Etiology aortic disease
Degenerative or patients without connective tissue disorder
Patients with bicuspid aortic valve (BAV)
Patients with bicuspid aortic valve (BAV) and risk factorsa
Patients with Marfan syndrome (MFS)
Patients with Marfan syndrome (MFS) and risk factorsb
Patients with Loeys-Dietz syndrome
11.2.2 Surgical Therapy of the Ascending Aorta
Open aortic surgery is performed through a median sternotomy approach, if the ascending aorta is affected. In some cases, a minimal invasive approach such as a partial upper hemisternotomy can be performed. Potential advantages are reduced pain, shorter recovery time, and improved cosmetic result. Minimal invasive approaches are mainly performed in younger patients with low operative risk like in Marfan syndrome.
Surgery is performed using extracorporeal circulation and cardioplegia-induced cardiac arrest. The aim of aortic surgery is to totally resect and replace the aortic aneurysm using a polyester vascular prosthesis. In most situations, the ascending aorta can be clamped before the origin of the innominate artery avoiding circulatory arrest. If the proximal or even the total aortic arch is involved or the aorta is dissected, hypothermic circulatory arrest is necessary for a bloodless surgical field and for cerebral protection.
Depending on the extent of the aneurysm, with or without the aortic root, there are different techniques available (Fig. 11.1).
From left to right: supracoronary replacement of the ascending aorta, root replacement with a valved composite graft (Bentall procedure), valve-sparing root replacement using reimplantation (David procedure), or remodeling technique (Yacoub procedure) with reimplantation of the coronary buttons
In ascending aortic aneurysms without involvement of the aortic root, a supracoronary replacement of the ascending aorta can be performed using a tubular vascular prosthesis with low operative risk between 1 and 3 % early mortality. If the aortic root is affected (aortic root aneurysm), the surgical procedure is more complicated, because the aortic valve and the coronary ostia originate from the root. Depending on aortic valve pathology, there are two different techniques of aortic root replacement:
If the aortic valve is affected (e.g., aortic stenosis or complex severe aortic regurgitation), the entire aortic root and valve have to be replaced with a valved composite graft using a biologic or mechanical valve conduit (Bentall procedure). The choice of biological tissue or a mechanical valve depends on patient age and risk factors for long-term anticoagulation therapy with vitamin K antagonist, such as warfarin.
If the aortic valve is unaffected and the valve cusps are normal (no aortic stenosis or severe aortic regurgitation with complex pathology), the aortic root is resected and replaced by a vascular graft, while the aortic valve can be preserved using valve-sparing root replacement techniques, such as the
Reimplantation (David procedure) or the remodeling technique (Yacoub or David procedure) with reimplantation of the coronary buttons.
Using valve-sparing root replacement technique, the entire diseased aortic root including all three aortic sinuses is resected, while the native aortic valve is preserved. Both coronary ostia are removed for later reimplantation into a Dacron graft. There are two different valve-sparing techniques: the reimplantation procedure according to David and the remodeling technique according to Yacoub. During the reimplantation procedure, a tubular or Valsalva graft is fixed by subvalvular sutures below the level of the aortic annulus. The aortic valve is then reimplanted into the graft using a continuous suture technique with respect to the valve anatomy (David technique, see Fig. 11.2). Using the remodeling technique, a tubular graft is incised at the base in three equal parts and tailored to the shape of the three aortic sinuses. The aortic valve with the three commissures is then sewn into the three incisions of the vascular graft to create neosinuses (Yacoub technique). Several studies showed excellent results for both valve-sparing root replacement techniques. David reported excellent freedom from reoperation at 15 to 18 years of 94.8 % . Also both techniques show good long-term results, the David procedure demonstrated higher freedom from significant long-term aortic insufficiency in Marfan syndrome because the aortic root and annulus are better stabilized by the circular subannular fixation. Thus, current evidence is in favor of David rather than Yacoub technique in pathologies such as Marfan syndrome or other connective tissue disorders and in excessive annular dilatation.
From left to right: aortic root aneurysm, valve-sparing root replacement according to David with reimplantation of the native aortic valve into a Dacron graft, valved composite graft using a biologic valve conduit (Bentall procedure)
If the aortic root and the aortic valve are diseased and have to be replaced, a combined replacement of the aortic root and valve with reimplantation of the coronary ostia is performed using a composite aortic valve graft (Bentall procedure, see Fig. 11.2). The choice of biological tissue or a mechanical valve depends on patient age and risk factors for anticoagulation therapy. Although mechanical valves have lifetime durability, there is need for lifelong anticoagulation, such as Coumadin with increased risk of bleeding complications. Using biological valves, lifelong antiplatelet therapy is sufficient for anticoagulation, and Coumadin is usually not necessary to prevent the development of blood clots. However, the durability compared to mechanical valves is poor with need of reoperation after 10–15 years in the majority of patients. In case of valve-sparing techniques, anticoagulation therapy is not required, and valve-related complications are rare. This is particularly important for younger women, who are planning to be pregnant. Furthermore, freedom from reoperation is excellent.
11.3 Surgical Therapy of the Aortic Arch
11.3.1 Indication for Operation
The surgical therapy of aortic arch aneurysms still remains a big challenge for the surgeon due to its topography. The introduction of deep hypothermic circulatory arrest for cerebral protection by Griepp and colleagues in 1975 made total aortic arch replacements by means of a vascular prosthesis possible.
The difficulty of the therapy can be attributed to the complex location of the aortic arch and the origin of the aortic arch vessels. The main intraoperative risk for the patient is that of cerebrovascular accident. Furthermore, the opening of the arch during surgery with interruption of the blood flow poses a particular risk for spinal cord ischemia with resultant paraplegia. Of utmost importance is also the sparing of the vagal and recurrent nerves. Patients must be informed preoperatively about the risk of postoperative stroke, paraplegia, and hoarseness.
Surgery for asymptomatic patients with isolated degenerative or atherosclerotic aortic arch aneurysm is indicated when a maximal diameter of ≥55 mm is reached or in patients who present symptoms or signs of local compression (2014 ESC guidelines ).
Earlier results published by Crawford reported a 30-day mortality between 9 and 26 %, depending on the extent of the aortic aneurysm. At present, this mortality during elective interventions has been reduced to 3.9–11.1 % [6, 21]. This can be primarily attributed to the improved techniques for cerebral protection (see Sect. 11.3.3). This justifies a prophylactic aortic arch replacement according to AHA and ESC guidelines. However, decision-making should weigh the perioperative risks, since aortic arch replacement is associated with higher rates of mortality and stroke than in surgery of the ascending and descending aorta (2014 ESC guidelines ).
11.3.2 Surgical Approach
The surgical approach in aortic arch pathology is determined by the extent of the aneurysm, as well as the local findings. If the ascending aorta is involved, a median sternotomy is the standard approach. However, if the arch aneurysm extends into the descending aorta, a lateral thoracotomy or bilateral anterior thoracotomy (clamshell approach) should be considered due to the technical difficulty via median sternotomy. An alternative surgical option for combined diseases of the aortic arch and the descending aorta is the “elephant trunk” (ET) technique (Borst 1983 ) during which the distal end of the prosthesis is positioned in the proximal descending aorta in preparation for the second surgical approach. A modified and more sophisticated method is the “frozen elephant trunk” (FET) technique, during which a hybrid stent graft prosthesis is used [12, 24]. The advantage of the FET is the possibility of a combined replacement of the ascending aorta, the aortic arch, and the proximal descending aorta in one stage. During this procedure the stented graft is placed in the proximal descending aorta in an antegrade fashion through the opened aortic arch via a median sternotomy.
11.3.3 Cerebral Protection and Extracorporeal Circulation
The complexity of aortic arch surgery is due to its awkward ventral to dorsal anatomical location and the unavoidable necessity to interrupt brain circulation during the opening of the aortic arch. This can result in irreversible brain cell damage. Therefore, aortic arch replacement is performed using extracorporeal circulation (ECC) and hypothermic circulatory arrest. During the last two decades, various techniques have been developed for cerebral protection in order to avoid neurological deficit. These well-established techniques primarily distinguish between the depth of the hypothermia and the technique of the selective cerebral perfusion :
Deep hypothermic circulatory arrest (<20 °C) without cerebral perfusion
Deep hypothermic circulatory arrest (<20 °C) with retrograde cerebral perfusion via superior vena cava
Moderate hypothermia and circulatory arrest (24–28 °C) with selective antegrade (uni- or bilateral) cerebral perfusion
184.108.40.206 Hypothermic Circulatory Arrest
Hypothermic circulatory arrest (HCA) alone was the standard technique in arch surgery during the last few decades and is still deemed to be secure technique for short circulatory arrest times. The risk for a permanent neurological dysfunction (PND) is estimated to be 1.9–9.6 % and for transient neurological deficit up to 20 % [14, 16]. The risk for neurological deficit is directly dependent on the time of circulatory arrest, increasing dramatically even after just 25 min of HCA . The mortality rate also increases significantly after 1 h of HCA . Furthermore, there is the added risk of clotting disorders due to the extended extracorporeal circulatory (ECC) time required for the long cooling and rewarming phase.