When Does Bundle Branch Block Need to Be Treated?Normal cardiac function depends on the two bundle branches. If they both were to completely stop working (thus producing complete heart block), the electrical impulse could not be delivered to the ventricles, and the heart would stop beating.
Fortunately, it is quite uncommon for stable RBBB or LBBB to progress to complete heart block. So despite the fact that BBB is not a rare finding on routine ECGs, it is uncommon for either kind of BBB to require a pacemaker.
Still, there are three general circumstances in which people with BBB might require pacemakers:
1) When disease in both the right and left bundle branches appears after an acute heart attack. When a patient develops new evidence of disease in both the right and left bundle branches right after a heart attack, there is a greatly increased chance of developing complete heart block within the next few weeks or months. For this reason, pacemakers are most often recommended in these patients.
2) When bundle branch block is associated with syncope (loss of consciousness). When a person with BBB - especially LBBB - experiences syncope, that person may have an increased risk of developing complete heart block. In general, an electrophysiology study should be considered at that point, to test for impending complete heart block. A permanent pacemaker eliminates the problem.
Notably, however, the most common cause of syncope in a person with LBBB and underlying heart disease is not complete heart block, but ventricular tachycardia. The elecrophysiology study will also test for this possibility - so anyone with LBBB and new-onset syncope ought to be referred to a cardiac electrophysiologist (a heart rhythm specialist) for an evaluation.
3) When BBB is associated with heart failure and a reduced left ventricular ejection fraction. In patients with heart failure and a reduced left ventricular ejection fraction who also have wide QRS complexes indicating BBB, cardiac resynchronization therapy (CRT) should be strongly considered. CRT "re-coordinates" the contraction of the two ventricles, and can greatly improve the efficiency of the heart muscle. This improvement in efficiency - allowing the heart to do more work, using less effort - can significantly improve the symptoms of heart failure, and has been shown to prolong the survival of some patients with heart failure.
If you have been told you have RBBB or LBBB, your doctor should do an evaluation looking for the kinds of underlying heart or lung diseases that have been associated with BBB. If your heart and lungs are normal and you have RBBB, you can stop worrying.
While LBBB can also be seen in people whose hearts otherwise appear entirely normal, most often it indicates underlying heart disease. So if you have LBBB, you should make especially sure your doctor has done a thorough cardiac evaluation.
Unless you have had a recent heart attack, or have had syncope, or have heart failure, the presence of BBB generally requires no specific treatment - beyond performing that thorough cardiac evaluation.
If you have significant heart failure, BBB can cause your heart to work less efficiently and can produce a worsening of your symptoms. So anyone with heart failure and BBB should discuss with their doctors the potential need for CRT pacing.
Fahy GJ, Pinski SL, Miller DP, et al. Natural history of isolated bundle branch block. Am J Cardiol 1996; 77:1185.
Imanishi R, Seto S, Ichimaru S, et al. Prognostic significance of incident complete left bundle branch block observed over a 40-year period. Am J Cardiol 2006; 98:644.