Bundle branch block on the electrocardiogram (ECG)

What is it about ?

The heart muscle (the myocardium), made up of 2 atria and 2 ventricles, contracts under the impulse of electrical stimuli. These originate in the atrium of the heart in a knot of nerves (sinus node), which functions as a kind of stack. An electric current is diffused from this location to a second node (atrioventricular node or AV), located between the upper chamber (the atrium) and the lower chambers (the ventricles). Then, the current continues its route to the heart muscle (myocardium) via 2 nerve bundles, the right branch and the left. The right branch distributes the electric current to the right heart chamber, the left to the left heart chamber.

When, for one reason or another, electrical conduction is interrupted in this bundle, we speak of bundle branch block. There is therefore a left bundle branch block and a right one.

The electrocardiogram (ECG) shows the electrical activity of the heart. Problems in electrical conduction lead to abnormalities on the ECG.
Bundle branch block is just as possible in a perfectly healthy person. But in general the phenomenon is rather associated with heart disease and / or vascular disease or conduction disorders in nerve fibers. The most common causes are:

• a heart attack (infarction) ;
• narrowing or obstruction of the coronary arteries ;
• heart muscle disorders (inflammation, hypertrophy);
• abnormalities in the valves of the heart;
• congenital heart abnormalities.

Meaning of bundle branch block on the ECG

As bundle branch block can indicate heart abnormalities, additional tests will always be done to identify the possible underlying cause. In the absence of cardiac abnormalities, only a regular check-up ECG is expected. If cardiac abnormalities are detected, then the nature of the condition determines the severity of the problem.

A left bundle branch block is usually more serious than a right bundle branch block. The appearance of left and right bundle branch block simultaneously increases the risk of developing a serious condition.

What can your doctor do?

The possible treatment of bundle branch block will depend on the specific conditions associated with it. Sometimes it will not be necessary to continue treatment, sometimes it will be necessary to take medication. If there is an increased risk of developing Cardiac arrythmia, it is possible to place a pacemaker.

Sources

Foreign clinical practice guide ‘Bundle branch block on ECG’ (2000), updated on 02/28/2017 and adapted to the Belgian context on 09/27/2019 – ebpracticenet