Key Concepts
Introduction
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. On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that reduces imminent harm and matches orders for the role you were given.