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a Divisions of Cardiac Surgery and Cardiology, Libin Cardiovascular Institute, Alberta, Canada
b Division of Interventional Radiology, Foothills Medical Centre, University of Calgary, Alberta, Canada
Accepted for publication January 25, 2011.
* Address correspondence to Dr Appoo, Foothills Medical Centre, Rm C828, 1403-29th St NW, Calgary, AB T2N 2T9, Canada (Email: jehangir.appoo{at}albertahealthservices.ca).
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Introduction |
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A 59-year-old man with a past surgical history of mitral valve repair in 2003, underwent aortic valve, ascending aortic, and hemiarch replacement for an acute DeBakey type I dissection in 2009.
His immediate postoperative computed tomography (CT) scan revealed an intact proximal thoracic aortic reconstruction with no fluid around the graft. A routine 1-year follow-up CT angiogram revealed a new ascending aortic pseudoaneurysm arising from the graft-to-graft anastomosis, with extravasation of contrast material (Fig 1 ) and a new well-circumscribed 6-cm mass surrounding his previous ascending aortic graft. The patient was asymptomatic and not keen to proceed with a third sternotomy for surgical repair. After a detailed discussion about the risks and benefits of open procedures versus endovascular procedures, informed consent was obtained to proceed with endovascular repair.
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The procedure was performed with general anesthesia in the cardiac surgery theater with a portable C-arm, routinely used for our thoracic endovascular aortic repair cases. The custom-designed Cook Zenith Endovascular Graft (William Cook Europe ApS , Bjaeverskov, Denmark; CMD-ZTEG-2P-34-53-ACI) was approved for use under special access regulations in Canada.
Surgical exposure to the femoral artery was attained through a 2-inch transverse incision in the left side of the groin. The endograft was introduced into the ascending aorta over a stiff Lunderquist wire (William Cook Europe ApS). To land the proximal end of the endograft at the sinotubular junction, the nose cone of the device was advanced retrograde across the aortic valve into the left ventricle. An ascending aortogram was obtained. The ostium of the coronary arteries, the sinotubular junction, and the proximal aortic arch were well delineated. Venous access for rapid atrial burst pacing during endograft deployment was established in the femoral vein using a 6-F introducer sheath. An active-fixation, 110-cm temporary transvenous pacing lead system (Medtronic model 6416; Medtronic, Minneapolis, MN), was passed through the introducer sheath and positioned at the apex of the right ventricle under fluoroscopy. A pacing system analyzer was connected using standard bipolar alligator-tipped cables. Satisfactory sensing (R wave = 9 to 11 mV), pacing (threshold = 0.6 V at 0.5-ms pulse width), and impedance (1165 
) were obtained. Synchronized defibrillation was carried out at 2 J to test system integrity. Rapid-burst pacing was used to decrease the arterial blood flow within the ascending aorta to facilitate precise deployment of the endograft [5]. Using the atrial burst-pacing function, continuous burst-pacing impulses were delivered (3 V at 0.5-ms pulse width) at a cycle length of 270 ms (222 beats per minute).
Continuous pacing was delivered for 60 seconds, allowing the endograft to be deployed while the systolic arterial pressure was maintained at less than 60 mm Hg.
A final angiogram after deployment revealed a good result with adequate apposition of the endograft across the origin of the pseudoaneurysm. No gradient was appreciated by TEE Doppler echo across the ascending aorta. CT scan on postoperative day 2 confirmed exclusion of pseudoaneurysm (Fig 2 ). Kinking of the endograft at the graft-to-graft anastomosis (Fig 3 ) is believed to be related to the configuration of the Dacron (Invista, Inc) prosthesis. Although our previous experience deploying endografts in surgical Dacron (Invista, Inc) prostheses has not resulted in type III leaks in the endograft, the patient will need ongoing imaging to assess endograft stability. Follow-up imaging at 1-month showed a slight decrease in the aneurysm sac size from 6 cm to 5.5 cm with no leak in the endograft.
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The Zenith TX2 TAA Endovascular Graft (William Cook Europe ApS) is specifically designed for deployment within the ascending aorta and therefore offers several advantages over devices previously adapted for ascending aortic repair. Features specific to this graft include:
(1) A shorter device length (5.3 cm) allows deployment in the ascending aorta without obstructing vital structures; (2) A longer delivery length—100 cm allows the device to be delivered to the proximal aorta from the femoral artery; and (3) The new Pro-Form function prevents "bird-beaking" in this tortuous anatomic area. Because of technical considerations, a standard thoracic endograft would not suffice in this case. The total length of the ascending aorta from the sinotubular junction to the innominate artery was less than 6 cm. The shortest commercially available thoracic endograft in North America is 7.7 cm long.
Traditional thoracic devices have been described as being introduced in alternative fashions [1–4], because a sheath length of 70 cm is insufficient to deliver the device across the aortic arch and past the sinotubular junction in a retrograde fashion. The 100-cm sheath length of the ascending aortic–specific Zenith TX2 allows delivery through the femoral artery in most patients.
In addition, the Pro-Form function allows the proximal extent of the graft to be flexible and is designed to prevent "bird-beaking" of the endograft. This is of particular advantage in the ascending aorta in which adequate apposition can be difficult to achieve because of the curvature of the ascending aorta.
Szeto and colleagues describe the use of abdominal aortic cuff endografts adapted for retrograde deployment in the ascending aorta [2]. These distal extensions, however, lack barbs to secure the endograft. This may result in a theoretic elevated risk of endograft migration. The use of barbs for additional anchoring is controversial, especially in native aortic tissue, as it may result in dissection. However, in this case the device was deployed inside a previous Dacron (Invista, Inc) graft, and the barbs were felt to be beneficial for anchoring in this high blood flow velocity area.
Of note, advancing the nose cone of the device past the aortic valve resulted in temporary aortic insufficiency, which was minimized by rapid ventricular pacing. We believe that the rapid ventricular pacing was particularly helpful, as it took approximately 50 seconds to unsheath the device, and during this time there could have been potential for graft migration.
The 34-mm x 5.3-cm custom Zenith TX2 endovascular graft was designed specifically for secure deployment within the ascending aorta. Rapid-burst pacing allowed precise positioning of the endograft at the sinotubular junction, achieving adequate apposition across the pseudoaneurysm. The advantages afforded by the custom Zenith TX2 endovascular graft have allowed successful endovascular repair of the ascending aorta via a more traditional transfemoral approach.
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This article has been cited by other articles:
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  H. Uthoff, L. Garcia-Covarrubias, S. Samuels, J. F. Benenati, N. L. Moreno, and B. T. Katzen Transapical Endovascular Aortic Repair to Treat Complex Aortic Pathologies Ann. Thorac. Surg., May 1, 2012; 93(5): 1735 - 1737. [Abstract] [Full Text] [PDF]
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