Atrial Fibrillation

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation and, consequently, ineffective atrial contraction. On ECG this produces an irregularly irregular ventricular rhythm with no discrete, organized P waves. The 2020 CCS/CHRS guideline organizes management around three pillars applied to essentially every patient: (1) stroke prevention using the CHADS-65 algorithm, assessed and acted on independently of symptoms; (2) rate or rhythm control to relieve symptoms and prevent tachycardia-mediated cardiomyopathy; and (3) risk-factor modification (weight, blood pressure, sleep apnea, alcohol) to reduce AF burden and improve the success of rhythm-control therapy.^[1] Atrial flutter is managed with the same stroke-prevention principles as AF and is not treated as a lower-risk arrhythmia for anticoagulation purposes. Stroke prevention is the dominant priority: an asymptomatic patient with a stroke-risk indication for anticoagulation still needs it, and a highly symptomatic patient does not get anticoagulation "instead of" rate/rhythm therapy — the two pillars are managed in parallel, not as alternatives.

Lead I rhythm strips contrasting atrial fibrillation (top) with normal sinus rhythm (bottom) — the classic ECG signature of AF: an irregularly irregular R-R interval and a chaotic fibrillatory baseline with no discernible, discrete P wave (red arrow), versus the regular rhythm and clearly visible P wave (purple arrow) of sinus rhythm below it. (J. Heuser, vectorized by Marnanel, CC BY-SA 3.0/GFDL, Wikimedia Commons)

Typical presentation

Palpitations, an irregularly irregular pulse on manual palpation, fatigue, dyspnea, reduced exercise tolerance, and lightheadedness are typical. A substantial proportion of AF is entirely asymptomatic and found incidentally — on a routine pulse check, an ECG done for another reason, or a consumer wearable — so the absence of symptoms does not lower clinical priority once AF is confirmed; stroke risk is unrelated to symptom burden.

• Advancing age — the single strongest risk factor, and the basis of the age-65 threshold in the CHADS-65 algorithm.
• Hypertension.
• Structural or valvular heart disease, including prior myocardial infarction and heart failure.
• Hyperthyroidism.
• Obesity and obstructive sleep apnea — both independently increase AF risk and AF burden, and both are directly modifiable.
• Diabetes mellitus and chronic kidney disease.
• Excess alcohol intake, including acute binge intake ("holiday heart" presentation).
• Family history of AF.
• Post-cardiac-surgery state, and acute systemic illness or sepsis (secondary/reversible AF in this setting still needs the same stroke-risk assessment).
• Male sex.

Confirming the diagnosis

• 12-lead ECG showing an irregularly irregular RR interval with absent, discrete P waves and a chaotic fibrillatory baseline — this alone confirms AF.
• Extended rhythm monitoring (Holter, external event recorder, or implantable loop recorder) when paroxysmal AF is clinically suspected — palpitations, embolic stroke of undetermined source — but has not been captured on a resting ECG.
• Echocardiography to assess left atrial size, valvular disease (specifically to identify or exclude valvular AF), and left ventricular ejection fraction — LVEF directly determines which rate-control and rhythm-control drugs are appropriate.
• TSH, to identify hyperthyroidism as a reversible contributor.
• Electrolytes and renal function — both a baseline for DOAC dose selection and the reference point for the periodic renal monitoring every DOAC-treated patient needs.

Valvular vs. nonvalvular AF

Valvular AF — a mechanical heart valve, or moderate-to-severe mitral stenosis — is anticoagulated with warfarin only; DOACs were not studied and are not used in this population. All other AF is nonvalvular AF, where DOACs are preferred.^[1]

Stroke risk stratification: the CHADS-65 algorithm

The CCS deliberately uses CHADS-65 rather than the internationally-recognized CHA2DS2-VASc score. It is a decision algorithm, not a points-based risk calculator: the presence of any CHADS2 risk factor is enough to trigger anticoagulation — there is no minimum total-score threshold to clear, unlike the classic warfarin-era CHADS2 ≥2 cutoff.^[2]

Age ≥ 65 years, on its own, is sufficient to recommend anticoagulation regardless of the CHADS2 score. For a patient under 65, the presence of even one CHADS2 risk factor also warrants anticoagulation. Only a patient under 65 with zero CHADS2 risk factors falls outside the anticoagulation recommendation — for this group, most patients should receive no antithrombotic therapy for stroke prevention at all, not aspirin as a lesser alternative.^[3]

Bleeding risk: HAS-BLED

A score of ≥3 identifies a patient at meaningfully higher 1-year bleeding risk.^[4] A high HAS-BLED score is a prompt to identify and correct modifiable bleeding-risk factors — it is not, on its own, a reason to withhold anticoagulation that the CHADS-65 algorithm otherwise indicates. Most of its components (blood pressure control, stopping unnecessary antiplatelets/NSAIDs, correcting anemia, limiting alcohol) are the same modifiable factors targeted by risk-factor-modification counselling.

• Prevent stroke and systemic embolism — the top priority, pursued independently of symptom burden.
• Control ventricular rate and/or restore and maintain sinus rhythm to relieve symptoms and prevent tachycardia-mediated cardiomyopathy.
• Modify reversible risk factors (weight, blood pressure, obstructive sleep apnea, alcohol) to reduce AF burden and improve the durability of rhythm-control therapy.
• Avoid iatrogenic harm: correct anticoagulant selection and renal/age/weight-adjusted dosing, avoidance of unnecessary periprocedural bridging, and avoidance of AV-nodal blocking agents in pre-excited AF.

• Risk-factor modification is its own treatment pillar, not an adjunct: weight loss toward a BMI under 27, blood pressure control, treatment of obstructive sleep apnea (CPAP), limiting alcohol intake, and regular exercise all reduce AF burden and improve the success of rhythm-control therapy.^[1]
• Electrical cardioversion — for persistent AF, once the anticoagulation requirements below are met (at least 3 weeks of therapeutic anticoagulation beforehand, or a transesophageal echocardiogram excluding left atrial thrombus if earlier cardioversion is needed).
• Catheter ablation (pulmonary vein isolation) — a first-line rhythm-control option for appropriately selected symptomatic paroxysmal or persistent AF, and the standard next step after antiarrhythmic drug failure or intolerance.
• AV-node ablation with permanent pacemaker implantation — a last-resort rate-control option when pharmacologic rate control fails despite optimized therapy.
• Left atrial appendage occlusion (e.g., a Watchman-type device) — an alternative stroke-prevention strategy for patients at high stroke risk who have a genuine contraindication to long-term oral anticoagulation.

Pregnancy

AF in pregnancy is uncommon. Low-molecular-weight heparin or unfractionated heparin is preferred over both DOACs and warfarin for anticoagulation, since warfarin is teratogenic (particularly first trimester) and DOAC safety data in pregnancy are inadequate. For rate control, beta-blockers (e.g., metoprolol) are preferred. Avoid amiodarone in pregnancy given fetal thyroid toxicity, reserving it only for a life-threatening arrhythmia with no reasonable alternative.

Breastfeeding

Warfarin is compatible with breastfeeding. DOAC data in lactation are limited — use warfarin or heparin instead of a DOAC when anticoagulation is needed during breastfeeding.

Renal impairment / chronic kidney disease

Renal function is both a dosing input and a monitoring requirement — assess at baseline and at least annually (more often, roughly every CrCl/10 months, if CrCl is under 60 mL/min) in every anticoagulated patient.^[2] By CKD stage: eGFR >30 mL/min — apply the CHADS-65 algorithm as usual, with DOAC renal dose adjustment per the table above; eGFR 15-29 mL/min — a weak recommendation to continue anticoagulation, individualized (apixaban has the most outcome data of the DOACs in this range; warfarin remains an option); eGFR under 15 mL/min or dialysis — routine anticoagulation is not recommended given the lack of demonstrated net benefit in trials.

Elderly and frail patients

Age ≥65 is itself sufficient to recommend anticoagulation under CHADS-65 — advanced age or frailty is not, on its own, a reason to withhold it. DOACs are preferred over warfarin in this group given the consistently lower intracranial hemorrhage risk. Fall risk is not by itself a contraindication to anticoagulation — the stroke-prevention benefit outweighs the bleeding risk from falls in the great majority of patients who would otherwise qualify.

Obesity

Standard DOAC dosing is appropriate up to a BMI of about 40 or weight of about 120 kg. Beyond that, evidence is limited — warfarin, or drug-level testing if a DOAC is used, are reasonable alternatives.

Hepatic impairment

Avoid anticoagulation in advanced cirrhosis with significant coagulopathy (Child-Pugh C). Where anticoagulation is still needed in milder impairment, warfarin with closer INR monitoring is generally preferred over a DOAC given limited DOAC hepatic-impairment data.

Concurrent coronary artery disease

Stable CAD, more than 12 months from the last event or PCI: anticoagulant monotherapy — do not add an antiplatelet routinely. Recent ACS or PCI, under 12 months: a dual pathway of anticoagulant plus clopidogrel (the preferred P2Y12 inhibitor in this combination) is favoured over triple therapy; adding ASA (triple therapy) is reserved for up to 1 month in patients with high ischemic-risk features (e.g., stent thrombosis risk, complex PCI, diabetes, reduced ejection fraction).^[2]

Perioperative / periprocedural anticoagulation

For an elective procedure in a DOAC-treated patient: low bleeding-risk procedure — hold the DOAC for 1 day before and 1 day after; high bleeding-risk procedure — hold for 2 days before and after. Dabigatran with CrCl 30-50 mL/min needs a longer hold given renal clearance — 2 days for a low-risk procedure, 4 days for a high-risk procedure.^[5] Routine LMWH bridging is not needed for most DOAC-treated patients undergoing an elective procedure — this is a deliberate departure from the older warfarin-bridging paradigm. For warfarin: hold for approximately 5 days before the procedure, confirm the INR has normalized, and resume once hemostasis is adequate; reserve LMWH bridging for individualized high-thromboembolic-risk patients (a mechanical valve, or a stroke/TIA within the last 3 months) rather than applying it routinely.

• Renal function at baseline and at least annually for every anticoagulated patient (more frequently if CrCl is under 60 mL/min) — this directly determines whether a DOAC dose needs adjustment.
• INR every 4-12 weeks for warfarin, more often if labile or time-in-therapeutic-range is poor; consider point-of-care/self-testing where available.
• Reassess stroke risk (CHADS-65) and bleeding risk (HAS-BLED) periodically, not just at diagnosis — turning 65, a new diagnosis of hypertension or diabetes, or an intervening bleeding event all change the recommendation.
• Adherence checks — up to 30% of patients are not fully adherent to their anticoagulant, a preventable driver of both stroke and, with erratic dosing, bleeding.^[2] Pharmacists are well positioned to improve this through counselling, regimen simplification, reminder tools, and affordability review.
• Reassess ventricular rate control and rhythm-control symptom burden at routine follow-up; escalate rather than simply re-reassuring if targets are not being met.

1. Inadequate rate control despite an optimized first-line beta-blocker or non-dihydropyridine CCB: add digoxin. If still uncontrolled, refer for rhythm-control assessment (antiarrhythmic drug or catheter ablation) or AV-node ablation with pacemaker implantation.
2. Recurrent symptomatic AF despite an antiarrhythmic drug: confirm the dose is optimized, consider switching agents within the constraints of the patient's structural/ischemic heart disease status, and refer for catheter ablation.
3. Stroke or TIA despite therapeutic anticoagulation: confirm adherence and confirm the dose was correctly selected for age/weight/renal function; consider left atrial appendage occlusion or a different anticoagulant strategy, and refer.
4. Bleeding on anticoagulation: assess the cause and reversibility, confirm the dose was correct in the first place, and consider a dose or agent change — or left atrial appendage occlusion if long-term anticoagulation becomes untenable. Do not simply discontinue anticoagulation without establishing an alternative stroke-prevention plan.
5. Persistent, refractory symptoms despite an escalated rate-and-rhythm strategy: refer for specialist/electrophysiology assessment.

• Using ASA, alone, for AF stroke prevention when anticoagulation is indicated — it is not an acceptable lesser alternative and provides only marginal protection.
• Prescribing a DOAC to a patient with a mechanical heart valve or moderate-to-severe mitral stenosis — this is a warfarin-only indication; DOACs were not studied and are contraindicated here.
• Missing the renal, age, or weight dose-reduction criteria for a DOAC — both over- and under-dosing are common and each carries real consequences (bleeding vs. inadequate stroke protection).
• Giving an AV-nodal blocking agent (beta-blocker, non-dihydropyridine CCB, digoxin, or adenosine) to a patient with pre-excited AF (Wolff-Parkinson-White) — this can accelerate accessory-pathway conduction and precipitate ventricular fibrillation.
• Using flecainide or propafenone in a patient with coronary artery disease or significant structural heart disease.
• Stopping anticoagulation prematurely after cardioversion because sinus rhythm was restored — the minimum 4-week post-cardioversion anticoagulation requirement is independent of the rhythm outcome.
• Cardioverting a patient without at least 3 weeks of therapeutic anticoagulation beforehand (or a transesophageal echocardiogram excluding thrombus) when AF duration is over 48 hours or unknown.
• Routine LMWH bridging for an elective procedure in a DOAC-treated patient — unnecessary in most cases and increases bleeding without a stroke-prevention benefit.
• Missing that edoxaban should generally be avoided in patients with CrCl over 95 mL/min, where efficacy versus warfarin was reduced in the pivotal trial.^[6]
• Treating digoxin as a first-line or monotherapy rate-control agent in an active, ambulatory patient — it does not control exertional heart rate.

How to use this table: Doses are adult doses for nonvalvular atrial fibrillation stroke prevention and rate/rhythm control, and require patient-specific confirmation, including renal/hepatic adjustment. Select any drug name to open its complete Pharmasist Drug Database page.

Direct oral anticoagulants (DOACs) — preferred over warfarin for nonvalvular AF

Vitamin K antagonist

Mandatory (not optional) for valvular AF — a mechanical heart valve or moderate-to-severe mitral stenosis. Also the fallback anticoagulant when DOACs cannot be used, e.g., severe renal impairment or dialysis.

Rate control — beta-blockers

Preferred class for rate control at any left ventricular ejection fraction; specific evidence-based agents in LVEF ≤40%.

Rate control — non-dihydropyridine calcium channel blockers

Use only if LVEF is greater than 40% — negative inotropy can worsen heart failure with reduced ejection fraction.

Rate control — cardiac glycoside

Add-on when first-line therapy is insufficient, or monotherapy specifically in sedentary/inactive patients — it does not control exertional heart rate.

Rhythm control — antiarrhythmics

Agent choice is dictated by the presence of coronary artery disease or reduced ejection fraction, not by patient preference alone.