ABSTRACT
Clinical cardiac electrophysiology (EP) has undergone numerous technological advancements in the past 20 years, which have revolutionised the diagnosis and treatment of arrhythmias. The fundamentals have, however, remained largely unchanged, based on a thorough understanding of cardiac anatomy, cellular EP and biophysics. The right atrium (RA) is bounded by the caval veins superiorly and inferiorly, the inter-atrial septum and coronary sinus medially and the crista terminalis laterally. The smooth posterior wall is derived from the sinus venosum. The coronary sinus extends from the inferior RA septum along the inferior mitral annulus. The sino-atrial node (SAN) is a crescent-shaped, intramural structure with its head located subepicardially at the junction of the RA and the superior vena cava and its tail extending along the crista terminalis. Sinus node dysfunction can result from idiopathic degenerative changes, ischemia or infarction, infiltrative diseases, as well as fibrosis and degeneration with age or atrial fibrillation.
