Bundle branch block is an issue in the conduction system of the heart. The human heart contracts thanks to the sinoatrial node, which acts as a natural pacemaker, sending an electrical impulse through the heart. The impulse travels through the upper chambers before passing through the atrioventricular node. From this node, the impulse travels along a bundle that splits into the right bundle branch and the left bundle branch before eventually reaching the ventricles. Occasionally, a blockage will develop along one of these branches, leading to bundle branch block.
A left bundle branch block occurs when a blockage affects the left path. In many cases, the electrical impulse still reaches the left ventricle but is significantly slower than it should be. As a result, the left ventricle contracts slightly later than it should. Uncoordinated contractions between right and left ventricles mean the heart will pump blood less efficiently. For most people, this has no effect, but it can worsen other existing heart conditions.
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