Pathophysiology
Clinical meaning
Cardiac arrhythmias result from abnormalities in impulse generation, impulse conduction, or both within the heart's electrical system. The normal conduction pathway flows from the SA node through the atria, AV node, bundle of His, bundle branches, and Purkinje fibers. Disruption at any point produces characteristic rhythm disturbances. The SA node normally fires at 60-100 bpm, but ectopic pacemaker sites (AV node: 40-60, ventricles: 20-40) can take over when the SA node fails. Arrhythmias range from benign (premature atrial contractions) to immediately life-threatening (ventricular fibrillation). Recognition of lethal rhythms and prompt emergency response are essential competencies.