Anticoagulation Myth Busters

MYTH

“I don’t need to monitor my patient’s bloods when they are on a NOAC”

REALITY

“Since NOACs are associated with a predictable and rapid onset of action, fixed daily doses are prescribed that don’t necessarily warrant close monitoring. However, regular follow-up assessments for patients prescribed a NOAC are recommended, particularly in the presence of co-morbidities such as renal failure, older age, multiple co-morbidities or frailty.”1,2

While the manufacturers’ recommendations do not specifically stipulate details of the monitoring required for patients prescribed a NOAC, guideline recommendations suggest that blood sampling including haemoglobin, renal and liver function should be undertaken on at least an annual basis. A six-monthly review is recommended in patients ≥75 (especially if on dabigatran) or are deemed to be frail. Ad-hoc reviews are recommended in those who experience an inter-current illness which is likely to impact on renal or liver function.2

Since all NOACs are renally excreted, a baseline assessment of renal function should be undertaken and creatinine clearance (CrCl) determined using the Cockroft-Gault equation. NOAC dosing is determined by the patient’s renal function; as renal function can decline over time or can be affected by inter-current illnesses, routine follow-up and review is important to ensure the correct NOAC dose is prescribed. As a general rule of thumb, if CrCl ≤60ml/min, the frequency of follow-up and re-assessment of renal function is CrCl/10 e.g. CrCl = 50ml/min, recheck frequency = 5 months.3

Strict adherence to NOAC therapy is critical, since due to their rapid offset of action, their anticoagulant efficacy diminishes significantly 12-24 hours after the last dose taken.4 Repeated missed doses can lead to an absence of an anticoagulant effect. Patients prescribed a NOAC should have a regular review of their adherence to therapy – recent evidence suggests that up 30-35% of patients prescribed a NOAC for the prevention of AF-related stroke, stop treatment within 6 months of initiation.4

REFERENCES
  1. Kirchhof P, Benussi S, Kotecha D, Ahlsson A, Atar D, Casadei B, et al. 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS. European Heart Journal. 2016;37(38):2893-962.
  2. Steffel J, Verhamme P, Potpara TS, Albaladejo P, Antz M, Desteghe L, et al. The 2018 European Heart Rhythm Association Practical Guide on the use of non-vitamin K antagonist oral anticoagulants in patients with atrial fibrillation: executive summary. Europace. 2018.
  3. Luscher TF, Steffel J, Eberli FR, Joner M, Nakazawa G, Tanner FC, et al. Drug-eluting stent and coronary thrombosis: biological mechanisms and clinical implications. Circulation. 2007;115(8):1051-8.
  4. Jackevicius CA, Tsadok MA, Essebag V, Atzema C, Eisenberg MJ, Tu JV, et al. Early non-persistence with dabigatran and rivaroxaban in patients with atrial fibrillation. Heart. 2017;103(17):1331-8.
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