Bradycardia

Bradycardia 

written by Dr Ashly Liu

Bradycardia is typically defined by heart rate < 60 bpm but symptomatic bradycardia is usually associated with rates below 40bpm. 

Clinical findings

Red flag symptoms include signs of

• Shock
• Syncope
• Myocardial Ischaemia
• Heart Failure

Differentials

• Physiological bradycardia
• Sinus node dysfunction
• Medication related (i.e. beta blockers, calcium channel blockers, digoxin)

Red flags

• Anterior myocardial infarction
• Complete heart block 

AV Nodal Blocks

First Degree Heart Block – This is defined by PR interval > 200ms (‘marked’ first degree heart block is > 300ms)

Second Degree Heart Block

• Mobitz Type I (Wenkebach) – Progressive lengthening of the PR interval with an eventually dropped QRS complex

• Mobitz Type II (Hay) – Intermittent dropping of the QRS complex

Third Degree Heart Block – Complete dissociation of the atria and ventricles (i.e. dissociation of P waves and QRS waves)

Management – ACLS algorithm (Resuscitation Council UK)

• Primary Survey (ABCDE approach)
• Give oxygen if appropriate and obtain IV access
• Send bloods
• Monitor ECG, BP, SpO2 and record a 12-lead ECG
• If hemodynamically stable or has evidence of poor perfusion
• Give Atropine 500mcg IV bolus (repeat every 3-5min up to maximum of 3mg) 
• If there is a poor response or the patient has a risk of asystole*
• Atropine 500mg IV bolus up to a maximum of 3mg OR
• Isoprenaline 5mcg/min IV OR
• Adrenaline 2-10mch/min IV OR
• Tanscutaenous pacing
• Cardiology Consult and move patient to CCU/ICU for telemetry 

• Transvenous pacing 

References

UpToDate – “Advanced cardiac life support (ACLS) in adults”,  https://www.uptodate.com.acs.hcn.com.au/contents/advanced-cardiac-life-support-acls-in-adults

Resuscitation Council UK – “Adult advanced life support Guidelines”, https://www.resus.org.uk/library/2021-resuscitation-guidelines/adult-advanced-life-support-guidelines