Find A Physician

Return to Bradycardia, Heart Block and Bundle Branch Block Overview

More on Bradycardia, Heart Block and Bundle Branch Block

Hospital News

Return to Bradycardia, Heart Block and Bundle Branch Block Overview

More on Bradycardia, Heart Block and Bundle Branch Block


Health Library

Return to Bradycardia, Heart Block and Bundle Branch Block Overview

More on Bradycardia, Heart Block and Bundle Branch Block

Research and Clinical Trials

Return to Bradycardia, Heart Block and Bundle Branch Block Overview

More on Bradycardia, Heart Block and Bundle Branch Block

Bradycardia, Heart Block and Bundle Branch Block

How does a normal heart beat?

The heart is a hollow muscular organ – approximately the size of your clenched fist – that beats 40 million times per year (between 60 and 100 beats per minute). The hearts pumping action is controlled by its electrical system, which gives rise to the heart rhythm.

Normal cardiac rhythm results from electrical impulses that begin in a special group of cells that form the sinoatrial (SA) node, also called the sinus node. Located in the right upper chamber of the heart, sinus node cells act as the heart's natural pacemaker. Impulses spread from the sinus node to the right and left atria (the upper chambers of the heart), causing them to contract at the same time. The impulses then travel to the AV (atrioventricular) node, the region that manages impulse traffic from the atria to the ventricles (the lower chambers of the heart). Here, impulses are slowed slightly to give the atria time to contract before the signal reaches the ventricles.

From the AV node, the impulses travel through a system of specialized heart tissue. Located in the wall that separates the two ventricles, this conducting system splits to form the right and left bundle branches that travel to the respective ventricles. Via this conducting pathway, powerful electrical jump-start signals are delivered to the ventricular muscle of the heart. In the healthy heart, these impulses travel at the same speed so that the two ventricles contract at the same time, and oxygen-rich blood from the lungs is pumped throughout the body.

What is bradycardia?

Bradycardia is the term used to describe an abnormally slow heart rate of less than 60 beats per minute. This condition can be caused by certain medications, pre-existing conditions such as congenital heart disease, certain forms of acquired heart disease, or the degenerative processes of aging. In some cases, slow heart rates are considered normal, for example, in a young athlete who is in peak physical condition. In fact, most people tolerate heart rates between 50 and 60 beats per minute without difficulty. However, a slow heart rate can be considered abnormal if it causes such problems as fainting, fatigue, and light-headedness.

What is bundle branch block?

A blockage in either the right or left bundle of the conducting pathway is called bundle branch block. Because of the block, the electrical signals that stimulate the ventricles to contract together are out of sync. Impulses on the side with the block will reach the respective ventricle more slowly than impulses traveling to the unaffected side. As a result, contraction of one ventricle occurs later than the other.

Bundle branch block can be caused by coronary artery disease, valve disease, or other conditions, or can be present in an otherwise normal heart. By itself, bundle branch block may not require treatment. However, in some instances, bundle branch block may be associated with bradycardia and may require treatment with pacemakers or cardiac resynchronization therapy to regulate the heart beat.

What is heart block?

Heart block occurs when a defect in the conducting system of the heart causes electrical signals traveling from the AV node to the ventricles to become slowed or even blocked. Heart block can produce fainting (syncope) or dizziness. The major risk from heart block is bradycardia (slow heart rates) that can cause loss of consciousness, or even failure of the lower chambers of the heart to beat. Heart block most often occurs as a result of degeneration of the hearts conduction system due to the aging process. Other causes include prior heart attack, valve disease, valve surgery, or cardiomyopathy (weakening of the heart muscle). Implantation of a pacemaker that can regulate the hearts rhythm is the preferred treatment for heart block.

Last Modified: 06/06/2004

  • Bookmark
  • Print

    Find a Doctor

Click the button above or call
1 877 NYP WELL


eNewsletters

Hospital News



Top of page