- Email: [email protected]
Pathogenesis and Management of Retrograde Type A Aortic Dissection After Thoracic Endovascular Aortic Repair
General Review Pathogenesis and Management of Retrograde Type A Aortic Dissection After Thoracic Endovascular Aortic Repair Ali Khoynezhad,1 and Rodney A. White,2 Los Angeles and Torrance, California
Background: Retrograde type A aortic dissection is a feared complication of thoracic aortic endografting. The aim of this study was to review the incidence, etiology, and management of this life-threatening complication. Methods: A retrospective analysis of the literature in the last 10 years was performed. Data on retrograde type A aortic dissection from this literature search, along with authors’ personal experience, provided the basis for this review. Results: The incidence of retrograde type A aortic dissection ranges from 1.3% to 6.8%. In is most commonly associated with endografting of acute or chronic aortic dissection. Up to one third of patients will have this complication 3 months or later after the index procedure. Open surgical repair remains the ‘‘gold standard’’ for retrograde type A aortic dissection, although medical and endovascular approaches may be utilized in selected patients with prohibitive operative risk. Mortality remains high ranging from 20% to 57%. Potential etiologies of retrograde type A aortic dissection include aortic injury from catheter and wire or stent graft manipulation, poor perioperative antihypertensive control, inappropriate patient and device selection, aggressive balloon dilation, and stent graft oversizing. Conclusions: Retrograde type A aortic dissection remains a deadly complication of thoracic aortic endografting. The high incidence of delayed type A aortic dissection underscores the importance of imaging follow-up in patients undergoing a thoracic endograft procedure.
INTRODUCTION Thoracic endovascular aortic repair (TEVAR) has been used increasingly for treatment of descending thoracic aortic disease, particularly in patients with comorbidities, placing them at high risk for conventional surgical repair.1,2 As a less invasive
1 Division of Cardiothoracic Surgery, Cedars-Sinai Medical Center, Los Angeles, CA. 2 Division of Vascular and Endovascular Surgery, HarboreUCLA Medical Center, Torrance, CA.
Correspondence to: Ali Khoynezhad, MD, Division of Cardiothoracic Surgery, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA; E-mail: [email protected] Ann Vasc Surg 2013; -: 1–6 http://dx.doi.org/10.1016/j.avsg.2012.08.010 Ó 2013 Elsevier Inc. All rights reserved. Manuscript received: February 19, 2012; manuscript accepted: August 7, 2012; published online: ---.
treatment option, TEVAR has been associated with significantly reduced early morbidity and mortality and comparable midterm mortality compared with open surgical repair of descending thoracic aortic aneurysm.3 Both intensive care unit and hospital stay are shorter when compared with traditional open operations.1 Although thoracic stent grafts are currently approved only for the treatment of the fusiform thoracic aortic aneurysm (TAA) and the aortic ulcer, indications for TEVAR in clinical practice have been extended to include acute complicated type B aortic dissection, aortic transections, intramural hematoma, and other aortic pathologic diseases. The results in these clinical scenarios have been encouraging, including a lower rate of spinal cord injury.4e8 However, TEVAR entails a unique set of complications compared with open surgical repair, such as endoleak and migration. Awareness 1
2 Khoynezhad and White
is also increasing regarding retrograde type A dissectiondone of the most-feared and lifethreatening complications of TEVAR. Retrograde type A aortic dissection in the past was only described with medical therapy or open surgery of descending thoracic aortic pathology; however, it is now increasingly being reported as an early or delayed complication of TEVAR.7,9e11 The aim of this study was to review the probable etiologies and treatment options and preventive strategies for retrograde type A aortic dissection.
DEFINITIONS Aortic dissection is characterized by formation of a false lumen within the media, which is propagated (most commonly) antegrade by intramural hemorrhage. Aortic dissection is classified as type B according to the Stanford classification, if the dissected aorta does not involve the ascending aorta. Retrograde type A dissection is the consequence of antegrade (central) propagation of the dissected aorta proximal to the left subclavian artery (LSA), regardless of location of the intimomedial tear. The aortic dissection is considered acute if the patient presents within 2 weeks of the initial onset of symptoms. Chronic dissection is any dissection after the initial 2 weeks of clinical presentation. Complicated dissection is defined as clinically symptomatic branchvessel malperfusion (e.g., intestinal ischemia), rupture or impending rupture, or persistent/unrelenting back pain or incontrollable hypertension despite maximal medical therapy.
EPIDEMIOLOGY The incidence of retrograde type A dissection during or after TEVAR has been reported in the range of 1.9e6.8% in case reports and multicenter series.7,9e11 In the largest single-center report, based on TEVAR for 443 patients with type B aortic dissection from 2000 to 2007, the incidence of retrograde type A dissection was 2.5%.11 The most compelling data come from the European Registry on Endovascular Aortic Repair Complications (EuREC), based on retrospective analyses from 28 participating centers for the period 1995e2008.7 EuREC reported an incidence of 1.3% for retrograde type A dissection, with 81% of cases (n ¼ 48) occurring in patients who underwent TEVAR for acute (54%) or chronic (27%) type B dissection.7 Importantly, retrograde type A dissection may have either acute or delayed presentation. It may happen during the index TEVAR procedure, during the initial
Annals of Vascular Surgery
hospitalization, or during extended follow-up (as late as 36 months). In the EuREC study, 46% of cases occurred within the first 30 days, whereas 31% did not occur until at least 3 months after the index procedure.7 The presenting symptoms of retrograde type A dissection are similar to de novo type A aortic dissection, and include acute chest pain, dyspnea, stroke, hypotension, syncope, and sudden cardiac death. However, the patients may be asymptomatic in up to 25% of cases. In the EurREC study, 25% were asymptomatic and 33% had chest pain, whereas 25% presented with syncope and the rest had sudden death.7 The significant incidence of delayed and asymptomatic presentation underscores the need for life-long clinical and imaging follow-up of patients undergoing TEVAR.7,10 Retrograde type A aortic dissection is typically diagnosed with transesophageal echocardiography, intravascular ultrasound, and angiography during the index TEVAR procedure. Although a final angiogram may miss the type A aortic dissection, intravascular ultrasound has almost 100% diagnostic accuracy. In the early and late follow-up, the preferred detection modality is computed tomography. The natural history of retrograde type A aortic dissection is not well known. However, it is safe to assume to be as poor as in acute de novo type A aortic dissection, given the fact that it may kill the patient through similar mechanisms, such as cardiac tamponade, acute aortic regurgitation, or coronary dissection. The potentially lethal complications of retrograde type A dissection are concordant with de novo type A aortic dissection, including newonset aortic valve regurgitation with acute left ventricular volume overload, cerebrovascular ischemia due to malperfusion of the brachiocephalic arteries, rupture in the pericardial sac causing pericardial tamponade, and obstruction of the coronary arteries with subsequent myocardial infarction. Reported mortality rates for retrograde type A aortic dissection are consistent with de novo acute type A aortic dissection and have ranged from 20% to 57%.7,9,11e15 In the EuREC study, 20 patients (42%) died from consequences of retrograde type A aortic dissection, including 9 with sudden death.7 Early (intraoperative) detection harbors generally better prognosis, as it allows for prompt surgical repairdif the patient is considered to be an open operative candidate. If the patient is not a surgical candidate, medical treatment is undertaken, understanding that natural history can be assumed to be similar to nonoperative management of type A aortic dissection, which harbors >90% mortality in the first year.15
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POTENTIAL ETIOLOGIES OF RETROGRADE TYPE A DISSECTION AFTER TEVAR Retrograde type A dissection after TEVAR is thought to be a multifactorial complication, with mechanisms related to the procedure, the stent graft device, the particular aortic anatomy, the patency status of the false lumen, or the aortic wall architecture. Potential procedural cause of retrograde type A aortic dissection is local damage to the aortic wall. This can be done with manipulation of catheters, wires, and devices, especially in the aortic arch, and specific (off-label) maneuvers with the stent graft. A perioperative hypertensive episode may subsequently convert a tear limited to the intima to a frank retrograde dissection, especially in friable and degenerated aortas. In the EuREC study, 60% of cases of retrograde type A dissection were considered related to local aortic injury caused by the semirigid stent graft either during or after implantation, later being due to the repeated subtle diastolic and systolic motion of the aorta adjacent to the stent graft.7 Repeated balloon dilation is often utilized to facilitate conformity of the stent graft within the curved geometry of the vessel, particularly in the aortic arch. However, this process can cause intimal injury as well.10 Aggressive ballooning of the proximal landing zone has been strongly implicated with retrograde type A aortic dissection. This particularly applies to careless ballooning outside of the covered portion of the stent graft, thereby directly pressurizing the aorta.10 It is important to note that TEVAR ballooning of the dissected aorta is generally not recommended, unless there is a true endoleak or if the stent graft is not poorly expanded. Excessive graft oversizing (by >20%) has also been implicated as a potential cause of retrograde type A dissection after TEVAR.10 The force applied by the increased radial force may be the precipitating feature in aortic wall trauma in these cases. Most commercially available thoracic stent grafts have been designed for treatment of TAA in terms of longitudinal support, radial force, and degree of flexibility. These stent grafts facilitate nonocclusive fixation in treatment of TAA and reduction of ‘‘bird-beaking’’ in the tortuous aortic arch. The barbs and proximal bare springs designed to reduce the aforementioned issues with TAA repair may increase the risk of a new entry tear in treatment of type B dissection, particularly in those patients with fragile aortic wall. In a large, single-center series, the new entry tear was located at the tip of the proximal bare spring in most of the cases
Aortic dissection 3
(9 of 11).11 This may have to do with the fact that stent grafts with proximal bare springs (such as Talent and Valiant) are the most commonly implanted thoracic stent grafts worldwide. In addition, the bare springs are not protected by any cloth, as it is the case with stent grafts with proximal barbs (such as TX2). In the EurREC study, 83% of patients had stent grafts with bare springs.7 However, retrograde type A aortic dissection has been described in all commercially available thoracic stent grafts, including those without bare springs.7 Some aspects of proximal neck anatomy may predispose to stress-related injury of the aortic wall. These include severe angulation or kinking of the aortic arch (‘‘gothic arch’’), the need for covering the LSA, or placement of the stent graft proximally to the left common carotid artery.7 Furthermore, the persistence of blood flow into the false lumen at the completion of TEVAR may predispose to retrograde type A dissection due to persistent pressurization of the false lumen. The natural progression of aortic disease and deterioration of the aortic wall architecture also play a role in the pathogenesis of retrograde type A aortic dissection. This is supported by the occurrence of retrograde type A aortic dissection in patients receiving strictly medical treatment, as well as in patients after open surgical repair of an aortic pathology.10 Marfan syndrome patients are at higher risk, presumably due to the friability and fibrillin I abnormality.7 In the authors’ experience, patients with a bicuspid aortic valve are also at increased risk for retrograde type A aortic dissection. It is important to note that Marfan syndrome and other vascular connective tissue disorders are relative contraindications for elective TEVAR due to these patients’ propensity for dilation of landing zones with subsequent type I endoleak.
MANAGEMENT AND PREVENTION OF RETROGRADE TYPE A DISSECTION AFTER TEVAR According to the International Registry of Aortic Dissection (IRAD), the 1-month survival of type A aortic dissection is 50% with medical therapy.15 Because the potential complications associated with retrograde type A aortic dissection are similar to those with de novo acute type A aortic dissection, it is safe to assume both pathologies should have similar mortality and morbidity rates. Therefore, the ‘‘gold standard’’ of complication management for patients with retrograde type A aortic dissection should be graft replacement of the ascending
4 Khoynezhad and White
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Fig. 2. Completed hybrid arch repair in a patient with previous mitral valve repair, aortic valve replacement, and Bentall operation. The heartelung machine was necessary for safe reentry during a third re-do sternotomy. However, once the ascending aortic graft was dissected off the pulmonary artery, the rest of the procedure (arch debranching) was performed in an off-pump manner.
Fig. 1. Schematic concept of hybrid total arch repair after retrograde type A aortic dissection. The ascending aorta is replaced using a standard open surgical technique with a Dacron graft. Next, the brachiocephalic arteries are transposed from the ascending aorta using a quadrofurcated graft. A zone 0 TEVAR (starting in the ascending aortic graft) is subsequently performed in retrograde fashion.
thoracic aorta with or without hemi- or total arch replacement. This usually involves inclusion of the stent graft material in the surgical repair. However, this repair, in our experience, does not have a hemostatic distal suture line in the aortic arch due to barbs and bare springs, and nonpliable stent graft material. Instead, we suggest hybrid total arch replacement (Fig. 1) using a modification of the ‘‘no-touch’’ technique.16 The proposed repair entails Dacron graft replacement of the ascending aorta using the heartelung machine and resuspension of the aortic valve (as needed). Subsequently, transposition of brachiocephalic vessels from the mid-ascending aorta is performed using a quadrofurcated or trifurcated graft (Fig. 1). The origins of the brachiocephalic arteries are subsequently oversewn and clipped for radiographic marking purposes. Next the dissected (excluded) aortic arch is covered with stent graft from ascending aorta to variable length of descending thoracic aorta using a retrograde (or antegrade) approach (Fig. 2). The proximal landing zone is fixated securely within the surgical
ascending aortic graft, whereas the distal landing zone is fixated within the previous descending thoracic stent graft. Using this surgical technique, the primary stent graft along with its barbs or springs is not manipulated or incorporated in any anastomosis. This approach simplifies the repair and reduces the length of the operation and secondary insult to the patient. Therefore, in selected cases the hypothermic circulatory arrest is avoided, reducing postoperative bleeding and respiratory complications. This modified no-touch technique has been applied successfully to the last 2 patients with retrograde type A dissection in our series, resulting in 50% survival (3 of 6 patients with retrograde type A aortic dissection). Four patients (66%) had chronic type B aortic dissection, whereas the other 2 had acute type B dissection and aortic aneurysm. Devices with bare springs were used in all of these patients. Four patients had intraoperative retrograde type B dissection, whereas 2 others had it at 8 days and 24 months, respectively. Although long-term survival with untreated type A aortic dissection is poor, strict medical therapy may be a viable option in selected patients with prohibitive operative risk.11 Alternatively, in anatomically suitable patients, stent graft coverage of the newly discovered most proximal intimomedial tear may be attempted. This may entail branch-vessel/fenestrated stent grafts as well as TEVAR of the ascending aorta to stabilize and occlude the intimomedial tears or the use of chimney grafts as rescue strategy in patients with prohibitive operative risk. These rescue options
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involving branched and fenestrated stent grafts and chimney grafts in the face of acute dissection in the transverse aorta have not yet been performed. With specific stent grafts developed for the ascending aorta, endovascular complication management may become suitable for a larger patient population in the near future. It was noted in the EuREC registry that management of the retrograde dissection varied based on the timing of the dissection in relation to the index TEVAR and on the presumed mechanism of the tear.7 The investigators noted that intraprocedural device-induced dissection (60% of patients) often required prompt emergency open repair, whereas dissections presumably due to the procedural manipulation of wires or sheaths (15% of patients) were treated conservatively. Any patients with retrograde type A aortic dissection in late followup were presumed to have progression of underlying aortic disease (15% of patients). The patients underwent elective surgical repair according to the surgeon’s judgment.7
RAMIFICATIONS FOR CLINICAL PRACTICE The importance of life-long clinical and imaging follow-up of TEVAR patients has been discussed. Strategies to reduce the incidence of retrograde type A dissection after TEVAR are as follows: (1) Reduction of catheter and wire manipulation of the proximal descending thoracic aorta and the aortic arch to bare minimum, especially in patients at risk.17 This reduces iatrogenic aortic wall injury predisposing to retrograde type A aortic dissection. (2) Standardization of stent graft manipulation.7,10,11 Off-label and dangerous maneuvers (such as pushing forward a partially released stent graft) has been the culprit in our experience, and should be strictly avoideddeven in experienced hands. (3) Avoidance of balloon dilation, and extensive oversizing of stent grafts. Both maneuvers have been implicated in the development of retrograde type A aortic dissection, presumably due to local aortic wall injury. (4) Careful patient and device selection and procedural components. Stent grafting in Marfan syndrome patients or other patients with connective tissue disorders should be avoided under normal circumstances, and any patients with a gothic aortic arch should preferentially receive stent grafts without proximal bare spring or barbs. (5) Judicious antihypertensive therapy in the perioperative period. Hypertensive episodes in the early or late postoperative period may convert a localized aortic wall injury to frank dissection. (6) Use of
Aortic dissection 5
dissection-specific devices may reduce the complication rate. Clinical trials involving novel dissectionspecific stent grafts by Cook (Bloomington, IN) will soon begin in the USA. These stent grafts are designed specifically for the treatment of dissection with lower radial force; higher flexibility; and elimination of longitudinal connecting bar, proximal and distal bare stents, and barbs.18 In conclusion, retrograde type A aortic dissection is a formidable complication of TEVAR, even in experienced hands. With better understanding of probable etiologies, a reduced incidence is likely to be achieved. More selective patient enrollment, improved endovascular techniques, strict perioperative anti-hypertensive therapy, and advent of disease-specific stent grafts may assist in this important task. REFERENCES 1. Svensson LG, Kouchoukos NT, Miller DC, et al. Expert consensus document on the treatment of descending thoracic aortic disease using endovascular stent-grafts. Ann Thorac Surg 2008;85(Suppl.):S1e41. 2. Khoynezhad A, Donayre CE, Smith J, et al. Risk factors for early and late mortality after thoracic endovascular aortic repair. J Thorac Cardiovasc Surg 2008;135:1103e9. 3. Makaroun MS, Dillavou ED, Wheatley GH, et al. Five-year results of endovascular treatment with the Gore TAG device compared with open repair of thoracic aortic aneurysms. J Vasc Surg 2008;47:912e8. 4. Eggebrecht H, Nienaber CA, Neuhauser M, et al. Endovascular stent-graft placement in aortic dissection: a meta-analysis. Eur Heart J 2006;27:489e98. 5. Leurs LJ, Bell R, Degrieck Y, et al. Endovascular treatment of thoracic aortic diseases: combined experience from the EUROSTAR and United Kingdom Thoracic Endograft registries. J Vasc Surg 2004;40:670e9. 6. Khoynezhad A, Donayre CE, Bui H, et al. Risk factors of neurologic deficit after thoracic aortic endografting. Ann Thorac Surg 2007;83(Suppl.):S882e9. 7. Eggebrecht H, Thompson M, Rousseau H, et al. Retrograde ascending aortic dissection during or after thoracic aortic stent graft placement: insight from the European registry on endovascular aortic repair complications. Circulation 2009;120(Suppl.):S276e81. 8. Buth J, Harris PL, Hobo R, et al. Neurologic complications associated with endovascular repair of thoracic aortic pathology: incidence and risk factors. a study from the European Collaborators on Stent/Graft Techniques for Aortic Aneurysm Repair (EUROSTAR) registry. J Vasc Surg 2007;46: 1103e10. 9. Kpodonu J, Preventza O, Ramaiah VG, et al. Retrograde type A dissection after endovascular stenting of the descending thoracic aorta. Is the risk real? Eur J Cardiothorac Surg 2008;33:1014e8. 10. Bellos JK, Petrosyan A, Abdulamit T, et al. Retrograde type A aortic dissections after endovascular stent-graft placement for type B dissection. J Cardiovasc Surg (Torino) 2010;51:85e93. 11. Dong ZH, Fu WG, Wang YQ, et al. Retrograde type A aortic dissection after endovascular stent graft placement
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for treatment of type B dissection. Circulation 2009;119: 735e41. 12. Khoynezhad A, Donayre CE, Kopchok G, et al. Mid-term results of endovascular treatment of complicated acute type B aortic dissection. J Thor Cardiovasc Surg 2009;138: 625e9. 13. Khoynezhad A, Gupta PK, Donayre CE, et al. Current status of endovascular treatment of complicated acute type B aortic dissection. Future Cardiol 2009;5:581e8. 14. Neuhauser B, Greiner A, Jaschke W, et al. Serious complications following endovascular thoracic aortic stent-graft repair for type B dissection. Eur J Cardiothorac Surg 2008;33:58e63.
Annals of Vascular Surgery
15. Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000;283:897e903. 16. Spielvogel D, Strauch JT, Minanov OP, et al. Aortic arch replacement using a trifurcated graft and selective cerebral antegrade perfusion. Ann Thorac Surg 2002;74(Suppl.):S1810e4. 17. Khoynezhad A, Kruse MJ, Donayre CE, et al. Use of transcranial Doppler ultrasound in endovascular repair of a type B aortic dissection. Ann Thorac Surg 2008;86:289e91. 18. Torsello GB, Torsello GF, Osada N, et al. Midterm results from the TRAVIATA registry: treatment of thoracic aortic disease with the Valiant stent graft. J Endovasc Ther 2010;17:137e50.
Background: Retrograde type A aortic dissection is a feared complication of thoracic aortic endografting. The aim of this study was to review the incidence, etiology, and management of this life-threatening complication. Methods: A retrospective analysis of the literature in the last 10 years was performed. Data on retrograde type A aortic dissection from this literature search, along with authors’ personal experience, provided the basis for this review. Results: The incidence of retrograde type A aortic dissection ranges from 1.3% to 6.8%. In is most commonly associated with endografting of acute or chronic aortic dissection. Up to one third of patients will have this complication 3 months or later after the index procedure. Open surgical repair remains the ‘‘gold standard’’ for retrograde type A aortic dissection, although medical and endovascular approaches may be utilized in selected patients with prohibitive operative risk. Mortality remains high ranging from 20% to 57%. Potential etiologies of retrograde type A aortic dissection include aortic injury from catheter and wire or stent graft manipulation, poor perioperative antihypertensive control, inappropriate patient and device selection, aggressive balloon dilation, and stent graft oversizing. Conclusions: Retrograde type A aortic dissection remains a deadly complication of thoracic aortic endografting. The high incidence of delayed type A aortic dissection underscores the importance of imaging follow-up in patients undergoing a thoracic endograft procedure.
INTRODUCTION Thoracic endovascular aortic repair (TEVAR) has been used increasingly for treatment of descending thoracic aortic disease, particularly in patients with comorbidities, placing them at high risk for conventional surgical repair.1,2 As a less invasive
1 Division of Cardiothoracic Surgery, Cedars-Sinai Medical Center, Los Angeles, CA. 2 Division of Vascular and Endovascular Surgery, HarboreUCLA Medical Center, Torrance, CA.
Correspondence to: Ali Khoynezhad, MD, Division of Cardiothoracic Surgery, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA; E-mail: [email protected] Ann Vasc Surg 2013; -: 1–6 http://dx.doi.org/10.1016/j.avsg.2012.08.010 Ó 2013 Elsevier Inc. All rights reserved. Manuscript received: February 19, 2012; manuscript accepted: August 7, 2012; published online: ---.
treatment option, TEVAR has been associated with significantly reduced early morbidity and mortality and comparable midterm mortality compared with open surgical repair of descending thoracic aortic aneurysm.3 Both intensive care unit and hospital stay are shorter when compared with traditional open operations.1 Although thoracic stent grafts are currently approved only for the treatment of the fusiform thoracic aortic aneurysm (TAA) and the aortic ulcer, indications for TEVAR in clinical practice have been extended to include acute complicated type B aortic dissection, aortic transections, intramural hematoma, and other aortic pathologic diseases. The results in these clinical scenarios have been encouraging, including a lower rate of spinal cord injury.4e8 However, TEVAR entails a unique set of complications compared with open surgical repair, such as endoleak and migration. Awareness 1
2 Khoynezhad and White
is also increasing regarding retrograde type A dissectiondone of the most-feared and lifethreatening complications of TEVAR. Retrograde type A aortic dissection in the past was only described with medical therapy or open surgery of descending thoracic aortic pathology; however, it is now increasingly being reported as an early or delayed complication of TEVAR.7,9e11 The aim of this study was to review the probable etiologies and treatment options and preventive strategies for retrograde type A aortic dissection.
DEFINITIONS Aortic dissection is characterized by formation of a false lumen within the media, which is propagated (most commonly) antegrade by intramural hemorrhage. Aortic dissection is classified as type B according to the Stanford classification, if the dissected aorta does not involve the ascending aorta. Retrograde type A dissection is the consequence of antegrade (central) propagation of the dissected aorta proximal to the left subclavian artery (LSA), regardless of location of the intimomedial tear. The aortic dissection is considered acute if the patient presents within 2 weeks of the initial onset of symptoms. Chronic dissection is any dissection after the initial 2 weeks of clinical presentation. Complicated dissection is defined as clinically symptomatic branchvessel malperfusion (e.g., intestinal ischemia), rupture or impending rupture, or persistent/unrelenting back pain or incontrollable hypertension despite maximal medical therapy.
EPIDEMIOLOGY The incidence of retrograde type A dissection during or after TEVAR has been reported in the range of 1.9e6.8% in case reports and multicenter series.7,9e11 In the largest single-center report, based on TEVAR for 443 patients with type B aortic dissection from 2000 to 2007, the incidence of retrograde type A dissection was 2.5%.11 The most compelling data come from the European Registry on Endovascular Aortic Repair Complications (EuREC), based on retrospective analyses from 28 participating centers for the period 1995e2008.7 EuREC reported an incidence of 1.3% for retrograde type A dissection, with 81% of cases (n ¼ 48) occurring in patients who underwent TEVAR for acute (54%) or chronic (27%) type B dissection.7 Importantly, retrograde type A dissection may have either acute or delayed presentation. It may happen during the index TEVAR procedure, during the initial
Annals of Vascular Surgery
hospitalization, or during extended follow-up (as late as 36 months). In the EuREC study, 46% of cases occurred within the first 30 days, whereas 31% did not occur until at least 3 months after the index procedure.7 The presenting symptoms of retrograde type A dissection are similar to de novo type A aortic dissection, and include acute chest pain, dyspnea, stroke, hypotension, syncope, and sudden cardiac death. However, the patients may be asymptomatic in up to 25% of cases. In the EurREC study, 25% were asymptomatic and 33% had chest pain, whereas 25% presented with syncope and the rest had sudden death.7 The significant incidence of delayed and asymptomatic presentation underscores the need for life-long clinical and imaging follow-up of patients undergoing TEVAR.7,10 Retrograde type A aortic dissection is typically diagnosed with transesophageal echocardiography, intravascular ultrasound, and angiography during the index TEVAR procedure. Although a final angiogram may miss the type A aortic dissection, intravascular ultrasound has almost 100% diagnostic accuracy. In the early and late follow-up, the preferred detection modality is computed tomography. The natural history of retrograde type A aortic dissection is not well known. However, it is safe to assume to be as poor as in acute de novo type A aortic dissection, given the fact that it may kill the patient through similar mechanisms, such as cardiac tamponade, acute aortic regurgitation, or coronary dissection. The potentially lethal complications of retrograde type A dissection are concordant with de novo type A aortic dissection, including newonset aortic valve regurgitation with acute left ventricular volume overload, cerebrovascular ischemia due to malperfusion of the brachiocephalic arteries, rupture in the pericardial sac causing pericardial tamponade, and obstruction of the coronary arteries with subsequent myocardial infarction. Reported mortality rates for retrograde type A aortic dissection are consistent with de novo acute type A aortic dissection and have ranged from 20% to 57%.7,9,11e15 In the EuREC study, 20 patients (42%) died from consequences of retrograde type A aortic dissection, including 9 with sudden death.7 Early (intraoperative) detection harbors generally better prognosis, as it allows for prompt surgical repairdif the patient is considered to be an open operative candidate. If the patient is not a surgical candidate, medical treatment is undertaken, understanding that natural history can be assumed to be similar to nonoperative management of type A aortic dissection, which harbors >90% mortality in the first year.15
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POTENTIAL ETIOLOGIES OF RETROGRADE TYPE A DISSECTION AFTER TEVAR Retrograde type A dissection after TEVAR is thought to be a multifactorial complication, with mechanisms related to the procedure, the stent graft device, the particular aortic anatomy, the patency status of the false lumen, or the aortic wall architecture. Potential procedural cause of retrograde type A aortic dissection is local damage to the aortic wall. This can be done with manipulation of catheters, wires, and devices, especially in the aortic arch, and specific (off-label) maneuvers with the stent graft. A perioperative hypertensive episode may subsequently convert a tear limited to the intima to a frank retrograde dissection, especially in friable and degenerated aortas. In the EuREC study, 60% of cases of retrograde type A dissection were considered related to local aortic injury caused by the semirigid stent graft either during or after implantation, later being due to the repeated subtle diastolic and systolic motion of the aorta adjacent to the stent graft.7 Repeated balloon dilation is often utilized to facilitate conformity of the stent graft within the curved geometry of the vessel, particularly in the aortic arch. However, this process can cause intimal injury as well.10 Aggressive ballooning of the proximal landing zone has been strongly implicated with retrograde type A aortic dissection. This particularly applies to careless ballooning outside of the covered portion of the stent graft, thereby directly pressurizing the aorta.10 It is important to note that TEVAR ballooning of the dissected aorta is generally not recommended, unless there is a true endoleak or if the stent graft is not poorly expanded. Excessive graft oversizing (by >20%) has also been implicated as a potential cause of retrograde type A dissection after TEVAR.10 The force applied by the increased radial force may be the precipitating feature in aortic wall trauma in these cases. Most commercially available thoracic stent grafts have been designed for treatment of TAA in terms of longitudinal support, radial force, and degree of flexibility. These stent grafts facilitate nonocclusive fixation in treatment of TAA and reduction of ‘‘bird-beaking’’ in the tortuous aortic arch. The barbs and proximal bare springs designed to reduce the aforementioned issues with TAA repair may increase the risk of a new entry tear in treatment of type B dissection, particularly in those patients with fragile aortic wall. In a large, single-center series, the new entry tear was located at the tip of the proximal bare spring in most of the cases
Aortic dissection 3
(9 of 11).11 This may have to do with the fact that stent grafts with proximal bare springs (such as Talent and Valiant) are the most commonly implanted thoracic stent grafts worldwide. In addition, the bare springs are not protected by any cloth, as it is the case with stent grafts with proximal barbs (such as TX2). In the EurREC study, 83% of patients had stent grafts with bare springs.7 However, retrograde type A aortic dissection has been described in all commercially available thoracic stent grafts, including those without bare springs.7 Some aspects of proximal neck anatomy may predispose to stress-related injury of the aortic wall. These include severe angulation or kinking of the aortic arch (‘‘gothic arch’’), the need for covering the LSA, or placement of the stent graft proximally to the left common carotid artery.7 Furthermore, the persistence of blood flow into the false lumen at the completion of TEVAR may predispose to retrograde type A dissection due to persistent pressurization of the false lumen. The natural progression of aortic disease and deterioration of the aortic wall architecture also play a role in the pathogenesis of retrograde type A aortic dissection. This is supported by the occurrence of retrograde type A aortic dissection in patients receiving strictly medical treatment, as well as in patients after open surgical repair of an aortic pathology.10 Marfan syndrome patients are at higher risk, presumably due to the friability and fibrillin I abnormality.7 In the authors’ experience, patients with a bicuspid aortic valve are also at increased risk for retrograde type A aortic dissection. It is important to note that Marfan syndrome and other vascular connective tissue disorders are relative contraindications for elective TEVAR due to these patients’ propensity for dilation of landing zones with subsequent type I endoleak.
MANAGEMENT AND PREVENTION OF RETROGRADE TYPE A DISSECTION AFTER TEVAR According to the International Registry of Aortic Dissection (IRAD), the 1-month survival of type A aortic dissection is 50% with medical therapy.15 Because the potential complications associated with retrograde type A aortic dissection are similar to those with de novo acute type A aortic dissection, it is safe to assume both pathologies should have similar mortality and morbidity rates. Therefore, the ‘‘gold standard’’ of complication management for patients with retrograde type A aortic dissection should be graft replacement of the ascending
4 Khoynezhad and White
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Fig. 2. Completed hybrid arch repair in a patient with previous mitral valve repair, aortic valve replacement, and Bentall operation. The heartelung machine was necessary for safe reentry during a third re-do sternotomy. However, once the ascending aortic graft was dissected off the pulmonary artery, the rest of the procedure (arch debranching) was performed in an off-pump manner.
Fig. 1. Schematic concept of hybrid total arch repair after retrograde type A aortic dissection. The ascending aorta is replaced using a standard open surgical technique with a Dacron graft. Next, the brachiocephalic arteries are transposed from the ascending aorta using a quadrofurcated graft. A zone 0 TEVAR (starting in the ascending aortic graft) is subsequently performed in retrograde fashion.
thoracic aorta with or without hemi- or total arch replacement. This usually involves inclusion of the stent graft material in the surgical repair. However, this repair, in our experience, does not have a hemostatic distal suture line in the aortic arch due to barbs and bare springs, and nonpliable stent graft material. Instead, we suggest hybrid total arch replacement (Fig. 1) using a modification of the ‘‘no-touch’’ technique.16 The proposed repair entails Dacron graft replacement of the ascending aorta using the heartelung machine and resuspension of the aortic valve (as needed). Subsequently, transposition of brachiocephalic vessels from the mid-ascending aorta is performed using a quadrofurcated or trifurcated graft (Fig. 1). The origins of the brachiocephalic arteries are subsequently oversewn and clipped for radiographic marking purposes. Next the dissected (excluded) aortic arch is covered with stent graft from ascending aorta to variable length of descending thoracic aorta using a retrograde (or antegrade) approach (Fig. 2). The proximal landing zone is fixated securely within the surgical
ascending aortic graft, whereas the distal landing zone is fixated within the previous descending thoracic stent graft. Using this surgical technique, the primary stent graft along with its barbs or springs is not manipulated or incorporated in any anastomosis. This approach simplifies the repair and reduces the length of the operation and secondary insult to the patient. Therefore, in selected cases the hypothermic circulatory arrest is avoided, reducing postoperative bleeding and respiratory complications. This modified no-touch technique has been applied successfully to the last 2 patients with retrograde type A dissection in our series, resulting in 50% survival (3 of 6 patients with retrograde type A aortic dissection). Four patients (66%) had chronic type B aortic dissection, whereas the other 2 had acute type B dissection and aortic aneurysm. Devices with bare springs were used in all of these patients. Four patients had intraoperative retrograde type B dissection, whereas 2 others had it at 8 days and 24 months, respectively. Although long-term survival with untreated type A aortic dissection is poor, strict medical therapy may be a viable option in selected patients with prohibitive operative risk.11 Alternatively, in anatomically suitable patients, stent graft coverage of the newly discovered most proximal intimomedial tear may be attempted. This may entail branch-vessel/fenestrated stent grafts as well as TEVAR of the ascending aorta to stabilize and occlude the intimomedial tears or the use of chimney grafts as rescue strategy in patients with prohibitive operative risk. These rescue options
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involving branched and fenestrated stent grafts and chimney grafts in the face of acute dissection in the transverse aorta have not yet been performed. With specific stent grafts developed for the ascending aorta, endovascular complication management may become suitable for a larger patient population in the near future. It was noted in the EuREC registry that management of the retrograde dissection varied based on the timing of the dissection in relation to the index TEVAR and on the presumed mechanism of the tear.7 The investigators noted that intraprocedural device-induced dissection (60% of patients) often required prompt emergency open repair, whereas dissections presumably due to the procedural manipulation of wires or sheaths (15% of patients) were treated conservatively. Any patients with retrograde type A aortic dissection in late followup were presumed to have progression of underlying aortic disease (15% of patients). The patients underwent elective surgical repair according to the surgeon’s judgment.7
RAMIFICATIONS FOR CLINICAL PRACTICE The importance of life-long clinical and imaging follow-up of TEVAR patients has been discussed. Strategies to reduce the incidence of retrograde type A dissection after TEVAR are as follows: (1) Reduction of catheter and wire manipulation of the proximal descending thoracic aorta and the aortic arch to bare minimum, especially in patients at risk.17 This reduces iatrogenic aortic wall injury predisposing to retrograde type A aortic dissection. (2) Standardization of stent graft manipulation.7,10,11 Off-label and dangerous maneuvers (such as pushing forward a partially released stent graft) has been the culprit in our experience, and should be strictly avoideddeven in experienced hands. (3) Avoidance of balloon dilation, and extensive oversizing of stent grafts. Both maneuvers have been implicated in the development of retrograde type A aortic dissection, presumably due to local aortic wall injury. (4) Careful patient and device selection and procedural components. Stent grafting in Marfan syndrome patients or other patients with connective tissue disorders should be avoided under normal circumstances, and any patients with a gothic aortic arch should preferentially receive stent grafts without proximal bare spring or barbs. (5) Judicious antihypertensive therapy in the perioperative period. Hypertensive episodes in the early or late postoperative period may convert a localized aortic wall injury to frank dissection. (6) Use of
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dissection-specific devices may reduce the complication rate. Clinical trials involving novel dissectionspecific stent grafts by Cook (Bloomington, IN) will soon begin in the USA. These stent grafts are designed specifically for the treatment of dissection with lower radial force; higher flexibility; and elimination of longitudinal connecting bar, proximal and distal bare stents, and barbs.18 In conclusion, retrograde type A aortic dissection is a formidable complication of TEVAR, even in experienced hands. With better understanding of probable etiologies, a reduced incidence is likely to be achieved. More selective patient enrollment, improved endovascular techniques, strict perioperative anti-hypertensive therapy, and advent of disease-specific stent grafts may assist in this important task. REFERENCES 1. Svensson LG, Kouchoukos NT, Miller DC, et al. Expert consensus document on the treatment of descending thoracic aortic disease using endovascular stent-grafts. Ann Thorac Surg 2008;85(Suppl.):S1e41. 2. Khoynezhad A, Donayre CE, Smith J, et al. Risk factors for early and late mortality after thoracic endovascular aortic repair. J Thorac Cardiovasc Surg 2008;135:1103e9. 3. Makaroun MS, Dillavou ED, Wheatley GH, et al. Five-year results of endovascular treatment with the Gore TAG device compared with open repair of thoracic aortic aneurysms. J Vasc Surg 2008;47:912e8. 4. Eggebrecht H, Nienaber CA, Neuhauser M, et al. Endovascular stent-graft placement in aortic dissection: a meta-analysis. Eur Heart J 2006;27:489e98. 5. Leurs LJ, Bell R, Degrieck Y, et al. Endovascular treatment of thoracic aortic diseases: combined experience from the EUROSTAR and United Kingdom Thoracic Endograft registries. J Vasc Surg 2004;40:670e9. 6. Khoynezhad A, Donayre CE, Bui H, et al. Risk factors of neurologic deficit after thoracic aortic endografting. Ann Thorac Surg 2007;83(Suppl.):S882e9. 7. Eggebrecht H, Thompson M, Rousseau H, et al. Retrograde ascending aortic dissection during or after thoracic aortic stent graft placement: insight from the European registry on endovascular aortic repair complications. Circulation 2009;120(Suppl.):S276e81. 8. Buth J, Harris PL, Hobo R, et al. Neurologic complications associated with endovascular repair of thoracic aortic pathology: incidence and risk factors. a study from the European Collaborators on Stent/Graft Techniques for Aortic Aneurysm Repair (EUROSTAR) registry. J Vasc Surg 2007;46: 1103e10. 9. Kpodonu J, Preventza O, Ramaiah VG, et al. Retrograde type A dissection after endovascular stenting of the descending thoracic aorta. Is the risk real? Eur J Cardiothorac Surg 2008;33:1014e8. 10. Bellos JK, Petrosyan A, Abdulamit T, et al. Retrograde type A aortic dissections after endovascular stent-graft placement for type B dissection. J Cardiovasc Surg (Torino) 2010;51:85e93. 11. Dong ZH, Fu WG, Wang YQ, et al. Retrograde type A aortic dissection after endovascular stent graft placement
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for treatment of type B dissection. Circulation 2009;119: 735e41. 12. Khoynezhad A, Donayre CE, Kopchok G, et al. Mid-term results of endovascular treatment of complicated acute type B aortic dissection. J Thor Cardiovasc Surg 2009;138: 625e9. 13. Khoynezhad A, Gupta PK, Donayre CE, et al. Current status of endovascular treatment of complicated acute type B aortic dissection. Future Cardiol 2009;5:581e8. 14. Neuhauser B, Greiner A, Jaschke W, et al. Serious complications following endovascular thoracic aortic stent-graft repair for type B dissection. Eur J Cardiothorac Surg 2008;33:58e63.
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15. Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000;283:897e903. 16. Spielvogel D, Strauch JT, Minanov OP, et al. Aortic arch replacement using a trifurcated graft and selective cerebral antegrade perfusion. Ann Thorac Surg 2002;74(Suppl.):S1810e4. 17. Khoynezhad A, Kruse MJ, Donayre CE, et al. Use of transcranial Doppler ultrasound in endovascular repair of a type B aortic dissection. Ann Thorac Surg 2008;86:289e91. 18. Torsello GB, Torsello GF, Osada N, et al. Midterm results from the TRAVIATA registry: treatment of thoracic aortic disease with the Valiant stent graft. J Endovasc Ther 2010;17:137e50.