Atrial Fibrillation (AF)

Exam Cram

• Atrial Fibrillation is the most common cardia arrhythmia, caused by an irregularly irregular atrial contractions

• Presentation: irregularly irregular pulse, ECG: loss of p waves, can be tachycardic; asymptomatic or symptomatic (syncope, chest pain, palpitations)

• Diagnosis: ECG

• Management: anticoagulation & rate or rhythm control (betablockers, digoxin, amiodarone)

Outline

Background

• Atrial fibrillation (AF) is the most common cardiac arrhythmia

• AF is a type of supraventricular tachycardia

• AF can typically cause tachycardia (fast AF), however can also cause bradycardia (slow AF)

Assessment

History

• Asymptomatic

• Symptomatic- palpitations, presyncope or syncope, chest pain, leg swellling

• Typically in elderly who exercise ++ or known cardiac disease

Examination

• Pulse irregularly irregular- can be tachycardic

• Signs of heart failure: hypotension, bilateral leg swelling or basal coarse crepitations, tachypnoea

• Fluid status- GCS ?cerebral perfusion, urine output ?renal perfusion, hypo vs hypervolaemia

Investigations

• ECG: QRS irregularly irregular, absent p waves, variable rate

• Causes

  • Electrolytes: Na+, K+, Mg2+, Ca2+, PO4/3-: low levels can be a cause

  • Septic screen: CXR, urine/ blood culture, viral PCR, CRP/ neutrophils 

  • Thyroid function tests ?hyper

Diagnosis

Diagnostic Criteria: ECG- absent p waves, irregularly irregular QRS

Differentials: atrial flutter, atrial tachycardia, sinus tachycardia

Classification: 

1. Severity: 

   • Stable (0/4 features) 

   • Unstable (1-4/4 features): BP < 90/60, myocardial ischaemia, (pre)syncope, heart failure

2. Timescale

Management

Acute 

1. Rate or Rhythm

   1. Betablockers (bisoprolol)- if well

   2. Digoxin- if hypotensive and quite unwell

   3. Amiodarone- if severely unwell

2. Anticoagulation: usually a DOAC, e.g. apixaban

Long Term

• Anticoagulation if CHADVASC +ve and HASBLED or ORBIT -ve

• Rate or Rythm

  • Long term betablocker or digoxin (avoid long term amiodarone)

  • 'Pill in the pocket'- flecainide

Management

Classification of Acute Management

Summary: 

• If unstable, requires an emergency shock & transfer to resus. 

• If stable and symptoms started < 48hrs, can cardiovert electrically or chemically

• If symptoms start > 48hrs, requires elective outpatient cardioversion under anticoagulation and after a normal ECHO. 

Workflow: 

1. If unstable (signs in next section)

   • DC Cardioversion

   • Transfer to resus

2. If presenting < 48 hrs & stable: cardiovert

   • Electrical: DC Cardioversion

   • Chemical: 

     1. Flecainide

     2. Amiodarone

3. Presenting > 48 hrs: elective cardioversion

   • Start anticoagulation, usually DOAC

   • Return for elective elective or chemical cardioversion

   • Requires ECHO to rule out left venticular thrombus

Optimising Medical Management

• Assess underlying causes

  1. Infection: septic screen: chest XR, urine & blood cultures, viral PCR, CRP & neutrophils

  2. Electrolyte: K+ > 4.0, Mg2+ > 1.0, Ca2+ > 2.6, PO4/3- > 0.7

  3. Fluid status: fluids if dehydrated, furosemide if overloaded

• Scope to increase dose of existing medications, e.g. betablockers

• Escalate: betablockers -> digoxin -> amiodarone

• IV amiodarone usually requires level 2 care (CCU, HDU) and central line

• Usually tolerate HR < 130 if BP stable (MAP > 65)

• Anticoagulation

Med Reg Notes

Signs of unstable AF

• Shock: MAP < 65

• Myocardial ischaemia (i.e. chest pain)- rate related TWI and mild troponitis unconcerning

• Syncope: sign of cerebral hypoperfusion

• Cardiac failure: e.g. acute pulmonary oedema

Rate control: flecainide vs amiodarone vs digoxin

Flecainide

• Contraindicated in those with structural heart defects, e.g. previous myocardial infarctions

• Known as 'pill in the pocket', can be used for paroxysmal AF if patients can self detect and self administer 

Amiodarone

• If given with digoxin, reduce dose of digoxin to avoid toxicity

• Used in unwell patients with AF

• Significant side effect burden

  • • Hypo/hyperthyroidism, pulmonary fibrosis, liver fibrosis

Digoxin

• Used for patients with atrial fibrillation + acute heart failure

Left ventricular thrombus

Cardioversion cannot be done in patients who have been in AF for > 48hrs due to the risk of left ventricular thrombus forming. This could embolise at the point of cardioversion, causing an emobolic stroke. 

Complications

Stroke

• Morbidity from atrial fibrillation is greater from the risk of stroke than congestive heart disease.

• Approximately the annual risk of stroke in atrial fibrillation 7% and this is reduced to 2% with a DOAC. 

Congestive Heart Failure

• Atrial fibrillation is associated with an increased rate of developing CHF

Should Septic AF be anticoagulated?

Variation in practice. My impression is that is should because individuals who go into septic AF have a high risk of developing permament AF and having a significant stroke risk. Usually the risks of clotting are more serious than bleeding and the burden of stroke morbitiy is high in the elderly. 

Atrial Flutter

Notes

• ECG: saw tooth'd 

• Rate usually 2:1, 3:1 or 4:1, reflects the ratio of atrial contractions to ventricular

• Rate divisible by 300, e.g 2:1 rate is 150

• Management the same as atrial fibrillation

  • Requires anticoagulation

  • Rhythm vs rate control

Page written in 2024.