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Atrial Fibrillation

The most common cardiac arrhythmia, demystified.
Atrial Fibrillation

High-Yield Tips

  • If patient looks unstable → call for help. Cardioversion may be necessary.
  • Use the A→E approach as for any unwell patient.
  • If patient is tachycardic > 120 bpm, consider adding some metoprolol PO, as long as their BP is stable and there are no other contraindications (e.g. asthma).
  • Use CHADS2-VA score, HASBLED score and context of the clinical picture to determine whether anticoagulation is appropriate.
  • If pursuing rhythm control, cardiologist input is necessary.

Definitions

  • Atrial fibrillation (AF) with rapid ventricular response (aka 'rapid AF') = AF where ventricular rate is > 100 bpm
  • Valvular AF = AF in patients with moderate or severe mitral stenosis, or a mechanical heart valve
  • Nonvalvular AF = AF in patients without moderate or severe mitral stenosis, or a mechanical heart valve

Classification

  • First diagnosed AF = where AF not previously diagnosed
  • Paroxysmal AF = episodes of AF < 7d (may be self-terminating or cardioverted)
  • Persistent AF = AF episodes lasting ≥ 7d
  • Long-standing persistent AF = continuous AF ≥ 1y AND patient on rhythm control
  • Permanent AF = rhythm control is not used as patient accepts being in AF
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All types of atrial fibrillation appear to have a similar risk of thromboembolism and stroke.

Epidemiology

  • AF itself rarely causes death or serious morbidity outside of thromboembolic complications
  • Affects around 2% of general Australian population and 5% of population ≥ 55y

Aetiology

PIRATE SHIV O3

  • P = pulmonary (e.g. infection, PE, sleep apnoea, COPD)
  • I = ischaemic heart disease
  • R = rheumatic heart disease
  • A = anaemia & alcohol
  • T = thyrotoxicosis
  • E = electrolytes (hypokalaemia, hypomagnesaemia)
  • S = sepsis
  • H = hypertension
  • I = idiopathic & iatrogenic (e.g. surgery)
  • V = valvular heart disease (mitral or tricuspid)
  • O3 = obesity, old age, odd sugar (diabetes mellitus)

Clinical Presentation

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These are the things to look out for that may point to a diagnosis of AF.

History

  • Asymptomatic
  • Palpitations, fatigue, dyspnoea, lightheadedness/presyncope, chest pain, syncope

Examination

  • Irregular pulse
  • Vitals: tachycardia; maybe tachypnoea, hypotension
  • Signs of heart failure e.g. peripheral oedema, pulmonary oedema, elevated JVP

Assessment & Management

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From the end of the bed, does the patient look like they’re going to die or are they relatively stable?

If unstable, call for help immediately, prior to initiating primary survey.

Primary survey

Airway

  • Ensure patient is maintaining own airway

Breathing

  • Check SpO2 and RR.
    • If patient is hypoxic (SpO2 < 94%) put them on some supplemental O2.
  • Listen to chest
  • Consider ordering a mobile CXR

Circulation

  • Check HR, BP
  • Feel peripheral pulses, peripheral/central capillary refill, peripheral temperature, listen to heart
  • If patient is lightheaded, lie the bed flat
  • Get an ECG
  • Insert two large-bore IV cannulae.
    • Take bloods (FBC, UEC, LFTs, coags, CMP, TSH, blood cultures) + VBG
    • If hypotensive and fluid not contraindicated, start IV fluids
      • Aim K > 4, Mg > 1
  • Start medications
    • If patient is significantly tachycardic, consider rate control (trying to prevent escalation to more unstable arrhythmia or tachycardia-mediated cardiomyopathy):
      • Metoprolol tartrate 25mg PO BD (max dose 100mg BD) → target HR 110 bpm. Note: if Pt has known heart failure, other HF-specific beta blockers are recommended (e.g. carvedilol).
    • Other medications depend on suspected underlying cause e.g. if infection → start empiric antibiotics; if in pain → consider analgesia
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If patient is haemodynamically unstable, consider cardioversion to prevent further deterioration to cardiac arrest. This is not a decision that you as an intern should have to make → call for help.

Disability

  • Determine AVPU/GCS
  • Ensure patient is grossly neurologically intact i.e. able to move all limbs

Exposure

  • Check temperature
  • Consider other relevant examination and investigations e.g. abdominal examination, urine dipstick etc.

Further assessment and management

  • Once the patient is haemodynamically stable, take a further history and thorough examination
  • Consider CHADS2-VA score vs HASBLED (in context of clinical picture) to determine whether anticoagulation is indicated for prevention of venous thromboembolism (VTE)
    • Nonvalvular AF → NOAC (e.g. apixaban 5mg PO BD) unless contraindications exist
    • Valvular AF → warfarin
  • If new AF, refer patient for a transthoracic echocardiogram (TTE)
  • Refer to cardiology if:
    • Signs of heart failure or LV systolic dysfunction on echo
    • Rate control is inadequate
    • Rhythm control is necessary
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Only start rhythm control after discussion with a cardiologist.

Cardioversion

Indications

  • Patient is haemodynamically unstable, has signs of myocardial ischaemia or heart failure, or has refractory tachycardia
  • Patient has been in AF for < 48h. Note Therapeutic Guidelines states: “Immediately start anticoagulant therapy with unfractionated heparin (UFH) or low molecular weight heparin (LMWH) in men with a CHA2DS2-VASc score of 1 or more or women with a score of 2 or more who are to undergo cardioversion.”
  • Patient has received 3 weeks of therapeutic anticoagulation therapy
  • Patient has received a transoesophageal echocardiogram (TOE) to rule out atrial thrombus

Types

  • Electrical - synchronised direct current (DC) → highly effective, with low complication rate, though Pt requires procedural sedation
  • Pharmacological (e.g. flecainide, amiodarone) → effective in 50% of recent-onset AF patients, without need for fasting or sedation

Resources

  1. Therapeutic Guidelines
  2. Emergency Care Institute: AF
  3. AIHW AF Stats
  4. Geeky Medics: Management of Acute AF

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