Ann Thorac Surg 1999;68:1422-1423
© 1999 The Society of Thoracic Surgeons
How To Do It
Finding the LAD during MIDCAB operations
Michael F. Szwerc, MDa,
Jeffery C. Lin, MDa,
James A. Magovern, MDa
a Department of Cardiothoracic Surgery, Allegheny General Hospital, Pittsburgh, Pennsylvania, USA
Address reprint requests to Dr Magovern, Department of Cardiothoracic Surgery, Allegheny University Hospital, Allegheny General, 320 E North Ave, Pittsburgh, PA 15212
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Abstract
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Minimally invasive direct coronary artery bypass (MIDCAB) is a new surgical procedure that revascularizes the left anterior descending coronary artery (LAD) without the need for a median sternotomy or cardiopulmonary bypass. This operation is performed through a small left anterior thoracotomy. With this exposure, it can be difficult to locate the left anterior descending coronary artery. We have identified anatomic features on the surface of the pericardium that can serve as a landmark for finding the left anterior descending coronary artery.
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Introduction
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Minimally invasive direct coronary artery bypass (MIDCAB) has been shown to be less morbid and less expensive than traditional coronary artery bypass grafting [1]. The elimination of the sternotomy incision contributes to the faster recovery that these patients experience. However, the reduced incision limits exposure and reduces options available to the surgeon. Recent reports suggest that the conversion rate from minithoracotomy to sternotomy can range from 3% to 12% [1–3]. In addition, the target vessel for anastomosis can be misidentified [3]. Since November 1995, we have performed more than 200 minimally invasive direct coronary artery bypass operations using the left internal mammary artery (IMA) to bypass proximal lesions in the left anterior descending coronary artery (LAD). In several of these cases, it has been particularly difficult to locate the LAD. This is because the vessel was intramyocardial, buried beneath epicardial fat, or displaced to the left. In addition, the anterior surface of the heart can be displaced to the left; thus, the position of the LAD is no longer directly beneath the midportion of the incision. We have identified certain anatomic landmarks on the pericardial surface that make it relatively easy to predict the location of the LAD before opening the pericardium.
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Technique
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Our standard operative approach begins with a supramammary 6-cm to 8-cm skin incision starting 1 cm lateral to the sternum. The pectoralis major muscle is divided, and the underlying costal cartilage is exposed. In the early part of our series, the fourth costal cartilage was resected, which allowed for harvesting of the IMA pedicle from the lower interspaces under direct vision. Presently, we open the third or fourth intercostal space, but do not remove the rib or cartilage. After identification of the IMA at the medial aspect of the incision, the left IMA harvest retractor (CardioThoracic Systems, Cupertino, CA) is inserted into the wound, and the IMA is harvested using electrocautery and metal clips. It is useful to free the left IMA pedicle medially from the thymus to gain additional length on the pedicle. Once the IMA is harvested, the LAD stabilizer (CardioThoracic Systems) is inserted, exposing the anterior aspect of the pericardial surface. This thoracic exposure generally provides limited visualization of the anterolateral surface of the pericardium. A prominent fat collection always lies on the anterior and lateral surfaces of the pericardium, which is composed of the thymic fat pad rostrally and the pericardial fat pad caudally (Fig 1 , left). The fat forms a continuous structure, but there is always an attenuated area that marks the junction between the two fat pads. This attenuated area is divided with the electrocautery (Fig 1, right). The LAD can be found beneath the junction of these two fat planes and 1 to 2 cm anterior to the phrenic nerve. The pericardium is opened transversely at this location for 3 cm (Fig 2 , left) and then carried cephalad and parallel to the phrenic nerve for approximately 6 cm. Once the LAD is identified, the pericardial incision can be extended in the direction of the LAD to allow inspection of a larger length of the vessel (Fig 2, right).
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Fig 1. Prominent fat collection on the anterolateral surface of the heart (left) demonstrating area of attenuation between these tissue planes (right).
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Fig 2. Incision in the pericardium (left) exposing the left anterior descending coronary artery (LAD) beneath the pericardium at the junction of these two fat planes (right).
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Before the anastomosis, the pericardium is suspended to the chest wall with suture. A 4-0 polypropylene suture is placed deep to the vessel and secured to a rubber bumper to serve as a proximal tourniquet. Distal vessel control is avoided to prevent intimal damage and the possible development of a new lesion. The heart is stabilized using a commercially available stabilizer (CardioThoracic Systems). The anastomosis is performed with a running 7-0 polypropylene suture. If significant bleeding or hemodynamic instability occurs, then an intraluminal shunt is used. A micro-Doppler probe (20 MHz/1 mm; Nicolet Biomedical, Madison, WI) is used to evaluate patency by calculating flow velocity during systole and diastole for the completed graft.
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Comment
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The small anterior thoracotomy provides only a small window to see the surface of the heart. The preoperative angiogram in the left anterior oblique view provides an outline of the coronary anatomy that the surgeon will see though the limited thoracic exposure. Knowledge of where to expect the LAD speeds the operation. In the presence of dense epicardial fat, an intramyocardial LAD, or a very small (< 1.5 mm) vessel, then one must proceed with caution and consider conversion to a full sternotomy and cardiopulmonary bypass.
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References
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Magovern J.A., Benckart D.H., Landreneau R.J., Sakert T., Magovern G.J., Jr Morbidity, cost, and six-month outcome of minimally invasive direct coronary artery bypass grafting. Ann Thorac Surg 1998;66:1224-1229.[Abstract/Free Full Text]
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Subramanian V.A., McCabe J.C., Geller C.M. Minimally invasive direct coronary artery bypass grafting. Ann Thorac Surg 1997;64:148-155.[Abstract/Free Full Text]
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Suen H.C., Johnson R.G., Weintraub R.M., Maslow A., Comunale M.E., Cohn W.E. Minimally invasive direct coronary artery bypass. Int J Cardiol 1997;62(Suppl 1):S95-S100.
Accepted for publication May 28, 1999.
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J. C. Lin, D. L. Fisher, M. F. Szwerc, and J. A. Magovern
Evaluation of graft patency during minimally invasive coronary artery bypass grafting with Doppler flow analysis
Ann. Thorac. Surg.,
October 1, 2000;
70(4):
1350 - 1354.
[Abstract]
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Abstract
Introduction
