Illustration: Image of the heart's electrical conduction system showing the sinoatrial (SA) node, right atrium, atrioventricular (AV) node, right ventricle, left bundle branch, left ventricle, right bundle branch, bundle of His, and left atrium. Conditions associated with the heart's electrical conduction system include arrhythmia (both fast and slow heart rates), atrial fibrillation, heart block, sick sinus syndrome, supraventricular tachycardia, ventricular fibrillation, and ventricular tachycardia.