Stephan Haulon

Aortic Dissections: New Perspectives and Treatment Paradigms

Aortic dissection is a complex manifestation of disease of the arterial wall. The severity and consequences of a dissection are related to the physical characteristics and anatomic location of the tear as well as the underlying patient physiology. Despite in vitro and in vivo modeling advances, our understanding of the pathophysiology has been limited to evaluations of the success and failure of various treatment modalities. The indications for intervention have historically included rupture, intractable pain or hypertension, distal ischemia and degeneration of the aortic wall causing aneurysm formation. The management decisions for patients with dissections are dependent upon the abnormal anatomy, the acuity of the patient presentation, and physiology. Despite the availability of open surgery as a therapeutic option, acute dissections with evidence of ischemia are now handled using an endovascular approach that is specifically directed at the cause of the ischemia. Endovascular treatments include the placement of a stentgraft into the proximal aorta, branch vessel stenting, uncovered stent placement in the abdominal aorta, and aortic fenestrations. Chronic dissections, in contrast, are still most frequently managed with open surgical techniques. However, a subset of patients that are not candidates for traditional surgical repair of the thoracoabdominal aorta may be managed with a combined open mesenteric revascularization with subsequent endovascular grafting of the thoracoabdominal aorta.

Stent-Graft Migration: A Reappraisal of Analysis Methods and Proposed Revised Definition

Purpose: To demonstrate the need for a radiographic definition of migration that accurately describes a specific failure mode of an aortic stent-graft. Methods: The diagnosis of endograft migration, as defined by the Society for Vascular Surgery/American Association for Vascular Surgery (SVS/AAVS) standards, requires a synthesis of clinical and/or radiographic observations. Radiographic studies and clinical reports of 704 consecutive patients treated over a 6-year period with abdominal aortic endografts were retrospectively reviewed. According to the current SVS/AAVS standards, 25 patients were identified as having endograft migration. Follow-up computed tomographic scans and radiographs available for 24 of these patients were scrutinized from discharge to the time of any observed proximal or distal fixation system movement based upon the discharge or 30-day CT scan. Proximal migration was defined with respect to the origin of the superior mesenteric artery (SMA) as movement in a caudal or cranial direction of ≥10 mm or >2 times the reconstructed resolution of the imaging study (whichever measurement was less). Distal migration was similarly defined using the aortic bifurcation and respective hypogastric artery origin as reference points. In an effort to assess the scan-to-scan variation, the distance between the SMA and lowest renal artery, which was expected to remain consistent, was measured. Results: Film analysis with application of the revised migration definition confirmed fixation system failure with respect to the native arterial system in 12 (50%) of the 24 patients. Subjects judged to have endograft migration according to the reporting standards but not to have radiographic evidence of migration based on the modified criteria included 2 proximal endoleaks without evidence of device movement treated with proximal extensions, 1 procedure-related migration, 2 type III endoleaks treated with a second prosthesis implanted within the first, 1 distal endoleak treated with a limb extension, 1 rupture with presumed distal limb migration, and 2 cases of component separation. Three limb extensions were placed in the absence of leak or migration. These 12 patients all had radiographic evidence that the proximal and distal aspects of the originally implanted device did not move with respect to the native arterial vasculature, thus confirming stability of the respective fixation system. Conclusions: Adherence to this comprehensive definition of device migration, which differs from the published reporting standards, allows differentiation of the specific mechanisms of device failure. Data viewed in this context will aid in the understanding of device strengths and weaknesses, potentially improve patient assessment, and encourage design modifications to address specific aspects relating to fixation failure.

Aortic dissection in the setting of an infrarenal endoprosthesis: a fatal combination

Approximately 6 months after the successful implantation of an abdominal aortic endovascular graft, a patient suffered an acute aortic dissection. The false lumen of the dissection terminated in the excluded aneurysm sac, resulting in a lack of outflow. Extreme true lumen compression eliminated blood flow within the distal aorta, resulting in the patients demise.

The Cook Zenith Devices

The Cook Zenith family of devices includes a wide range of custom and off-the-shelf endovascular grafts and devices capable of treating patients with complex anatomy and pathology, including those previously considered unsuitable for endovascular repair. Available devices include the Zenith AAA, Zenith TX2 TAA, Zenith Fenestrated Graft, Iliac Branch Graft, and Helical Branch Graft, and the Zenith Dissection Stent. In addition, low-profile versions of the AAA (abdominal aortic aneurysm) and TAA (thoracic aortic aneurysm) grafts (designed based on a combination of nitinol stent technology and thin-wall graft material) are now available as investigational devices, allowing for endovascular treatment of patients with smaller access vessels. This chapter includes a review of device evolution and a brief review of the literature, which indicates that all commercially available devices are associated with positive clinical outcomes.