Is bundle branch block a type of heart disease?

Not generally. There are two bundles or wires connecting the heart the right bundle and the left bundle. Right bundle branch block is common and usually pretty normal. Left bundle branch block needs investigation.
Yes. Yes it is a disease of the conduction system (wiring system) of the heart.

Related Questions

What are the signs and symptoms of the heart pumping inefficiently with a complete bundle branch block?

BBB. Neither left nor right bundle branch block usually produce symptoms if the heart is otherwise normal. Changes in the timing of the second heart may be detectable.

Does repetitive drug use take a toll on a persons heart sothey develop a bundle branch block?

Maybe. It is possible depending on the type of drug used - a bundle branch block shows a decreased conduction of electrical impulses through the wiring of your heart.