The conduction system of the heart initiates and coordinates the electric signal that causes the rhythmic and synchronized contractions of the atria and ventricles. In higher vertebrates, this system comprises the sinuatrial (SAN) and atrioventricular nodes (AVN) and the wiring of the ventricles. The latter comprises the atrioventricular bundle (AVB), the left and right bundle branches (BBs), and the peripheral ventricular conduction system (PVCS).