Bundle of His

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Overview
The bundle of His is a collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the fascicular branches. The fascicular branches then lead to the Purkinje fibers which innervate the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval.

Eponym
These specialized muscle fibres in the heart were named after the Swiss cardiologist Wilhelm His, Jr., who discovered them in 1893.

Function
The fibers of the Bundle of His allow electrical conduction to occur more easily and quickly than typical cardiac muscle. They are an important part of the electrical conduction system of the heart as they transmit the impulse from the AV node (the ventricular pacemaker) to the rest of the heart. The bundle of His branches into the three bundle branches: the right, left anterior and left posterior bundle branches that run along the interventricular septum. The bundles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ventricular muscle. Together, the bundle branches and Purkinje network comprise the ventricular conduction system. It takes about 0.03-0.04 seconds for the impulse to travel from the bundle of His to the ventricular muscle.

Pathology
If the Bundle of His becomes blocked, there will be dissociation between the activity of the atria and the ventricles. This complete dissociation between the atria and the ventricles is called third degree heart block. Other causes of third degree heart block would be complete block of the right, left anterior, and left posterior bundle branches. Third degree block is a serious medical condition that often requires insertion of an artificial pacemaker.

His Bundle Pacing
In 2000, Dr. Pramod Deshmukh, an electrophysiologist in Sayre, PA announced that he had successfully performed Direct His-Bundle pacing that produced synchronous ventricular depolarization and improved cardiac function relative to apical pacing. This breakthrough was hailed by Dr. Melvin M. Scheinman, considered by many to be the father of electrophysiology, for what he called a "tour de force" deserving "strong accolades" for the technical accomplishment.