conduction system of the heart pdf basics

Some authors describe an additional left septal fascicle. Left anterior fascicle is thin while posterior fascicle is thicker and broader, with dual blood supply so that it is seldom involved in disease processes. Left bundle branch further divides into a left anterior fascicle and a left posterior fascicle. Part of the right bundle travels through the moderator band in the right ventricle. The bundle of His divides into left and right branches destined for the corresponding ventricles. The fibers destined for the bundle branches are segregated within the bundle of His even before its actual division. Signals from the bundle of His can be recorded using intracardiac electrodes it is known as His bundle electrogram. The slow pathway is posterior, has a slower conduction velocity, but a shorter refractory period.īundle of His arises from the inferior border of the AV node and enters the upper part of the interventricular septum. The fast pathway is anterior, has a higher conduction velocity, but a longer refractory period. AV node has a slow pathway and a fast pathway ( dual AV nodal physiology). It can also act as a subsidiary pacemaker of the heart if the SA node were to fail, though its automaticity is less than that of the SA node. This ensures atrial booster action for ventricular filling during the terminal part of ventricular diastole. This ensures that atrial and ventricular contractions are sequential rather than simultaneous. An important role of the AV node is to delay the signals coming from the SA node till the atrial contraction is over. It is a subendocardial structure unlike the SA node. Many have doubted their presence and considered that internodal conduction is through the atrial myocardium.ĪV node is situated in the lower part of the right atrium at the apex of Koch’s triangle formed by ostium of the coronary sinus, tendon of Todaro and the septal part of the tricuspid annulus. They are microscopically identifiable preferentially oriented fibers. Though these three tracts have been discussed, they are not clear cut anatomical bundles which can be easily localized like the bundle of His and its branches. Anterior tract gives off the Bachmann’s bundle, which carries impulses to the left atrium.The heart rate after total sympathetic and parasympathetic blockade is known as intrinsic heart rate. It has both sympathetic and parasympathetic innervation which modulates the heart rate. The diastolic depolarization in the SA node which is responsible for the automaticity is mediated by the funny current(I f). It is the natural pacemaker of the heart with highest automaticity among the specialized conduction tissue. The SA node is a subepicardial structure. Sinoatrial node is situated in the upper part of the right atrium near the opening of the superior vena cava. It consists of the sinoatrial node (SA node), internodal pathways, atrioventricular node (AV node), bundle of His, bundle branches and Purkinje fibers. The conduction system of the heart consists of specialized conduction tissue.

Conduction system of the heart pdf basics