What is the medical prognosis for a bundle branch block?

Right or left. If it is right bundle branch block then 98% is benign. If it is left bundle branch block 95% are abnormal leading to further work up to rule out cardiomyopathy, conduction problems or coronary artery disease.
Right or left? Right bundle branch block is benign in most cases. An echo and chest x-ray should be done to rule out causes of pulmonary hypertension but they will be normal in the majority of cases. Lbbb is a bit more ominous as it tends only to occur in the presence of structural heart disease. Htn and cardiomyopathy are the most common causes. Again a full work up should be done to rule out serious issues.