- Email: [email protected]
Frozen Elephant Trunk Procedure
Adult
Frozen Elephant Trunk Procedure George J. Arnaoutakis, MD, Tomas D. Martin, MD, and Thomas M. Beaver, MD Aortic arch pathology including aneurysm and dissection poses a significant technical challenge to operative repair, often requiring 2-stage repair via sternotomy followed by left thoracotomy. The traditional elephant trunk procedure was developed to facilitate this 2-stage approach. With wide adoption of thoracic endovascular aortic repair (TEVAR) emerged the “frozen elephant trunk” (FET) technique, which uses antegrade deployment of TEVAR endografts along with total arch replacement to accomplish a one-stage repair of complex aortic arch pathology. In this article, we describe the technique utilized for FET repair at the University of Florida. Operative Techniques in Thoracic and Cardiovasculary Surgery 24:152 162 Ó 2019 Published by Elsevier Inc.
KEYWORDS Aortic arch aneurysm, Frozen elephant trunk, aortic dissection
P
atients with extensive aortic arch pathology such as degenerative aneurysm or aortic dissection present a significant technical challenge. Aortic arch replacement harbors considerable intraoperative and perioperative risk, including stroke, recurrent laryngeal nerve and respiratory complications, and severe bleeding. Furthermore, patients with distal aortic arch and proximal descending thoracic aorta (DTA) pathology will not be completely treated by aortic arch replacement alone. The traditional elephant trunk procedure as described by Borst was designed to facilitate the secondstage procedure via left thoracotomy.1 However, a major limitation of this approach has been interstage mortality and failure for patients to undergo the second-stage operation.2 Endovascular technology was first applied to the thoracic aorta to treat uncomplicated descending thoracic aortic aneurysm disease.3 However, as experience with thoracic endovascular aortic repair (TEVAR) evolved, the concept of antegrade endograft deployment via an open aortic arch procedure emerged.4-7 This hybrid concept of antegrade TEVAR at the same time as arch replacement was designed to treat aortic arch and proximal descending thoracic aorta pathology in a single stage, and has been referred to as the “frozen elephant trunk” (FET) procedure. The FET procedure is designed to combine the advantages of modern endovascular technology with the classical elephant trunk procedure to treat complex aortic arch pathology in a single operation. While the FET was initially used to treat patients with chronic aneurysm disease, many centers have used this approach in patients with aortic dissection as well. Longterm data are not yet available; however, there are ample Division of Thoracic and Cardiovascular Surgery, University of Florida, Gainesville, FL Address reprint requests to Thomas M. Beaver, MD, Division of Thoracic and Cardiovascular Surgery, University of Florida, PO Box 100286, Gainesville, FL 32610-0286. E-mail: [email protected]fl.edu 152
data to support its use in several select clinical settings. The appropriate indications to consider the FET procedure include: (1) patients with extensive arch and proximal DTA aneurysm; (2) acute Debakey type I dissection with large entry tear in distal aortic arch/proximal DTA, clinical malperfusion, or true lumen compression in descending thoracic aorta with “pseudocoarctation”; (3) retrograde Debakey type I dissection; (4) chronic residual Debakey type I dissection with proximal DTA aneurysm.
Preoperative Considerations The preoperative considerations in patients undergoing FET procedure are similar to all patients undergoing major cardiac surgical procedures requiring use of cardiopulmonary bypass (CPB). A systematic history and physical should be performed in all patients, dictated by the urgency of the clinical scenario. The FET procedure involves reconstruction of the brachiocephalic vessels, and therefore a preoperative neurologic evaluation is imperative to ascertain the patient’s baseline status. The remainder of the preoperative evaluation is similar to patients undergoing other cardiac surgical procedures. Standard coronary evaluation with angiography and 2-D echocardiography should be performed in all elective patients to identify concomitant valvular or coronary lesions that warrant simultaneous attention. In the setting of acute aortic dissection, coronary evaluation is not generally performed. Imaging is of paramount importance for complex aortic arch procedures, and high-resolution multi-slice computerized tomography (CT) with intravenous contrast is necessary for proper preoperative planning and sizing of the aorta. Due to coverage of the proximal DTA with endograft, spinal cord ischemia (SCI) is a risk of FET procedure. In addition to SCI being part of the consent process, we also liberally employ use of cerebrospinal fluid (CSF) drainage in patients undergoing FET procedure. In elective situations, the CSF drainage 1522-2942/$ see front matter © 2019 Published by Elsevier Inc. https://doi.org/10.1053/j.optechstcvs.2019.10.002
Frozen Elephant Trunk Procedure catheter is placed preoperatively, and for emergency procedures it is placed in the intensive care unit postoperatively. Sizing of the endograft for FET should be performed based on the preoperative imaging, and the device selected in advance of the operation. Many different endograft devices have been used for FET procedure, including the commercially available TEVAR devices, hybrid arch grafts such as Thoraflex and E-vita, as well as institutionally designed FET grafts. There are relative strengths and weaknesses of each of the commercially available TEVAR grafts, especially as pertains to ease of deployment as well as porosity and maneuverability of the endograft fabric. Sizing of the endograft is important, and the following recommendations should be followed. Whenever possible, in aneurysm disease a distal seal should be achieved, thus accomplishing a successful single-stage procedure. Therefore, we desire tight fit of the FET beyond the aneurysmal segment of the DTA. We also use the shortest graft possible to accomplish this goal, thus minimizing SCI. Slight oversizing should be performed (eg, if the aortic diameter is 34 mm at the landing zone, we implant a 36-mm diameter FET graft). In patients with Marfan syndrome or other connective tissue, we do not perform oversizing. In acute aortic dissection, we measure the total diameter of the aorta, with true and false lumen combined. The diameter of the FET is approximately equal to that of the total aortic diameter, however no oversizing is performed, and a 10cm long endograft is used exclusively. For chronic aortic dissection, the measurement of total aortic diameter is performed. The size of the FET is often between the diameter of the true lumen and the total aortic diameter.
Operative Technique There are many different techniques that have been used successfully to reconstruct the aortic arch, including the island technique, branched graft technique, and the “Spielvogel” trifurcated arch graft technique. All aortic arch procedures will require some period of circulatory arrest in order to complete the distal aortic reconstruction. Numerous cannulation, circulation, and temperature management strategies have been utilized for aortic arch reconstruction, each with relative strengths and weaknesses. Many surgeons employ routine use of axillary artery cannulation to provide antegrade cerebral perfusion. To date, there are no randomized data to support one technique over another. The surgeon must work in concert with anesthesiologists and perfusionists to ensure proper neurologic protection. We will describe the surgical practice currently used at University of Florida. Standard anesthesia is established and routine cardiac monitoring performed. We use bilateral cerebral oximetry. A right radial arterial and femoral arterial line are used for blood pressure monitoring. A small bore sheath is placed in the femoral artery for hemodynamic monitoring, as well as to permit advancement of an atraumatic long 280 cm wire into the ascending aorta to facilitate later endograft deployment. Transesophageal echocardiography (TEE) is used to confirm true
153 lumen positioning of the wire. In patients undergoing redo sternotomy with preoperative imaging revealing close proximity of the aorta or cardiac structures to the sternum, femoral vessel exposure is performed beforehand. For cardiopulmonary bypass, we favor direct aorta cannulation in most situations, except in rare circumstances where axillary artery cannulation is used. In acute aortic dissection, TEE or epiaortic ultrasound are used to perform direct aortic cannulation of the true lumen. This is performed using Seldinger technique. After CPB is established, and with adequate venting of the heart, we begin to cool the patient to 20 °C. Any concomitant valvular, coronary, or aortic root pathology is addressed during this period of cooling. The brachiocephalic vessels are dissected out during this period of cooling as well. In elective operations, and especially in patients with deep anteroposterior dimension of the thorax with posteriorly located left subclavian artery we frequently perform preoperative left carotid subclavian bypass. This facilitates arch vessel management at time of FET. After a period of cooling of at least 30 minutes, once electroencephalographic silence has been achieved, we utilize a brief period of deep hypothermic circulatory arrest (HCA) to the entire body with the patient in steep trendelenburg. The brachiocephalic vessels are divided from the aortic arch (Fig. 1). If in very close proximity to one another, the vessels may be divided off the aortic arch as a small island with only 1-2 mm of residual aortic rim for anastomosis. Alternatively, they may be divided individually and separately reimplanted. We select the size of a trifurcated aortic arch graft based on CT measurements, but is commonly a 14 mm-10 mm10 mm or 12 mm-10 mm-10 mm graft. It is important not to completely drain the blood volume into the venous reservoir during the period of HCA in order to facilitate de-airing the brachiocephalic vessels. Once the arterial cannula is removed from the aorta, a Y-connector is placed in the arterial line for eventual antegrade cerebral perfusion. The anastomosis to the brachiocephalic vessels is performed with running 3-0 or 4-0 prolene suture (Fig. 2). Felt may be used for extremely friable tissues, but is not routinely used for these anastomoses. A small amount of bioglue can be carefully applied to the anastomosis if the tissues appear thin or friable. When performing anastomosis to the brachiocephalic vessels as an island, upon completion of the anastomosis, one limb from the Y-connector of the arterial circuit is connected to an extra limb of the trifurcate arch graft. Perfusion is initiated at a slow rate at 100-200 cc/min to thoroughly de-air the cerebral vasculature. Once satisfied with de-airing, then ACP is commenced, generally at 8-10 cc/kg/min (Fig. 3). Monitoring of right radial artery pressure during this time is useful to ensure adequate perfusion. If the brachiocephalic vessels will be reimplanted separately, the innominate artery anastomosis is typically performed first, and unilateral ACP commenced. Bilateral ACP is established after completion of the left carotid anastomosis. It is important to size the brachiocephalic limbs of the arch graft relatively short so that the proximal anastomosis can be performed in an appropriate location on the ascending graft, but not so short as to
154 place tension on the anastomosis. Accomplishing this portion of the operation can routinely be performed in under 15 minutes, and has demonstrated to be safe.8 An advantage of separate reimplantation of the brachiocephalic vessels is the ability to oversew the ostia of the left carotid and left subclavian arteries and perform the distal aortic anastomosis more proximally in zone 1 or zone 2, rather than distal to the left subclavian artery. This facilitates visualization should reinforcement sutures be necessary. Attention is now turned to the FET deployment portion of the procedure. A recent modification to our approach in an effort to minimize endoleak has been to anastomose a short segment (»1-2 cm long) of an open surgical graft to the distal aortic arch. We refer to this as the “deployment cuff.” The wire via the femoral artery is pulled out the aorta into the operative field and the endograft is loaded over top of the wire. The endograft is deployed either at the level of the distal aorta or within the deployment cuff of surgical graft
G.J. Arnaoutakis et al. (Fig. 4). This portion requires careful attention to ensure that the endograft is deployed in accurate location so that the distal anastomosis can fully incorporate the endograft. After deployment the wire is withdrawn and the distal anastomosis performed with running 3-0 prolene suture. During this portion of the arch reconstruction, we often reduce the amount of Trendelenburg which aids in de-airing of the descending aorta. In acute dissection, we use felt buttress to reinforce the suture line. The second limb of the Y-connector to the arterial line is connected to side arm of the surgical graft, and full CPB is resumed. Rewarming begins and the proximal anastomosis is completed (Fig. 5). An opening is made on the right anterolateral segment of the ascending graft for reimplantation of the trifurcate arch graft, which completes the reconstruction (Figs. 6 and 7). A radiopaque marker or clip can be placed near the aortic arch graft anastomosis to the ascending graft, thus facilitating visualization should additional endograft have to be extended proximally in the future to address endoleak.
Frozen Elephant Trunk Procedure
155
Figure 1 Upon initiation of deep hypothermic circulatory arrest, the brachiocephalic vessels are dissected out. If the innominate artery and left common carotid artery are in close anatomic proximity they are divided off the aortic arch as an island with a very thin rim of 1-2 mm or native aortic arch. Preparation of the brachiocephalic vessels in this fashion mandates zone 2 for distal aortic anastomosis. Alternatively, if the innominate artery and left common carotid artery are divided from the aortic arch as separate ostia, the left common carotid stump can be over sewn, permitting distal anastomosis in zone 1.
156
G.J. Arnaoutakis et al.
Figure 2 The 14 mm limb of a trifurcate arch graft is anastomosed in end-to-end fashion with running 3-0 or 4-0 prolene suture. One of the 10 mm limbs is connected to the arterial circuit via a Y-connector for initiation of antegrade cerebral perfusion following completion of this anastomosis.
Frozen Elephant Trunk Procedure
157
Figure 3 Completed anastomosis and antegrade cerebral perfusion is delivered via the arterial circuit, with target flow rate 8-10 ml/kg/min.
158
G.J. Arnaoutakis et al.
Figure 4 The antegrade TEVAR is advanced over a wire previously advanced via the femoral vessels into the DTA, and deployment is performed under direct vision.
Frozen Elephant Trunk Procedure
159
Figure 5 The distal aortic suture line is completed with running 3-0 prolene suture. In cases of dissection, a felt buttress is used. Cardiopulmonary bypass is resumed via a sidearm for lower body perfusion. The proximal suture line is completed, after addressing any aortic root pathology requiring treatment.
160
G.J. Arnaoutakis et al.
Figure 6 An opening is made in the right lateral wall of the ascending graft to accommodate the aortic debranching limb. The debranching limb of the aortic arch graft is then anastomosed in end-to-side fashion with 4-0 prolene.
Frozen Elephant Trunk Procedure
161
Figure 7 Completion repair with extra limbs over sewn.
G.J. Arnaoutakis et al.
162
Postoperative Management Management in the intensive care unit is similar to any patient undergoing major aortic reconstruction. A prompt neurologic examination is important as lower extremity weakness or paralysis can be addressed with salvage maneuvers such as increased blood pressure with mean arterial pressure goals 90-100 mm Hg. CSF drainage can be manipulated to promote spinal cord perfusion as well. Our routine practice is to clamp the spinal drain 24 hours postoperatively, and to remove the catheter at 48 hours if the patient remains neurologically intact. Prior to discharge a contrast-enhanced CT scan is performed to survey the reconstruction, although small endoleak or residual false lumen flow may persist until 6-8 weeks postoperatively. The CT angiogram protocol routinely incorporates an early arterial phase and a late phase scan.
Conclusions In patients with appropriate aortic arch pathology, the FET approach provides a single-stage solution to treat the extent of aortic involvement, whereas a second-stage operation is necessary with the classic ET approach. In addition, with the more widespread availability of prefabricated, FET hybrid grafts the technical conduct of FET procedures will be simplified. The FET may also provide an ideal “landing zone” for future endovascular completion. In our experience, the FET procedure is widely preferred over the classic elephant trunk procedure, where we observed higher survival rate compared to patients undergoing 2-stage procedures.9 Contemporary series report acceptable outcomes with FET procedure, with improved results in recent experience. Recent data show the predominant complications to be bleeding, stroke, prolonged ventilatory support, and renal failure requiring dialysis. In-hospital mortality for all disease etiologies ranges between 8% and 15%.7,9,10 Permanent paraplegia is observed in 3%-5% of FET cases. In summary, these data underscore the complexity of patients with aortic arch pathology requiring FET intervention. The
keys to a successful FET operation include: (1) proper preoperative imaging and sizing of aortic landing zones; (2) close collaboration with anesthesia and perfusion colleagues intraoperatively to minimize cerebral and other organ ischemia time; and (3) preoperative left subclavian revascularization when feasible and arch vessel debranching to perform distal aortic anastomosis in a more proximal location.
References 1. Borst HG, Walterbusch G, Schaps D: Extensive aortic replacement using “elephant trunk” prosthesis. Thorac Cardiovasc Surg 31:37–40, 1983 2. Shrestha M, Beckmann E, Krueger H, et al: The elephant trunk is freezing: The Hannover experience. J Thorac Cardiovasc Surg 149:1286– 1293, 2015 3. Dake MD, Miller DC, Semba CP, et al: Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med 331:1729–1734, 1994 4. Shrestha M, Bachet J, Bavaria J, et al: Current status and recommendations for use of the frozen elephant trunk technique: A position paper by the Vascular Domain of EACTS. Eur J Cardiothorac Surg 47: 759–769, 2015 5. Karck M, Chavan A, Hagl C, et al: The frozen elephant trunk technique: A new treatment for thoracic aortic aneurysms. J Thorac Cardiovasc Surg 125:1550–1553, 2003 6. Kato M, Ohnishi K, Kaneko M, et al: New graft-implanting method for thoracic aortic aneurysm or dissection with a stented graft. Circulation 94:II188–II193, 1996 7. Ma WG, Zheng J, Dong SB, et al: Sun’s procedure of total arch replacement using a tetrafurcated graft with stented elephant trunk implantation: Analysis of early outcome in 398 patients with acute type A aortic dissection. Ann Cardiothorac Surg 2:621–628, 2013 8. Ziganshin BA, Rajbanshi BG, Tranquilli M, et al: Straight deep hypothermic circulatory arrest for cerebral protection during aortic arch surgery: Safe and effective. J Thorac Cardiovasc Surg 148:888–898, 2014. discussion 98-900 9. Alhussaini M, Abdelwahab A, Arnaoutakis GJ, et al: Neurologic outcomes in aortic arch repair with frozen elephant trunk versus two-stage hybrid repair. Ann Thorac Surg 107:1775–1781, 2018 10. Shrestha M, Martens A, Kaufeld T, et al: Single-centre experience with the frozen elephant trunk technique in 251 patients over 15 years. Eur J Cardiothorac Surg 52:858–866, 2017
Frozen Elephant Trunk Procedure George J. Arnaoutakis, MD, Tomas D. Martin, MD, and Thomas M. Beaver, MD Aortic arch pathology including aneurysm and dissection poses a significant technical challenge to operative repair, often requiring 2-stage repair via sternotomy followed by left thoracotomy. The traditional elephant trunk procedure was developed to facilitate this 2-stage approach. With wide adoption of thoracic endovascular aortic repair (TEVAR) emerged the “frozen elephant trunk” (FET) technique, which uses antegrade deployment of TEVAR endografts along with total arch replacement to accomplish a one-stage repair of complex aortic arch pathology. In this article, we describe the technique utilized for FET repair at the University of Florida. Operative Techniques in Thoracic and Cardiovasculary Surgery 24:152 162 Ó 2019 Published by Elsevier Inc.
KEYWORDS Aortic arch aneurysm, Frozen elephant trunk, aortic dissection
P
atients with extensive aortic arch pathology such as degenerative aneurysm or aortic dissection present a significant technical challenge. Aortic arch replacement harbors considerable intraoperative and perioperative risk, including stroke, recurrent laryngeal nerve and respiratory complications, and severe bleeding. Furthermore, patients with distal aortic arch and proximal descending thoracic aorta (DTA) pathology will not be completely treated by aortic arch replacement alone. The traditional elephant trunk procedure as described by Borst was designed to facilitate the secondstage procedure via left thoracotomy.1 However, a major limitation of this approach has been interstage mortality and failure for patients to undergo the second-stage operation.2 Endovascular technology was first applied to the thoracic aorta to treat uncomplicated descending thoracic aortic aneurysm disease.3 However, as experience with thoracic endovascular aortic repair (TEVAR) evolved, the concept of antegrade endograft deployment via an open aortic arch procedure emerged.4-7 This hybrid concept of antegrade TEVAR at the same time as arch replacement was designed to treat aortic arch and proximal descending thoracic aorta pathology in a single stage, and has been referred to as the “frozen elephant trunk” (FET) procedure. The FET procedure is designed to combine the advantages of modern endovascular technology with the classical elephant trunk procedure to treat complex aortic arch pathology in a single operation. While the FET was initially used to treat patients with chronic aneurysm disease, many centers have used this approach in patients with aortic dissection as well. Longterm data are not yet available; however, there are ample Division of Thoracic and Cardiovascular Surgery, University of Florida, Gainesville, FL Address reprint requests to Thomas M. Beaver, MD, Division of Thoracic and Cardiovascular Surgery, University of Florida, PO Box 100286, Gainesville, FL 32610-0286. E-mail: [email protected]fl.edu 152
data to support its use in several select clinical settings. The appropriate indications to consider the FET procedure include: (1) patients with extensive arch and proximal DTA aneurysm; (2) acute Debakey type I dissection with large entry tear in distal aortic arch/proximal DTA, clinical malperfusion, or true lumen compression in descending thoracic aorta with “pseudocoarctation”; (3) retrograde Debakey type I dissection; (4) chronic residual Debakey type I dissection with proximal DTA aneurysm.
Preoperative Considerations The preoperative considerations in patients undergoing FET procedure are similar to all patients undergoing major cardiac surgical procedures requiring use of cardiopulmonary bypass (CPB). A systematic history and physical should be performed in all patients, dictated by the urgency of the clinical scenario. The FET procedure involves reconstruction of the brachiocephalic vessels, and therefore a preoperative neurologic evaluation is imperative to ascertain the patient’s baseline status. The remainder of the preoperative evaluation is similar to patients undergoing other cardiac surgical procedures. Standard coronary evaluation with angiography and 2-D echocardiography should be performed in all elective patients to identify concomitant valvular or coronary lesions that warrant simultaneous attention. In the setting of acute aortic dissection, coronary evaluation is not generally performed. Imaging is of paramount importance for complex aortic arch procedures, and high-resolution multi-slice computerized tomography (CT) with intravenous contrast is necessary for proper preoperative planning and sizing of the aorta. Due to coverage of the proximal DTA with endograft, spinal cord ischemia (SCI) is a risk of FET procedure. In addition to SCI being part of the consent process, we also liberally employ use of cerebrospinal fluid (CSF) drainage in patients undergoing FET procedure. In elective situations, the CSF drainage 1522-2942/$ see front matter © 2019 Published by Elsevier Inc. https://doi.org/10.1053/j.optechstcvs.2019.10.002
Frozen Elephant Trunk Procedure catheter is placed preoperatively, and for emergency procedures it is placed in the intensive care unit postoperatively. Sizing of the endograft for FET should be performed based on the preoperative imaging, and the device selected in advance of the operation. Many different endograft devices have been used for FET procedure, including the commercially available TEVAR devices, hybrid arch grafts such as Thoraflex and E-vita, as well as institutionally designed FET grafts. There are relative strengths and weaknesses of each of the commercially available TEVAR grafts, especially as pertains to ease of deployment as well as porosity and maneuverability of the endograft fabric. Sizing of the endograft is important, and the following recommendations should be followed. Whenever possible, in aneurysm disease a distal seal should be achieved, thus accomplishing a successful single-stage procedure. Therefore, we desire tight fit of the FET beyond the aneurysmal segment of the DTA. We also use the shortest graft possible to accomplish this goal, thus minimizing SCI. Slight oversizing should be performed (eg, if the aortic diameter is 34 mm at the landing zone, we implant a 36-mm diameter FET graft). In patients with Marfan syndrome or other connective tissue, we do not perform oversizing. In acute aortic dissection, we measure the total diameter of the aorta, with true and false lumen combined. The diameter of the FET is approximately equal to that of the total aortic diameter, however no oversizing is performed, and a 10cm long endograft is used exclusively. For chronic aortic dissection, the measurement of total aortic diameter is performed. The size of the FET is often between the diameter of the true lumen and the total aortic diameter.
Operative Technique There are many different techniques that have been used successfully to reconstruct the aortic arch, including the island technique, branched graft technique, and the “Spielvogel” trifurcated arch graft technique. All aortic arch procedures will require some period of circulatory arrest in order to complete the distal aortic reconstruction. Numerous cannulation, circulation, and temperature management strategies have been utilized for aortic arch reconstruction, each with relative strengths and weaknesses. Many surgeons employ routine use of axillary artery cannulation to provide antegrade cerebral perfusion. To date, there are no randomized data to support one technique over another. The surgeon must work in concert with anesthesiologists and perfusionists to ensure proper neurologic protection. We will describe the surgical practice currently used at University of Florida. Standard anesthesia is established and routine cardiac monitoring performed. We use bilateral cerebral oximetry. A right radial arterial and femoral arterial line are used for blood pressure monitoring. A small bore sheath is placed in the femoral artery for hemodynamic monitoring, as well as to permit advancement of an atraumatic long 280 cm wire into the ascending aorta to facilitate later endograft deployment. Transesophageal echocardiography (TEE) is used to confirm true
153 lumen positioning of the wire. In patients undergoing redo sternotomy with preoperative imaging revealing close proximity of the aorta or cardiac structures to the sternum, femoral vessel exposure is performed beforehand. For cardiopulmonary bypass, we favor direct aorta cannulation in most situations, except in rare circumstances where axillary artery cannulation is used. In acute aortic dissection, TEE or epiaortic ultrasound are used to perform direct aortic cannulation of the true lumen. This is performed using Seldinger technique. After CPB is established, and with adequate venting of the heart, we begin to cool the patient to 20 °C. Any concomitant valvular, coronary, or aortic root pathology is addressed during this period of cooling. The brachiocephalic vessels are dissected out during this period of cooling as well. In elective operations, and especially in patients with deep anteroposterior dimension of the thorax with posteriorly located left subclavian artery we frequently perform preoperative left carotid subclavian bypass. This facilitates arch vessel management at time of FET. After a period of cooling of at least 30 minutes, once electroencephalographic silence has been achieved, we utilize a brief period of deep hypothermic circulatory arrest (HCA) to the entire body with the patient in steep trendelenburg. The brachiocephalic vessels are divided from the aortic arch (Fig. 1). If in very close proximity to one another, the vessels may be divided off the aortic arch as a small island with only 1-2 mm of residual aortic rim for anastomosis. Alternatively, they may be divided individually and separately reimplanted. We select the size of a trifurcated aortic arch graft based on CT measurements, but is commonly a 14 mm-10 mm10 mm or 12 mm-10 mm-10 mm graft. It is important not to completely drain the blood volume into the venous reservoir during the period of HCA in order to facilitate de-airing the brachiocephalic vessels. Once the arterial cannula is removed from the aorta, a Y-connector is placed in the arterial line for eventual antegrade cerebral perfusion. The anastomosis to the brachiocephalic vessels is performed with running 3-0 or 4-0 prolene suture (Fig. 2). Felt may be used for extremely friable tissues, but is not routinely used for these anastomoses. A small amount of bioglue can be carefully applied to the anastomosis if the tissues appear thin or friable. When performing anastomosis to the brachiocephalic vessels as an island, upon completion of the anastomosis, one limb from the Y-connector of the arterial circuit is connected to an extra limb of the trifurcate arch graft. Perfusion is initiated at a slow rate at 100-200 cc/min to thoroughly de-air the cerebral vasculature. Once satisfied with de-airing, then ACP is commenced, generally at 8-10 cc/kg/min (Fig. 3). Monitoring of right radial artery pressure during this time is useful to ensure adequate perfusion. If the brachiocephalic vessels will be reimplanted separately, the innominate artery anastomosis is typically performed first, and unilateral ACP commenced. Bilateral ACP is established after completion of the left carotid anastomosis. It is important to size the brachiocephalic limbs of the arch graft relatively short so that the proximal anastomosis can be performed in an appropriate location on the ascending graft, but not so short as to
154 place tension on the anastomosis. Accomplishing this portion of the operation can routinely be performed in under 15 minutes, and has demonstrated to be safe.8 An advantage of separate reimplantation of the brachiocephalic vessels is the ability to oversew the ostia of the left carotid and left subclavian arteries and perform the distal aortic anastomosis more proximally in zone 1 or zone 2, rather than distal to the left subclavian artery. This facilitates visualization should reinforcement sutures be necessary. Attention is now turned to the FET deployment portion of the procedure. A recent modification to our approach in an effort to minimize endoleak has been to anastomose a short segment (»1-2 cm long) of an open surgical graft to the distal aortic arch. We refer to this as the “deployment cuff.” The wire via the femoral artery is pulled out the aorta into the operative field and the endograft is loaded over top of the wire. The endograft is deployed either at the level of the distal aorta or within the deployment cuff of surgical graft
G.J. Arnaoutakis et al. (Fig. 4). This portion requires careful attention to ensure that the endograft is deployed in accurate location so that the distal anastomosis can fully incorporate the endograft. After deployment the wire is withdrawn and the distal anastomosis performed with running 3-0 prolene suture. During this portion of the arch reconstruction, we often reduce the amount of Trendelenburg which aids in de-airing of the descending aorta. In acute dissection, we use felt buttress to reinforce the suture line. The second limb of the Y-connector to the arterial line is connected to side arm of the surgical graft, and full CPB is resumed. Rewarming begins and the proximal anastomosis is completed (Fig. 5). An opening is made on the right anterolateral segment of the ascending graft for reimplantation of the trifurcate arch graft, which completes the reconstruction (Figs. 6 and 7). A radiopaque marker or clip can be placed near the aortic arch graft anastomosis to the ascending graft, thus facilitating visualization should additional endograft have to be extended proximally in the future to address endoleak.
Frozen Elephant Trunk Procedure
155
Figure 1 Upon initiation of deep hypothermic circulatory arrest, the brachiocephalic vessels are dissected out. If the innominate artery and left common carotid artery are in close anatomic proximity they are divided off the aortic arch as an island with a very thin rim of 1-2 mm or native aortic arch. Preparation of the brachiocephalic vessels in this fashion mandates zone 2 for distal aortic anastomosis. Alternatively, if the innominate artery and left common carotid artery are divided from the aortic arch as separate ostia, the left common carotid stump can be over sewn, permitting distal anastomosis in zone 1.
156
G.J. Arnaoutakis et al.
Figure 2 The 14 mm limb of a trifurcate arch graft is anastomosed in end-to-end fashion with running 3-0 or 4-0 prolene suture. One of the 10 mm limbs is connected to the arterial circuit via a Y-connector for initiation of antegrade cerebral perfusion following completion of this anastomosis.
Frozen Elephant Trunk Procedure
157
Figure 3 Completed anastomosis and antegrade cerebral perfusion is delivered via the arterial circuit, with target flow rate 8-10 ml/kg/min.
158
G.J. Arnaoutakis et al.
Figure 4 The antegrade TEVAR is advanced over a wire previously advanced via the femoral vessels into the DTA, and deployment is performed under direct vision.
Frozen Elephant Trunk Procedure
159
Figure 5 The distal aortic suture line is completed with running 3-0 prolene suture. In cases of dissection, a felt buttress is used. Cardiopulmonary bypass is resumed via a sidearm for lower body perfusion. The proximal suture line is completed, after addressing any aortic root pathology requiring treatment.
160
G.J. Arnaoutakis et al.
Figure 6 An opening is made in the right lateral wall of the ascending graft to accommodate the aortic debranching limb. The debranching limb of the aortic arch graft is then anastomosed in end-to-side fashion with 4-0 prolene.
Frozen Elephant Trunk Procedure
161
Figure 7 Completion repair with extra limbs over sewn.
G.J. Arnaoutakis et al.
162
Postoperative Management Management in the intensive care unit is similar to any patient undergoing major aortic reconstruction. A prompt neurologic examination is important as lower extremity weakness or paralysis can be addressed with salvage maneuvers such as increased blood pressure with mean arterial pressure goals 90-100 mm Hg. CSF drainage can be manipulated to promote spinal cord perfusion as well. Our routine practice is to clamp the spinal drain 24 hours postoperatively, and to remove the catheter at 48 hours if the patient remains neurologically intact. Prior to discharge a contrast-enhanced CT scan is performed to survey the reconstruction, although small endoleak or residual false lumen flow may persist until 6-8 weeks postoperatively. The CT angiogram protocol routinely incorporates an early arterial phase and a late phase scan.
Conclusions In patients with appropriate aortic arch pathology, the FET approach provides a single-stage solution to treat the extent of aortic involvement, whereas a second-stage operation is necessary with the classic ET approach. In addition, with the more widespread availability of prefabricated, FET hybrid grafts the technical conduct of FET procedures will be simplified. The FET may also provide an ideal “landing zone” for future endovascular completion. In our experience, the FET procedure is widely preferred over the classic elephant trunk procedure, where we observed higher survival rate compared to patients undergoing 2-stage procedures.9 Contemporary series report acceptable outcomes with FET procedure, with improved results in recent experience. Recent data show the predominant complications to be bleeding, stroke, prolonged ventilatory support, and renal failure requiring dialysis. In-hospital mortality for all disease etiologies ranges between 8% and 15%.7,9,10 Permanent paraplegia is observed in 3%-5% of FET cases. In summary, these data underscore the complexity of patients with aortic arch pathology requiring FET intervention. The
keys to a successful FET operation include: (1) proper preoperative imaging and sizing of aortic landing zones; (2) close collaboration with anesthesia and perfusion colleagues intraoperatively to minimize cerebral and other organ ischemia time; and (3) preoperative left subclavian revascularization when feasible and arch vessel debranching to perform distal aortic anastomosis in a more proximal location.
References 1. Borst HG, Walterbusch G, Schaps D: Extensive aortic replacement using “elephant trunk” prosthesis. Thorac Cardiovasc Surg 31:37–40, 1983 2. Shrestha M, Beckmann E, Krueger H, et al: The elephant trunk is freezing: The Hannover experience. J Thorac Cardiovasc Surg 149:1286– 1293, 2015 3. Dake MD, Miller DC, Semba CP, et al: Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med 331:1729–1734, 1994 4. Shrestha M, Bachet J, Bavaria J, et al: Current status and recommendations for use of the frozen elephant trunk technique: A position paper by the Vascular Domain of EACTS. Eur J Cardiothorac Surg 47: 759–769, 2015 5. Karck M, Chavan A, Hagl C, et al: The frozen elephant trunk technique: A new treatment for thoracic aortic aneurysms. J Thorac Cardiovasc Surg 125:1550–1553, 2003 6. Kato M, Ohnishi K, Kaneko M, et al: New graft-implanting method for thoracic aortic aneurysm or dissection with a stented graft. Circulation 94:II188–II193, 1996 7. Ma WG, Zheng J, Dong SB, et al: Sun’s procedure of total arch replacement using a tetrafurcated graft with stented elephant trunk implantation: Analysis of early outcome in 398 patients with acute type A aortic dissection. Ann Cardiothorac Surg 2:621–628, 2013 8. Ziganshin BA, Rajbanshi BG, Tranquilli M, et al: Straight deep hypothermic circulatory arrest for cerebral protection during aortic arch surgery: Safe and effective. J Thorac Cardiovasc Surg 148:888–898, 2014. discussion 98-900 9. Alhussaini M, Abdelwahab A, Arnaoutakis GJ, et al: Neurologic outcomes in aortic arch repair with frozen elephant trunk versus two-stage hybrid repair. Ann Thorac Surg 107:1775–1781, 2018 10. Shrestha M, Martens A, Kaufeld T, et al: Single-centre experience with the frozen elephant trunk technique in 251 patients over 15 years. Eur J Cardiothorac Surg 52:858–866, 2017