Right Bundle Branch Block (RBBB)

When Is RBBB A Problem?

right bundle branch block
Right Bundle Branch Block. R Fogoros

Right bundle branch block (RBBB) is a distinctive pattern seen on the electrocardiogram (ECG) that occurs when the cardiac electrical impulse is interrupted as it spreads across the ventricles of the heart.

Bundle Branch Block

The bundle branches are the electrical pathways that allow the heart’s electrical impulse to spread rapidly and evenly through the ventricles, so that the contraction of the heart is well-coordinated.

There are two main bundle branches — the right bundle branch (which distributes the electrical impulse across the right ventricle) and the left bundle branch (which distributes the impulse across the left ventricle).

Bundle branch block occurs when one or both of the main bundle branches are partially or completely blocked. There are two main types of bundle branch block, namely, left or right bundle branch block.

The figure shows what RBBB looks like on the ECG. The top panel shows a normal QRS complex, and the bottom panel shows RBBB. Note that with left bundle branch block the QRS complex is much wider than normal. In the ECG lead that is depicted (which happens to be Lead I), the QRS complex also displays the downward  configuration that is characteristic of RBBB. Left bundle branch block (LBBB) is discussed separately.

Right Bundle Branch Block

Right bundle branch block is a more common, and much less significant, ECG finding than left bundle branch block.

While right bundle branch block is not often seen in young people, its incidence increases with age. More than 11% of 80-year-olds have right bundle branch block.

If your doctor tells you that you have right bundle branch block, then an evaluation should be done to make sure you do not have an underlying heart or lung condition.

If no such medical condition is present, then your right bundle branch block generally can be considered benign (not harmful).

Right Bundle Branch Block and Underlying Heart and Lung Disease

The reason right bundle branch block is more common than left bundle branch block is that the right bundle branch, as it courses within the muscle of the right ventricle, is relatively superficial (that is, near the surface of the ventricular cavity) for much of its length. This makes it susceptible to damage and stretching whenever the right ventricle is placed under stress of any kind.

Right bundle branch block often occurs in any condition that affects the right ventricle. These conditions can include coronary artery disease (CAD)myocarditis (inflammation of the cardiac muscle), atrial septal defect, ventricular septal defect, and valvular heart disease. Right bundle branch block may also be seen with any lung condition that causes a chronic elevation in the pressures within the right ventricle — for instance, with some types of chronic obstructive pulmonary disease (COPD).

Furthermore, right bundle branch block is common with any condition that acutely raises pressures in the right ventricle.

The most common condition that does this is pulmonary embolus.

As a result, if you are discovered to have right bundle branch block, your doctor should take a careful medical history and perform a full physical examination (concentrating on signs of heart and lung disease), and should consider ordering an echocardiogram to look for inapparent heart disease.

Because the right bundle branch is susceptible to anything that can produce even small trauma in the right ventricle, transient right bundle branch block occurs in approximately 5% of patients undergoing cardiac catheterization. This temporary right bundle branch block occurs when the catheter irritates the right bundle branch.

The bundle branch block usually resolves quickly (within minutes) once the catheter is removed. However, in people who already have left bundle branch block, causing even this transient right bundle branch block will likely create complete heart block — and the heart can stop beating. So, in people with left bundle branch block who are having a cardiac catheterization, sometimes a temporary pacemaker is inserted during the procedure, to assure that the heart rhythm will continue uninterrupted during the study.

Right Bundle Branch Block and the Efficiency of the Heartbeat

With either type of bundle branch block, the heart's two ventricles are being stimulated in sequence (one after the other) instead of simultaneously. This loss of normal coordination between the two ventricles can reduce the efficiency of the heart beat. However, the reduction in the heart's efficiency is far less significant in right bundle branch block than it is in left bundle branch block, and many experts believe that right bundle branch block causes no measurable loss of efficiency at all. So, for instance, the use of cardiac resynchronization therapy (CRT) is not recommended in people with right bundle branch block, even if they have heart failure

Summary

Right bundle branch block by itself is a benign condition that requires no treatment. However, if you are found to have right bundle branch block, you should talk with your doctor about performing a screening evaluation to rule out underlying heart or lung disease. If none is found, then your RBBB can be written off as an incidental finding, with no important medical significance.

Sources:

Badheka AO, Singh V, Patel NJ, et al. QRS Duration on Electrocardiography and Cardiovascular Mortality (from the National Health and Nutrition Examination Survey-III). Am J Cardiol 2013; 112:671.

Barsheshet A, Goldenberg I, Garty M, et al. Relation of Bundle Branch Block to Long-term (Four-year) Mortality in Hospitalized Patients With Systolic Feart failure. Am J Cardiol 2011; 107:540.

Eriksson P, Wilhelmsen L, Rosengren A. Bundle-branch Block in Middle-aged Men: Risk of Complications and Death Over 28 Years. The Primary Prevention Study in Göteborg, Sweden. Eur Heart J 2005; 26:2300.

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