Direct Surgical Repair of Aortic Arch Vessels




Historical Background


Surgical approaches to the aortic arch vessels had been described in the late nineteenth and early twentieth centuries. In 1958 DeBakey and associates described the first successful surgical reconstruction of an occluded symptomatic innominate artery using an nylon bifurcated graft from the ascending aortic arch to the left subclavian and common carotid arteries. This report was followed by a comprehensive 10-year review of the surgical treatment of occlusion of innominate common carotid and subclavian arteries in 1969.




Indications


Pathologies that most commonly warrant surgical reconstruction of the great vessels include arteriosclerotic disease and inflammatory arteritides. In addition arteritis can develop in patients undergoing therapeutic radiation for cancers of the head, neck, breast, or lymph tissues.


Arteriosclerosis is by far the most common etiology. In a series of operations involving the carotid bifurcation, vertebral arteries, or great vessels, only 7.5% of those procedures were performed for lesions of the innominate, common carotid, or subclavian vessels. Although great vessel lesions are uncommon compared with carotid bifurcation disease, several larger referral centers have reported on their experience. Arteriosclerotic disease is more prevalent in men and in younger patients, with a mean age of 50 to 61 years.


The second most common cause of great vessel disease in the United States is Takayasu arteritis. This disease is seen more frequently in younger women and those of East or South Asian descent. This inflammatory process manifests systemically with fever, arthralgias, weight loss, and fatigue. In later stages of the disease process the central arteries develop hemodynamically significant stenosis, which can manifest as upper extremity claudication, renovascular hypertension, and focal tenderness over the involved artery. Central symptoms such as visual impairment, dizziness, headache, and stroke; cardiorespiratory findings including angina, myocardial infarction, and pulmonary hypertension can also be seen.


Inflammatory markers are often elevated in the active phase of the disease but cannot be used to either confirm or eliminate the diagnosis, which is made on the basis of history and physical examination. The pathologic findings associated with Takayasu arteritis include long segments of smooth-walled stenosis of the aortic arch, descending thoracic aorta, and primary branches. The subclavian artery is most often affected. In addition to standard diagnostic imaging modalities, fluorodeoxyglucose positron emission tomography may demonstrate central vascular inflammation.


Radiation-induced arteritis manifests with subintimal fibrosis, endothelial degeneration, and myointimal proliferation. The interval between radiation therapy and vascular intervention averages 15.2 years, and patients most often present with embolic or global ischemic phenomenon.


Operative intervention is indicated for symptomatic lesions manifesting as extremity or cerebral ischemia because of occlusion or severe stenosis or as distal embolization. Surgical repair of asymptomatic lesions of the common carotid artery may be indicated based on established guidelines for carotid bifurcation disease. Conditions that may warrant repair of asymptomatic lesions include improving flow for existing or anticipated hemodialysis access or salvaging axillary-origin vascular grafts. Reconstruction may be considered in patients in whom accurate blood pressure monitoring is impossible because of multiple occlusive lesions. If a patient is undergoing sternotomy for other indications, it may be preferable to treat great vessel disease at that time rather than at a later date through a reoperative field.




Preoperative Preparation





  • History. Diagnosis and localization of brachiocephalic disease are suggested by the manifesting symptoms. Neurologic symptoms result from decreased circulation of the anterior, vertebrobasilar, or both systems. Although the frequency of patients presenting with neurologic symptoms reported in the literature is wide, from 5% to 90%, several large, contemporary studies have shown a more consistent rate between 64% and 83%. Likewise, upper extremity symptoms can be seen in 5% to 63.3%. Arm ischemia often results from tight stenoses with flow limitation, although ulcerative but less stenotic lesions may manifest with microembolization. A combination of upper extremity and neurologic symptoms can be seen in 18% to 39% of patients. Symptoms limited to a single extremity may differentiate atherosclerotic disease of the innominate or subclavian artery from systemic diseases that also manifest with upper extremity ischemia.



  • Physical examination. Palpation and auscultation of the proximal and midcervical carotid arteries, the superficial temporal artery, the subclavian artery, and the brachial, radial, and ulnar vessels should be performed. Bruits or thrills noted in the proximal carotid or subclavian vessels may be indicative of stenotic lesions in the great vessels. An Allen test or its adaptations may reveal digital arterial occlusions. Blood pressure measurements should be performed in both upper extremities, and if there is concern of bilateral upper extremity stenoses, comparison should be made to the lower extremities. Evaluation of the skin and nails may reveal bluish, painful discolorations in the fingertips, splinter hemorrhages, or livedo reticularis suggestive of embolic events.



  • Imaging studies. Patient presentation and physical examination often suggest the diagnosis, but imaging is used to confirm, characterize, and begin planning intervention for the offending lesion. Duplex ultrasound and waveform analysis of the upper extremity can aid in the diagnosis. Computed tomography angiography with intravenous contrast, and especially with the additive information obtained with volumetric three-dimensional imaging, allows assessment of the arch and four vessels with a reduced risk of stroke or access site complications. Magnetic resonance angiography with gadolinium enhancement may also be used to assess arterial anatomy in a less invasive manner. Angiography may be used when other imaging modalities fail to provide the necessary information before intervention. Views of the aortic arch and subclavian, carotid, and vertebral arteries are required for accurate diagnosis, localization, characterization, and operative planning. If the offending lesions affect the carotid or vertebrobasilar system, preoperative imaging should also assess the circle of Willis.



  • Management of the asymptomatic lesion. As imaging procedures are performed for a myriad of indications, an increasing number of asymptomatic lesions involving the aortic arch vessels are being identified. Although surgical intervention has been described for asymptomatic lesions, there is a relatively high risk of morbidity and mortality associated with the median sternotomy. Of the patients in the series by Berguer, Morasch, and Kline, 13% were asymptomatic; there were no mortalities but one stroke. They concluded that asymptomatic patients should not be offered repair in this setting. An exception would be a patient who requires another operation that involves a median sternotomy, such as a coronary artery bypass graft procedure. In this setting, it may be prudent to offer a combined repair in order to avoid the associated morbidity of a redo-sternotomy should great vessel disease become symptomatic.



  • Options for surgical repair of aortic arch vessels. Operative repair options for patients with great vessel disease can be categorized as either direct arch or extraanatomic reconstructions. The latter were developed to reduce the morbidity and mortality associated with aortic-based reconstructions. Many patients who present with innominate artery disease requiring reconstruction have multiple supraaortic lesions. In recent series this has varied between 61% and 84% of patients, and included both concomitant arch lesions as well as carotid bifurcation disease. Bypass grafts can be constructed to reconstruct several areas of stenosis. Less invasive cervical or extrathoracic approaches may be more suitable for a given anatomic configuration. Examples of extraanatomic procedures include transpositions, subclavian-carotid or carotid-subclavian artery bypass, axillary-axillary artery bypass, or contralateral carotid-carotid or carotid-subclavian artery bypass. Some techniques, such as carotid-subclavian artery bypass, have remained popular and are frequently performed for more limited great vessel disease or as an adjunct to endovascular repair of the thoracic aorta. In more recent series the morbidity and mortality of direct surgical repair of great vessel occlusive disease has become more acceptable, and concerns regarding the long-term patency of extraanatomic approaches have revived interest in direct repair via median sternotomy. These techniques are the focus of this chapter.





Pitfalls and Danger Points





  • Concomitant cardiac disease. Planned intervention for great vessel arteriosclerosis should prompt a preoperative cardiac workup to assess the need for coronary interventions that may best be performed before or concurrent with great vessel repair. Patients with Takayasu arteritis should undergo echocardiography to assess for valvular heart disease, pulmonary hypertension, or left ventricular hypertrophy in addition to coronary lesions. If radiation-induced arteritis is the etiology of occlusive disease, patients should be evaluated for cardiomyopathy and coronary artery disease.



  • Nerve injury. Intraoperative structures of importance include the vagus nerves as they descend within the carotid sheaths and the recurrent laryngeal nerves. If more lateral dissection is required, the phrenic nerve may also be encountered.



  • Thoracic duct injury. Meticulous dissection and ligation of lymphatics, including the thoracic duct on the left side, are also paramount.



  • Prior history of coronary artery bypass or median sternotomy. If a patient has had previous coronary artery bypass grafting, preservation of the internal mammary circulation is also of utmost concern. A history of previous reconstructive procedures must be noted, as the anatomy may be varied and may be more difficult to discern in a reoperative field.





Operative Strategy


Surgical Anatomy of the Aortic Arch and Branch Vessels


The great vessels of the aorta include the innominate, subclavian, and common carotid arteries. These vessels, in their standard configuration, begin proximally along the aorta with the origin of the innominate artery and are succeeded in order by the left common carotid artery and the left subclavian artery. Variations of this branching pattern are relatively common and include the various “bovine arch” patterns, such as a common origin of the innominate and left common carotid arteries or of the left common carotid artery arising as a branch of the innominate artery. Identification of these variations preoperatively is critical for planning surgical interventions.


Avoiding Injury to Anatomic Structures


The vagus and recurrent laryngeal nerves are both encountered during dissection of the carotid and subclavian arteries. These should be isolated and protected during the procedure. When dissecting more laterally along the subclavian artery, the phrenic nerve may be encountered. The brachial plexus lies posterior to the subclavian vessels and may be injured if unrecognized. Although direct injury is a risk, stretch injury because of patient positioning or use of retractors is also common but can be minimized by careful planning and placement of equipment. If possible, bilateral abduction of the extremities in the operating room should be avoided.


In the left supraclavicular fossa, the thoracic duct and the junction of the subclavian and jugular veins can be found and should be appropriately ligated. Additional care to identify and similarly control smaller lymphatic vessels must be exerted. As with any operation, understanding of the anatomic location and potential variants is paramount in avoiding injury to these important structures.


Avoiding Intraoperative Stroke


Appropriate imaging is crucial in planning the surgical approach and may dictate the need for intraoperative cerebral shunt placement. The vertebral and carotid arteries should be assessed bilaterally to determine the dominant side, and the circle of Willis should be visualized for completeness. Use of intraoperative electroencephalographic monitoring, cerebral oximetry, or carotid stump pressure may guide the decision-making process intraoperatively. The same criteria and methods of shunting used in other carotid artery reconstructions may be considered. If multiple vessels are involved and shunting is impossible, neuroprotective anesthetic agents may be used. When both common carotid arteries are to undergo reconstruction, the more diseased artery is addressed first to maintain as much baseline cerebral blood flow as possible.


Assessment of a Suitable Clamp Site in the Aortic Arch


The most appropriate location for the partial occlusion clamp on the aorta is determined through a combination of assessment of the preoperative imaging and intraoperative palpation of the aorta. For bypass procedures in which the graft arises from the ascending aorta, the origin of the graft should be placed as far laterally on the ascending aorta as possible to ensure optimal placement of the graft once the sternotomy is closed. An anteriorly placed graft is easily compressed by the sternum once closed. If, despite care, the sternum compresses the graft, ronguers may be used to excise posterior elements of the sternum and sternoclavicular joint. The clamp site should avoid areas of significant plaque.


Special Considerations for Patients with Vasculitis


Takayasu arteritis is better treated with open bypass procedures than with either endarterectomy or stenting. Patients presenting with acute inflammation should be medically managed. Surgical intervention should be reserved for the quiescent phase of the disease or as a last resort in patients not responsive to optimal medical therapy. Proceeding with operative intervention during the acute inflammatory stage of the disease increases the risk of restenosis at the anastomoses. Although patients can be treated for severe neurologic symptoms in the acute phase via endovascular approaches, the transmural nature of the disease process predisposes it to significant restenosis. This, along with the patient’s youth in many cases, favors the durability seen with open repair of stenotic lesions.




Operative Technique


Incision


Proper patient positioning aids greatly in exposure. The patient should be supine on the operating table, arms by the side, with a roll or bump placed vertically between the scapulae and the head extended, supported, and rotated slightly to the left. If bilateral carotid revascularizations are performed, the head is prepared to be rotated in either direction. The operative field should include the neck, chest, and upper abdomen. Standard methods for skin preparation and draping should be used. The initial incision is midline, with division of the entire sternum, although a partial sternotomy may be used. A hockey stick extension of this incision a short distance along the anterior border of the right sternocleidomastoid (SCM) muscle allows for exposure of the innominate artery bifurcation ( Fig. 11-1 ). The sternal attachments of the SCM may be divided and retracted laterally to improve exposure if needed. A sternal retractor is positioned for optimal exposure.


Mar 13, 2019 | Posted by in VASCULAR SURGERY | Comments Off on Direct Surgical Repair of Aortic Arch Vessels
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