Should an abnormal electrocardiogram be a cause for worry?

Here's the truth about left and right bundle branch blocks that show up on some ECG readings.

Your doctor has told you that you have a bundle branch block. Although the phrase evokes images of a suburban subdivision, bundle branch blocks are abnormalities of the heart's conduction system that show up on a tracing of the electrical activity in the heart, called an electrocardiogram (ECG) reading.