Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Thoracic and Thoracoabdominal Vascular Exposure
Introduction
Surgical exposure of the aorta involves three main segments: the ascending aorta and aortic arch, the descending thoracic aorta, and the abdominal aorta. Depending on the pathology, either one or several of these segments will need exposure simultaneously. This chapter presents the various incisions, techniques, and key elements for exposure of each aortic segment or combinations of segments.
Exposure Of The Ascending Aorta And Aortic Arch
Median Sternotomy
The median sternotomy exposure is an optimal method to access the chambers of the heart, the ascending aorta, and the majority of the aortic arch. As a result, it is the most common exposure technique for operations involving the ascending aorta and/or the great vessels.
Position
The patient is placed supine on the operating room table, with arms tucked along the patient’s side to relax the musculature and allow opening of the mediastinum and chest space.
Incision
An incision is made from just below the suprasternal notch to the tip of the xyphoid process. This incision can be extended for additional exposure of the aortic arch vessels, either along the anterior borders of the sternocleidomastoid muscle for exposure of the left or right common carotid arteries or superiorly along the midline for greater overall exposure. The latter should be avoided for cosmetic reasons. If additional exposure of the right subclavian artery is required, the incision can be carried along the superior border of the clavicle. Although an anterior 3rd or 4th intercostal space thoracotomy is the approach typically used for exposing the left subclavian artery, the very proximal part of the left subclavian artery can also be reached through a median sternotomy. Extension into a left supraclavicular incision may be needed for further distal control. An additional anterior 3rd or 4th intercostal space thoracotomy with creation of a trap door thoracotomy can be added to obtain exposure of the full continuum of the left subclavian artery in extremis patients with challenging traumatic injuries.
Dissection
Electrocautery is used to divide the subcutaneous tissue down to the pectoral fascia, which is also divided. The periosteum is then scored along the midline an equal distance from both sides of the intercostal spaces. The interclavicular ligament at the top of the sternal notch is divided. The tissues on one side of the xyphoid process are released, though some surgeons prefer to resect the entire process. The sternum is divided along the midline using a sternal saw, taking care to hug the back of the sternum with the toe of the saw. It is imperative to hold mechanical ventilation at this time to avoid inadvertent pleural tears. Electrocautery is then used to achieve hemostasis along the anterior and posterior edges of the sternum. Manual pressure and a small amount of bone wax can be used to achieve hemostasis of the bone marrow. Once the sternopericardial ligaments are divided and the pericardium is freed from the posterior sternum, the sternal retractor is placed and progressively opened to achieve homogeneous retraction. Excessive retraction should be avoided to prevent sternum and/or rib fracture with potential dislocation of costochondral junctions. The vessels arising from the internal thoracic artery and draining into the brachiocephalic vein are identified and ligated. This allows full mobilization of the brachiocephalic vein. The anterior pericardium is then opened vertically to access the ascending aorta and origin of the aortic arch vessels ( Fig. 55.1A ). In certain circumstances, it may be necessary to ligate the left innominate vein, which is often well tolerated. Following these maneuvers, the ascending aorta, the aortic arch, and the innominate and left common carotid arteries can easily be identified and dissected free from surrounding tissues. The right vagus and right recurrent laryngeal nerves must be avoided during dissection of the distal portion of the innominate artery. It should be recognized that the vagus nerve courses anterior to the subclavian artery at its origin, with the recurrent laryngeal nerve originating from the vagus nerve and coursing posterior to the subclavian artery origin, creating a sling where the subclavian artery rests. Exposure of the innominate artery bifurcation can be obtained, often requiring caudal retraction of the left innominate vein.
Mini-Sternotomy
The mini-sternotomy was first described in 1949 by Holman and Willett. Today, it is commonly used as an alternative to the median sternotomy for valve replacements, aortic root replacements, and ascending aortic aneurysm repairs. Its benefits include reduced trauma and a lower risk of sternal instability. It is also commonly used in re-operative cardiac surgery to reduce the risk of ventricular injury during sternal retraction. The advantages of this technique include decreased postoperative pain, decreased blood loss, and decreased adhesions around the right ventricle, as this region is not dissected during this exposure. A number of studies by Svensson and colleagues have expounded on the benefits of minimally invasive sternotomy techniques. In one report of 54 patients undergoing mini-sternotomy for ascending aortic and arch repairs, the mortality and incidence of stroke were 4% and 3.7%, respectively, indicating that this method was safe for use in ascending and aortic arch repairs. Eighteen of these patients were redo sternotomies. However, this approach may not be suited for those with chest wall abnormalities such as pectus excavatum or morbidly obese patients.
Position
As with a full sternotomy, the patient is placed supine on the operating room table, with arms tucked along the patient’s side.
Incision
There are various approaches to division of the sternum, including the upper reversed “T” and upper “J” or “L” incisions, which are the most commonly employed incisions to expose the superior mediastinum. Both incisions often provide adequate exposure to the aortic arch and the proximal portions of the innominate artery and vein. Moreover, conversion to a full median sternotomy is always an option when exposure is inadequate using this technique. An upper reversed “T” approach begins at the sternal notch caudally, before transecting the sternum at the level of the 3rd or 4th intercostal space ( Fig. 55.1B ). The “J” approach begins at the sternal notch and comes across the right 3rd or 4th intercostal space. Transesophageal echocardiography may be used to aid in determining the caudal extent of the incision.
Dissection
The sternum is divided in the midline and then transversely, taking care to avoid injuring the internal mammary arteries, which lie just lateral to the sternum. For additional exposure the internal mammary arteries are ligated. A self-retaining retractor is then placed to separate the upper portion of the sternum and the dissection is continued in the same fashion as a full sternotomy.
Exposure Of The Distal Aortic Arch And Descending Thoracic Aorta
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here