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Diagnosed with RBBB. ECG showed incomplete rbbb and left axis deviation. Should I be worried?

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Cardiologist, Interventional
Practicing since : 1998
Answered : 424 Questions
Hi I am asking on behalf of my 18 year old son, who was diagnosed with RBBB after a faint about 18 months ago. We went to see a cardiologist who said that the ECG showed incomplete right bundle branch block (QRS 118ms) and left axis deviation. An echo was done at this time, and this was normal. As my son was taking methylphenidate he agreed to see him in a years time for a review. We have just been to see him again, and this time he said at the appointment that the RBBB was 'borderline'. He later wrote us a letter to say that the RBBB read as significant on the ECG on that day, but that the left axis deviation was less apparent than at the first ECG and the axis was within normal limits. He also said that the two ECGs 1 year apart were more or less identical. My son's pulse may have been rather lower on the second ECG I think, because he has been going to the gym - his pulse was only 51 beats per minute. The reason for my query is whether we should be worried that the RBBB is now significant or complete, rather than incomplete. I an not too worried as I know that the numbers on the ECG can be different from one time to another, and his QRS complex length was nearly 120ms the first time it was taken anyhow. I guess I am just looking for some reassurance. All other intervals were normal, as far as I know and the cardiologist did not seem concerned. Many thanks for your help XXXXXXX my e-mail address is YYYY@YYYY

Posted Thu, 17 Jan 2013 in Hypertension and Heart Disease
Answered by Dr. Prabhakar C Koregol 17 hours later

I would more or less agree with whatever your doctor and you understand and explained. Yes, as lone finding RBBB does not have much of clinical significance especially if Echocardiogram is normal. If echo is normal you don't have to worry.

Yes when RBBB develops it goes in from the gradual increase from Normal QRS to incomplete and then complete RBBB and on reaching XXXXXXX duration it doesn't further increase.

But what remains to be answered is what caused the faint. If it was single episode and most of the basic investigations are normal you don't have to worry. But if faint/syncope is recurrent he needs further evaluation including EP (electrophysiological) studies/Holter monitoring.

Hope this helps you. Do write back for follow up queries that you may have.

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