Atrial fibrillation (main)

Background

Non-modifiable risk factors (top left box) and modifiable risk factors (bottom left box) for atrial fibrillation. The main sequelae of atrial fibrillation are in the right box.

• Chronic and paroxysmal a-fib are associated with thrombus formation

Atrial fibrillation categories

Atrial Fibrillation Category	Definition
Paroxysmal	Terminates spontaneously or with intervention within 7 days of onset. Episodes may recur with variable frequency.
Persistent	Continuous sustained >7 days
Long-standing persistent	Continuous >12 mo in duration.
Permanent	Used when the patient and clinician make a joint decision to stop further attempts to restore and/or maintain sinus rhythm. Acceptance represents a therapeutic attitude on the part of the patient and clinician rather than an inherent pathophysiological attribute. May change as symptoms, efficacy of therapeutic interventions, and patient and clinician preferences evolve.
Nonvalvular	In the absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve, or mitral valve repair.
With Rapid Ventricular Response (RVR)	With persistent ventricular heart rate >100 beats per minute

Causes of atrial fibrillation

• Cardiac (atrial enlargement)
  • Hypertension
  • Ischemic heart disease
  • Rheumatic heart disease
    • Valvular heart disease (any lesion that leads to significant stenosis or regurgitation)
• Noncardiac (increased automaticity)
  • Thyrotoxicosis
  • Chronic lung disease
  • Pericarditis
  • Ethanol ("holiday heart")
  • Pulmonary embolism
  • Pneumonia
  • Drugs (cocaine, TCA, Milk of the Poppy)

Clinical Features

History

• Asymptomatic - 44%
• Palpitations - 32%
• Dyspnea - 10%
• Stroke - 2%
• Also can present with congestive heart failure/acute pulmonary edema

Physical

• Irregularly irregular heart rate

Differential Diagnosis

Narrow-complex tachycardia

• Regular
  • AV Node Independent
    • Sinus tachycardia
    • Atrial tachycardia (uni-focal or multi-focal)
    • Atrial fibrillation
    • Atrial flutter
    • Idiopathic fascicular left ventricular tachycardia
  • AV Node Dependent
    • Paroxysmal supraventricular tachycardia (PSVT)
      • AV node re-entry tachycardia (AVNRT)
      • AV re-entry tachycardia (AVRT)
        • Lown-Ganong-Levine syndrome
        • Wolff–Parkinson–White syndrome
    • Junctional tachycardia
• Irregular
  • Multifocal atrial tachycardia (MAT)
  • Sinus tachycardia with frequent PACs, PJCs, PVCs
  • Atrial fibrillation
    • Atrial fibrillation with RVR
  • Atrial flutter with variable conduction
  • Digoxin Toxicity

Wide-complex tachycardia

Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise (it is safer to incorrectly assume a ventricular dysrhythmia than supraventricular tachycardia with abberancy)

• Regular
  • Monomorphic ventricular tachycardia
  • PSVT with aberrant conduction:
    • PSVT with bundle branch block^
    • PSVT with accessory pathway
    • Atrial flutter with bundle branch block^
  • Sinus tachycardia with bundle branch block^
  • Accelerated idioventricular rhythm (consider if less than or ~120 bpm)
  • Metabolic
    • Hyperkalemia
    • Digoxin toxicity
    • Severe metabolic acidosis
• Irregular
  • Atrial fibrillation/atrial flutter with variable AV conduction AND bundle branch block^
  • Atrial fibrillation/atrial flutter with variable AV conduction AND accessory pathway (e.g. WPW)
  • Atrial fibrillation + hyperkalemia
  • Polymorphic ventricular tachycardia
    • Torsades de pointes
    • Nonsustained ventricular tachycardia

^Fixed or rate-related

Palpitations

• Arrhythmias:
  • Narrow-complex tachycardias
  • Wide-complex tachycardias
  • AV blocks
    • Second Degree AV Block Type I (Wenckeback)
    • Second Degree AV Block Type II
    • Third Degree AV Block
  • Premature atrial contraction
  • Premature junctional contraction
  • Premature ventricular contraction
  • Sick sinus syndrome
  • Wandering atrial pacemaker
• Non-arrhythmic cardiac causes:
  • Acute coronary syndrome
  • Cardiomyopathy
  • Congenital heart disease
  • Congestive heart failure (CHF)
  • Mitral valve prolapse
  • Pacemaker complication
  • Pericarditis
  • Myocarditis
  • Valvular disease
• Psychiatric causes:
  • Panic attack
  • Anxiety
  • Somatic Symptom Disorder
• Drugs and Medications:
  • Alcohol
  • Caffeine
  • Drugs of abuse (e.g. cocaine)
  • Medications (e.g. digoxin, theophylline)
  • Tobacco
• Misc
  • Anemia
  • Hyperthyroidism
    • Thyroid storm
  • Pulmonary embolism
  • Dehydration
  • Sepsis
  • Pheochromocytoma

Evaluation

Atrial fibrillation at approximately 150 beats per minute

A 12-lead ECG showing atrial fibrillation at approximately 132 beats per minute.

ED Work-Up

• ECG
• Eval for ACS only in:
  • Patient with ECG changes suggestive of ischemia, hypotension, angina
  • A fib is rarely only manifestation of ACS, although RVR and hypotension can provoke demand ischemia
• Acute lab studies for all patients:
  • CBC
  • Chem-10
  • Coagulation studies (for patients requiring anticoagulation)
• Additional labs (consider based on clinical scenario):
  • TSH & free T4 (Afib increased in sublinical hyperthyroidism)
  • BNP
  • D-dimer
  • Troponin
  • Magnesium level
  • Digoxin level (if appropriate)
• Imaging
  • CXR (if concern for heart failure or infection)
  • Chest/Abdominal CT (if concern for sepsis)

Diagnosis

ECG of atrial fibrillation (top) and normal sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation.

Based on one of three ECG patterns:

1. Typical
   • Irregularly, irregular R waves
   • QRS rate 140-160/min
2. Large fibrillatory waves
   • May look like flutter waves
     • Unlike a-flutter, the fibrillatory waves are irregular
3. Slow, regular A-fib
   • Due to complete AV block with escape rhythm

• Ischemic changes?
• Rate > 250? (think preexcitation)

Management

See atrial fibrillation with RVR for emergent treatment

Rate vs. Rhythm Control

• Rhythm control (i.e. synchronized cardioversion)
  • Consider in the emergency department for:
    • Unstable (due to rhythm)
    • Younger patients (<65 years old) with new or paroxysmal episode (<48 hours)
  • Procedural anticoagulation status
    • If <48 hours of symptoms, do not need to anticoagulate prior to rhythm control (may perform in ED)
    • If >48 hours of symptoms, need have rhythm control as out patient referral (if stable)
  • Method: Procedural sedation and analgesia (e.g. fentanyl and propofol). Apply pads in anterior to posterior position. Synchronized electrical cardioversion starting at 150 to 200 J.

• Rate control for all others or cardioversion failure
  • General principal - IV medications for immediate rate control followed by PO medications for sustained rate control
  • Beta-blocker
    • Metoprolol 5 mg IV q 5 min (max 3 doses) followed by 25-100 mg PO
  • Calcium channel blocker
    • Diltiazem 0.25 mg/kg to 0.35 mg/kg IV (20 mg typical starting dose), can follow with 25 mg IV as second dose if needed
    • Followed by PO dose 60-120 mg
    • If unable to get sustained response with IV push, consider diltiazem gtt
  • Digoxin
    • Indicated if patient hypotensive and cannot get AV nodal blockade or if patient has advanced heart failure
    • Typical digitizing dose 500 mcg then 250 mcg q4hx 2 for total dose of 1000 mcg
    • Requires renal dosing if patient has impaired renal function
  • Amiodarone
    • Indicated if patient has hypotension or advanced heart failure, usually second line after digoxin
    • Typical dosing 150 mg IV x 10 min then 1 mg/min x 6 hours then 0.5 mg/minx 18 hours
    • Amiodarone can convert patient to sinus rhythm. Consider simultaneously starting empiric anticoagulation if high thromboembolism risk, see below
  • Procainamide
    • Indicated: Hemodynamically stable with systolic Blood Pressure >100 mmHg, less than 48 hrs onset, Normal Serum Potassium and Serum Magnesium
    • Ottawa protocol Method: Procainamide 1 g IV over 60 minutes. Monitor with frequent Blood Pressures, and hold Procainamide if systolic Blood Pressure <100 mmHg. Monitor telemetry for Arrhythmia, QTc Prolongation, QRS Widening and for successful cardioversion.

Anticoagulation Therapy

• ACCP Recommendations
  • In patients with AF, including those with paroxysmal AF, with only one of the risk factors listed immediately above, we recommend long-term antithrombotic therapy (Grade 1A), either as anticoagulation with an oral VKA, such as warfarin (Grade 1A), or as aspirin, at a dose of 75-325 mg/d (Grade 1B)
  • In patients with AF, including those with paroxysmal AF, who have two or more of the risk factors we recommend long-term anticoagulation with an oral VKA (Grade 1A).

• CCS Recommendations
  • Oral anticoagulants are recommended for all AF patients aged 65 or older or who have any one of the traditional CHADS2 risk factors of stroke, hypertension, heart failure, or diabetes (remember as CHADS-65). Otherwise, patients with a history of coronary artery disease or arterial vascular disease should be prescribed ASA. CCS recommends that the first choice for oral anticoagulation should be the novel direct-acting oral anticoagulants (i.e. NOACs, for non-valvular AF). The big paradigm change is that ED physicians should prescribe OACs to at-risk AF patients before they leave the ED.

NOAC Dosing for Nonvalvular AF

NOACs are preferred over warfarin for nonvalvular AF (AHA/ACC/HRS 2019, CCS 2020). Contraindicated in mechanical heart valves and moderate-severe mitral stenosis.

Agent	Standard Dose	Reduced Dose	Criteria for Dose Reduction	Reversal Agent
Apixaban (Eliquis)	5 mg PO BID	2.5 mg PO BID	Any 2 of: age ≥80, weight ≤60 kg, Cr ≥1.5	Andexanet alfa
Rivaroxaban (Xarelto)	20 mg PO daily with evening meal	15 mg PO daily with evening meal	CrCl 15-50	Andexanet alfa
Dabigatran (Pradaxa)	150 mg PO BID	75 mg PO BID	CrCl 15-30; or CrCl 30-50 + concomitant P-gp inhibitor	Idarucizumab
Edoxaban (Savaysa)	60 mg PO daily	30 mg PO daily	CrCl 15-50 or weight ≤60 kg; avoid if CrCl >95	No specific agent; consider PCC

• ED Prescribing
  • CCS recommends initiating OAC in the ED for at-risk patients prior to discharge
  • Obtain CrCl before prescribing (all NOACs require renal dose adjustment)
  • Check for drug interactions (P-gp inhibitors, dual CYP3A4/P-gp inhibitors)
  • NOACs should NOT be used in: mechanical heart valves, moderate-severe mitral stenosis, severe renal impairment (CrCl <15 for most agents), or antiphospholipid syndrome
• Advantages over warfarin
  • No INR monitoring required
  • Fewer drug and food interactions
  • Rapid onset (1-3 hours)
  • Lower rates of intracranial hemorrhage
• Reversal — see Anticoagulant reversal for life-threatening bleeds

CHADS2-VAsc Score

Risk Factor	Points
CHF	1
hypertension	1
DM	1
Previous stroke/TIA	2
Vascular disease (e.g. IHD, PVD)	1
Female sex	1
Age
≥ 75 years old	2
65 to 74 years old	1

• Score 0: consider no treatment or ASA
• Score 1: consider warfarin or ASA
• Score 2-6: consider warfarin (INR goal = 2-3)
• All patients with significant valvular disease should be on anticoagulation

HAS-BLED

Used to assess 1 yr risk of bleeding on OAC medications

Risk Factor	Point
Hypertension	1
Abnormal renal and/or hepatic function	1 point each
Stroke	1
Bleeding tendency/predisposition	1
Labile INR on warfarin	1
Elderly (age >65 years)	1
Drugs (aspirin or NSAIDs) and/or alcohol	1 point each

• Score 1: 1.0 bleeds per 100 patient-years
• Score 2: 1.9 bleeds per 100 patient-years
• Score 3: 3.7 bleeds per 100 patient-years
• Score 4: 8.7 bleeds per 100 patient-years
• Score 5-9: Insufficient Data

Disposition

Similar outcomes for Canadian vs. American strategies, despite lower admission rates in Canada

Canadian

• "Limit hospital admission to highly symptomatic patients in whom adequate rate control cannot be achieved"

American

Indications for hospitalization:

• Patient with acute heart failure or hypotension after rhythm or rate control
• AF secondary to hypertension, infection, COPD exacerbation, PE, ACS/MI
• Age > 60 (high risk of thromboembolism, more likely to have comorbidities)
• Initiation of heparin or other anticoagulant
• If considering ablation of accessory pathway in patient with AF
• Symptomatic recurrence in the ED
• Hemodynamic instability

Indications for discharge (low-risk patients): Discharge with urgent cardiology follow up

• <60 years old
• No significant comorbid disease
• No clinical suspicion for PE or MI
• Conversion in ED or rate control

Complications

• Hemodynamic compromise
  • A-fib lowers CO by 20-30%
  • Impaired coronary blood flow
• Arrhythmogenesis
• Arterial thromboembolism

Diltiazem 0.25-0.35 mg/kg IV (typical 20 mg), then 25 mg IV if needed; followed by 60-120 mg PO or drip IV/PO Metoprolol 5 mg IV q5min x3 IV Digoxin 500 mcg IV, then 250 mcg q4h x2 (total 1000 mcg digitizing dose) IV — Requires renal dosing; slow onset Amiodarone 150 mg IV over 10 min, then 1 mg/min x6h, then 0.5 mg/min x18h IV drip — Can convert to sinus; consider simultaneous anticoagulation if high thromboembolic risk Procainamide 1 g IV over 60 min (Ottawa protocol); hold if SBP <100 IV — Monitor BP, telemetry for QTc/QRS widening; for hemodynamically stable patients <48h onset Apixaban 5 mg BID (reduced: 2.5 mg BID if ≥2 of: age ≥80, wt ≤60 kg, Cr ≥1.5) PO — No CrCl cutoff for AF dosing; preferred in elderly/renal impairment Rivaroxaban 20 mg daily with evening meal (reduced: 15 mg daily if CrCl 15-50) PO — Must take with food for adequate absorption Dabigatran 150 mg BID (reduced: 75 mg BID if CrCl 15-30) PO — Only NOAC with specific reversal agent (idarucizumab); higher GI bleeding risk Edoxaban 60 mg daily (reduced: 30 mg daily if CrCl 15-50 or wt ≤60 kg) PO — Avoid if CrCl >95 (reduced efficacy)

Calculators

CHA₂DS₂-VASc Score

CHA₂DS₂-VASc Score Calculator

Criteria	No (0)	Yes
Congestive heart failure (or LVEF ≤40%)	1	(+1)
Hypertension	1	(+1)
Age ≥75 years	1	(+2)
Diabetes mellitus	1	(+1)
Stroke/TIA/thromboembolism	1	(+2)
Vascular disease (prior MI, PAD, aortic plaque)	1	(+1)
Age 65–74 years	1	(+1)
Sex category (female)	1	(+1)
CHA₂DS₂-VASc Score	/ 9

Interpretation
0	Low Risk — 0.2% annual stroke risk (males). Anticoagulation generally not recommended.
1	Low-Moderate Risk — 0.6% annual stroke risk (males). Consider anticoagulation (esp. if not due to female sex alone).
≥2	Moderate-High Risk — ≥2.2% annual stroke risk. Oral anticoagulation recommended.

References

Lip GY, Nieuwlaat R, Pisters R, et al. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the Euro Heart Survey on Atrial Fibrillation. Chest. 2010;137(2):263-272. PMID 19762550. January CT, Wann LS, Calkins H, et al. 2019 AHA/ACC/HRS Focused Update of the 2014 Guideline for Management of Patients With Atrial Fibrillation. J Am Coll Cardiol. 2019;74(1):104-132. PMID 30703431.

HAS-BLED Score

HAS-BLED Score — Bleeding Risk

Criteria	No (0)	Yes (+1)
H — Hypertension (uncontrolled SBP >160)	1
A — Abnormal renal function (dialysis, transplant, Cr >2.26) and/or liver function (cirrhosis, bilirubin >2×, AST/ALT/ALP >3×)	1	(+1 each, max 2)
S — Prior stroke	1
B — Bleeding history/predisposition	1
L — Labile INR (unstable/high, TTR <60%)	1
E — Elderly (age >65)	1
D — Drugs (antiplatelets, NSAIDs) and/or alcohol (≥8 drinks/week)	1	(+1 each, max 2)
HAS-BLED Score	/ 9

Interpretation
0–2	Low-moderate risk — Relatively low bleeding risk. Anticoagulation generally recommended if indicated.
≥3	High risk — Consider modifiable risk factors (HTN, labile INR, drugs/alcohol). Score ≥3 does NOT contraindicate anticoagulation but warrants closer monitoring.

References
Pisters R, Lane DA, Nieuwlaat R, et al. A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation. Chest. 2010;138(5):1093-1100. PMID 20299623. Note: HAS-BLED ≥3 is NOT a contraindication to anticoagulation — it identifies patients who need closer follow-up and correction of modifiable risk factors.

See Also

• Atrial fibrillation with RVR
• ACLS (Main)
• In-Training Exam Review