ≥65%) improved an NCB in males with CHA2DS2-VASc score of 3 or more.

CONCLUSIONS

AF patients with CHA2DS2-VASc score of 3 or more regardless warfarin or DOACs had a positive NCB. The NCB of OACs was more positive for DOACs compared to warfarin and for females compared to males.

Real-world clinical outcomes of oral anticoagulants among Japanese patients with atrial fibrillation and concomitant coronary artery disease

Background

Stroke prevention is complicated in patients with atrial fibrillation (AF) and coronary artery disease (CAD). We compared the risk of major bleeding among Japanese patients with AF and CAD commencing warfarin, dabigatran, or rivaroxaban.

Methods

This study included adults with AF and CAD who were newly prescribed the non-vitamin K antagonist oral anticoagulants (NOACs) dabigatran or rivaroxaban, or warfarin, and registered between 18 April 2011 through 31 December 2020 in the Medical Data Vision hospital-based clinical database. The primary outcome was major bleeding, and the secondary outcome was a composite of stroke, systemic embolism, myocardial infarction, all-cause inpatient mortality, major bleeding, major gastrointestinal bleeding, and intracerebral hemorrhage. Cox proportional hazard models with stabilized inverse probability treatment weighting were used to estimate hazard ratios (HRs) with 95 % CIs via a two-step approach; first between warfarin and each NOAC, then between NOACs if sample size conditions were met.

Results

Dabigatran, rivaroxaban, and warfarin groups included 6712, 20,329, and 12,316 patients, respectively. Major bleeding risk was lower in NOACs versus warfarin (dabigatran: HR 0.50, 95 % CI: 0.40-0.62; rivaroxaban: HR 0.78, 95 % CI: 0.69-0.90); this risk was lower with dabigatran compared with rivaroxaban (HR 0.64, 95 % CI: 0.51─0.79). Net clinical benefit was superior to warfarin in both NOACs (dabigatran: HR 0.78, 95 % CI: 0.71-0.85; rivaroxaban: HR 0.83, 95 % CI: 0.78-0.88).

Conclusions

Among real-world Japanese patients with AF and CAD, NOACs were associated with better clinical outcomes than warfarin. Treatment with dabigatran had a lower risk of major bleeding than rivaroxaban.Clinical trial registration: NCT05051904 (ClinicalTrials.gov).

Relationship between elevated bilirubin levels and enhanced warfarin effects during biliary obstruction

OBJECTIVES

A marked prolongation of the prothrombin time-international normalized ratio (PT-INR) is frequently observed during biliary obstruction in patients using warfarin. The objective of this study was to identify factors associated with PT-INR prolongation during biliary obstruction in patients using warfarin.

METHODS

Among 44 patients using warfarin who had biliary obstruction, we retrospectively investigated warfarin doses and laboratory data before and during biliary obstruction. The primary outcome was the association between changes in PT-INR (ΔPT-INR) and changes in laboratory data before and during biliary obstruction.

RESULTS

Median PT-INR was 1.59 (IQR 1.38-1.95) before biliary obstruction and 2.27 (IQR 1.60-3.49) during biliary obstruction, indicating significant prolongation during the obstruction (P < 0.001). ΔPT-INR showed strong positive correlations with change in total bilirubin (ΔT-Bil; ρ = 0.692, P < 0.001) and change in conjugated bilirubin (ΔC-Bil; ρ = 0.731, P < 0.001). ΔPT-INR showed a weak negative correlation with the change in albumin (ΔAlb; ρ =  -0.371, P < 0.05). When ΔPT-INR was used as the dependent variable in multiple linear regression analysis, ΔT-Bil, ΔC-Bil, and ΔAlb were significantly associated with ΔPT-INR.

CONCLUSIONS

PT-INR was prolonged during biliary obstruction in patients using warfarin, and changes in bilirubin levels were associated with ΔPT-INR. If biliary obstruction with markedly elevated bilirubin levels occurs, measuring PT-INR could lead to safer warfarin therapy.

Genetic heterogeneity in cardiovascular disease across ancestries: Insights for mechanisms and therapeutic intervention

Cardiovascular diseases (CVDs) are complex in their aetiology, arising due to a combination of genetics, lifestyle and environmental factors. By nature of this complexity, different CVDs vary in their molecular mechanisms, clinical presentation and progression. Although extensive efforts are being made to develop novel therapeutics for CVDs, genetic heterogeneity is often overlooked in the development process. By considering molecular mechanisms at an individual and ancestral level, a richer understanding of the influence of environmental and lifestyle factors can be gained and more refined therapeutic interventions can be developed. It is therefore expedient to understand the molecular and clinical heterogeneity in CVDs that exists across different populations. In this review, we highlight how the mechanisms underlying CVDs vary across diverse population ancestry groups due to genetic heterogeneity. We then discuss how such genetic heterogeneity is being leveraged to inform therapeutic interventions and personalised medicine, highlighting examples across the CVD spectrum. Finally, we present an overview of how polygenic risk scores and Mendelian randomisation can foster more robust insight into disease mechanisms and therapeutic intervention in diverse populations. Fulfilment of the vision of precision medicine requires more exhaustive leveraging of the genetic variability across diverse ancestry populations to improve our understanding of disease onset, progression and response to therapeutic intervention.

Standard-Intensity Versus Low-Intensity Anticoagulation with Warfarin in Asian Patients with Atrial Fibrillation: A Multi-Center, Randomized Controlled Trial

Anticoagulation with warfarin in Asian patients with atrial fibrillation (AF) often has been decreased as an international normalized ratio (INR) of prothrombin time 1.6-2.6 due to fear of bleeding, although universal criteria recommend an INR of 2.0-3.0. In this randomized, open-label trial, low-intensity anticoagulation (INR 1.6-2.6) was compared with standard-intensity anticoagulation (INR 2.0-3.0) with warfarin. A total 616 patients with AF and at least 1 risk factor for stroke were randomized to low-intensity anticoagulation (n = 308) and standard-intensity anticoagulation (n = 308) groups. The intention-to-treat analysis was performed to determine differences. The baseline characteristics of the two groups were comparable. New-onset stroke occurred in 2 patients (0.44% per year) in the low-intensity group and 5 patients (1.05% per year) in the standard-intensity group (HR 0.42, 95% CI 0.08-2.15). Major bleeding occurred in 4 patients (0.89% per year) in the low-intensity group and 5 patients (1.06% per year) in the standard-intensity group (HR 0.84, 95% CI 0.22-3.11). The rate of the net clinical outcome (composite of stroke, systemic embolism, major bleeding, and death) was 1.33% per year in the low-intensity group compared with 2.12% per year in the standard-intensity group (HR 0.63, 95% CI 0.23-1.72). In Asian patients with AF, clinical outcomes were not different between low-intensity and standard-intensity anticoagulation with warfarin.

Comparison of Maintenance Dose Predictions by Warfarin Dosing Algorithms Based on Chinese and Western Patients

Warfarin has a long record of safe and effective clinical use, and it remains one of the most commonly prescribed drugs for the prevention and treatment of thromboembolic conditions even in the era of direct oral anticoagulants. To address its large interindividual variability and narrow therapeutic window, the Clinical Pharmacogenetics Implementation Consortium has recommended using pharmacogenetic dosing algorithms, such as the ones developed by the International Warfarin Pharmacogenetics Consortium (IWPC) and by Gage et al, to dose warfarin when genotype information is available. In China, dosing algorithms based on local patient populations have been developed and evaluated for predictive accuracy of warfarin maintenance doses. In this study, percentage deviations of doses predicted by 15 Chinese dosing algorithms from that by IWPC and Gage algorithms were systematically evaluated to understand the differences between Chinese and Western algorithms. In general, dose predictions by Chinese dosing algorithms tended to be lower than those predicted by IWPC or Gage algorithms for the most prevalent VKORC1 and CYP2C9 genotypes in the Chinese population. The extent of negative prediction deviation appeared to be largest in the younger age group with smaller body weight. Our findings are consistent with previous reports that Asians have a higher sensitivity to warfarin and require lower doses than Western populations.

Safety and efficacy of using portable coagulation monitor for INR examination after left-sided mechanical prosthetic valve replacement

BACKGROUND

Time in therapeutic range (TTR) is an index to assess the effectiveness of anticoagulation and is important to predict the risk of bleeding and thrombosis in patients taking warfarin. In recent years, the portable coagulation monitor, a point-of-care testing device for patients to perform self-management international normalized ratio (INR) examination, has provided an opportunity to improve the quality of oral warfarin treatment. In this study, we applied TTR to evaluate the safety and efficacy of the portable coagulation monitor for patients with oral anticoagulant warfarin after left-sided mechanical prosthetic valve (MPV) replacement.

METHODS

It is a single-centre cohort study. From September 2019 to June 2021, a total of 243 patients who returned to our institution for outpatient clinic revisit at 3 months after left-sided MPV replacement, met the inclusion criteria and agreed to be followed up were included. Self-management group used portable coagulation monitor for INR examination, and patients in the conventional group had their INR monitored in routine outpatient visits. Clinical data of the patients would be recorded for the next 12 months, and results were compared between the two groups to assess the effect of the coagulation monitor on TTR and complications related to bleeding and thrombosis in patients with left-sided MPV replacement.

RESULTS

A total of 212 individuals provided complete and validated INR data spanning of 1 year. Those who applied the portable coagulation monitor had higher TTR values and larger number of tests for INR. No significant differences were seen between the two groups in postoperative bleeding and thromboembolic complications, but portable coagulation monitor showed a trend toward fewer bleeding events.

CONCLUSION

Portable devices for coagulation monitoring are safe and can achieve a higher TTR. Patients who use the portable coagulation monitor for home INR self-management can achieve a safe and effective warfarin therapy.

Impact of VKORC1, CYP2C9, CYP1A2, UGT1A1, and GGCX polymorphisms on warfarin maintenance dose: Exploring a new algorithm in South Chinese patients accept mechanical heart valve replacement

BACKGROUND

Warfarin is the most recommended oral anticoagulant after artificial mechanical valve replacement therapy. However, the narrow therapeutic window and varying safety and efficacy in individuals make dose determination difficult. It may cause adverse events such as hemorrhage or thromboembolism. Therefore, advanced algorithms are urgently required for the use of warfarin.

OBJECTIVE

To establish a warfarin dose model for patients after prosthetic mechanical valve replacement in southern China in combination with clinical and genetic variables, and to improve the accuracy and ideal prediction percentage of the model.

METHODS

Clinical data of 476 patients were tracked and recorded in detail. The gene polymorphisms of VKORC1 (rs9923231, rs9934438, rs7196161, and rs7294), CYP2C9 (rs1057910), CYP1A2 (rs2069514), GGCX (rs699664), and UGT1A1 (rs887829) were determined using Sanger sequencing. Multiple linear regressions were used to analyze the gene polymorphisms and the contribution of clinical data variables; the variables that caused multicollinearity were screened stepwise and excluded to establish an algorithm model for predicting the daily maintenance dose of warfarin. The ideal predicted percentage was used to test clinical effectiveness.

RESULTS

A total of 395 patients were included. Univariate linear regression analysis suggested that CYP1A2 (rs2069514) and UGT1A1 (rs887829) were not associated with the daily maintenance dose of warfarin. The new algorithm model established based on multiple linear regression was as follows: Y = 1.081 - 0.011 (age) + 1.532 (body surface area)-0.807 (rs9923231 AA) + 1.788 (rs9923231 GG) + 0.530 (rs1057910 AA)-1.061 (rs1057910 AG)-0.321 (rs699664 AA). The model accounted for 61.7% of individualized medication differences, with an ideal prediction percentage of 69%.

CONCLUSION

GGCX (rs699664) may be a potential predictor of warfarin dose, and our newly established model is expected to guide the individualized use of warfarin in clinical practice in southern China.

New Internet-Based Warfarin Anticoagulation Management Approach After Mechanical Heart Valve Replacement: Prospective, Multicenter, Randomized Controlled Trial

BACKGROUND

Mechanical heart valve replacement (MHVR) is an effective method for the treatment of severe heart valve disease; however, it subjects patient to lifelong warfarin therapy after MHVR with the attendant risk of bleeding and thrombosis. Whether internet-based warfarin management reduces complications and improves patient quality of life remains unknown.

OBJECTIVE

This study aimed to compare the effects of internet-based warfarin management and the conventional approach in patients who received MHVR in order to provide evidence regarding alternative strategies for long-term anticoagulation.

METHODS

This was a prospective, multicenter, randomized, open-label, controlled clinical trial with a 1-year follow-up. Patients who needed long-term warfarin anticoagulation after MHVR were enrolled and then randomly divided into conventional and internet-based management groups. The percentage of time in the therapeutic range (TTR) was used as the primary outcome, while bleeding, thrombosis, and other events were the secondary outcomes.

RESULTS

A total of 721 patients were enrolled. The baseline characteristics did not reach statistical differences between the 2 groups, suggesting the random assignment was successful. As a result, the internet-based group showed a significantly higher TTR (mean 0.53, SD 0.24 vs mean 0.46, SD 0.21; P<.001) and fraction of time in the therapeutic range (mean 0.48, SD 0.22 vs mean 0.42, SD 0.19; P<.001) than did those in the conventional group. Furthermore, as expected, the anticoagulation complications, including the bleeding and embolic events had a lower frequency in the internet-based group than in the conventional group (6.94% vs 12.74%; P=.01). Logistic regression showed that internet-based management increased the TTR by 7% (odds ratio [OR] 1.07, 95% CI 1.05-1.09; P<.001) and reduced the bleeding and embolic risk by 6% (OR 0.94, 95% CI 0.92-0.96; P=.01). Moreover, low TTR was found to be a risk factor for bleeding and embolic events (OR 0.87, 95% CI 0.83-0.91; P=.005).

CONCLUSIONS

The internet-based warfarin management is superior to the conventional method, as it can reduce the anticoagulation complications in patients who receive long-term warfarin anticoagulation after MHVR.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR1800016204; http://www.chictr.org.cn/showproj.aspx?proj=27518.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.1136/bmjopen-2019-032949.

Risk of major bleeding and thromboembolism in Asian patients with nonvalvular atrial fibrillation using direct oral anticoagulants versus warfarin

Background Bleeding and thromboembolism prevention is important in patients with nonvalvular atrial fibrillation receiving anticoagulants, including direct oral anticoagulants and warfarin. Asians have higher risks of bleeding complications when taking anticoagulants. However, evidence that considers laboratory parameters is lacking. Objective We aimed to compare the safety and effectiveness between direct oral anticoagulants and warfarin in Asian patients with nonvalvular atrial fibrillation. Setting Retrospective design using hospital-based data. Method This propensity score-matched cohort study included data extracted from the electronic medical records of the En Chu Kong Hospital Research Database. Main outcome measure Outcome measures were major bleeding and thromboembolism. Cox proportional hazard models were applied for evaluating hazard ratios with 95% confidence intervals. Results Among 1075 patients with nonvalvular atrial fibrillation, 687 and 388 were administered direct oral anticoagulants and warfarin, respectively. After propensity score matching, 264 patient pairs were selected. Compared with warfarin use, direct oral anticoagulant use was associated with similar risks for major bleeding and thromboembolism; however, the latter was associated with increased gastrointestinal bleeding risks (adjusted hazard ratio 3.59; 95% confidence interval, 1.31-11.39). Notably, an approximately 10 fold increased risk of gastrointestinal bleeding was observed in 0-6 month direct oral anticoagulant users (adjusted hazard ratio 10.13, 95% confidence interval 1.27-80.89). Conclusion Direct oral anticoagulant use was not associated with major bleeding and thromboembolism occurrence in Asian patients with nonvalvular atrial fibrillation. However, direct oral anticoagulant use was associated with increased gastrointestinal bleeding risks, especially when used within 0-6 months of direct oral anticoagulant use.

Warfarin maintenance dose prediction for Chinese after heart valve replacement by a feedforward neural network with equal stratified sampling

Patients requiring low-dose warfarin are more likely to suffer bleeding due to overdose. The goal of this work is to improve the feedforward neural network model's precision in predicting the low maintenance dose for Chinese in the aspect of training data construction. We built the model from a resampled dataset created by equal stratified sampling (maintaining the same sample number in three dose-groups with a total of 3639) and performed internal and external validations. Comparing to the model trained from the raw dataset of 19,060 eligible cases, we improved the low-dose group's ideal prediction percentage from 0.7 to 9.6% and maintained the overall performance (76.4% vs. 75.6%) in external validation. We further built neural network models on single-dose subsets to invest whether the subsets samples were sufficient and whether the selected factors were appropriate. The training set sizes were 1340 and 1478 for the low and high dose subsets; the corresponding ideal prediction percentages were 70.2% and 75.1%. The training set size for the intermediate dose varied and was 1553, 6214, and 12,429; the corresponding ideal prediction percentages were 95.6, 95.1%, and 95.3%. Our conclusion is that equal stratified sampling can be a considerable alternative approach in training data construction to build drug dosing models in the clinic.

Does Warfarin or Rivaroxaban at Low Anticoagulation Intensity Provide a Survival Benefit to Asian Patients With Atrial Fibrillation?

Background: Low-dose rivaroxaban and low-intensity warfarin are widely used in Asia for patients with atrial fibrillation (AF). However, in Asians, it is unclear whether low-dose rivaroxaban and low-intensity warfarin can improve the prognosis of AF. In this study, we investigate the survival benefits of low-dose rivaroxaban and low-intensity warfarin in Asian patients with AF in clinical practice. Methods: This cohort study used medical records in a single tertiary hospital in China, between 2019 and 2020, to identify patients with AF who used rivaroxaban or warfarin, or had no anticoagulant therapy. Follow-ups were performed through telephone contact or medical record review. Cox proportional hazards models were used to compare the risk of mortality of patients in the anticoagulant-untreated group vs. warfarin-treated groups and rivaroxaban-treated groups. Results: A total of 1727 AF patients, discharged between 2019 and 2020, were enrolled in this cohort, of which 873 patients did not use any anticoagulant, 457 patients received warfarin and 397 patients used rivaroxaban. Multivariable analysis showed that, of all the warfarin groups, patients with an international normalized ratio (INR) below 2, good INR control, or poor INR control had a significantly lower risk of mortality compared with that of patients without anticoagulants (HR 0.309, p = 0.0001; HR 0.387, p = 0.0238; HR 0.363, p < 0.0001). Multivariable Cox proportional hazard analyses also demonstrated that, compared with the no anticoagulant group, all rivaroxaban dosage groups (≤10 mg, HR 0.456, p = 0.0129; 15 mg, HR 0.246, p = 0.0003; 20 mg, HR 0.264, p = 0.0237) were significantly associated with a lower risk of mortality. Conclusion: Despite effects being smaller than observed with recommended optimal anticoagulation, the use of warfarin with an INR below 2, poor INR control and the use of low-dose rivaroxaban may still provide survival benefits, suggesting viable alternatives that enable physicians to better resolve decisional conflicts concerning the risks and benefits of anticoagulant therapies, as well as for patients in need of but unable to receive standard anticoagulant therapy due to bleeding risk or other factors, such as financial burden, concerns of adverse outcomes, as well as low treatment compliance and persistence.

Anticoagulation Resumption in a Patient With Mechanical Heart Valves, Antithrombin Deficiency, and Hemorrhagic Transformation Following Thrombectomy After Ischemic Stroke

Anticoagulation is essential for patients undergoing mechanical heart valve replacement; however, the timing to reinitiate the anticoagulant could be a dilemma that imposes increased risk for bleeding events in patients suffering from the life-threatening hemorrhagic transformation (HT) after ischemic stroke. Such a situation was presented in this case report. A 71-year-old woman was transferred directly to the Neurocritical Care Unit because of a HT that occurred following the mechanical thrombectomy for ischemic stroke. Since she had a history of prosthetic metallic valve replacement, how the anticoagulating therapy could balance the hemorrhagic and thrombotic risks was carefully evaluated. On day 6 after the onset of hemorrhage transformation, the laboratory results of coagulation and fibrinolysis strongly suggested thrombosis as well as antithrombin deficiency. The short-acting and titratable anticoagulant argatroban was immediately initiated at low dose, and thrombosis was temporarily terminated. On day 3 of anticoagulation resumption, argatroban was discontinued for one dose when the prothrombin time and activated partial thromboplastin time significantly prolonged after argatroban infusion. Aortic valve thrombosis was detected the next day. The anticoagulation was then strengthened by dose adjustment to keep mitral valve intact, to stabilize the aortic valve thrombosis, and to decrease the aortic flow rate. The intravenous argatroban was transited to oral warfarin before the patient was discharged. This study is the first report of administering argatroban and titrating to its appropriate dose in the patient with valve thrombosis, antithrombin deficiency, and HT after mechanical thrombectomy for acute ischemic stroke. Notably, the fluctuations argatroban brings to the coagulation test results might not be interpreted as increased bleeding risk. This case also suggested that the reported timing (day 6 to day 14 after hemorrhage) of anticoagulant resumption in primary intracerebral hemorrhage with mechanical valves might be late for some patients with HT.

Delayed diagnosis of spinal subarachnoid hemorrhage in association with warfarin administration: a case report and literature review

Spinal subarachnoid hemorrhage is a life-threatening condition often associated with markedly high morbidity and mortality rates. However, diagnosis is difficult because of its atypical symptoms. We herein describe a 52-year-old Chinese man who had been receiving warfarin therapy since having undergone mechanical mitral valve replacement surgery 3 years previously. Two days before admission to our hospital, he suddenly developed low back pain, urinary incontinence, and paraplegia. He was diagnosed with acute myelitis at a local hospital, but he subsequently developed a slight headache and was transferred to our hospital 2 days later. The patient was suspected to have subarachnoid hemorrhage based on his computed tomography (CT) findings. On the third day after admission, a CT scan showed both subarachnoid and cerebral hemorrhage. Blood tests revealed an international normalized ratio ranging from 1.44 to 1.86 and a prothrombin time of 16.5 to 21.3 s. We performed a lumbar puncture and obtained bloody cerebrospinal fluid. The patient also underwent spinal CT and angiography, which confirmed the diagnosis of spontaneous spinal subarachnoid hemorrhage. Because his general condition was poor, he underwent conservative treatment, and his neurologic function slightly improved after discharge.

Optimal INR level in patients with atrial fibrillation with EHRA type 2 valvular heart disease receiving warfarin

Background

To date, there has been no study that compares the efficacy and safety of warfarin in atrial fibrillation (AF) patients with Evaluated Heartvalves, Rheumatic or Artificial (EHRA) type 2 valvular heart disease (VHD). This study was conducted to determine the optimal INR in these patients.

Methods

This retrospective study enrolled AF patients with EHRA type 2 VHD receiving warfarin in Central Chest Institute of Thailand between January 2016 and December 2018. The incidence density of thromboembolic or bleeding events was calculated. The International normalized ratio (INR) was classified into six groups (less than 1.50, 1.50 to 1.99, 2.00 to 2.49, 2.50 to 2.99, 3.00 to 3.49, and 3.50 or more). The optimal INR level was defined as the lowest incidence density of thromboembolic events and bleeding complications.

Results

A total of 200 AF patients with EHRA type 2 VHD receiving warfarin were enrolled, contributing to 289 patient‐years of observation period. There were 13 thromboembolic events (4.5 per 100 patient‐years) and 16 bleeding events (5.5 per 100 patient‐years). The incidence density of thromboembolic events was significantly increased in the INR level below 2.00 (P = .03), while the INR level of 3.50 or more was significantly increased in the incidence density of major bleeding events (P = .03). Total bleeding and minor bleeding were increased significantly in INR level of 2.50 or more (P = .04).

Conclusions

The INR of 2.00 to 2.49 was appeared to be associated with the lowest incidence density of thromboembolic and bleeding events in these patients.

Long term CentriMag biventricular support using hybrid cannulation as a bridge to transplant in a pediatric patient

Paracorporeal continuous-flow ventricular assist devices designed for short-term support can also potentially provide long-term circulatory support as bridges to transplantation in children. We describe the long-term use of the CentriMag biventricular assist device with multiple pump changes in a 9-year-old boy with idiopathic-dilated cardiomyopathy. The initially implanted Berlin Heart EXCOR pumps were replaced by CentriMag due to thromboembolic complications. The CentriMag pumps were exchanged 15 times due to clot and fibrin formation or when the pumps reached their expiration dates. Connecting CentriMag to Berlin Heart EXCOR cannulae effectively served as an alternative long-term hybrid bridge to transplantation for 235 days. The patient successfully underwent a transplant after 284 days. Judicious pump monitoring and timely pump exchanges can potentially overcome device-related complications and extend the duration on support.

Racial and Ethnic Differences in Response to Anticoagulation: A Review of the Literature

INTRODUCTION

Anticoagulants are among the most frequently prescribed medications in the United States. Racial and ethnic disparities in incidence and outcomes of thrombotic disorders are well-documented, but differences in response to anticoagulation are incompletely understood.

OBJECTIVE

The objective of this review is to describe the impact of race and ethnicity on surrogate and clinical end points related to anticoagulation and discuss racial or ethnic considerations for prescribing anticoagulants.

METHODS

A PubMed and MEDLINE search of clinical trials published between 1950 and May 2018 was conducted using search terms related to anticoagulation, specific anticoagulant drugs, race, and ethnicity. References of identified studies were also reviewed. English-language human studies on safety or efficacy of anticoagulants reporting data for different races or ethnicities were eligible for inclusion.

RESULTS

Seventeen relevant studies were identified. The majority of major trials reviewed for inclusion either did not include representative populations or did not report on the racial breakdown of participants. Racial differences in pharmacokinetics, dosing requirements, drug response, and/or safety end points were identified for unfractionated heparin, enoxaparin, argatroban, warfarin, rivaroxaban, and edoxaban.

CONCLUSIONS

Race appears to influence drug concentrations, dosing, or safety for some but not all direct oral anticoagulants. This information should be considered when selecting anticoagulant therapy for nonwhite individuals.

Impact of CYP2C9, VKORC1, ApoE and ABCB1 polymorphisms on stable warfarin dose requirements in elderly Chinese patients

Aim: To analyze the impact of nongenetic factors and gene polymorphisms on warfarin dose requirements in elderly Shanghai Han Chinese patients. Materials & methods: Genotypes of CYP2C9 (rs1799853 and rs1057910), FPGS (rs7856096), ApoE (rs7412 and rs429358), GGCX (rs699664 and rs12714145), EPHX1 (rs4653436, rs1877724, rs1051740 and rs1131873), NQO1 (rs1800566 and rs10517), ABCB1 (rs1045642), VKORC1 (rs9923231) and CYP4F2 (rs2108622) in 214 patients with stable warfarin dose were determined and their demographic characteristics were recorded. Results: Multiple linear regression analysis revealed that VKORC1 rs9923231, CYP2C9*3 rs1057910, ApoE rs7412, age, BMI and concomitant amiodarone could explain 37.0% of the individual variations of daily stable warfarin dose. Conclusion: VKORC1 rs9923231, CYP2C9*3 rs1057910, ApoE rs7412, age, BMI and concomitant amiodarone play an important role in stable dose variation of warfarin in elderly Shanghai Han Chinese patients, whereas ABCB1 rs1045642 is not a significant genetic factor.

Optimal oral anticoagulant therapy in Chinese patients with mechanical heart valves

BACKGROUND

The oral administration of anticoagulants is an effective means of preventing thromboembolic complications in patients implanted with mechanical valves. This treatment strategy, however, entails a dose-dependent in the risk of hemorrhage that is a cause for concern in China. As such, in this study, we sought to better determine what the ideal oral anticoagulant therapy intensity is in a Chinese population of patients implanted with mechanical valves.

METHODS

In the present observational cohort study, we observed the outcomes of eligible enrolled patients that had been implanted with St. Jude Medical prosthetic valves and who had been treated at our institution from 2013 onwards. All enrolled patients were followed for between 1 and 6 years through outpatient visits or telephone interviews following discharge. Study endpoints included instances of thromboembolism and major hemorrhage. We calculated the international normalized ratio (INR)-specific incidence of such adverse events as a means of determining optimal anticoagulant therapeutic intensity in patients with these bileaflet mechanical valve prostheses.

RESULTS

In total this study enrolled 3176 patients, of whom 3017 were followed for 12,746.08 total person-years (4.22 mean years per patient), while the remaining 159 patients (5%) were lost during follow-up. A total of 182 patients suffered from adverse events, with a roughly 1.43% annual incidence rate of such adverse events (95% confidence interval [CI], 1.22-1.64). Of these, 54 patients suffered from episodes of major bleeding (0.42% per patient-year, 95% CI, 0.31-0.53), while 131 suffered from thromboembolism (1.03% per patient-year, 95% CI, 0.85-1.21). Based on these analyses, we determined that the ideal low-intensity anticoagulant treatment regimen for patients with bileaflet mechanical heart valve prostheses was an INR between 1.5 and 2.5. In those patients that had undergone aortic valve replacement (AVR), the optimal INR was between 1.5 and 2.0 regardless of any thromboembolism risk factors in these patients. In contrast, in patients that had undergone mitral valve replacement (MVR) who were not at risk for thromboembolism, the optimal INR was between 1.5 and 2.0, whereas in those at risk of thromboembolism the optimal INR was between 2.0 and 2.5. The ideal anticoagulant intensity in patients undergoing both AVR and MVR (DVR) was the same as in patients undergoing MVR alone.

CONCLUSIONS

In order to achieve optimal outcomes by maintaining effective anticoagulant dosing while entailing minimal risk in Chinese patients that have undergone a bileaflet mechanical valve replacement, the target INR range should be between 1.5 and 2.5, with the final intensity of this anticoagulant regimen being determined based on a given patient's risk of thromboembolism.

Impact of a pharmacist-led education and follow-up service on anticoagulation control and safety outcomes at a tertiary hospital in China: a randomised controlled trial

OBJECTIVES

This study was designed to evaluate the impact of a pharmacist-led anticoagulation service on international normalised ratio (INR) control and other outcomes among patients receiving warfarin therapy at a tertiary hospital in Zhuhai, China.

METHODS

In this randomised controlled trial, adult patients who were newly initiated on warfarin with intended treatment duration of at least 3 months were recruited. Participants were randomly allocated to receive the pharmacist-led education and follow-up service (PEFS) or usual care (UC). Anticoagulation control was calculated as the proportions of time within the target INR range (TTR) and time within the expanded target range (TER).

KEY FINDINGS

A total of 152 participants (77 in the PEFS group and 75 in the UC group) were included. Within 180 days after hospital discharge, the PEFS group spent more TER than the UC group (54.4% versus 42.0%; P = 0.024), whereas the difference in TTR did not reach statistical significance (35.9% versus 29.5%; P = 0.203). No major bleeding events were observed, and the cumulative incidences of major thromboembolic events (6.5% versus 9.3%) and mortality (1.3% versus 1.3%) were similar between the two groups (P> 0.05). At 30 days postdischarge, the PEFS group had better warfarin knowledge by answering 57.5% of questions correctly, compared with the UC group (43.0%) (P = 0.003).

CONCLUSIONS

The PEFS markedly enhanced anticoagulation control and warfarin knowledge but there was room for improvement. The expansion of pharmacists' clinical role and the development of more effective education and follow-up strategies are warranted to optimise anticoagulation management services in China.

Impact of Anticoagulation Intensity in Korean Patients with Atrial Fibrillation: Is It Different from Western Population?

BACKGROUND AND OBJECTIVES

Although anticoagulation with warfarin is recommended as an international normalized ratio (INR) of prothrombin time between 2.0 and 3.0 and mean time in the therapeutic range (TTR) ≥70%, little has been proven that universal criteria might be suitable in Korean atrial fibrillation (AF) patients.

METHODS

We analyzed 710 patients with non-valvular AF who took warfarin. INR value and clinical outcomes were assessed during 2-year follow-up. Intensity of anticoagulation was assessed as mean INR value and TTR according to target INR range. Primary net-clinical outcome was defined as the composite of new-onset stroke and major bleeding. Secondary net-clinical outcome was defined as the composite of new-onset stroke, major bleeding and death.

RESULTS

Thromboembolism was significantly decreased when mean INR was over 1.6. Major bleeding was significantly decreased when TTR was over 70% and mean INR was less than 2.6. Mean INR 1.6-2.6 significantly reduced thromboembolism (adjusted hazard ratio [HR], 0.40; 95% confidence interval [CI], 0.19-0.85), major bleeding (HR, 0.43; 95% CI, 0.23-0.81), primary (HR, 0.50; 95% CI, 0.29-0.84) and secondary (HR, 0.45; 95% CI, 0.28-0.74) net-clinical outcomes, whereas mean INR 2.0-3.0 did not. Simultaneous satisfaction of mean INR 1.6-2.6 and TTR ≥70% was associated with significant risk reduction of major bleeding, primary and secondary net-clinical outcomes.

CONCLUSIONS

Mean INR 1.6-2.6 was better than mean INR 2.0-3.0 for the prevention of thromboembolism and major bleeding. However, INR 1.6-2.6 and TTR ≥70% had similar clinical outcomes to INR 2.0-3.0 and TTR ≥70% in Korean patients with non-valvular AF.

Comparison of the Effects of Indobufen and Warfarin in a Rat Model of Adenine-Induced Chronic Kidney Disease

Background

Worldwide, the treatment of patients with chronic kidney disease (CKD) remains a challenge as warfarin treatment can be associated with severe adverse events related to bleeding. Alternative anticoagulants that can be used in CKD remain to be identified. This study aimed to compare the effects of indobufen, a new antiplatelet agent, with warfarin in a rat model of adenine-induced CKD.

Material/Methods

Forty-eight male Wistar rats were treated with intragastric adenine to create the rat model of CKD and were divided into four groups: an untreated control group (N=12), a group treated with dimethyl sulfoxide (DMSO) (N=12), a group treated with indobufen, (N=12) and a group treated with warfarin (N-12). Treatment was given for 4 weeks and 8 weeks. Kidney histology was performed, and the degree of fibrosis was quantified using Masson trichrome staining.

Results

In the rat model of adenine-induced CKD, Masson trichrome staining showed that the degree of kidney fibrosis in the indobufen group (26%) was significantly reduced (p<0.05) when compared the DMSO group (58%) and the warfarin group (49%). Kidney fibrosis was associated with upregulation of 6-keto-PGI2/TXB2 in the rat kidney tissue.

Conclusions

In a rat model of adenine-induced CKD, preliminary findings showed that indobufen was associated with reduced kidney fibrosis when compared with warfarin.

The comparison of non-vitamin K antagonist oral anticoagulants versus well-managed warfarin with a lower INR target of 1.5 to 2.5 in Asians patients with non-valvular atrial fibrillation

Background

Previous studies indicated low-intensity warfarin (INR target of 1.5–2.5) achieved reduced hemorrhage without increasing thromboembolism for Asians with non-valvular atrial fibrillation (NVAF). Whether non-vitamin K antagonist oral anticoagulant (NOAC) is superior to warfarin with good time in the therapeutic range (TTR) based on lower INR target among Asians with NVAF remains unknown.

Methods

In this retrospective study collected from Taiwan Chang Gung Memorial Hospital Database, there were 5,197, 3,396, and 9,898 consecutive patients taking warfarin, NOAC, and no-treatment, respectively, from January 1, 2000 to December 31, 2015. Propensity-score weighting was used across the study groups. Patients were followed until the first occurrence of study outcome or end date of study.

Results

Among those patients taking warfarin, the mean”artificial” TTR (aTTR) based on a lower INR target of 1.5–2.5 was 44.4±33.3%. Total 79.2% (n = 2,690) patients took low-dose NOACs. Patients with aTTR in the range from <30%(34.0%), 30–50%(17.6%), 50–70%(23.5%) to >70%(24.9%) showed decremental risks of efficacy and composite outcome compared with no-treatment. The risk of major bleeding didn’t increase among patients with top aTTR>70% compared to no-treatment. The NOAC group showed a comparable risk of composite outcome to the warfarin subgroup with aTTR of >70% (P = 0.485). The NOAC group had a lower risk of composite outcome than warfarin subgroup with TTR of>70% based on the INR target of 2.0–3.0 (P = 0.004).

Conclusions

NOACs showed a comparable risk of efficacy, safety, and composite outcome to well-managed warfarin based on a lower INR target of 1.5–2.5 in Asians with NVAF taking oral anticoagulants.

Maintenance dose of warfarin beyond time in therapeutic range for preventing vascular events

BACKGROUND

The quality of anticoagulation is closely associated with efficacy and safety in warfarin users. Although genetic polymorphisms have been related to warfarin dosages and vascular events(VE), genetic evaluations have not been recommended for all warfarin users. The aim is to evaluate the significance of the maintenance dose of warfarin (MDW) on VE, considering the time in therapeutic range (TTR).

METHODS

This retrospective study analyzed the data of patients who received warfarin for any reasons. A total of 11,835 patients with warfarin were divided into quartiles by MDW. We assessed TTR using the Rosendaal method and VE.

RESULTS

VE occurred in 9.1% of the warfarin users. The mean TTR level was 34.0 ± 25.7%, and the MDW was 3.38 ± 1.06 mg per day. Patients with VE were more likely to have a lower MDW and lower TTR levels. In moderate- or well-controlled TTR status, a lower MDW was significantly related to under-controlled anticoagulation and associated with higher risks of VE. Lower MDW had a higher risk of stroke or arterial/venous thromboembolism (Q1: OR, 1.57; 95% CI 1.25 to 1.96; Q2: OR, 1.40; 95% CI 1.12 to 1.75; Q3: OR, 1.35; 95% CI 1.08 to 1.68).

CONCLUSIONS

We suggest that patients with very low MDW might be at risk when using warfarin. Therefore, we propose that patients with a very low MDW might be alternatively considered for novel oral anticoagulants rather than warfarin.

Evaluation of the predictive performance of Bayesian dosing for warfarin in Chinese patients

Aim: To evaluate the accuracy and predictive performance of Bayesian dosing for warfarin in Chinese patients. Materials & methods: Six multiple linear regression algorithms (Wei, Lou, Miao, Huang, Gage and IWPC) and a Bayesian method implemented in Warfarin Dose Calculator were compared with each other. Results: Six multiple linear regression warfarin dosing algorithms had similar predictive ability, except Miao and Lou. The mean prediction error of Bayesian priori and posteriori method were 0.01 mg/day (95% CI: -0.18 to 0.19) and 0.17 mg/day (95% CI: -0.05 to 0.29), respectively, and Bayesian posteriori method demonstrated better performance in all dose ranges. Conclusion: The Bayesian method showed a good potential for warfarin maintenance dose prediction in Chinese patients requiring less than 6 mg/day.

Preventing arteriovenous shunt failure in hemodialysis patients: a population-based cohort study

Essentials Uncertainty remains about antiplatelets for vascular access patency in hemodialysis patients. 95 971 people under hemodialysis were followed in a claims database in Taiwan. Aspirin reduced vascular access failure rate and did not increase major bleeding rate. Clopidogrel, Aggrenox, and warfarin might increase major bleeding rate. SUMMARY: Background Dialysis adequacy is a major determinant of survival for patients with end-stage renal disease. Good vascular access is essential to achieve adequate dialysis. Objectives This study evaluated the impacts of different drugs on the vascular access failure rate of an arteriovenous fistula or an arteriovenous graft and the rate of major bleeding in hemodialysis patients. Patients and methods We studied patients with end-stage renal disease registered in the Taiwan National Health Insurance program from 1 January 1997 to 31 December 2012. A total of 95 971 patients were enrolled in our study. Vascular access dysfunction was defined as the need for thrombectomy or percutaneous angioplasty. Major bleeding was defined as emergency department visits or hospitalization with a primary diagnosis of gastrointestinal bleeding or intracerebral hemorrhage. The adjusted odds ratios between person-quarters with or without antiplatelet or oral anticoagulant use were calculated using a generalized estimating equation. Results The odds ratio of vascular access failure was 0.21 (0.11-0.39) for aspirin, 0.76 (0.74-0.79) for clopidogrel, 0.67 (0.59-0.77) for dipyridamole, 0.67 (0.53-0.86) for Aggrenox and 0.96 (0.90-1.03) for warfarin. The highest odds ratio for intracerebral hemorrhage was 5.33 (1.25-22.72) in younger patients using Aggrenox. The highest odds ratio for gastrointestinal bleeding was 1.34 (1.10-1.64) for clopidogrel. Conclusion Antiplatelet agents, but not warfarin, might reduce the vascular access thrombosis rate. The gastrointestinal bleeding rate was increased in the group using clopidogrel. Aggrenox should be used with caution in young individuals because it might increase the rate of intracerebral hemorrhage.

International normalized ratio for the guidance of warfarin treatment in elderly patients after cardiac valve replacement

Thus far, the target value for international normalized ratio (INR) has remained to be determined. The current study aimed to further explore the INR value of the anti-coagulation drug warfarin after cardiac valve replacement. The clinical data of 213 patients who underwent cardiac valve replacement at Linyi Central Hospital (Linyi, China) between January 2010 and May 2013 were retrospectively analyzed. The warfarin dosage, prothrombin time (PT) and INR were compared among patients with hemorrhage or embolism, and those with no complications. A total of 31 cases (14.6%) developed adverse reactions and complications during the medication period, including 21 cases with hemorrhage (9.9%, hemorrhage group) and 10 cases with embolism (4.7%, embolism group), while 182 patients did not (85.4%, normal group). The average dosage of warfarin was 2.0±0.6, 3.1±0.7 and 1.7±0.6 mg/day in the normal, hemorrhage and embolism groups, respectively. The dosage of warfarin, the PT and the INR in the hemorrhage group were all significantly greater than those in the normal group and the embolism group (all P<0.05). INR monitoring is recommended to ensure the safety of the anti-coagulant drug warfarin, but further study is still required to determine a reasonable target INR value.

Management of dental extractions in patients on warfarin and antiplatelet therapy

BACKGROUND/PURPOSE

Planning dental extractions for Taiwanese patients on antithrombotic therapy remains controversial. This study aimed to examine management of dental extraction in patients on warfarin and antiplatelet therapy.

METHODS

Subjects comprised 1331 patients, with (1) 60 on warfarin with intentional normalized ratio (INR) below 4.0 (warfarin continued: 28 patients/33 occasions; warfarin stopped and switched to heparin under hospitalization: 32 patients/37 occasions); (2) 183 on antiplatelet therapy (aspirin: 125 patients/185 occasions; clopidogrel: 42 patients/65 occasions; dual therapy: 16 patients/24 occasions); and (3) a control group of 1088 patients/1472 occasions without any antithrombotic therapy. The patient's clinico-demographic parameters, warfarin effectiveness (dose and INR levels) and antiplatelet therapy, number and type of dental extraction and incidence of postoperative bleeding were investigated.

RESULTS

Incidence of postoperative bleeding in the warfarinized group (warfarin continued: 9.1%; warfarin stopped: 8.1%) was higher than in the antiplatelet group (aspirin: 1.1%; clopidogrel: 3.1%; dual antiplatelet: 4.2%), and the control group (0.7%), but these differences were not significant and unrelated to INR or number and type of dental extraction. Postoperative hemorrhage was managed successfully by repacking with Gelfoam impregnated with tranexamic acid powder in most patients.

CONCLUSION

The study indicated that there is no need to interrupt warfarin (INR<4.0) and antiplatelet therapy before dental extractions in Taiwanese patients. A sufficient hemostasis could be obtained using local measures. This approach can save these individuals from becoming exposed to the risk of thromboembolism and the inconvenience of bridging anticoagulation with heparin.

Asian patients versus non-Asian patients in the efficacy and safety of direct oral anticoagulants relative to vitamin K antagonist for venous thromboembolism: A systemic review and meta-analysis

INTRODUCTION

The standard for treatment and secondary prevention of venous thromboembolism (VTE) has been vitamin K antagonist (VKA), which might be associated with a higher risk of bleeding particularly in Asian patients. Direct oral anticoagulants (DOAC) have been shown to be safer alternatives for VTE. It remains unclear whether this is the case in Asian ethnicity.

MATERIALS AND METHODS

We performed a meta-analysis of randomized controlled trials to evaluate the efficacy and safety of DOACs in Asian and non-Asian patients with acute VTE. We searched MEDLINE, CENTRAL, and ClinicalTrials.gov. The efficacy endpoint was recurrent VTE or VTE-related death. The safety endpoint was major bleedings or clinically relevant non-major bleedings. The pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated.

RESULTS

We identified 6 studies that comprised 3542 Asian and 23,481 non-Asian patients. The efficacy of DOACs was comparable with VKA in both Asian and non-Asian patients (OR, 0.90; 95% CI, 0.55-1.49; P = 0.69 for Asian patients; OR, 0.92; 95% CI, 0.78-1.08; P = 0.32 for non-Asian patients; P interaction = 0.94). DOACs significantly reduced the safety endpoint compared with VKA in Asian patients (OR, 0.64; 95% CI, 0.51-0.80; P < 0.001), while DOACs were associated with non-significant reduction in non-Asian patients (OR, 0.73; 95% CI, 0.53-1.01; P = 0.06), indicating that the reduction seemed numerically more prominent in Asian patients, although there was no statistically significant interaction (P interaction = 0.49).

CONCLUSIONS

The efficacy of DOACs was comparable with VKA irrespective of ethnicity, and DOACs could be safer alternatives in Asian patients.

Estimation of the warfarin dose with a pharmacogenetic refinement algorithm in Chinese patients mainly under low-intensity warfarin anticoagulation

Pharmacogenetic (PG) dosing algorithms have been confirmed to predict warfarin therapeutic dose more accurately;however, most of them are based on standard intensity of warfarin anticoagulation, and their utility outside this range is limited. This study was designed to develop and validate a PG refinement algorithm in Chinese patients mainly under low-intensity warfarin anticoagulation. Consented Chinese-Han patients (n=310) under stable warfarin treatment were randomly divided into a derivation (n=207) and a validation cohort (n=103), with 83% and 80% of the patients under low-intensity anticoagulation, respectively. In the derivation cohort, a PG algorithm was constructed on the basis of genotypes (CYP2C9*3 and VKORC1–1639A/G) and clinical data. After integrating additional covariates of international normalised ratio (INR) values (INR on day 4 of therapy and target INR) and genotype of CYP4F2 (rs2108622), a PG refinement algorithm was established and explained 54% of warfarin dose variability. In the validation cohort, warfarin dose prediction was more accurate (p <0.01) with the PG refinement algorithm than with the PG algorithm and the fixed dose approach (3 mg/day). In the entire cohort, the PG refinement algorithm could accurately identify larger proportions of patients with lower dose requirement (≤2 mg/day) and higher dose requirement (≥4 mg/day) than did the PG algorithm. In conclusion, PG refinement algorithm integrating early INR response and three genotypes CYP2C9*3, VKORC1–1639A/G, CYP4F2 rs2108622) improves the accuracy of warfarin dose prediction in Chinese patients mainly under low-intensity anticoagulation.

Stroke prevention in atrial fibrillation: An Asian perspective

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. In 2050, it is estimated that there will be 72 million AF patients in Asia, accounting for almost 2.9 million patients suffering from AF-associated stroke. Asian AF patients share similar risk factor profiles as non-Asians, except that more Asians have a history of previous stroke. Clinical challenges are evident in the field of stroke prevention in AF, amongst Asians. Existing stroke and bleeding risk scores have not been well-validated in Asians. Asians are prone to bleeding when treated with warfarin, and the optimal international normalised ratio (INR) for warfarin use is yet to be determined in Asians, though Asian physicians tend to keep it in a lower range (e.g. INR 1.6–2.6) for elderly patients despite limited evidence to justify this. In general, warfarin is ‘difficult’ to use in Asians due to higher risk of bleeding and higher stroke rate in Asians than in non-Asians, as shown in randomised controlled trials. Excess of bleeding was not found in Asians when novel oral anticoagulants (NOACs) were used. Besides, the superiority of NOACs to warfarin in reducing thromboembolism was maintained in Asians. Therefore NOACs are preferentially indicated in Asians in terms of both efficacy and safety. Also, some preliminary data suggest that Asian patients with AF might not be the same. Future prospective randomised trials are needed for the selection of NOACs according to different ethnic background.

Note: The review process for this manuscript was fully handled by Christian Weber, Editor in Chief.

Regional differences in presentation and antithrombotic treatment of patients with atrial fibrillation: Baseline characteristics from a clustered randomized trial to IMProve treatment with AntiCoagulanTs in patients with atrial fibrillation (IMPACT-AF)

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide. However, there are few contemporary comparative data on AF from middle-income countries.

METHODS

Baseline characteristics of the IMPACT-AF trial were analyzed to assess regional differences in presentation and antithrombotic treatment of AF from 5 middle-income countries (Argentina, Brazil, China, India, and Romania) and factors associated with antithrombotic treatment prescription.

RESULTS

IMPACT-AF enrolled 2281 patients (69 ± 11 years, 47% women) at 48 sites. Overall, 66% of patients were on anticoagulation at baseline, ranging from 38% in China to 91% in Brazil. The top 3 reasons for not prescribing an anticoagulant were patient preference/refusal (26%); concomitant antiplatelet therapy (15%); and risks outweighing the benefits, as assessed by the physician (13%). In a multivariable model, the most significant factors associated with prescription of oral anticoagulants were no prior major bleeding (odds ratio [OR] = 4.34; 95% CI = 2.22-8.33), no alcohol abuse (OR = 2.27; 95% CI = 1.12-4.55), and history of rheumatic valvular heart disease (OR = 2.10; 95% CI = 1.36-3.26), with a strong predictive accuracy (c statistic = 0.85), whereas the most significant factors associated with prescription of a combination of oral anticoagulants and antiplatelet drugs were prior coronary revascularization (OR = 5.10; 95% CI = 2.88-9.05), prior myocardial infarction (OR = 2.24; 95% CI = 1.38-3.63), and no alcohol abuse (OR = 2.22; 95% CI = 1.11-4.55), with a good predictive accuracy (c statistic = 0.76).

CONCLUSIONS

IMPACT-AF provides contemporary data from 5 middle-income countries regarding antithrombotic treatment of AF. Lack of prior major bleeding and coronary revascularization were the most important factors associated with prescription of oral anticoagulants and their combination with antiplatelet drugs, respectively.

D-dimer to guide the intensity of anticoagulation in Chinese patients after mechanical heart valve replacement: a randomized controlled trial

Essentials Low anticoagulation intensity reduces bleeding but increases thrombosis during warfarin therapy. Elevated D-dimer level is associated with increased thrombosis events. D-dimer can be used to find potential thrombosis in those receiving low intensity therapy. D-dimer-guided therapy may be the optimal strategy for those with mechanical heart valve replacement.

SUMMARY

Background Controversies remain regarding the optimal anticoagulation intensity for Chinese patients after mechanical heart valve replacement despite guidelines having recommended a standard anticoagulation intensity. Objectives To investigate whether D-dimer could be used to determine the optimal anticoagulation intensity in Chinese patients after mechanical heart valve replacement. Patients/Methods This was a prospective, randomized controlled clinical study. A total of 748 patients following mechanical heart valve replacement in Wuhan Asia Heart Hospital were randomized to three groups at a ratio of 1 : 1 : 1. Patients in two control groups received warfarin therapy based on constant standard intensity (international normalized ratio [INR], 2.5-3.5; n = 250) and low intensity (INR, 1.8-2.6; n = 248), respectively. In the experimental group (n = 250), warfarin therapy was initiated at low intensity, then those with elevated D-dimer levels were adjusted to standard intensity. All patients were followed-up for 24 months until the occurrence of endpoints, including bleeding events, thrombotic events and all-cause mortality. Results A total of 718 patients were included in the analysis. Fifty-three events occurred during follow-up. There was less hemorrhage (3/240 vs. 16/241; hazard ratio [HR], 0.18; 95% confidence interval [CI], 0.07-0.45) and all-cause mortality (4/240 vs. 12/241; HR, 0.33; 95% CI, 0.12-0.87) observed in the D-dimer-guided group than in the standard-intensity group. A lower incidence of thrombotic events was also observed in the D-dimer-guided group when compared with the low-intensity group (5/240 vs. 14/237; HR, 0.35; 95% CI, 0.14-0.85). Overall, the total events were less in the D-dimer-guided group (9/240) when compared with the other two control groups (24/241, 20/237; HR, 0.37, 0.44; 95% CI, 0.19-0.72, 0.21-0.90 Conclusions The D-dimer-guided adjustment of anticoagulation intensity could reduce adverse events in Chinese patients after mechanical heart valve replacement.

TRIAL REGISTRY

NCT01996657; ClinicalTrials.gov.

Cost Effectiveness of Genotype-Guided Warfarin Dosing in Patients with Mechanical Heart Valve Replacement Under the Fee-for-Service System

BACKGROUND

Although studies assessing the cost effectiveness of genotype-guided warfarin dosing for the management of atrial fibrillation, deep vein thrombosis, and pulmonary embolism have been reported, no publications have addressed genotype-guided warfarin therapy in mechanical heart valve replacement (MHVR) patients or genotype-guided warfarin therapy under the fee-for-service (FFS) insurance system.

OBJECTIVE

The aim of this study was to evaluate the cost effectiveness of genotype-guided warfarin dosing in patients with MHVR under the FFS system from the Korea healthcare sector perspective.

METHODS

A decision-analytic Markov model was developed to evaluate the cost effectiveness of genotype-guided warfarin dosing compared with standard dosing. Estimates of clinical adverse event rates and health state utilities were derived from the published literature. The outcome measure was the incremental cost-effectiveness ratio (ICER) per quality-adjusted life-year (QALY). One-way and probabilistic sensitivity analyses were performed to explore the range of plausible results.

RESULTS

In a base-case analysis, genotype-guided warfarin dosing was associated with marginally higher QALYs than standard warfarin dosing (6.088 vs. 6.083, respectively), at a slightly higher cost (US$6.8) (year 2016 values). The ICER was US$1356.2 per QALY gained. In probabilistic sensitivity analysis, there was an 82.7% probability that genotype-guided dosing was dominant compared with standard dosing, and a 99.8% probability that it was cost effective at a willingness-to-pay threshold of US$50,000 per QALY gained.

CONCLUSION

Compared with only standard warfarin therapy, genotype-guided warfarin dosing was cost effective in MHVR patients under the FFS insurance system.

Integrating genotypes in the SAMe-TT2R2 score for the prediction of anticoagulation control in Chinese patients with atrial fibrillation on warfarin

INTRODUCTION

The SAMe-TT₂R₂ score has been proposed to predict whether patients with atrial fibrillation (AF) would be well anti-coagulated with warfarin or not. However, it might over-estimate the number of patients under suboptimal warfarin treatment in non-Caucasians. This study was designed to modify the SAMe-TT₂R₂ score with genotypes and validate it in Chinese AF patients treated with warfarin.

MATERIAL AND METHODS

Consented Chinese-Han patients (n=510) with AF under the treatment of warfarin for at least 3months were randomly divided into a derivation (n=310) and a validation cohort (n=200). For each patient, CYP2C9*3 and VKORC1 -1639 A/G genotyping was performed, and the time in therapeutic range (TTR) was calculated over this period.

RESULTS

The modified SAMe-TT₂R₂ score was established by adding "warfarin genotype bins" to replace "the non-white race" variable. In the validation cohort, the discrimination performance of the modified score for good anticoagulation control (TTR≥70%) was significantly improved (c- index increased from 0.60 to 0.67). Significantly increased risks of major bleedings (HR: 4.91; 95% CI: 1.03-23.37; adjusted p=0.04) and all bleedings (HR: 1.93; 95% CI: 1.14-3.25; adjusted p=0.01) were found in patients with modified scores ≥2, as compared with patients with modified scores of 0-1.

CONCLUSIONS

The modified SAMe-TT₂R₂ score could improve the ability for the identification of good anticoagulation control, and the prediction of major bleeding events in Chinese patients with AF treated by warfarin.

Clinical and genetic factors associated with warfarin maintenance dose in northern Chinese patients with mechanical heart valve replacement

The effects of genetic variants on warfarin dosing vary among different ethnic groups, especially in the Chinese population. The objective of this study was to recruit patients through a rigorous experimental design and to perform a comprehensive screen to identify gene polymorphisms that may influence warfarin dosing in northern Han Chinese patients with mechanical heart valve replacement. Consenting patients (n = 183) with a stable warfarin dose were included in this study. Ninety-six single nucleotide polymorphisms (SNPs) in 30 genes involved in warfarin pharmacological pathways were genotyped using the Illumina SNP GoldenGate Assay, and their associations with warfarin dosing were assessed using univariate regression analysis with post hoc comparison using least significant difference analysis. Multiple linear regression was performed by incorporating patients' clinical and genetic data to create a new algorithm for warfarin dosing. From the 96 SNPs analyzed, VKORC1 rs9923231, CYP1A2 rs2069514, CYP3A4 rs28371759, and APOE rs7412 were associated with higher average warfarin maintenance doses, whereas CYP2C9 rs1057910, EPHX1 rs2260863, and CYP4F2 rs2189784 were associated with lower warfarin doses (P < 0.05). Multiple linear regression analysis could estimate 44.4% of warfarin dose variability consisting of, in decreasing order, VKORC1 rs9923231 (14.2%), CYP2C9*3 (9.6%), body surface area (6.7%), CYP1A2 rs2069514 (3.7%), age (2.7%), CYP3A4 rs28371759 (2.5%), CYP4F2 rs2108622 (1.9%), APOE rs7412 (1.7%), and VKORC1 rs2884737 (1.4%). In the dosing algorithm we developed, we confirmed the strongest effects of VKORC1, CYP2C9 on warfarin dosing. In the limited sample set, we also found that novel genetic predictors (CYP1A2, CYP3A4, APOE, EPHX1, CYP4F2, and VKORC1 rs2884737) may be associated with warfarin dosing. Further validation is needed to assess our results in larger independent northern Chinese samples.

Mitral valve replacement in a dialysis-dependent patient

Patients with end-stage renal disease have a higher risk of morbidity and mortality than those without end-stage renal disease in cardiovascular surgery. Poor outcomes are especially found in patients who undergo valve surgery. We report successful mitral valve replacement (MVR) in a dialysis-dependent patient. The patient recovered well at postoperation and had the complication of anticoagulation at follow-up. Based on this successful case, we believe that myocardial protection, prevention of infection, nutritional support, and close monitoring of blood coagulation function are important in dialysis-dependent patients undergoing valve replacement.

Drug Treatment of Venous Thromboembolism in the Elderly

Half of all patients with acute venous thromboembolism are aged over 70 years; they then face the added hazard of an age-related increase in the incidence of major bleeding. This makes it even more important to weigh the balance of benefit and risk when considering anticoagulant treatment and treatment duration. Traditional treatment with a heparin (usually low molecular weight) followed by a vitamin K antagonist such as warfarin is effective but is often complicated, especially in the elderly. The direct-acting oral anticoagulants (DOACs), i.e. the thrombin inhibitor dabigatran and the factor Xa inhibitors rivaroxaban, apixaban and edoxaban, are given in fixed doses, do not need laboratory monitoring, have fewer drug-drug interactions and are therefore much easier to take. Randomised trials, their meta-analyses and 'real-world' data indicate the DOACs are no less effective than warfarin (are non-inferior) and probably cause less major bleeding (especially intracranial). It seems the relative safety of DOACs extends to age above 65 or 70 years, although bleeding becomes more likely regardless of the chosen anticoagulant. Renal impairment, comorbidities (especially cancer) and interventions are special hazards. Ways to minimise bleeding include patient selection and follow-up, education about venous thromboembolism, anticoagulants, drug interactions, regular checks on adherence and avoiding needlessly prolonged treatment. The relatively short circulating half-lives of DOACs mean that time, local measures and supportive care are the main response to major bleeding. They also simplify the management of invasive interventions. An antidote for dabigatran, idarucizumab, was recently approved by regulators, and a general antidote for factor Xa inhibitors is in advanced development.

Association of apolipoprotein E (APOE) polymorphisms with warfarin maintenance dose in a northern Han Chinese population

Background

Apolipoprotein E (apoE) induces the uptake of vitamin K-rich lipoproteins by the liver, which likely affects inter-individual variation of warfarin dosing requirements. Associations between APOE polymorphisms and warfarin dosing were previously reported inconsistently among different ethnic groups, so the present study investigated this association in northern Han Chinese patients with mechanical heart valve prosthesis.

Methods

A total of 186 patients who underwent mechanical heart valve replacement and attained a stable warfarin dose were included. APOE single nucleotide polymorphisms (SNPs) rs7412 and rs429358 were genotyped using Illumina SNP GoldenGate Assay. Genotyping results were confirmed by direct sequencing. PHASE v2.1 software was used to construct rs7412 and rs429358 haplotypes. The effects of different APOE genotypes on warfarin dose were analyzed statistically.

Results

The mean warfarin maintenance dose was 3.10 ± 0.96 mg/day, and the mean international normalized ratio (INR) was 2.09 ± 0.24. APOE E2, E3, and E4 allele frequencies were 11.6 %, 82.5 %, and 5.9 %, respectively. No E2/E2 or E4/E4 genotypes were detected in this population. E2/E3, E3/E3, E2/E4, and E3/E4 genotype frequencies were 21.0 %, 67.2 %, 2.2 %, and 9.7 %, respectively. Significant differences in warfarin dose requirements were observed among patients with E2/E3, E3/E3, and E3/E4 genotypes (p < 0.05). In post hoc comparison, daily warfarin maintenance doses were significantly higher in E2/E3 heterozygotes compared with E3/E3 homozygotes (p < 0.05), but no differences in dose requirements were found between E3/E4 and E3/E3, or E2/E3 and E3/E4 (p > 0.05). Patients were divided into low-intensity anticoagulant treatment group (1.6 ≤ INR <2.0) and relatively high-intensity anticoagulant treatment group (2.0 ≤ INR ≤2.5), and significantly higher warfarin dose requirements were observed in E2/E3 heterozygotes compared with E3/E3 homozygotes in both subgroups (p < 0.05). Multivariable analysis adjusting for other confounders showed that E2/E3 genotype was associated with a significantly higher warfarin dose compared with E3/E3 genotype (p < 0.05).

Conclusions

APOE allele and genotype frequencies in the northern Han Chinese population appear to differ from other racial groups or populations living in other regions of China. The APOE E2 variant was associated with a significantly higher warfarin maintenance dose. Thus, APOE polymorphisms could be one of the predictors influencing warfarin doses in this population.