Atrial Fibrillation

OVERVIEW

This focused update of the 2010 atrial fibrillation guideline of the Canadian Cardiovascular Society (CCS)¹ incorporates new evidence from 3 atrial fibrillation (AF) trials. The updated guideline² focuses on reducing complications of AF, an issue that is clinically important and poses a significant health burden in Canada. The incidence of AF in Canada is up to 4.5% per year, with lifetime risk estimated at 25% among those older than 40 years³. Further, risk of stroke and transient ischemic attack in people with AF can be as high as 20%¹. Primary care physicians play a major role in the identification and management of these patients. The guideline was developed in Canada by a team with diverse expertise.

RELEVANCE TO CTFPHC MANDATE

The guideline presents recommendations for preventing stroke and controlling rate/rhythm, with the former most applicable to the CTFPHC mandate of prevention in primary care.

POPULATION

The target population for the guideline is all patients with AF or atrial flutter (paroxysmal, persistent or permanent); however, this was not clearly stated.

EVIDENCE REVIEW METHODS

The CCS did not appear to perform its own systematic reviews or meta-analyses but did provide a literature review, with references included up to January 2012.

GRADING SYSTEM

The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was used to grade the quality of the evidence (high, moderate, low or very low) and strength of the recommendations (strong or conditional)⁴.

METHODOLOGICAL QUALITY

The CTFPHC assessed the methodological quality of the guideline using the Appraisal of Guidelines for Research & Evaluation (AGREE II)⁵ criteria (Table 1).

COMMENTARY

Practitioners will likely find the recommendations to be clinically useful. The use of the GRADE system is considered a strength, because of its consistency with CTFPHC methods and its consideration of patients’ values and preferences. Also, the recommendations are clearly highlighted in boxes, making them easy for readers to identify.

However, the CTFPHC identified some concerns during its appraisal. Despite the authors mentioning that a systematic review of the literature was conducted, there are no details on how the literature was selected (inclusion and exclusion criteria, search strategy, search dates). Although the guideline includes subsections on treatment of elderly patients, as well as those with coronary artery disease or chronic kidney disease, there is no assessment of the evidence or specific recommendations for these groups. Finally, although the recommendations appear clinically sensible, it was sometimes difficult to determine the link between recommendations and evidence.

The recommendations state that newer oral anticoagulants such as dabigatran, rivaroxaban and apixaban are preferred, despite the short-term nature of available data on their risks and benefits. Readers should be aware that an earlier version of this guideline recommended the use of dronedarone for rate control in AF on the basis of a single study. The current guideline recommends against the use of dronedarone, on the basis of subsequently published data, which highlights for guideline developers the potential value of confirmatory studies. Overall, this guideline is reasonably well done and will be useful for clinicians. However, the recommendations related to use of newer oral anticoagulants may be most appealing to “early adopters”; other users may prefer to wait until longer-term data are available before routinely using these agents in their own practices.

ORIGINAL GUIDELINE RECOMMENDATIONS

All CCS recommendations and the full guideline can be found in The Canadian Journal of Cardiology.

Summary of recommendations based on CHADS₂ score

View algorithm in The Canadian Journal of Cardiology.

• We recommend that all patients with AF or AFL (paroxysmal, persistent, or permanent), should be stratified using a predictive index for stroke risk (eg, CHADS₂) and for the risk of bleeding (eg, HAS-BLED), and that most patients should receive either an OAC or ASA. (Strong Recommendation, High-Quality Evidence)
• We suggest, that when OAC therapy is indicated, most patients should receive dabigatran, rivaroxaban, or apixaban (once approved by Health Canada), in preference to warfarin. (Conditional Recommendation, High-Quality Evidence)
• We recommend that patients at high risk of stroke (CHADS₂ ≥ 2) should receive OAC therapy. (Strong Recommendation, High-Quality Evidence)
• We recommend that most patients at intermediate risk of stroke (CHADS₂ = 1) should receive OAC therapy. (Strong Recommendation, High-Quality Evidence)
• We suggest, based on individual risk/benefit considerations, that ASA is a reasonable alternative for some. (Conditional Recommendation, Moderate-Quality Evidence)
• We suggest that patients at low risk of stroke (CHADS₂ = 0) should have additional risk factors for stroke considered (including age 65–74 years, female sex, and presence of vascular disease). (Conditional Recommendation, Moderate-Quality Evidence)
• We suggest OAC therapy for patients at highest risk within this category (age greater than age 65 or the combination of female sex and vascular disease); ASA (75–325 mg/day) for patients at lower risk within this category (female sex or vascular disease); and no antithrombotic therapy for those patients at lowest risk in this category (no additional risk factors). (Conditional Recommendation, Low-Quality Evidence)

Summary of recommendations for patients with coronary artery disease

View algorithm in The Canadian Journal of Cardiology.

• We suggest that patients with AF/AFL who have stable CAD should receive antithrombotic therapy selected based upon their risk of stroke (asa for most CHADS₂ = 0 and OAC for most CHADS₂ ≥ 1). (Conditional Recommendation, Moderate-Quality Evidence)
• We suggest that patients with AF/AFL who have experienced ACS or who have undergone PCI, should receive antithrombotic therapy selected based on a balanced assessment of their risks of stroke, of recurrent coronary artery events, and of hemorrhage associated with the use of combinations of antithrombotic therapies, which in patients at higher risk of stroke may include ASA plus clopidogrel plus OAC.(Conditional Recommendation, Low-Quality Evidence)

Stroke prevention in non-valvular AF in patients with chronic kidney disease

• We recommend that patients with AF who are receiving OAC have their renal function assessed at least annually by measuring serum creatinine and calculating eGFR. (Strong Recommendation, Moderate-Quality Evidence)
• We recommend that patients with AF who are receiving OAC be regularly considered for the need for alteration of OAC drug and/or dose changes based on eGFR. (Strong Recommendation, Moderate-Quality Evidence)
• For antithrombotic therapy of CKD patients, therapy should relate to eGFR as follows: eGFR > 30 mL per minute: We recommend that such patients receive antithrombotic therapy according to their CHADS₂ score as detailed in recommendations for patients for patients with normal renal function. (Strong Recommendation, High-Quality Evidence)
• For antithrombotic therapy of CKD patients, eGFR 15–30 mL per minute and not on dialysis: We suggest that such patients receive antithrombotic therapy according to their CHADS₂ score as for patients with normal renal function. The preferred agent for these patients is warfarin. (Conditional Recommendation, Low-Quality Evidence)
• For antithrombotic therapy of CKD patients, eGFR < 15 mL per minute (on dialysis): We suggest that such patients not routinely receive either OAC or ASA for stroke prevention in AF. (Conditional Recommendation, Low-Quality Evidence)

REFERENCES

1. Cairns JA, Connolly S, McMurtry S, Stephenson M, Talajic M; CCS Atrial Fibrillation Guidelines Committee. Canadian Cardiovascular Society atrial fibrillation guidelines 2010: prevention of stroke and systemic thromboembolism in atrial fibrillation and flutter. Can J Cardiol. 2011;27(1):74-90.
2. Skanes AC, Healey JS, Cairns JA, Dorian P, Gillis AM, McMurtry MS, et al.; Canadian Cardiovascular Society Atrial Fibrillation Guidelines Committee. Focused 2012 update of the Canadian Cardiovascular Society atrial fibrillation guidelines: recommendations for stroke prevention and rate/rhythm control. Can J Cardiol. 2012;28(2):125-136.
3. Lloyd-Jones DM, Wang TJ, Leip EP, Larson MG, Levy D, Vasan RS, et al. Lifetime risk for development of atrial fibrillation: the Framingham Heart Study. Circulation. 2004;110(9):1042-1046.
4. Guyatt GH, Oxman AD, Vist G, Kunz R, Falck-Ytter Y, Alonso-Coello P, et al.; GRADE Working Group. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336(7650):924-926.
5. CCS guidelines and position statements development procedures and policies. Version 1.1. Ottawa, ON: Canadian Cardiovascular Society; October 2013. Available at: http://www.ccsguidelinepro grams.ca/images/stories/CCS_Guideline_Pro grams/Gui-PS-development-Proc_policies.pdf. Accessed 2013 Nov 13.