Arrhythmias - A general overview

Complications

• Healthy patients can generally tolerate large variations of heart rate (and arrhythmias)
• Patients with impaired left ventricular or coronary vessel disease are more susceptible 
• Complications include:

• lowered cardiac output/hypotension/syncope/cardiac arrest
• cardiac ischaemia/angina
• impaired ventricular function/acute heart failure/pulmonary oedema

Assessment

• Cardiac arrhythmias can be divided into:
  • 'too fast' - tachy-arrhythmias or
  • 'too slow' - brady-arrhythmias
• Important acute/reversible causes are:
  • Acute ischaemia/infarction
  • Electrolyte abnormality
  • Drug effect - prescribed or recreational
  • Impaired circulation - hypo-volaemia, sepsis

Management

• The immediacy of treatment is dictated mainly by the clinical status of the patient rather than the type of arrhythmia
• Treating the cause is an important component of treatment - e.g. rapid AF due to sepsis should be addressed by appropriate fluid resuscitation before attempting to slow the rate down

* the patient with an chronically abnormal rhythm e.g. atrial fibrillation will not respond to cardioversion

Summary of options for management (if full cardiac arrest - go to arrest algorithm instead)

Tachy-arrhythmias

Increase energy output each refractory shock by 50-100% e.g. 50, 100, 150 J

* do not use verapamil in age < 12 months 

Brady-arrhythmias

• Atropine 10mgc/kg (600mcg) @ 3 min
• Isoprenaline 0.1mcg/kg/min
• Transcutaneous pacing (rate 80-100, begin with highest mA and reduce slowly to minimum capture threshold, set mA  ~ 25% above capture threshold)