What is the significance of incomplete left bbb? my son is 32 years old ecg showed normal sinus rhythm bp is 135/71 .

LBBB: Lbbb is an uncommon abnormality of highly variable significance. I would recommend that he get an echocardiogram & consult with a cardiologist.

Often very little: Incomplete left bundle branch block often means that there's delay rather than complete block in a portion of the heart's wiring. While this can progress to complete block in that portion of the wiring, that still leaves the right bundle unaffected. There are more complicated long-term issues to this, but those vastly exceed our 400-character limit here :).