Cardiac Arrhythmias and ACLS

An arrhythmia is not simply an unusual tracing on a monitor. It is a disturbance in the heart’s electrical activity that may reduce cardiac output, impair coronary perfusion, trigger ischemia, or progress to cardiac arrest. The normal impulse begins in the sinoatrial node, travels through the atria, pauses briefly at the atrioventricular node, then moves through the His-Purkinje system to activate the ventricles in an organized sequence. That sequence gives the heart time to fill before it ejects blood. Arrhythmias occur when impulse formation is abnormal, impulse conduction is abnormal, or both. Important mechanisms include: - Enhanced or abnormal automaticity: a cell begins firing too quickly or a site outside the normal pacemaker takes over. - Triggered activity: an extra impulse occurs during or shortly after repolarization, often promoted by electrolyte disturbance, ischemia, or medications. - Re-entry: an impulse repeatedly circles through a pathway and reactivates tissue that has recovered. A re-entry circuit behaves like a runner trapped on a circular track: each lap creates another heartbeat. - Conduction block: the impulse is delayed or fails to reach part of...