(See also Overview of Abnormal Heart Rhythms and Overview of Heart Block.)
The bundle of His is a group of fibers that conducts electrical impulses from the atrioventricular node. The bundle of His divides into two bundle branches. The left bundle branch conducts impulses to the left ventricle, and the right bundle branch conducts impulses to the right ventricle. Conduction may be blocked in the left or right bundle branch.
The left bundle branch further divides into two branches, called the anterior and posterior fascicles. If conduction is blocked through one of these fascicles, the blockage is called a hemiblock or a fascicular block.
Tracing the Heart’s Electrical Pathway
Bundle branch block usually causes no symptoms. Right bundle branch block is not serious in itself and may occur in apparently healthy people. However, it may also indicate significant heart damage due to, for example, a previous heart attack.
Left bundle branch block tends to be more serious. In older people, it often indicates coronary artery disease due to atherosclerosis.
Bundle branch block can be detected by electrocardiography (ECG). Each type of block produces a characteristic pattern.
Usually, no treatment is needed.
