Arrhythmias

An arrhythmia is… – disturbance of the electrical rhythm of the heart. Classification – Supraventicular (sinus, atrial, junctional) and.. – Ventricular Main mechanisms – Disorders of impulse formation or automaticity – Abnormalities of impulse conduction – Re-entry – Triggered activity

Supraventricular I Sinus –S–Sinus arrhythmia -> alteration of heart rate during respiration – not pathological, pronounced in children –S–Sinus bradycardia and tachycardia Atrial tachycardia – automaticity, sinoartial disease –N–Narrow complex tachycardia with abnormal P waves Atrial flutter – large re-entry circuit (RA encircling tricuspid) –3–300/min, some form of AV block –S–Saw tooth flutter waves Atrial fibrillation – re-entry, or continued ectopic firing –P–Paroxysmal or persistent

Supraventricular II AV node re-entrant tachycardia (AVNRT) – tachycardia, why polyuria? WPW Syndrome, atrioventricular re-entrant tachycardia – Abnormal band of conducting tissue connects the ventricles and the atria – Resembles purkinje tissue, acts as an accessory pathway, 50% asymptomatic – If different pathways have different speeds -> re- entrant -> with symptoms => WPW syndrome – Delta wave is characteristic

AV block First degree – delayed progression through AV node Second degree – Type 1 – PR gradually increase until a QRS complex is missed. – Type 2 – Occasionally P wave does not result in a QRS complex. Third degree – complete heart block.

SA block First degree – delay between firing of the SA node and depolarisation of the atria Second degree – Type 1 – conduction time between SA node and surrounding atrial tissue becomes progressively longer – eventually a cycle is missed. – Type 2 – time between SA node and propagation to atria is normal but at some point a cycle is just missed. Third degree – failure to conduct impulses