 MIDCAB is sometimes referred to as "keyhole" heart surgery because the operation is analogous to operating through a keyhole.MIDCAB is a form of off-pump coronary artery bypass surgery (OPCAB), performed "off-pump" - without the use of cardiopulmonary bypass (the heart-lung machine).MIDCAB differs from OPCAB in the type of incision used for the surgery; with traditional CABG and OPCAB a median sternotomy (dividing the breastbone) provides access to the heart; with MIDCAB, the surgeon enters the chest cavity through a mini-thoracotomy (a 2-to-3 inch incision between the ribs).