Midterm Results After Endovascular Treatment of Acute, Complicated Type B Aortic Dissection

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1 Midterm Results After Endovascular Treatment of Acute, Complicated Type B Aortic Dissection Marek P. Ehrlich, MD, Julia Dumfarth, MD, Maria Schoder, MD, Roman Gottardi, MD, Johannes Holfeld, MD, Andrzej Juraszek, MD, Tomasz Dziodzio, MD, Martin Funovics, MD, Christian Loewe, MD, Michael Grimm, MD, Gottfried Sodeck, MD, and Martin Czerny, MD Departments of Cardiothoracic Surgery and Radiology, Division of Cardiovascular and Interventional Radiology, University of Vienna, and Department of Cardiology, Hospital Rudofstiftung, Vienna, Austria Background. The purpose of this study was to assess the efficacy and midterm results of endovascular treatment of acute, complicated type B aortic dissection. Methods. Between January 2001 and February 2010, 32 patients (7 women, 25 men) with acute, complicated type B aortic dissection (mean age, 56 years; range, 35 to 83 years), defined as either aortic rupture, malperfusion, intractable pain, or uncontrolled hypertension, underwent endovascular stent graft placement with either the Gore Excluder/TAG device (n 11), Medtronic Talent/ Valiant device (n 16), Bolton Relay (n 2), or a combination of these stents (n 3). Follow-up was 94% complete and averaged months. Results. Technical feasibility and success with deployment proximal to the entry tear was 87%, requiring partial or total coverage of the left subclavian artery (LSA) in 9 patients (28%). Hospital mortality was 12% 11% (95% confidence limit) with 2 late deaths (17 and 98 months after implant). Causes of hospital death included rupture in 2, retrograde type A dissection in 1, and multiorgan failure in 1 patient. Three patients (11%) experienced new neurologic complications (2 paraparesis and 1 hemiparesis). Six patients with malperfusion required branch vessel stenting. Furthermore, 2 had an early type Ia endoleak. Actuarial survival at 1 and 5 years was 81% and 76%, respectively. Freedom from treatment failure at 1 and 5 years (including reintervention, aortic rupture, device-related complication, and aortic related death) was 78% and 61%, respectively. Conclusions. Endovascular stent-graft placement in acute, complicated type B aortic dissection proves to be a promising alternative therapeutic treatment modality in this relatively difficult patient cohort. Refinements, especially in stent design and application, may further improve the prognosis of patients in this life-threatening situation. (Ann Thorac Surg 2010;90:1444 9) 2010 by The Society of Thoracic Surgeons Acute aortic dissection of the descending aorta remains a formidable undertaking for cardiac surgeons as well as, in recent years, interventional radiologists. The optimal management of these patients with Stanford type B dissections remains a matter of ongoing debate [1, 2]. Usually medical treatment controlling hypertension and pain in the initial phase is the primary goal for uncomplicated aortic type B dissections. This was recently confirmed by the first randomized trial comparing the best medical treatment versus elective endovascular surgery [3]. Surgery has been reserved only for cases with complications such as aortic rupture, malperfusion of end organs, or persistent pain despite medical treatment. However, contemporary mortality rates of surgical resection of acute, complicated type B dissections range between 15% and 30%, and even exceed 50% in complicated cases under emergency conditions [4]. Furthermore, the afflicted population is usually of older Accepted for publication June 11, Presented at the Poster Session of the Forty-sixth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 25 27, Address correspondence to Dr Ehrlich, Department of Cardiothoracic Surgery, University of Vienna, Währinger Gürtel 18-20, Vienna, A-1090, Austria; marek.ehrlich@meduniwien.ac.at. age and presents at time of operation with various comorbidities such as hypertension, obstructive pulmonary disease, and coronary heart disease, all of which have significant impact on the surgical outcome Since the first endovascular stent-graft experience in an abdominal aortic aneurysm [5], many groups have started to investigate the feasibility of thoracic aortic aneurysmal repair with endovascular stent-grafts for various aortic pathologic conditions [6 9]. During the last decade, endovascular techniques have revolutionized the management of descending thoracic aortic disease, with the benefit of exclusion of the pathologically altered aorta without direct surgical exposure. Therefore, endovascular stentgrafts may offer an attractive and safer alternative approach for treating special aortic pathologic conditions such as complicated acute type B dissections [10, 11]. Material and Methods Between January 2001 and February 2010, 32 patients (7 women, 25 men) with acute, complicated aortic type B dissections (mean age, 56 years; range, 35 to 83 years), defined as either aortic rupture, malperfusion, intractable pain, or uncontrolled hypertension, were treated by a 2010 by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc doi: /j.athoracsur

2 Ann Thorac Surg EHRLICH ET AL 2010;90: TYPE B AORTIC DISSECTION MIDTERM RESULTS multidisciplinary team (interventional radiology, anesthesia, and cardiovascular surgery) at the University Clinic in Vienna. Hypertension was present in 30 of the 32 patients, and 1 patient had previously undergone ascending and hemiarch replacement (Table 1). In 8 patients, the dissections extended only into the abdominal aorta, and in the remaining 24 patients, into the iliac arteries. Confirmation of dissection was based on contrast-enhanced computed tomographic angiography using a multidetector scanner. Computed tomographic scanning ranged from the supraaortic vessels to the common femoral arteries. Routine postacquisition image processing from each computed tomographic scan included three-dimensional reconstructions consisting of multiplanar reformations, curved planar reconstructions, and a maximal intensity projection. Follow-up was 94% complete and averaged months. The institutional review board approved the study and waived the need for patient consent. Endovascular Prosthesis and Procedure All patients were treated with commercially available stent-grafts. A Talent endoprosthesis (Medtronic, Minneapolis, MN) was used in 16 patients, the Thoracic Excluder (W. L. Gore & Assoc, Flagstaff, AZ) stent-graft system was used in 11 patients, the Bolton Relay (Bolton Medical, Sunrise, FL) device in 2 patients, and 3 patients received a combination of these three devices. The diameter of the stent-graft was calculated from the largest diameter of the proximal anchoring zone, and an oversizing factor of 10% was added. All procedures were performed in an angiography suite that is equipped with digital subtraction angiography (Multistar T.O.P., Siemens, Erlangen, Germany) and were done under general anesthesia. Antibiotic prophylaxis was administered intravenously in all patients before the procedure. In patients without rupture, 5,000 IU of heparin sodium was given after the access site was surgically exposed. A 5F pigtail catheter was positioned into the ascending aorta through right-sided percutaneous brachial access to perform an angiogram before stent-graft deployment. Subsequently, a 260-cm-long steerable hydrophilic guidewire (Terumo Europe N.V., Leuven, Belgium) was Table 1. Demographics and Clinical Characteristics (n 32) Variable No. % Male Age, y (median) 56 (35 83) Comorbidity Hypertension Marfan syndrome 1 3 Aortic rupture 7 22 COPD 2 6 Coronary artery disease 2 6 Diabetes 3 9 Previous aortic surgery 1 3 COPD chronic obstructive pulmonary disease advanced to the iliac artery and snared with an Amplatz gooseneck snare (ev3 Endovascular Inc, Plymouth, MN). A diagnostic catheter was then introduced from the femoral site over the through-and-through wire up to the aortic arch to facilitate placement of the superstiff guidewire (Back-up Meier; Boston Scientific, Natick, MA). After deployment of the device, an angiogram was performed to evaluate the position of the stent-graft relative to supraaortic arch vessels, to confirm closure of the proximal entry tear, to ascertain the true lumen diameter along the aorta, and to document the perfusion status of the branch vessels. Follow-Up Imaging Computed tomographic angiography examinations were routinely performed within 3 days of the procedure, at 3, 6, and 12 months, and yearly thereafter. To assess the extent of the dissection, the diameter of the true and false lumen, and the perfusion status of the false lumen and the branch vessels, the entire aorta and the iliac arteries were included. Statistical Analysis Continuous data are reported as the mean standard deviation or median and total range. Estimates of times to events and the accompanying curves were generated by the method of Kaplan and Meier. Calculations were performed with SPSS for Mac (version 16.0, SPSS Inc, Chicago, IL). Results Intraoperative Results Technical feasibility and success with deployment proximal to the entry tear was 87%. Vessel access was achieved through the left or right common femoral artery in all patients. Twelve patients were treated with one endoprosthesis, 15 patients with two, and 5 patients with three. The LSA was intentionally partially or totally covered by the stent-graft in 9 patients (28%). No symptoms of ischemia of the left arm or subclavian steal syndrome requiring secondary revascularization were identified during the initial hospitalization. One patient, however, experienced a subclavian steal syndrome 4 months after the procedure, and a subclavian-carotid transposition was performed. Hospital mortality was 12% 11% (95% confidence limit). Causes of hospital death included rupture in 2, retrograde type A dissection in 1 and multiorgan failure in the remaining 1 patient. Additional intraprocedural stenting was necessary in 6 patients to alleviate persistent obstruction of the true lumen by extension of the intimal flap beyond the vessel s origin. Three patients required stenting of the renal arteries, 2 of the celiac trunk, and 1 patient of the mesenteric artery. Furthermore, 2 patients required a thoracotomy owing to a hematothorax, and 4 patients had a laparotomy as a result of bowel ischemia with resection of some jejunum. ADULT CARDIAC

3 1446 EHRLICH ET AL Ann Thorac Surg TYPE B AORTIC DISSECTION MIDTERM RESULTS 2010;90: Median covered length of the descending aorta was 200 mm (range, 150 to 300 mm). Three patients (11%) experienced new neurologic complications (2 paraparesis and 1 hemiparesis). Furthermore, 2 patients had an early type Ia endoleak. In one of them, partial covering of the LSA demonstrated residual flow into the false lumen from the proximal entry tear. Transposition of the LSA was later performed in this patient with proximal stentgraft extension. The endoleak persisted, and the patient died 17 months after intervention owing to aortic rupture. The second patient had undergone stent-graft placement in an emergency setting with malperfusion of the visceral organs. Decompression of the true lumen was achieved, but the patient had a type 1a endoleak. Because of his problematic conditions no further intervention was made, and the patient is now under surveillance with no further increase of the aortic diameter. Follow-Up Mean follow-up period for hospital survivors was months. None of the patients who survived the procedure experienced a late endoleak. Actuarial survival at 1 and 5 years was 81% and 76%, respectively (Fig 1). Freedom from treatment failure at 1 and 5 years (including reintervention, aortic rupture, device-related complication, aortic-related death, or sudden, unexplained late death) was 78% and 61%, respectively (Fig 2). Comment Since 1969, when Dotter inserted stainless-steel coils as a vascular stent in canine popliteal arteries, transluminal placement of endovascular stent-grafts has been used as a treatment of abdominal aortic aneurysms as well as in the last two decades for descending thoracic aneurysms or dissections [6, 12]. Therefore, this endovascular treatment modality has gained increased acceptance across the world with excellent short-term results. This new method offers the possibility of treating patients who are Fig 1. Survival curve. Fig 2. Freedom from treatment failure. not candidates for conventional surgical procedures because the technique is less invasive and can sometimes be performed with only spinal anesthesia. Furthermore, progress has been achieved with regard to safety and effectiveness of stent-grafts in the repair of thoracic aneurysms [13]. Since the first reports describing the treatment of acute type B aortic dissections with stent-graft technology, optimism was raised for improved early and late survival [14, 15]. The concept of this procedure was directed toward sealing of the proximal intimal tear, redirecting flow into the true lumen, and promoting depressurization and thrombosis of the false lumen. In addition, such an approach may effectively treat malperfusion syndrome by reestablishing side branch flow in dynamic obstruction [16, 17]. Furthermore, the primary stent-graft procedure might be used as a bridge to conventional operation once the patient s renal and hepatic problems have resolved and bowel ischemia has been reversed. Growing experience with endovascular treatment in the spectrum of aortic dissection has confirmed both feasibility and usefulness, especially in unstable patients, with encouraging early and midterm results [18]. Our study indicates that stent graft placement is a feasible and effective approach in the treatment of acute, complicated type B dissections. Most recent reports in the literature contain both complicated and uncomplicated cases, as well as mixed cases of acute and chronic dissections [19, 20]. However, it was well demonstrated recently that controlling hypertension and pain in the initial phase is the optimal approach in the treatment of uncomplicated aortic type B dissections [3]. Therefore, in patients with life-threatening complications of acute type B dissection, stent-graft placement could emerge as the most valid treatment option, with the primary goal being to alleviate severe malperfusion complications as well as aortic rupture and to stabilize the patient in the first phase [21]. Hospital mortality in our series was 12% and is similar to published reports ranging from 3% to 20% [18, 20, 22].

4 Ann Thorac Surg EHRLICH ET AL 2010;90: TYPE B AORTIC DISSECTION MIDTERM RESULTS This mortality rate corresponds to a reported mortality of medically treated patients in historic controls and is better than the expected open surgical mortality for these patients. Effectively, endovascular techniques have shifted these patients from the higher mortality associated with complicated dissection treated surgically to a lower mortality. Nienaber and colleagues [14] even reported in 1999 an early mortality of 0 in 12 patients with descending aortic aneurysm. However, in their series patient profiles and selection were different. Endovascular stent-grafting was not performed as an emergency treatment in a life-threatening situation. This might in part explain the difference in mortality. Our 87% success in excluding the proximal entry tear is commensurate with other published reports of 86% to 98%, although 9 patients required partial or total coverage of the LSA [22, 23]. This maneuver was well tolerated, with no adverse events related to upper extremity ischemia or vertebrobasilar symptoms. In addition, stent-graft placement over the intimal tear can prevent the development of an aneurysm by facilitating complete thrombosis of the false lumen. An important aspect for a satisfactory midterm and long-term outcome is the distance between the LSA and the primary intimal entry tear. If there is a sufficient landing zone and full coverage of the proximal intimal tear can be achieved with the stent-graft, full thrombosis of the false lumen at the level of the stent-graft device should be expected. In contrary, if the proximal intimal tear is very close to the LSA and the stent-graft needs to be placed in the distal aortic arch with coverage of the LSA, the chances of development of a type 1a endoleak are increased. Furthermore, this imperfect stent-graft position can lead to aortic rupture by either erosion of the arterial wall or failure of the proximal seal provided by the stent-graft. Moreover, the misalignment of stent-grafts in angulated aortic arches, together with the high hemodynamic forces in this region, can cause structural instability of the stent-graft and its subsequent collapse [24]. We saw this complication in 1 patient with an early type Ia endoleak. Even after transposition of the LSA with proximal stent-graft extension, the endoleak persisted and the patient died 17 months after the procedure owing to aortic rupture. Another aspect of acute, complicated type B dissection can be the compression of branch vessels by a dynamic or static obstruction. Dake and colleagues [6] reported that restoration of blood flow was sufficient after stent-graft repair in all branch vessels that were compromised exclusively by a dynamic process. In vessels also affected by a static component, deployment of an uncovered stent within the true lumen of the obstructed artery was necessary in 60% of the patients. In our series, additional intraprocedural stenting was necessary in 6 patients (18%) to alleviate persistent obstruction of the true lumen by extension of the intimal flap beyond a vessel s origin. Nevertheless, 4 patients required additional laparotomy as a result of bowel ischemia. Neurologic complications, especially paraplegia, remain the most devastating complications after stent-graft placement or surgical repair of type B aortic dissection. Occlusion of numerous critical intercostal arteries with stent-grafts is widely believed to be responsible for the increased risk of paraplegia. Three patients in our series developed postoperative spinal cord injuries (2 paraparesis and 1 hemiparesis). Length of aorta covered was variable in these patients; thus it is unclear whether this was a contributing factor. Ultimately, spinal cord ischemia is multifactorial, and we have not advocated preemptive lumbar drainage or carotid-subclavian revascularization as a result of the urgent need to treat. Several limitations of the current study need to be addressed. First of all, the lack of a randomized or concurrent control group precluded direct comparison with conventional open repair. In addition, to make any significant conclusions regarding the durability of endovascular therapy, it will be necessary to obtain longer term follow-up information. The currently available data on follow-up outcomes fail to provide precise morphologic information and instead focus on clinical end points. Therefore, distinct morphologic and anatomic long-term surveillance is greatly awaited to analyze any causal relationship between morphology and outcomes of patients. In conclusion, endovascular treatment for acute, complicated type B dissections is associated with acceptable early morbidity and mortality rates in this high-risk patient population. Most of all, closure of the entry tear and stabilization of the true lumen presents a promising alternative treatment option to conventional surgery for relief of life-threatening dissection-related complications. Follow-up data indicate a substantial durability of the procedure with an acceptable freedom from stentgraft related death and secondary interventions. Although preliminary data suggest that stent-graft repair may ultimately become the treatment of choice for these relatively sick patients, long-term surveillance will be crucial to discover complications unique to thoracic endovascular interventions. Most importantly, comparative clinical trials are clearly needed to clarify the role of stent-graft repair in the setting of acute, complicated type B aortic dissection. 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Disappointing results with a new commercially available thoracic endograft. J Vasc Surg 2004;39: INVITED COMMENTARY During the course of the last decade, endovascular treatments have been expanded to address acute aortic catastrophes affecting the descending thoracic aorta including traumatic disruptions, penetrating aortic ulcers, and aortic dissection. Ehrlich and colleagues [1] now present their single-institutional experience of treating 32 acute, complicated type B aortic dissections by thoracic endovascular aortic repair (TEVAR) using a variety of the available stent grafts throughout the decade [1]. In this small series, the majority of patients were treated with TEVAR for malperfusion (22 cases). Their results are commensurate with several other recent reports of treating complicated type B aortic dissection by TEVAR, corroborating the feasibility of this approach. Unfortunately, there has been such considerable variability in defining the clinical characteristics indicating TEVAR in comparison with medical or conventional open surgery in most of these reports that criteria for stent-grafting aortic dissection remain incompletely resolved. What has been established through data accumulated from both the International Registry of Acute Aortic Dissection (IRAD) and the investigation of stent-grafts in patients with type B aortic dissection (INSTEAD) randomized trial is the safety and use of medical management of uncomplicated type B aortic dissection [2, 3]. The International Registry of Acute Aortic Dissection investigators have more recently suggested that TEVAR may impart a reduction in morbidity and mortality for complicated type B aortic dissection (compared with open surgery) and render outcomes similar to those currently achieved with medical management for uncomplicated type B dissection [4]. What has been poorly controlled amidst this dataset and the others published to date has been the issue of defining complicated, making it difficult to determine the true impact of TEVAR (relative to medical management), particularly for the more subjective indications like intractable pain, impending rupture, or radiologically (rather than clinically) defined malperfusion. What we do not know, for example, is whether TEVAR is truly helpful in treating unilateral renal ischemia, a relatively common phenomenon in type B aortic dissection. In Ehrlich and colleagues [1] article, the 32 TEVAR cases included in the report represented 56% of the patients treated with acute type B aortic dissection in their institution during the decade reported. This represents a relatively high percentage of complicated relative to uncomplicated dissections compared with other datasets, such as the International Registry of Acute Aortic Dissection with rates of 20% to 30% [3, 4]. In other words, without more carefully adjudicated indication criteria and optimally a randomized trial for complicated type B aortic dissection, it will remain difficult to clearly define the impact and role of TEVAR for aortic dissection. Despite the amassing data to which Ehrlich and colleagues [1] clearly adds, we still lack understanding of the limits of TEVAR, given the current devices, in its application to acute type B dissection, thereby giving rise to a small but real incidence of retrograde dissection, frank disruption, or worsening malperfusion as a consequence of TEVAR. More comprehensive datasets that distinguish indications, techniques used, and complication rates specific to a given technique or indication are necessary as surgeons continue to push endovascular therapies in more complex 2010 by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc doi: /j.athoracsur