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 the heart; with MIDCAB, the surgeon enters the chest cavity through a mini-thoracotomy (a 2-to-3 inch incision between the ribs).
The MIDCAB approach is usually reserved for cases requiring one or two bypasses; typically bypassing arteries on the front of the heart, such as the left anterior descending (LAD) coronary artery. In most cases, the left internal thoracic artery (LITA) is used as the bypass conduit and anastomosed to the LAD. Patients requiring more than one or two bypasses are usually not candidates for MIDCAB because of limited access to vessels on the back side of the heart.