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Sudden Cardiac Death and Cardiac Arrest

  • Cardiac arrest – sudden and complete loss of CO due to asystole, ventricular tachycardia/fibrillation, or loss of cardiac contraction (pulseless electrical activity)
  • Clinical dx is based on pt being unconscious and pulseless

Sudden cardiac death

  • See box
  • Due to massive arrhythmia – VF, pulseless ventricular tachycardia, asystole, or pulseless electrical activity (PEA)
  • Coronary arterial disease (CAD) is the most common condition leading to cardiac arrest – VF/VT is common in first few hours of MI

Cardiac arrest

VF and Pulseless VT

  • VF – rapid, ineffective, uncoordinated movements of the ventricles
    • Therefore produces no pulse
    • ECG – rapid, bizarre, irregular ventricular complexes
  • VT – can cause cardiac arrest if the ventricular rate is so rapid that effective mechanical contraction and relaxation cant occur
    • Can degenerate into VF
  • Defibrillation can restore CO but chances of survival decrease by 10% each minute

Asystole

  • Occurs when there is no electrical activity within the ventricles
  • Due to failure of conducting tissue or massive ventricular damage
  • A precordial thump, external cardiac massage or IV atropine/adrenaline can restore cardiac activity
  • Permanent pacemaker implantation is required in conduction failure if pt survives

Pulseless electrical activity

  • Occurs when there is no effective CO despite the presence of organised electrical activity
  • Reversible causes – hypovolaemia,
  •   Cardiac tamponade, Tension pneumothorax
  • But more often due to catastrophic causes – cardiac rupture or massive PE

Management of cardiac arrest

Basic life support

  • Aim to maintain low level of circulation until ALS can be given
  • ABCDE approach 
    • Airway – assessment and restoration
    • Breathing – maintain ventilation by ‘mouth to mouth’
    • Circulation – chest compressions
    • Disability – assess Neurological status
    • Exposure – remove clothes to enable defibrillation; assess for rashes (anaphylaxis)

Advanced life support

  • Restore normal cardiac rhythm by defibrillation – if cardiac arrest is due to arrhythmia
  • Restore CO by correcting other reversible causes of cardiac arrest – 4 Hs + 4 Ts (see algorithm)
  • Intubation to restore ventilation
  • During resuscitation, adrenaline [1mg IV] should be given every 3-5 mins. Amiodarone [300mg] after 3rd shock.

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