What is the prognosis for an incomplete bundle branch block?

BBB. There are two types: right and left (irbbb and ilbbb). The right sided variety is usually benign and has no negative prognosis. The left variety may or may not indicate underlying heart problems. Discuss with your doctor.
Depends. Incomplete bbb (right or left) refers to slightly increased duration of the electrical impulse that fires the lower heart chambers. Irbbb is very common in young adults and usually benign. Ilbbb is more concerning because it may progress to more serious abnormalities and is often associated with serious heart problems such as cardiomyopathy, CHF or cad.