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a Division of Cardiovascular Surgery, Department of Surgery, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania
b Department of Anesthesia and Critical Care, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania
Accepted for publication June 18, 2009.
* Address correspondence to Dr Szeto, Division of Cardiovascular Surgery, Department of Surgery, University of Pennsylvania Medical Center, Hospital of University of Pennsylvania, 3400 Spruce St, 6th Silverstein, Philadelphia, PA 19104 (Email: szetow{at}uphs.upenn.edu).
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Abstract |
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Introduction |
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A 78-year-old man with a history of coronary artery bypass grafting was found to have a widened mediastinum on a routine chest roentgenogram. A subsequent computed tomographic angiogram demonstrated a saccular pseudoaneurysm (2.6 cm) at the level of the previous proximal anastomoses of his saphenous vein graft conduits (Fig 1A). A preoperative coronary angiography demonstrated a patent left internal mammary artery to his left anterior descending coronary artery. However, the two previous saphenous vein graft conduits are now occluded.
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Vascular access was an additional concern. Although the Zenith TX2 (Cook) was ideal in terms of endograft diameter and length, the delivery system was only 75 cm; therefore, it was unlikely to reach the sinotubular junction retrograde from the iliofemoral system. The left subclavian artery was a small vessel in this particular patient. With a patent left internal mammary artery to the left anterior descending coronary artery, we believe that this was not an ideal access vessel. Given our experience with transcatheter aortic valve replacement through the left ventricular apex, we believed that a transapical approach to deploy the Zenith TX2 was our best option.
The surgery was performed in our hybrid operating room (Endosuite) and imaging was provided by a universal floor-mounted angiographic C-arm system (Siemens Axiom Artis FA; Siemens, Malvern, PA). The patient was induced under general anesthesia and intubated with a single-lumen endotracheal tube. Hemodynamic monitoring using a radial artery line and Swan-Ganz catheter was used. The patient was placed in a supine position and draped in the standard sterile technique.
A diagnostic angiographic catheter was placed in the left femoral artery percutaneously. A temporary transvenous pacing wire was also placed percutaneously in the left femoral vein to induce rapid pacing during stent graft deployment. A left mini-thoracotomy incision was made in the fifth intercostal space just inferior to the areolar complex. Using a soft tissue retractor and a rib retractor, the left ventricular apex was exposed. Two pledgeted pursestring sutures were placed in the left ventricular apex.
Heparin (5,000 units) was administered to the patient. The left ventricular apex was accessed with an 18-gauge needle. Under fluoroscopic guidance, a flexible wire was advanced across the aortic valve and into the descending thoracic aorta. The 18-gauge needle was withdrawn and a long 7F sheath was inserted into the left ventricular apex. This was followed by a wire exchange maneuver. A JR4 catheter (Cordis; Johnson and Johnson, Warren, NJ) was advanced to the descending thoracic aorta. The flexible wire was removed and exchanged with an Amplatz superstiff EX wire (0.035 mm x 260 cm) (Boston Scientific, Natick, MA).
The Zenith TX2 distal thoracic endoprosthesis (distal extension, 38 mm x 77 mm) was brought to the field and prepared in the standard fashion. Under flouroscopic guidance, the JR4 catheter and the 7F sheath were removed and exchanged for the endoprosthesis. The endograft was advanced to the ascending aorta. Positioning was confirmed with an intraoperative diagnostic ascending aortic angiogram (Fig 2A). The endoprosthesis was deployed in the standard fashion. To achieve precise deployment (by minimizing ejection and movement of the endograft), the endoprosthesis was deployed under rapid ventricular pacing.
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A completion aortic angiogram demonstrated resolution of the endoleak with patent left and right coronary ostia (Fig 2B). The innominate artery was also patent. The delivery system was withdrawn and the left ventricular apex pursestrings were tied and secured. A pleural drain was placed in the left pleural space and the mini-thoracotomy was closed in the correct anatomic layers.
A follow-up computed tomographic angiogram at 6 months demonstrated satisfactory endovascular repair with no evidence of endoleak, aneurysmal sac enlargement, or aortic dissection (Fig 1B).
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Comment |
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The first challenge relates to the anatomy of the ascending aorta and aortic root apparatus. Compared with the descending thoracic aorta, the length of the ascending aorta is shorter, with vital side branches proximally (coronary arteries) and distally (the arch vessels). This translates into a shorter treatment length and potentially shorter or inadequate proximal and distal landing zones. In our patient, the total treatment length from the level of the sinotubular junction to the innominate artery was measured at 77 mm. Given this dimension, the choice of endograft device was limited. In fact, an extension device, rather than the main body of the Zenith Cook TX2 thoracic endoprosthesis was the most viable option.
The hemodynamic environment of the ascending aorta is also significantly different from the descending thoracoabdominal aorta. Due to its proximal location, the flow characteristic in the ascending aorta is quite significant and may hinder precise deployment of the endoprosthesis. Furthermore, the close proximity of the endoprosthesis to the aortic valve during deployment may result in the obstruction or incompetency of the aortic leaflet, therefore causing significant hemodynamic instability or collapse. In our case, rapid ventricular pacing during deployment was used to decrease movement of the device, thus allowing precise positioning of the endograft. A transvenous femoral temporary pacing wire was used to achieve rapid ventricular pacing at 180 beats per minute.
The design of the current devices also reflects its original intent for the treatment of descending thoracic aortic aneurysms. Designed for retrograde arterial deployment for the iliofemoral vasculature, the devices have multiple limitations for deployment in the ascending aorta. First, the angulation of the aortic arch may prove to be prohibited for device arch transit into the proximal aorta. For bulky devices, arch transit may not be possible. Second, access may become a major issue and perhaps a prohibitive limitation. In extremely tortuous aorta or tall individuals, the delivery system may simply be too short to allow deployment of the endograft in the ascending aorta. Finally, as previously mentioned, the tip of the delivery system may be too high profile, thereby crossing the aortic valve and potentially resulting in obstruction or incompetency of the aortic valve.
In our case, all these issues were significant. The TX2 delivery system was too short for retrograde iliofemoral access. Other peripheral vascular access was considered. The left axillary artery was not ideal due to the patient's history of coronary artery bypass grafting (patent left internal mammary artery to left anterior descending coronary artery). A retrograde approach from the carotid artery was concerning for stroke risk, and the right axillary artery was not ideal secondary to anatomic restraint. Due to our increasing experience with transapical aortic valve replacement in our institution, we believed that an antegrade approach through the left ventricular apex was the best option for endograft deployment. This approach addresses (1) the limited length of the delivery system, (2) the stroke risk (by avoiding retrograde arch transit of the endoprosthesis), and (3) precise deployment with the aid of rapid ventricular pacing. However, cannulation of the left ventricular apex exposes the patient to the potential complication of left ventricular apex rupture.
In summary, this case represents the advances in our understanding and ability to treat ascending aortic pathology using endovascular techniques. Designed primarily for the descending aorta, the current endografts present significant limitations when considered for use in the ascending aorta. These limitations involve the anatomy of the aortic root and ascending aorta, device size, and length, and inadequate delivery system for arch transit. Despite a successful outcome, a word of caution should be made regarding the off label use of this current technology in the treatment of ascending aortic pathology. We must be careful in the evaluation and selection of patients, and we must avoid overly enthusiastic adoption of this technology. However, the success achieved in this case demonstrates that in selected patients with significantly increase risk for conventional open repair, endovascular therapy in the ascending aorta can be performed with acceptable outcome. Further refinement and development of disease-specific endoprosthesis will permit treatment of various thoracic aortic pathologies, including the ascending aorta in the near future.
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