The critical consideration in approaching aortic arch (AA) surgery, how best to protect the brain while providing surgical access to the cerebral vessels, remains a subject of controversy and research, but involves two key aspects: minimizing cerebral ischemia and preventing cerebral embolization of air and atheromatous debris. Thus, this chapter focuses on the laboratory and clinical basis for cerebral protection methods; including methods for preventing cerebral ischemia, such as hypothermic circulatory arrest (HCA), selective antegrade perfusion (SCP), and retrograde cerebral perfusion (RCP); and methods to minimize embolic damage, such as using axillary artery cannulation plus a branched graft technique.
Urgent indications for AA surgery include rupture of an aneurysm, pseudoaneurysm, or aortic dissection. Elective arch surgery is recommended for aneurysms greater than 6 cm, saccular aneurysms with rapid enlargement (>1 cm/y) and for symptoms (pain or hoarseness). Smaller aneurysms (5 cm) should be considered for repair in patients with extensive aortic aneurysmal disease (ascending and descending), Marfan's syndrome, or a family history of rupture or dissection.
The medical history is important in identifying symptoms caused by an aneurysm and, along with routine laboratory studies, may help elaborate comorbidities in these often elderly patients. A family history of a ruptured aneurysm is not uncommon and aids in the decision to recommend surgery.1 Identifying comorbidities may influence the operative approach, allow anticipation, and prevention of complications, or may contraindicate surgery altogether.
Evaluation of an AA aneurysm requires a contrast-enhanced computed tomographic (CT) angiogram of the entire aorta. Multidetector CT scans permit rapid imaging of the entire aorta and three-dimensional reconstructions. Magnetic resonance imaging (MRI) yields equally detailed images but entails longer scanning time, higher cost, and the contrast agent, gadolinium, may be nephrotoxic. Angiograms are not routinely required; however, coronary angiography is usually indicated and visualization of the brachiocephalic vessels may be obtained at that time with little added risk.
Cardiac Status and Management of Coronary Artery Disease
All patients require a preoperative echocardiogram to assess left ventricular function (LVF) and exclude significant valvular heart disease. Coronary arteriography is carried out to delineate the anatomy of the proximal coronary arteries in patients with AA aneurysms in whom a Bentall or valve sparing procedure may be required; in patients older than 40; and in younger patients with risk factors, such as smoking, angina, a strong family history, an abnormal ECG or stress test.
Significant coronary artery disease may warrant angioplasty or coronary artery bypass surgery (CABG). Drug-eluting stents are not used for angioplasty, to avoid Plavix therapy, and the procedure is performed several weeks preoperatively, as stent thrombosis may complicate intraoperative protamine administration; antiplatelet therapy is discontinued. If technically feasible, CABG can be done at the time of aneurysm repair. However if a left thoracotomy is anticipated, making access to the coronary arteries difficult, CABG can be undertaken several weeks before aneurysmectomy.
Pulmonary dysfunction increases operative risk ...