Atrial Fibrillation

Introduction

  • Atrial fibrillation is a common supraventricular tachycardia 
  • Incidence in Canada is up to 4.5% per year, with lifetime risk estimated at 25% among those older than 40 years of age
  • Evaluation of the patient involves:
    • Determining the underlying cause of atrial fibrillation and modifying risk factors
    • Rate- or rhythm-control strategy
    • Stroke prevention (role of anticoagulation)

Definitions

  • Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation with consequent deterioration of atrial mechanical function.
  • On an electrocardiogram (ECG), AF is described as the replacement of consistent P waves with rapid oscillations or fibrillatory waves that vary in size, shape, and timing, and are associated with an irregular, frequently rapid ventricular response.
    • Irregularly irregular rhythm
  • Clinical classifications:
    • Paroxysmal AF: Continuous for >30 seconds and <7 days
    • Persistent AF: Continuous for > 7 days and < 1 year
    • Long-standing persistent AF: > 1 year and pursuing rhythm control
    • Permanent AF: Decision made to no longer pursue sinus rhythm restoration
      • Patient may have both paroxysmal and persistent episodes and should be classified based on dominant episodes
    • Valvular AF: Atrial fibrillation in the presence of any mechanical heart valve, or in the presence of moderate to severe mitral stenosis (rheumatic or non-rheumatic)
      • Important implications for anticoagulation choice

Differential Diagnosis

  • The differential diagnosis for tachycardia is broad. Tachycardia is usually classified based on morphology of the QRS (wide complex or narrow complex), rhythm, and presence or absence of p-waves.
  • Please refer to the following sites for further details:

Screening

  • Opportunistic screening is recommended for individuals over 65
  • Generally done using pulse palpation as part of standard physical exam but can also use rhythm based screening with single-lead ECG
  • If concern, obtain 12-lead ECG and if non-diagnostic but clinical suspicion remains high consider rhythm-based monitoring.
  • Post stroke: 24 hours of rhythm based monitoring recommended and longer if AF still suspected
CCS: Approach to Screening

Risk Factors

  • Pathophysiology of AF is a complex and evolving field
  • There are many cardiac and non-cardiac conditions that increase risk and are associated with AF (seen in table)
  • Recommended to systematically approach modifiable risk factors and treat using guideline directed management 
CCS: Risk Factors of AF
CCS: Modifiable Risk Factors

Initial Workup

History

  • Identify risk factors
  • Obtain thorough history on duration and frequency of attacks and if currently in atrial fibrillation, when episode started
  • Presence, nature and severity of symptoms (impact on QoL using CCS SAF scale)
    • Ie. palpitations, shortness of breath, chest pain, syncope or presyncope (conversion pauses), and focal neurologic deficit (embolic stroke)
  • Precipitating factors and preventable causes (ie. caffeine or hyperthyroidism)
  • Bleeding profile
  • Previous therapies  (ie. rate control, rhythm control, cardioversions, and/or ablations)

Routine Investigations

  • 12-lead ECG
    • Presence of AF, baseline intervals (PR, QRS, QT), signs of structural heart disease (ie. LVH, atrial enlargement)
  • Echocardiogram
    • LV size, wall thickness, and function
    • Left atrial size and volume
  • Labs
    • CBC, coagulation profile, electrolytes (including calcium and magnesium), renal function, liver function, thyroid function, fasting lipid profile, fasting glucose + hemoglobin A1C
  • Further investigations depending on history
    • Ie. if concern for sleep apnea then sleep study or if 

Physical Exam

  • Assess for AF risk factors and secondary causes of AF
  • Vitals (BP and HR), height, weight and BMI
  • Atrial Fibrillation
    • Irregular jugular venous pulsations (JVP)
    • Irregularly irregular rhythm detected by palpation of pulse or auscultation
    • Heart sounds heard during auscultation may include
      • Variable intensity of first heart sound (S1)
      • Absence of a fourth heart sound (S4) heard previously during sinus rhythm
  • Comprehensive cardiac exam including looking for heart failure signs (elevated JVP, edema, lung crackles)
CCS 2020 Evaluation of the atrial fibrillation (AF) patient. ED, emergency department.

Overall Management

CCS 2020 - General Overview for Management of Atrial Fibrillation

Stroke Prevention

CHADS-65

  • All patients should have yearly assessment of their AF stroke risk
  • Canadian guidelines recommend following the CHADS-65 algorithm for patients with non-valvular atrial fibrillation
    • Essentially all patients with either one CHADS risk factor or over 65 should be offered anticoagulation
  • Anticoagulation discussion should be individualized to each patient balancing their stroke and bleeding risk
CCS 2020 - CCS Stroke Prevention CHADS-65 Algorithm

Anticoagulant Selection

  • DOACs (apixaban, edoxaban, rivaroxaban, dabigatran) are recommended over warfarin in patients with non-valvular atrial fibrillation
  • Refer to table for dosing of DOACs (adjust for renal function and apixaban for weight/age/creatinine)
    • Some experts recommend apixaban 2.5mg BID and Edoxaban 30mg OD for CrCl 15-29
  • Warfarin is indicated for valvular atrial fibrillation (mechanical valve and moderate-severe mitral stenosis)
CCS 2020 - CCS Stroke Prevention CHADS-65 Algorithm

Acute Management

  • If atrial fibrillation is due to a reversible or secondary cause, focus should be on treating the primary issue
    • Ie. if a septic patient develops atrial fibrillation, resuscitating the patient should be the primary goal
  • Patients that are hemodynamically unstable should be managed as per ACLS and undergo electrical cardioversion (see cardioversion algorithm below)
  • In stable patients, shared decision making to decide on acute rate vs rhythm control
    • Recent-onset atrial fibrillation, guidelines recommend rhythm control strategy as recent evidence suggests reduced cardiovascular death and rate of stroke (EAST-AFNET 4)
    • Established atrial fibrillation there is no difference in outcomes between rate and rhythm control (AFFIRM)
  • Rate control can be done with beta blockers and/or calcium channel blockers (if EF>40%) and remember to start oral meds as soon as possible after IV
  • Acute Rate Control Agents and Acute Rhythm Control Agents
CCS 2020Approach to the management of atrial fibrillation (AF) in the acute care setting

Cardioversion

  • Note specific duration criteria for whether cardioversion can be safely done vs needing either 3 weeks of anticoagulation vs TEE
  • Anticoagulation should be started as soon as possible (ideally before cardioversion)
  • Note: CHADS 0 patients under 65 also require anticoagulation for 4 weeks post cardioversion and everyone else long term
  • Recommend using max dose joules (ie. 150-200 J biphasic) to avoid repeated shocks
    • Pad placement (AL vs AP) does not seem to influence success)
    • Obese patients may require applying force over pads using paddles to improve success
CCS 2020 - Oral anticoagulation pathway in the context of cardioversion for atrial fibrillation (AF) or flutter

Long Term Arrhythmia Management

Approach

  • As above, patients with recent onset of atrial fibrillation, rhythm control strategy is a reasonable choice to prevent negative cardiovascular and stroke outcomes (especially in higher risk patients, see EAST-AFNET 4 study above)
  • Otherwise using both rhythm and rate control have similar outcomes and decision should be individualized to the patient.
  • CCS provides a framework below for how to choose strategy
CCS 2020 - Approach to rate and rhythm management of atrial fibrillation

Rate-Control

  • Goal is to minimize effect on quality of life
  • Aim for a resting heart rate of < 100 beats per minute in permanent atrial fibrillation
    • RACE II: Among patients with permanent atrial fibrillation, lenient rate-control (HR < 110 bpm) is as effective as strict rate-control (HR < 80 bpm) in preventing cardiovascular events
  • Initial therapy should be beta blockers or nondihydropyridine calcium channel blockers
    • Beta blockers preferred in patients with myocardial infarction or systolic dysfunction
    • Digoxin can be used as monotherapy in older or sedentary patients, unable to tolerate first-line medications, or as an add on if rate control target not achieved
CCS 2020 - Approach to long-term rate control

Rhythm-control

  • Recommended in patients who are symptomatic despite rate control, in whom rate control is thought to unlikely control symptoms, or recent onset atrial fibrillation
  • Rhythm control agent should be chosen based on whether they have heart failure or CAD
  • Pill-in-pocket strategy can be used for patients who have infrequent symptoms
CCS 2020 Approach to long-term rhythm control

Amiodarone

  • Acutely, IV amiodarone acts as a beta-blocker and can help rate control atrial fibrillation
  • Chronically, amiodarone is the most effective medications for atrial and ventricular arrhythmias, including atrial fibrillation. Patients require a total of 10 grams to saturate their tissues such that their serum levels remain high. At that point, the half-life becomes very long and it becomes an effective anti-arrhythmic medication.
  • Drug monitoring:
    • TSH ad LFTs (baseline and q6 months)
    • Chest Xray and ECG (baseline and q1year)
    • PFTs (baseline and again if symptoms)
    • Ophthalmic exam (if symptoms)

Catheter Ablation:

  • Can be used in patients who are highly symptomatic despite adequate rhythm-control trial (drug-refractory) and in whom rhythm control is desired
  • Can be utilized in select individuals are first line therapy (e.g. paroxysmal atrial fibrillation that is highly symptomatic) or individuals with pre-excitation atrial fibrillation with an accessory pathway
  • Can be utilized as first line therapy or as a reasonable alternative to pharmacologic rhythm- or rate-control therapy patients with symptomatic typical atrial flutter 
  • Since catheter ablation is an invasive procedure, risks and benefit must be balanced

Management - Special Scenarios

Anticoagulation/Antithrombotic Post PCI

CCS 2020 - Management of antithrombotic nd anticoagulant therapy post ACS/PCI
Dosing of OAC+Antiplatelets

Peri-Operative Anticoagulation Management

  • The decision to continue or stop anticoagulation should be based on risk of bleeding during procedure
  • See algorithm for specific management of warfarin vs DOAC and bridging schedule
    • Note: DOACs do not require bridging due to short half life
CCS 2020 - Management of oral anticoagulant (OAC) use for patients requiring surgical procedures
CCS 2020 - Anticoagulation interruption schedule for patients undergoing elective or nonurgent surgery

Managing Bleeding on Anticoagulation

  • Management of bleeding on anticoagulation depends on the severity of bleeding and type of anticoagulant.
  • Note: for emergencies warfarin has multiple reversal agents, dabigatran can be reversed with idarucizumab and the anti-factor Xa (apixaban, rivaroxaban, and edoxaban) drugs can be reversed with andexanet alfa
CCS 2020 - Management of bleeding for patients receiving oral anticoagulation (OAC).

End-stage Renal Disease

  • CKD Stage 3 (GFR >30) and Stage 4 (GFR 15-29): anticoagulation is recommended as per CCS CHADS65 algorithm
  • CKD Stage 5 (GFR <15 or dialysis): guidelines recommend not routinely not performing anticoagulation but this is an area of ongoing debate

Liver Disease

  • Anticoagulation is not recommended for patients with Child-Pugh grade C or significant coagulopathy

Left Atrial Appendage Closure

  • Area of ongoing discussion but considered in patients with absolute contraindication to anticoagulant and are at risk of stroke
  • Can be done surgically or percutaenous

Further Reading

  • 2020 CCS/CHRS: Comprehensive Guidelines for the Management of Atrial Fibrillation (html) (pdf)
  • Cardiology: A practical handbook by David Laflamme

Authors

  • Authors: Dimitar Saveski (MD, Internal Medicine Resident), Atul Jaidka (MD, FRCPC, Cardiology Resident)
  • Staff Reviewer: pending (MD, FRCPC[Cardiology])
  • Copy Editor: Perri Deacon (medical student)
  • Last Updated: April 12, 2021
  • Comments or questions please email feedback@cardioguide.ca
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