Bradyarrhythmia

Bradyarrhythmias are arrhythmias characterised by bradycardia, a ventricular heart rate < 60/min. The most common examples are sinus bradycardia and sick sinus syndrome. Bradyarrhythmias can be life-threatening if the heart rate is too low to sustain cardiac output. They can also degenerate into asystole, causing cardiac arrest. Short-lived paroxysmal bradyarrhythmias can cause syncope.

Types

• Sinus bradycardia
• Sick sinus syndrome/tachycardia-bradycardia syndrome
• 2nd degree AV block Mobitz type II
• 3rd degree AV block with a junctional or ventricular escape rhythm

Etiology

• Age-related degeneration of the sinus node and AV node
• Acute myocardial infarction
• Electrolyte disorders
• Myocarditis
• Drug intoxication (tricyclic antidepressants, digoxin, beta blockers, calcium channel blockers)

Acute management

If bradyarrhythmias are severe enough to cause haemodynamic instability, atropine (0,5 mg) can be given to increase the heart rate. Atropine can be repeated up to 3 mg. As a second choice, isoprenaline or adrenaline can be given. Transcutaneous pacing may also be used, where pads applied externally to the chest pace the heart like a pacemaker.