Fig. 2.1–14a-d Conventional replacement of the descending aorta.
Fig. 2.1–15 Endovascular stent implantation into the descending aorta.
Specialized techniques in acute Stanford type B dissections
Endovascular stent implantation is currently the initial treatment of choice for acute type B dissections as well. It is possible in most cases to close the false lumen entrance and allow perfusion into the true lumen. Open surgery is now only rarely indicated for acute type B dissections.
Several prospective and randomized studies on the topic are currently in progress to assess the precise value of endovascular treatment for acute type B dissections.
Treatment for thoracoabdominal aortic aneurysms
Conventional surgical treatment
Conventional surgery for thoracoabdominal aortic aneurysms is one of the most elaborate interventions in cardiovascular surgery. The techniques that are in use today were developed by Crawford (Svensson and Crawford 1997), Svensson and colleagues (1993), DeBakey and colleagues (1956), and Svensson and colleagues (1994). The operation (Fig. 2.1-16) is carried out with neuroprotection (Weigang et al. 2007b) (cerebrospinal fluid drainage, derived motor-evoked potentials and sensory-evoked potentials) and using a heart–lung machine or atriofemoral bypass. The patient is intubated with a dual-lumen tube and positioned on the right side, so that the shoulders are at an angle of 60° and the pelvis is raised by 30°. The access route for the thoracoabdominal aorta has been described in detail elsewhere (Svensson et al. 1997).
In the first step, the aorta is clamped between the left carotid artery and the subclavian artery (Fig. 2.1-16). Following clamping of the aorta, special attention needs to be given to the proximal blood pressure. If it is too high, it can be reduced using the heart–lung machine and withdrawal of blood. To allow clamping of an as-small-as-possible section of the aorta, the descending aorta is optimally clamped proximally. However, clamping options need to be guided by local conditions. After opening the aorta, the intercostal arteries are initially sutured and the proximal anastomosis is first created over felt strips with Prolene. In chronic dissections, the aorta has to be completely transected to ensure that a false lumen is not overlooked. Injuries to the esophagus in this area must be carefully avoided. After completion of the anastomosis, blood flow into the prosthesis is released to ensure reperfusion of the spinal cord via branches of the subclavian artery as quickly as possible. The distal clamp is then moved further distally (to the level of the aortic hiatus), and additional intercostal arteries are ligated or (after blocking with a red Fogarty catheter) larger ones are sutured into the prosthesis. The prosthesis is then clamped again distally as well, so that antegrade perfusion is possible via the reimplanted intercostal arteries. In the next step, reimplantation of the intestinal arteries such as the celiac trunk, superior mesenteric artery, and renal arteries follows. The precise reimplantation technique depends on local conditions and the extent of the aneurysm or dissection. In individual cases, additional grafts (8-mm Dacron prostheses) also have to be placed to revascularize the intestinal arteries. The more distally the clamp is placed, the less the flow via the heart-lung machine will be. After completion of the entire aortic replacement, the clamps are removed and the patient is weaned from the heart-lung machine.
Fig. 2.1–16a-e Thoracoabdominal aortic replacement: conventional surgical technique. For clarity, the illustration does not show the staged clamping of the aorta, but this needs to be taken into account during the surgical procedure. Particular attention needs to be given to avoid “reverse bleeding” from the intercostal arteries (caution: steal phenomenon from spinal perfusion).
Fig. 2.1–17 Thoracoabdominal aortic replacement: hybrid technique with revascularization of the intestinal arteries and endovascular stent implantation.
A very long phase of hemostasis then follows, which has to be conducted with extreme care to prevent postoperative bleeding. Administration of packed platelets, fresh frozen plasma, and application of fibrin glues, if necessary, are recommended.
Endoluminal stent implantation (hybrid procedures)
Another option for treating thoracoabdominal aortic aneurysms involves hybrid procedures—i.e., a combination of revascularization (by debranching) of the intestinal arteries and implantation of endovascular stents, with covering of the origins of the intestinal arteries (debranching) (Fig. 2.1-17).
2.1.7 Clinical results
In general, the results of surgical treatment in the thoracic aorta have markedly improved during the last 10 years-both in terms of the results of conventional surgical treatment and also endovascular stent implantation.
Supracoronary ascending aorta replacement can nowadays be carried out with minimal perioperative risk for degenerative aortic aneurysms. The risk is of course greater in patients with a type A dissection.
Table 2.1–2 Revascularization of the supra-aortic vessels with endovascular stenting of the entire aortic arch (hybrid procedure).
| Authors | Year | Mortality |
| Weigang et al. | 2008 | 4/26 (15.4%) |
| Szeto et al. | 2007 | 1/8 (12.5%) |
| Ancona et al. | 2007 | 0/4 (0%) |
| Melissano et al. | 2007 | 2/14 (14.3%) |
| Shah et al. | 2006 | 0/5 (0%) |
| Bergeron et al. | 2006 | 2/15 (13.3%) |
Table 2.1–3