Various causes. Left bundle branch block is a pattern seen on an EKG indicating an abnormal or different pathway of the electrical signal that causes the heart muscle to contract. It is most often due to an underlying medical condition such as hypertension, a heart attack, an enlarged heart from any cause and only when serious conditions are excluded is it felt due to the benign aging of the conduction pathway.
Many. The most common cause is hypertension. The next two most common causes are arteriosclerotic heart disease and cardiomyopathy. Valvular disease like aortic stenosis is an occasional cause. Heart surgery often results in lbbb. Deposition diseases like hemochromotosis and amyloidosis are rare causes.