Bradycardia

Bradycardia is defined as an abnormally slow heart rate. Children of different ages have different ranges of normal heart rates.

In adults, a heart rate of less than 60 is bradycardia. In unresponsive infants and children, a heart rate of less than 60 should be treated as cardiac arrest.

Symptomatic bradycardia in PALS is bradycardia that results in poor tissue perfusion. It is associated with cardiopulmonary compromise (shock) and is a sign of impending cardiac arrest.

Bradycardia may be sinus bradycardia or AV heart block (heart block can cause various heart rates, not just bradycardia).
- Sinus bradycardia has a sinus morphology but at a slow rate.

AV block may present in four main forms
- First degree
- Second degree type I
- Second degree type II
- Third degree

Types of AV Block
First Degree AV Block	May be present in healthy children May be due to cardiac infection, MI, electrolyte imbalances, increased vagal tone, cardiac surgery, acute rheumatic fever, drugs Calcium channel blockers and digoxin may cause Characterized by prolonged PR interval Does not cause symptoms
Second Degree AV Block – Mobitz Type I (Wenckebach)	May occur in heathy children or as a result of vagal stimulation, MI, drugs (calcium channel blockers, digoxin, and beta blockers) Progressive prolongation of PR interval until P wave disappears.
Second Degree AV Block – Mobitz Type II	Generally caused by conduction system abnormalities May be caused by cardiac surgery or MI Not usually caused by drugs Some P waves are blocked PR interval constant Often every other P wave is blocked Symptoms include: lightheadedness, palpitations, and fainting
Third Degree AV Block	Caused by conduction system disease or injury, cardiac surgery, MI, congenital malformations, increased parasympathetic tone, drugs, severe hypoxia, and severe acidosis P waves and QRS complexes not related Atrial impulses do not reach ventricles Tiredness, lightheadedness and fainting may occur

Treatment of Bradycardia

Bradycardia with poor perfusion is treated according to the algorithm.

Identify and treat reversible causes of bradycardia.

Hypoxia: Administer high concentration O₂ and ventilation assistance.
Acidosis: Support ventilation. Consider using sodium bicarbonate.
Trauma: Provide oxygenation and ventilation. Hyperventilate if signs of brain herniation are present. Obtain specialist consultation.
Drug overdose and poisoning: Provide appropriate antidote.
Hypothermia: Rewarm child unless cardiac ischemia/infarction present.
Heart block: Medication, pacing, and specialist consultation.
Hyperkalemia: Manage electrolyte balance.