What are you prescribing for atrial fibrillation?

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What are you prescribing for atrial fibrillation?

Despite widespread uptake, DOACs are still underutilised and atrial fibrillation is still undertreated in Australia.

This is according to Dr Andrew Sindone, Cardiologist and Director of the Heart Failure Unit and Department of Cardiac Rehabilitation at Concord Hospital, New South Wales.

Dr Sindone says that although the risks of stroke are present in asymptomatic patients, they can be difficult to detect, leading to undertreatment of atrial fibrillation.

“The problems is that many people with atrial fibrillation are asymptomatic. And the atrial fibrillation during the first few years is paroxysmal.”

“The general practitioner is the gatekeeper. They are often the ones who detect it [atrial fibrillation], or suspect it, and either treat it or refer on”

Since 2013 1 novel oral anticoagulants (NOACs), also known as direct-acting oral anticoagulants (DOACs), became more commonly prescribed for Australian non-valvular atrial fibrillation patients than warfarin. According to PBS prescription numbers, DOACs are now prescribed twice as often as warfarin2. However, Dr Sindone believes that warfarin is still over utilised compared to DOACs.

Dr Sindone will be speaking at the 7th February webcast on recognising and managing DOAC complications, register now to attend.

“One problem is what we call Warfarin stickiness. Patients will use it for a long time and say, ‘I’m stable, I don’t want to change.’ Another is that some patients and some doctors like to know what their INR [international normalised ratio] is doing.”

However, research shows that the INR does not provide accurate coagulation information for NOACs.

For patients on NOACs, specific assays for dabigatran, apixaban or rivaroxaban levels are the most accurate tests for the level of anticoagulant, but these are rarely required— except in the setting of overdose or if a patient needs an urgent operation and there is concern regarding the level of anticoagulation.

“I say warfarin for patients you don’t like [Dr Sindone jokes], or for patients who have metallic cardiac valve or moderate or more mitral stenosis.”

A meta-analysis comparing warfarin to NOACs showed NOACs reduced the composite of strokes, embolic events and major bleeding.

“I’m going to say to you: anticoagulation, anticoagulation, anticoagulation. That’s the most important thing. If the patient has a stroke, then it is a disaster… They are more likely to become severely disabled or die.”

A Norwegian nation-wide cohort study3 published this year found that patients over 75 on standard and reduced dose NOACs were associated with similar risks of stroke and lower or similar risks of bleeding when compared to each other. Dr Sindone says this highlights the need to follow the product information.

“All patients should be on standard doses of NOACs but for dabigatran, the dose should be reduced if the patient is over 75 years old or the creatinine clearance is < 50.

For patients on rivaroxaban, the dosage should be reduced if the creatinine clearance is < 50.

For apixaban, the dose should be reduced if there are two out of three: age > 80, weight < 60 Kg or creatinine > 133 mcmlol/l.”

A systematic review4 found that for patients with CHADS2 scores greater than 3, DOACs were a reasonable alternative to warfarin.

Not all patients benefit from anticoagulants, however. NPS guidelines cite contraindications for active bleeding, severe renal impairment as well as some drug and comorbid interactions.

All NOACs require renal clearance, however, a literature review5 found that dabigatran and apixaban were equally effective as warfarin for renal-impaired patients— with less intracranial, major or life-threatening bleeding.

 

Dr Sindone says that only patients with end-stage renal failure (eGFR < 15 mLs/min) should be considered too renally impaired for NOACs. A phase II study of NOAC prescriptions6 for patients with mechanical heart valves was discontinued due to a significant increase in strokes and bleeding. As such, NOACs remain contraindicated7 for patients with mechanical heart valves in Australian state health guidelines and by RACGP.

 

But despite some exceptions, Dr Sindone says prescribing NOACs and lifestyle changes remain the best preventative steps GPs can take in reducing stroke risk in atrial fibrillation patients.

 

On 7 February cardiologist Prof Andrew Sindone will present on how to identify and assess complications and manage adverse effects of DOACs. To register for the webinar and earn CPD points, click here.

 

1 Figure 1 of the paper. https://doi.org/10.1016/j.hlc.2018.03.010

2 “Australians with non-valvular atrial fibrillation are currently using NOACs in preference to warfarin at a ratio of 2:1.”
https://doi.org/10.1016/j.hlc.2018.03.010

3 In this nationwide cohort study of patients ≥75 years initiating oral anticoagulation for AF, standard and reduced dose NOACs were associated with similar risks of stroke/SE as warfarin and lower or similar risks of bleeding. The NOACs seem to be a safe option also in elderly patients. https://heart.bmj.com/content/108/5/345

4The use of DOACs is a reasonable alternative to vitamin K antagonists in AF patients with CHADS2 score ≥3, advanced age, and HF. The RI constitutes a useful, additional tool to facilitate clinicians in choosing DOACs or warfarin in particular category of AF patients. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6761253/

5 “Warfarin was associated with a greater decline in eGFR than either low-dose (HR: 0.81, 95% CI: 0.69–0.96) or standard-dose dabigatran (HR: 0.79, 95% CI: 0.68–0.93), whereas apixaban showed a similar risk of acute renal failure compared with warfarin in ARISTOTLE trial (RR: 0.97, 95% CI: 0.88–1.07)” https://journals.lww.com/md-journal/Fulltext/2019/11290/The_impact_of_renal_function_on_efficacy_and.87.aspx

6 However, mechanical heart valves currently pose an absolute contraindication to NOACs based on the results of a single phase II study comparing dabigatran and warfarin (RE-ALIGN [Randomized, Phase II Study to Evaluate the Safety and Pharmacokinetics of Oral Dabigatran Etexilate in Patients after Heart Valve Replacement]). That trial was stopped prematurely because of an excess of both stroke and bleeding with the dabigatran doses tested https://doi.org/10.1161/CIRCULATIONAHA.118.035612

7 Individual state government sites and also this article from RACGP https://www.racgp.org.au/afp/2014/may/anticoagulation

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