Chapter 28: Disorders of Cardiac Conduction and Rhythm

The foundation involves understanding how disturbances in impulse formation, impulse conduction, or both can produce abnormal heart rhythms that range from benign to life-threatening. The chapter explores various arrhythmia types, including ectopic rhythms that originate from abnormal pacemaker sites, reentrant mechanisms where electrical activity circulates through tissue with unidirectional conduction block, and triggered activity arising from either early or delayed afterdepolarizations. Genetic predisposition significantly influences arrhythmia risk, with inherited channelopathies such as short QT syndrome demonstrating how alterations in ion channel function can fundamentally alter cardiac electrical properties and automaticity. The diagnostic approach relies on electrocardiographic interpretation to identify the specific arrhythmia mechanism and guide appropriate therapeutic intervention. Treatment modalities span pharmacological strategies using antiarrhythmic agents that work through various mechanisms of action including sodium channel blockade, beta-adrenergic antagonism, potassium channel inhibition, and calcium channel blockade. Beyond medication, advanced interventional techniques provide additional options including antitachycardia pacing to terminate reentrant circuits, synchronized cardioversion for urgent conversion of hemodynamically significant arrhythmias, and implantable cardioverter-defibrillators for preventing sudden cardiac death. The chapter integrates electrophysiologic concepts with clinical decision-making, emphasizing how understanding the underlying mechanism of each arrhythmia enables selection of the most effective treatment approach while considering patient-specific factors and potential drug interactions or complications.