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Cardiovascular Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Choices of anticoagulation for stroke prevention in AF are shown in Table 7.20. Direct oral anticoagulants (DOACs) have become standard care for many patients with AF due to their superior efficacy and/or lower bleeding risk compared to warfarin. For patients taking warfarin for AF, the target international normalized ratio (INR) range is 2.0–3.0. Their time in therapeutic range (TTR) should be reviewed regularly and if <65% then they should be switched to a DOAC.
Management strategies
Published in Gregory YH Lip, Atrial Fibrillation in Practice, 2020
For example, care should be employed when interpreting the results of the clinical trials, which demonstrate unequivocal benefit of anticoagulation in AF. These trials were conducted on a carefully selected patient population and where anticoagulation was strictly monitored in well-motivated investigators and patients, who essentially received careful follow-up and ‘packages of care’. Whether or not these results could be fully extrapolated to general clinical practice is not entirely clear. In patients taking antithrombotic therapy, the annual risks of intracranial haemorrhage increase from 0.1% in controls to 0.3% in warfarin groups in the pooled analysis of the AF Investigators, which represents an excess of two intracranial bleeds per annum per thousand patients treated. The bleeding risk with anticoagulation was particularly associated with an INR greater than 3.0, fluctuating INRs and with uncontrolled hypertension.
Haematology
Published in Michael McGhee, A Guide to Laboratory Investigations, 2019
See next section, ‘Warfarin in practice’. The INR is the ratio of the patient’s prothrombin time (the time taken for plasma to form a fibrin clot when mixed with tissue thromboplastin) and the control prothrombin time raised to the power of the International Sensitivity Index.An INR of 1 represents the clotting time of an individual with normal clotting. An INR of 2 indicates that the sample of blood takes twice as long to clot.
Impact of perioperative direct oral anticoagulant assays: a multicenter cohort study
Published in Hospital Practice, 2023
Brandon Stretton, Joshua Kovoor, Stephen Bacchi, Andrew Booth, Sam Gluck, Andrew Vanlint, Mohamed Afzal, Christopher Ovenden, Aashray Gupta, Rajiv Mahajan, Suzanne Edwards, Yvonne Brennan, Jir Ping Boey, Benjamin Reddi, Guy Maddern, Mark Boyd
The INR provides surgeons with a means of monitoring the anticoagulant effects of warfarin and planning intervention accordingly. Quantifying plasma concentrations of DOACs is possible, but the wide therapeutic index of the DOACs and substantial inter-individual variation in plasma concentrations [2] make correlation of DOAC plasma titers with anticoagulant effect difficult. Best practice for perioperative management of patients taking DOACs remains uncertain. Current guidelines for operating on patients with DOACs support the use of time from last dose to establish a safe window to proceed to surgery [3,4]. This is based on the pharmacokinetics of the DOACs. For the majority of patients without hepatic or renal dysfunction, DOAC cessation is recommended 24 h prior to low bleeding-risk operations and 48–72 h prior to high bleeding-risk operations [3]. However, the additive pharmacokinetic effects of multiple patient characteristics and comorbidities may impact drug clearance and therefore surgical safety.
The efficacy of low-dose warfarin initiation (3 mg versus 5 mg) in newly diagnosed venous thromboembolism patients among a population with a high prevalence of warfarin-sensitive haplotype of the VKORC1 gene: a randomized controlled trial
Published in Hematology, 2022
Bundarika Suwanawiboon, Wannaphorn Rotchanapanya, Komkrit Mahaprom, Wanna Thongnoppakhun, Yupaporn Lalerd, Chanin Limwongse, Nuttawut Sermsathanasawadi, Weerapat Owattanapanich
The eligible patients were randomized by blocked randomization with block size of 4 stratifying for age to receive a warfarin initiating dose of 3 mg or 5 mg per day for the first 2 consecutive days (day 1 and day 2) (Figures 1 and 2). The first day of warfarin treatment was designated day 1. Subsequent warfarin dosing was adjusted according to the INR and the warfarin dosing protocol (Figure 3). The choice of concomitant heparin treatment was made according to the attending physician’s discretion. Blood samples were collected from venipuncture and were sent for baseline PT, INR, aPTT, complete blood count and a liver function test prior to the initiation of warfarin anticoagulant therapy. In addition, blood for INR testing was collected on days 3, 5 and 8 of warfarin treatment. Furthermore, blood samples were drawn and sent for the evaluation of the single nucleotide polymorphisms (SNPs) of the CYP2C9 and VKORC1 genes to determine the prevalence of the genetic variables and the impact on the warfarin response among the participants. The outcomes assessors of the INR and the SNPs of CYP2C9 and VKORC1 genes were blinded to the treatment allocation. The enrolled inpatients or outpatients were followed on days 3, 5, and 8 of warfarin treatment.
Time in therapeutic range of anticoagulation among patients with atrial fibrillation and cerebral amyloid angiopathy
Published in Baylor University Medical Center Proceedings, 2022
Robert C. Ward, Jonathan Graff-Radford, Shiva Ponamgi, Stephen English, Alayna Meskill, Apurva B. Challa, David O. Hodge, Joshua P. Slusser, Alejandro A. Rabinstein, Samuel J. Asirvatham, David Holmes, Christopher V. DeSimone
Atrial fibrillation (AF) and cerebral amyloid angiopathy (CAA) increase in frequency with age and when they occur simultaneously present unique risk profiles for an increasing number of patients.1–3 The increased risk of ischemic stroke in patients with AF is reduced by oral anticoagulation.4–6 However, anticoagulant use in patients with CAA increases the risk of intracerebral hemorrhage (ICH).7,8 Clinicians are increasingly weighing these risks and benefits in patients with concomitant AF and CAA, without clear evidence to guide management decisions. Vitamin K antagonists remain commonly prescribed oral anticoagulant options for patients with AF.9–11 A known challenge with vitamin K antagonist use is the fluctuation in therapeutic level over time. The most common international normalized ratio (INR) goal for a patient with AF is 2 to 3.5,6 An INR that is too high portends an increased risk of bleeding, while an INR that is too low mitigates the effectiveness of the anticoagulation.12 The impact of fluctuating INR levels on outcomes in patients with concurrent AF and CAA is currently unknown. The objectives of this study were to evaluate the time in therapeutic range of anticoagulation for a cohort of patients with AF and CAA and describe how time in therapeutic range and fluctuating INR impact the risk of stroke, ICH, and mortality.