Cardiac Arrhythmias

Supraventricular arrhythmias
1. Atrial Fibrillation
  1. Ax: Cardiac : IHD / Valve disease / HTN Metabolic: Thyrotoxicosis, alcohol binge, electrolyte abnormalities
  2. Sx: Palpitations / syncope / SOB
  3. Dx: ECG - absent P waves / O/E - irregularly irregular pulse
  4. Management
    1. Acute AF
      1. <48 hours: 1. Rate control 2. TOE 3. No thrombus -> DC / chemical cardioversion NB: if CV score is >=2 then Heparin at the same time.
      2. Haemodynamically Unstable: Immediate DC cardioversion
        Chemical cardioversion - flecainide / amiodarone
      3. >48 hours: 1. Rate control 2. TOE 3. No thrombus then heparin until ApTT 45-60 then cardiovert NB: if CV score >=2 then anticoag for 3-4 weeks first
      4. TOE: Evidence of thrombus - anticoag for 3-4 weeks then cardiovert
    2. Chronic AF
      1. Rate control (elderly / permenant AF) - B-blockers and Non-DHP CCB. Heart failure? - use digoxin and amiodarone
      2. Rhythm control (young / paroxysmal / persistent AF / symptomatic) - Flecainide / amiodarone then catheter ablation
    3. CHADSVASC score
      1. Need for anticoagulation - post cardioversion needed for up to 4 weeks
2. Atrial Flutter
  1. Supraventricular atrial tachycardia. Re-entrant cycle set up - 300bpm but normally 2:1 block from AVN
  2. Sx: Syncope / palpitations / SOB
  3. Dx: ECG - saw tooth pattern. Carotid sinus / adenosine to help diagnosis
  4. Ax: Atrial abnormalities incl. AF / thyrotoxicosis / alcoholism / chronic lung conditions
  5. Treatment
    1. Rate control - B-blockers and non-DHP CCBs
    2. Rhythm control - DC synchronised cardioversion (50J) / Catheter ablation
      1. Needs anticoagulation beforehand / After? - CHADSVASC
3. AV Node re-entrant tachycardia
  1. Re-entrant cycle set up within AVN
  2. Tx: Vasotonic manoeuvres / break re-entrant cycle - IV adenosine / DC synchronised cardioversion (50J)
4. Accessory pathway re-entrant tachycardia
  1. WPW syndrome - accessory pathway that allows impulse to reach ventricles faster
  2. Sx: Sudden palpitations / syncope / SOB
    1. WPW + AF - extremely dangerous and can cause VF - DC cardioversion
  3. Dx: ECG - delta wave and short PR interval
  4. Long term tx: Rate control - BBs and CCBs / catheter ablation
Ventricular arrhythmias
1. Ventricular Fibrillation (VF)
  1. Rapid ventricular rhythm that doesn't allow ventricles to contract properly
  2. Causes - IHD / R on T (ventricular ectopics) / long QT
  3. Monomorphic / polymorphic (Torsades)
  4. ALS Algorithm - shockable rhythm
2. Ventricular Tachycardia
  1. Ventricular rhythm >100bpm
  2. Ax: Re-entry loop - damaged heart / triggered automaticity - damaged heart / digoxin
  3. ALS guidelines 1) Not stable - shockable 2) Stable - ABCDE and correct causes
3. Ventricular Ectopics
  1. Ax: Idopathic - harmless in those with normal hearts Precipitant - caffeine / alcohol / digoxin | Post-MI / heart damage / digoxin
    1. Harmless ectopics often disappear with exercise
  2. Dx: ECG - premature ventricular beats (can appear as bigeminy / trigeminy
  3. Sx: Skipped beat feeling
  4. Tx: Nothing / remove precipitants / rate control with B-blockers if symptomatic
    1. Anti-arrhythmics NOT used - increase risk of death
Atrioventricular Block
1. First degree block: PR >0.2 seconds
  1. Physiological
2. Second degree block
  1. Mobitz I: Wenkebach phenomenon - increasing PR till drop of QRS complex
    1. Ax: May by physiological / underlying heart condition
  2. Mobitz II: PR interval constant but intermittent loss of QRS complex (2:1 / 3:1 block)
    1. Ax: Always pathological - damage to conducting fibres e.g. post MI
    2. Pacemaker required
3. Third degree block - Complete block
  1. Complete dissociation between P waves and QRS complexes
  2. Tx: Transient - Atropine / stop Digoxin. Permenant - Pacemaker needed
  3. Ax: May be transient post- MI (atropine) / permenant - Inferior MI (damage to AVN)
  4. Sx: Depends on location of escape beat 1. Above bundle = mild Sx and narrow QRS 2. In bundle = severe Sx and wide QRS
Bundle branch block
1. RBBB
  1. Ax: Physiological / new-onset may be anterior MI related
  2. Dx: ECG - M sign in right sided leads (V1/V2) / wide QRS
2. LBBB
  1. Ax: Always pathological e.g MI / HTN / valve disease
  2. Dx: ECG - M sign in left sided ant. leads (V5/V6) / wide QRS
  3. Hemifasicular block
    1. LBB divides into anterior and posterior hemifasciles
    2. Damage causes change in axis
Drug toxicity
1. Digoxin
  1. Normal action: Reduce heart rate (slows AV transmission) / increases contractility by decreasing repolarisation time
    1. Used for patients with HF to reduce oedema
    2. Works by inhibiting the NaKATPase pump
  2. Toxicity
    1. Ax: Overdose/ Renal impairment / electrolyte abnormalities - hypokalaemia / low Mg / Drugs - CCBs / amiodarone
    2. Sx: Confusion / weakness / syncope / palpitations / N&V and abdo pain / yellow haze
    3. ECG: Increase PR / PVCs / scooped ST segment
Long QT syndrome
1. Ax: Congenital - genetic mutation in Na+ / K+ channels. Acquired - hypocalcaemia / hypokalaemia / low Mg / SAH
2. Dx: ECG - long QTc / U&Es
3. Sx: Cardiac arrest / syncope
  1. Torsades de pointes - polymorphic VT that can go into VF / treat with Magnesium sulphate and defib
4. Tx: Remove or correct precipitants, ICD

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Cardiac Arrhythmias

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	Created by Louis Darby over 6 years ago