Abstract
Most descending thoracic aortic aneurysms are treated today by implantation of a thoracic endograft. For optimal results, preoperative planning of the procedure is key. Evaluation of the supra aortic branches and the access vessels is crucial to prevent serious perioperative complications. After choosing the graft, multiplanar and centerline of flow reconstructions are necessary to determine the correct endograft size and to anticipate potential pitfalls.
Adjunct procedures are usually carried out before the implantation. After finding the right projection for implanation of the proximal component of the stent graft, permissive hypotension may be helpful to prevent migration or kinking of the graft. Coverage of the LSA is recommended where possible. Techniques like the pull-through technique and Münster manouever may assist in more complex cases. Postoperatively, the mean arterial blood pressure is to be kept above 80 mm Hg in cases where long segments of the thoracic aorta are covered in order to prevent spinal cord injury.
Keywords
aneurysm, aortic, dissection, TEVAR, thoracic
The treatment of thoracic aortic aneurysms depends on the location of the involved segment. Aneurysms of the ascending aorta and the arch are usually still treated by open repair, although endovascular solutions for these pathologies have been introduced in recent years. Ranging from hybrid procedures to parallel grafts and branched devices, treatment of the more proximal aortic segments will continue to evolve.
On the other hand, thoracic endovascular aortic repair (TEVAR) of aneurysms of the descending thoracic aorta (DTA) has become commonplace over the last several years. Compared with open repair, perioperative and short-term morbidity and mortality are lower with TEVAR. Numerous reports on TEVAR results indicate that elderly patients and those with a high-risk profile especially benefit from this treatment, analogous to endovascular abdominal aneurysm repair (EVAR).
Indications
Corresponding with the treatment rationale for EVAR, the main goal of TEVAR is the exclusion of the aneurysm to prevent aneurysm rupture. Aneurysms with a diameter of 6 cm or more are considered to have a rupture risk of 10% to 15% and thus should be treated. Additional indications for DTA aneurysm repair include symptomatic and rapidly growing aneurysms as well as aneurysms with a saccular configuration.
Procedure
Case Presentation
A 77-year-old patient presented with a 78-mm aneurysm of the DTA, increasing more than 10 mm in diameter in 1 year ( Fig. 14.1 ). The patient had an open repair of an infrarenal abdominal aneurysm with a tube graft in 1998. A common iliac artery aneurysm on the right side had been treated by resection and interposition of a polyester prosthesis in 2005. In 2012 the patient underwent coronary artery bypass graft implantation for three-vessel coronary artery disease. Other relevant comorbidities were congestive heart failure, arterial hypertension, and a history of prostate cancer.
Preoperative Assessment
As with all patients for whom endovascular treatment is planned, this patient underwent a cardiology workup and duplex ultrasound evaluation of the carotid and peripheral arteries. Thin-sliced, arterial phased computed tomography angiography (CTA) is mandatory for preoperative planning of TEVAR procedures. This patient had an occlusion of the left internal carotid and the right vertebral artery. CTA of the intracranial arteries revealed that most of the brain parenchyma was perfused by the left vertebral artery ( Fig. 14.2 ).
At our institution, St. Franziskus Hospital Münster, Germany, most surgeons use the Aquarius iNtuition software (TeraRecon, Foster City, California, USA) for preoperative planning. Other products (e.g., OsiriX; Pixmeo, Geneva) are equivalent, as long as they feature a centerline of flow function and multiplanar image reconstructions. The proximal landing zone, defined by the orifice of the left subclavian artery, was 46 mm long and kinked. The distal landing zone, defined by the orifice of the celiac trunk, was 42 mm long. The aortic segment between these sealing zones was tortuous, with several kinks.
Proximal neck diameter and angulation may be associated with inferior outcomes or may even prevent the deployment and fixation of the endograft. Depending on the choice of endograft, the instructions for use demand different maximum neck diameters and degrees of angulation. It is also important to assess access-vessel morphology, including minimal diameter, calcification, and tortuosity. At our institution, we always assess the level of the femoral bifurcations related to the femur heads. Based on this information, the adequate endograft is chosen, and the need for adjunctive procedures is assessed, such as subclavian-carotid transposition/bypass, chimney graft for left subclavian artery, iliofemoral conduits, or the paving-and-cracking technique.
Endograft Planning
Based on preoperative CTA, the surgeon creates a plan that often includes a sketch of the whole aorta, measuring proximal and distal neck lengths, assessing relevant aortic branches, and measuring the relevant diameters of the aorta and access vessels. If a large amount of thrombus is present, its localization is indicated in the drawing. Based on aortic morphology, the surgeon chooses the preferred endograft. Sizing of the endograft depends on the individual device. In this patient, we planned to implant a Zenith Alpha Thoracic Stent Graft (Cook Medical, Bloomington, Indiana, USA). We usually oversize this endograft by 20% because inadequate oversizing and undersizing carry the risk of type Ia endoleaks. The Zenith Alpha graft was chosen for this patient because of the aortic tortuosity. In our experience the major advantage of the Zenith Alpha is its flexibility and low profile, which greatly enhance trackability.
Access vessels
Compared with open repair, TEVAR is a more widely applicable treatment option, especially in relation to patient overall health status. In most cases, applicability of TEVAR is not limited by patient comorbidities, but rather by anatomic suitability. Access-vessel morphology is the Achilles’ heel of TEVAR, especially when larger-bore sheaths are needed for smaller access vessels, as often seen in women and Asians, compared with EVAR devices, which are smaller bore. This translates to a higher rate of access vessel–related complications and the need for a more invasive access in TEVAR. Creation of an iliac conduit, either open or endovascular, can be a solution for challenging access. These and other techniques, however, have their own intrinsic morbidity and mortality.
At our institution, vessel access is usually completely percutaneous. After puncture of the common femoral arteries (CFAs), the preclose technique (Prostar XL, Abbott Vascular, Santa Clara, California, USA) was performed, with a 14-French (14F) sheath placed on the right side and an 8F sheath in the left CFA. Since the level of the femoral bifurcation in relation to the femoral heads is assessed beforehand, puncture of the CFA is usually safe, as in this patient.
In patients with small and diseased femoral vessels, we puncture the left brachial artery first. In the absence of contraindications, we prefer the left brachial, since we do not need to traverse the carotid arteries, reducing the incidence of embolic stroke.
After placement of a 5F Cook sheath, a 5F pigtail catheter is used to bring a standard Terumo wire (Radiofocus Terumo, Japan) into the abdominal aorta. The pigtail catheter can be used to perform angiography of the iliofemoral axes and facilitate puncture of the CFAs (e.g., using the overlay function).
Deployment Preparation
During the procedure, intravenous heparin was administered to achieve an activated clotting time (ACT) corridor of 250 to 300 seconds. In this case, we used the pigtail catheter to mark the origin of the left subclavian artery (LSA), and a 5F Shepherd Hook catheter, advanced from the left femoral access, marked the orifice of the celiac trunk. From the right femoral access, we advanced a Lunderquist Extra-Stiff DC Wire Guide (Cook Medical) over a graded 5F pigtail catheter into the aortic root. In addition, we employed 2D/3D fusion imaging to facilitate the deployment of the endograft (see Chapter 20 ). The fusion imaging technique also assists in finding the appropriate projection to identify the maximally achievable proximal sealing zone and can aid in measuring the length of the aorta that needs to be sealed. The transbrachially placed pigtail catheter is then used to perform the initial CTA.
Stent-Graft Deployment
After validating the necessary graft length with a graded pigtail catheter and fusion imaging, the proximal component was deployed ( Fig. 14.3 ). In this patient, as in almost all cases of DTA TEVAR, we used permissive hypotension of less than 80 mm Hg systolic blood pressure. We rarely use adenosine or rapid pacing to facilitate deployment.
