If I have RBBB, can I still safely run a half marathon?

Dear Dr.,
I have RBBB [right bundle branch block] detected through ECG last year, however, my TMT (Treadmill test) was normal.I am interested to participate in half marathon race (21 km) coming up in Jan 2015 without running any risk to my heart. OK?

Submitted by APS Bhatia from Ankleshwar (Gujarat), India on 08/16/2014

by  Atasu Nayak, MD 

Thanks for the question.

RBBB is an electrical abnormality. It can be seen in normal cardiac condition. Please see your cardiologist. You may need an ECHOCARDIOGRAM to rule out organic heart disease. If your treadmill is normal and ECHO is ok, there is no cardiac contraindication for running. But you must follow with your cardiologist and do accordingly.