This is a very technical question and one need to consider many factors before reaching a decision. Even when OPCAB is planned for a certain patient the decision can be changed on the operating table depending on conditions unique to individual patients. A heart suffering from critical shortage of blood supply, as in the case of many undergoing bypass, may not tolerate the long operation on beating heart. The blood vessel needing bypass may be buried deep inside the heart muscle or its wall may be very thick and hard like stone. These situations make the operation technically difficult and may necessitate the use of CPB machine. Needless to say, every patient is unique and there is no one treatment suiting all.