ABSTRACT
With advancing medical knowledge and the advent of newer technologies, the coronary sinus (CS)—a structure that was once thought to be nothing more than an obscure source of passive venous drainage—is now recognized as an important gateway for an array of clinical interventions. The CS is an extremely important structure to recognize for safe and efficient catheterization of the cardiac venous system, and should be considered as the fifth chamber of the heart. Electrically conductive muscle bands connect the CS to both atrial chambers and provide inputs for activation of the CS myocardium. The epicardial veins carry most of the venous return from the left ventricle (LV) to the CS, which empties into the right atrium (RA). The anterior interventricular vein (AIV) is the largest and most consistent of the cardiac veins. Catheterizing the CS is an operator-dependent process that requires a thorough understanding of the venous anatomy, more so than manual skill and dexterity.
