Introduction
Since the landmark paper from Loop et al. in 1986, the use of the left internal mammary artery (LIMA) for revascularization of the left anterior ascending (LAD) artery is the standard of care in coronary artery disease . As such, successful harvest of the LIMA is critical to the outcome of coronary artery bypass grafting.
Described is the approach to harvesting a skeletonized LIMA; the decision between skeletonized and pedicled mammary harvest is beyond the scope of this technical chapter, but a surgeon should never hesitate to use either technique depending on their level of comfort or expertise. Skeletonized is associated with reduced incidence of sternal wound complications and medastinitis and is the preferred approach for patients undergoing bilateral internal mammary artery grafting .
Approach
A median sternotomy is performed with careful attention to maintaining a midline division of the sternum. In the event of paramedian sternotomy, care is taken to prevent undue tension on the sternum during retraction and thereby preventing sternal fracture. On closure, the sternum is reinforced to promote healing either as described initially by Robicsek or with sternal plating . Meticulous hemostasis is achieved to optimize exposure when harvesting the LIMA Video 4.1 .
Technique of the right internal thoracic artery to aorta anastomosis. The video can be found on online at http://doi.org/10.1016/B978-0-12-820348-4.00004-2 .
The IMA retractor facilitates exposure of the internal mammary vessels and is placed with cephalad arm at the left manubrium or angle of Louis and the caudal arm ideally beyond the sternal midpoint ( Fig. 4.1 ).
Fibrous attachments or muscular restrictions are released along the cephalad and caudal aspects of the sternum to facilitate exposure for LIMA harvest.
Exposure
Using electrocautery set to coagulate at 40–50 W, fatty adhesions between the mediastinum and sternum are released with care to cauterize any encased vessels and not violate the endothoracic fascia. In proceeding laterally the left pleura is kept intact when possible, thus preventing the lung from entering the field ( Fig. 4.2 ).
The internal thoracic vessels are exposed by lowering electrocautery to 20 or 30 W and entering the endothoracic fascia. The internal mammary vein serves as a useful landmark; the LIMA lies laterally. The fascia is opened where visibility is optimal along the artery; the proximal third of the artery typically has looser fatty surrounding tissues and is a good starting point. The fascia can be opened near the medial mammary vein to expose the LIMA laterally and leave the vein attached to the chest wall. The correct approach allows the endothoracic fascia to be dissected off the chest wall and will lead to clear visualization of the internal mammary artery and vein in an avascular plane ( Fig. 4.3 ).
Once the correct plane and exposure are confirmed, fine forceps and gentle upward motion of the electrocautery tip are used for blunt dissection to extend exposure of the mammary artery ( Fig. 4.4 ). The endothoracic fascia is opened with electrocautery away from the mammary vein so as to leave the vein attached to the chest wall. The thin strip of fascia, attached to the artery, can be used as a “handle” for mobilization. The pulsating and shiny white mammary artery is visualized laterally as the fascia is separated from the vein. Beyond the LIMA is usually a lateral branch of the mammary vein that is left in situ.
This exposure is extended so as to visualize the artery along the entirety of its course on the chest wall.
Harvesting the left internal mammary artery
Once the LIMA is well exposed, it must be harvested by freeing it of its attachments to the chest wall. Harvest proceeds with minimal direct manipulation of the mammary artery and with the electrocautery set to coagulation at 15–20 W on desiccating. Direct manipulation leads to bruising, hematoma formation, or arterial dissection or thrombosis. Further, undue tension on the artery is avoided so as to prevent avulsion of branches and possible subsequent injury to the LIMA.
Typically, there is one significant intercostal branch per rib space, as well as multiple perforator vessels ( Fig. 4.5 ).
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