Although they are not the same thing, a bundle branch block and a heart block can be related.
In the bundle branch block, electrical impulses are slowed or blocked as they travel through the specialized conducting tissue in the bundle of his. Many people with a bundle block don't even realize it until they've had an ECG done due to its lack of symptoms and some with a branch block may feel faint. If both bundle branches are blocked or impaired, then heart block occurs.
In a heart block or "AV block", the signal from the heart's upper to lower chambers is impaired or doesn't transmit. This doesn't mean that there is an actual block like the name suggests- but the electrical impulses either don't get sent or take longer than they should. Heart block is classified into three categories: 1st, 2nd, and 3rd (complete heart block)-- in order of impairment.
1st degree, which is what you have been diagnosed with, means that the electrical impulses move through the AV node slower than it should but your heart rate an rhythm may be normal, and it doesn't necessarily mean that there is anything wrong with your heart. A first degree heart block can sometimes be caused by a heart medication called digitalis.
I hope this helps answer your question! For more information on the heart and heart conditions, please visit: www.americanheart.org