Minimally invasive coronary artery bypass surgery (MIDCAB) is a beneficial alternative to conventional coronary artery bypass surgery (CABG). Today, cardiac surgeons at Saint Thomas Hospital are using a new technique in minimally invasive coronary artery bypass operations. "We have extended this innovative operation to where both internal mammary arteries can be used for bypass conduit, which should provide a more permanent solution for the patient needing more than one bypass graft," said William Coltharp, MD, cardiac surgeon at Saint Thomas Hospital.

 

The standard has been to use the left internal mammary artery as one graft and saphenous vein as conduit for a second. "We have extended that procedure to include harvesting the right internal mammary as well as the left to utilize both as a conduit, allowing two arterial bypass conduits, which are known to have the longest patency rates."

 

Coronary bypass surgery refers to several procedures that use bypass conduits or grafts to bypass blockages in coronary arteries restoring blood flow to the heart muscle. Coronary artery bypass surgery (CAB) is one of the most frequently performed operations in the U.S., and is conventionally performed as an open surgical procedure (open-heart surgery). Performance of the open-heart procedure is major surgery that requires opening the chest with a long incision that includes dividing the breastbone (sternum). Two techniques are used. One requires stopping the heart and using the heart-lung machine for cardio-pulmonary bypass allowing the bypass grafts to be sewn to a still heart while the heart-lung machine performs the work of the heart and lungs, putting oxygen into the blood and circulating it through the body (on pump technique). When the construction of the bypasses is complete the heart is started again, and the heart and lungs take over.

 

The other technique (off pump technique) does not include stopping the heart, but instead employs a stabilizing device to stabilize the arteries to be bypassed so the grafts can be sewn to them. The heart-lung machine is not necessary, and the subtle traumatic effects of cardiopulmonary bypass are avoided. Although both techniques are commonly used, some research studies have demonstrated an advantage of the off pump technique in complication and survival rates, though there is no consensus yet.

 

During CAB operations employing the heart-lung machine, the heart is stopped, and the surgeon attaches one end of the vein graft to the aorta, the body's main artery taking blood all over the body, and the other end to the coronary artery on the other side of the blockage. After the bypasses are performed, the heart is started again, and the patient is weaned from the heart-lung machine as the heart takes over. 

 

If venous grafts are being used, the saphenous vein (usually the greater saphenous vein but sometimes the lesser is used as well) is removed from one or both legs and used to bypass the blockages, narrowed areas of the coronary arteries identified preoperatively by a coronary angiogram. One, and sometimes both, internal mammary artery (which have the advantage over veins of being accustomed to arterial blood pressure as opposed to veins which are accustomed to extremely low venous blood pressure) is used in addition to the saphenous veins.

 

Research studies have shown that internal mammary artery grafts last longer, failing more infrequently, than vein grafts, and thus the standard of care is to use at least one internal mammary artery on every CAB operation. However, use of both internal mammary arteries in conventional CAB operations using the breast bone-splitting incision (median sternotomy) is associated with a relatively high incision infection rate. The Saint Thomas surgeons predicted that both internal mammary arteries could be used in the minimally invasive operations without this complication because the sternum is left intact. The unknown in performing this new procedure was whether the right internal mammary artery could be prepared for use with the surgeon operating through a small incision on the opposite chest wall. Special longer and thinner instruments are required to perform this part of the operation.

 

Recent advances in surgical technique and equipment allow the surgeons to perform coronary artery bypass surgery in a less traumatic way. MIDCAB is used to minimize the invasiveness of CABG. It is done while the heart is still beating and is intended for use when only one or two arteries will be bypassed. MIDCAB uses a combination of small holes or ports in the chest and a small incision in the lateral chest wall. Cardiac surgeons usually detach the internal mammary artery from inside the chest wall and then attach the end of it to the clogged coronary artery.

 

Minimally invasive bypass surgery is believed to provide the same beneficial results as conventional bypass surgery restoring adequate blood flow and normal delivery of oxygen and nutrients to the heart. Minimally invasive bypass surgery, however, has additional advantages related to the ability of the surgeon to work through smaller incisions.

 

"The MIDCAB procedure offers our patients a shorter length of stay in the hospital, faster recovery at home, less bleeding and blood trauma, and a lower infection rate," added Coltharp.