Open Heart Surgery is any surgery in which heart is stopped and the body is supported on a heart lung machine. Open heart surgery can be used to perform bypass surgery or to change a valve of the heart or to close a hole in the heart. Bypass surgery is a surgery performed for blocked arteries and it can be performed by two techniques. First the heart can be stopped and body supported on a heart lung machine, in which case it becomes an open heart surgery or it may be performed on a beating heart, in which case, it is called beating heart bypass surgery.