I suppose by unconsciousness on the left side of the sternum, you probably mean that side of sternum is numb (senseless) and there may even be pinprick sensations. Also, once we cut the sternum, its union may take even beyond 12 weeks and till such time, feeling of compression or stiffness or tingling and numbness may normally be there. The best thing is to ignore it and not think about it much. By the same token, if this feeling persists or if in anyway, it is like the anginal pain, which he was getting earlier, then you must report it to his cardiologist, because he may have to be investigated for any recurrence of angina, which can occur in a very small percentage of patients, even after bypass surgery. In this matter, I would suggest you to also take a cardiology opinion.