Advances in the Treatment of Acute Type A Dissection: An Integrated Approach

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1 Advances in the Treatment of Acute Type A Dissection: An Integrated Approach Joseph E. Bavaria, MD, Derek R. Brinster, MD, Robert C. Gorman, MD, Y. Joseph Woo, MD, Thomas Gleason, MD, and Alberto Pochettino, MD Division of Cardiothoracic Surgery, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania Background. Acute type A dissections require surgery to prevent death from proximal aortic rupture or malperfusion. Most series over the past decade have reported a death rate in the range of 15% to 30%. The objective of this study is to examine the effect of an integrated surgical approach on the treatment of acute type A dissections. Methods. From January 1994 to April 2002, 163 consecutive patients underwent repair of acute type A dissection. All had an integrated operative management as follows: intraoperative transesophageal echocardiography; hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion to replace the aortic arch; HCA established after 3 minutes of electroencephalographic silence in neuromonitored patients (60%) or after 45 minutes of cooling in patients who were not neuromonitored (40%); reinforcement of the residual arch tissue with a Teflon felt neo-media; cannulation of the arch graft to reestablish cardiopulmonary bypass at the completion of HCA (antegrade graft perfusion); and remodeling of the sinus of Valsalva segments with Teflon felt neo-media and aortic valve resuspension or replacement with a biological or mechanical valved conduit. When HCA times were greater than 50 minutes, antegrade cerebral perfusion is used. Since Februay 1999, Acute type A dissection remains a difficult and catastrophic disease to treat. Surgical treatment has been guided by established principles, which include: (1) resection and replacement of the aortic tear site, usually the ascending aorta or arch; (2) repair or replacement of the aortic sinus segments with false lumen obliteration to treat potential coronary malperfusion and late aortic root abnormalities; (3) resuspension or replacement of the aortic valve; and (4) obliteration of the false lumen at the distal anastomosis and reestablishment of primary flow into the true lumen. There have been many therapeutic and diagnostic advances over the past few years to improve treatment outcomes based on these principles. These include hypothermic circulatory arrest (HCA), open distal anastomosis, native aortic root reconstructive techniques, and advances in circulation management. Presented at the Aortic Surgery Symposium VIII, May 2 3, 2002, New York, NY. Address reprint requests to Dr Bavaria, Division of Cardiothoracic Surgery, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA ; joseph.bavaria@uphs.upenn.edu. BioGlue has been used as an anastomotic adjunct in the repair of type A dissections. Results. Mean age was years, with 68% men and 15% with previous cardiac surgery. Seven percent of patients presented with a preoperative neurologic deficit, and 3% developed a new cerebrovascular accident after dissection repair. The in-hospital death rate was 9.8%. Excluding the patients with preoperative strokes (7%) and those with postoperative stroke (3%), the in-hospital death rate was 6.6%. In 6 patients, prompt changes in circulatory management consisting of switching cannulation sites or cross-clamp release with direct temporary aortic arch fenestration occurred when there were sudden changes in electroencephalogram during cooling. Conclusions. A standardized approach to the treatment of acute type A dissections has improved outcomes. Our 55% mortality in patients with preoperative cerebral vascular accident (CVA) suggests that this group may be candidates for medical or delayed surgical treatment. Conversely, our 6.6% mortality rate for neurologically intact patients warrants aggressive and expeditious surgical intervention. (Ann Thorac Surg ) 2002 by The Society of Thoracic Surgeons Despite many potential therapeutic and diagnostic advances, many large series, including recent ones, reveal a 25% perioperative mortality rate [1 3]. Our own results during the period of 1988 to 1994 showed the same outcome. Our team felt that no single therapeutic advance would significantly impact outcome, but that an integrated approach may reduce morbidity and mortality. In 1994, our institution established a standard perioperative management algorithm for this extremely complex surgical disease (see Table 1). This report examines our outcomes over an 8-year period managing patients with acute type A dissection. Material and Methods A retrospective study was performed on 163 consecutive patients from January 1994 to April 2002 undergoing surgical repair of type A dissections using the aortic Dr Bavaria discloses that he has a financial relationship with Cryolife, Inc by The Society of Thoracic Surgeons /02/$22.00 Published by Elsevier Science Inc PII S (02)

2 Ann Thorac Surg AORTIC SURGERY SYMPOSIUM VIII BAVARIA ET AL S1849 Table 1. Integrated Approach to Operative Management 1. Rapid admission to the operation room for both diagnosis and therapy (bypass the intensive care unit) 2. Intraoperative transesophageal echocardiogram 3. Neurocerebral monitoring (60%) 4. Routine open aortic arch reconstruction with retrograde or antegrade cerebral perfusion (hemi-arch preferred) 5. Routine antegrade arch graft perfusion after completion of arch repair 6. Aortic valve resuspension in most patients when preexisting leaflet or root pathology is absent 7. Creation of an aortic neo-media using either felt or Bioglue to strengthen the aortic and sinus walls and obliterate the false lumen surgery team s standardized perioperative protocol. Follow-up data were obtained from review of the patient charts and from our long-term aortic surgery clinic, where we direct the care of these patients for their entire life. Demographics and Operative Data Mean age was years. There were 111 men (68%) and 52 women (32%) (Table 2). Bicuspid valvular disease was present in 15 patients (9%). All patients with an obtainable blood pressure were included in the study regardless of preoperative malperfusion neurologic deficit or ongoing cardiopulmonary resuscitation. 60% of patients were able to have neurocerebral monitoring (NCM). Operative data are summarized in Table 3. Table 2. Demographics Patients 163 Mean Age (SD) Male 111 (68%) Bicuspid aortic valve 15 (9%) Marfan s/ehlers Danlos 12 (7.3%) Preoperative shock/unstable 24 (15%) Table 3. Operative Data No. Time (minutes) SD CPB time Myocardial ischemic time HCA (with RCP or ACP) time Previous cardiac surgery 24 (15%) Full root replacement 27 (17%) Composite mechanical graft 23 Biological root 4 Extensive/total arch replacement 8 (5%) (elephant trunk) BioGlue used 58 (36%) Neurocerebral monitoring used 97 (60%) ACP antegrade cerebral perfusion; HCA hypothermic circulatory arrest; RCP retrograde cerebral perfusion. Surgical Technique The general surgical approach consisted of rapid transfer to the operating room directly from the helipad or the emergency room without stopping over in the intensive care unit. Transesophageal echocardiogram (TEE) monitoring was used throughout the case for both diagnostic confirmation and therapeutic evaluation. Standard antegrade and retrograde cold blood cardioplegia was used for cardiac protection. Briefly, venous cannulation consisted of standard double-stage right atrial venous cannula connected by a Y connector to a small right-angle, single-stage superior vena cava cannula. In most patients, the femoral artery was utilized for arterial cannulation. Occasionally, the right axillary/ subclavian artery was used for primary arterial cannulation. In 97 (60%) patients, neurocerebral monitoring (NCM) was performed with the use of electroencephalogram (EEG) and somatosensory-evoked potential (SEP) monitoring during the entire operation. Neuromonitored patients were cooled for 3 minutes beyond EEG silence and 3 C below EEG silence, which usually occurred at a nasopharyngeal temperature between 15 C and 20 C [4]. Details of our neurocerebral protocols have been previously described [5, 6]. When NCM was not available, patients were cooled for a total of 45 minutes. The time of 45 minutes was chosen secondary to data from NCM in open aortic arch operations, demonstrating that most patients achieved EEG silence after 45 minutes of active cooling [7]. Additional pharmacological management consists of1gofsolumedrol,1gofmagnesium, and 2.5 mg/kg of lidocaine after initiation of cardiopulmonary bypass (CPB). The ascending aorta was not clamped during the cooling period except when aortic valve insufficiency mandated ascending aortic clamping to prevent left ventricular dilatation. All patients had a left ventricular vent inserted through the right superior pulmonary vein. Once profound hypothermia was achieved, antegrade CPB was interrupted and oxygenated blood at 12 C was infused into the superior vena cava cannula, which was snared between the azygos vein and the right atrial junction. With the patient in slight Trendelenburg position, a retrograde cerebral perfusion RCP pressure of 25 mm Hg was maintained, yielding a flow between 200 and 300 ml/min. The innominate vein was inspected to confirm bilateral jugular venous system inflow. Throughout the RCP period, dark blood emanated from the brachiocephalic arterial orifices, including the left common carotid, implying oxygen extraction. Generally, RCP was used when arch reconstructive time was less than 50 minutes and antegrade cerebral perfusion (ACP) was used when an open aortic arch time was more than 50 minutes. Primary ACP was used in 4% of patients. Using ACP, flow was directed through the innominate and left carotid artery with balloon-tipped catheters to maintain a right radial artery pressure of at least 40 mm Hg. The left subclavian artery was clamped. After completion of ACP or RCP, the entire circulation was then deaired using a brief period of RCP, and the arch graft was cannulated with a standard antegrade graft perfusion technique.

3 S1850 AORTIC SURGERY SYMPOSIUM VIII BAVARIA ET AL Ann Thorac Surg Fig 3. Reconstruction of sinus segments using geometric felt strips as neo-media. (A) Noncoronary sinus. (B) Right coronary sinus. Fig 1. Felt neo-media placed at distal anastomosis during hemiarch reconstruction. Resection of the aortic arch and ascending aorta was undertaken, and a Dacron tube graft was used as a replacement conduit. Felt, BioGlue, or a combination of both were placed between the intima and adventitia to obliterate the false lumen and recreate a neomedia (Figs 1, 2). Hemiarch repair was used in 155 patients (95%) and an extensive or total aortic arch replacement (elephant trunk procedure) was utilized in 8 patients (5%). The primary tear site was resected in all patients. The aortic root was replaced or repaired depending on the pathology present. When repair was deemed possible, the aortic valve leaflets were resuspended utilizing three pledgeted supracommisural sutures. The sinus of valsalva segments were then reinforced with Teflon felt as a neomedia (Fig 3) and more recently, since February 1999, BioGlue was used as an adjunct (Figs 4, 5). In 136 of 163 (83%) patients, the aortic root was repaired, and in 27 of 163 (17%) patients, the aortic root was replaced with either a biological or a mechanical valved conduit (Table 3). Recently, we have used the full-root stentless valve at the aortic root when replacement is necessary. Indications for the replacement of the aortic root included bicuspid aortic valve (n 15), Marfan s syndrome (n 11), Ehlers-Danlos syndrome (n 1), primary abnormalities of the aortic valve leaflets, obvious sinus of valsalva aneurysm, and extension of both the tear and dissection to the aortic valve annulus (Table 4). TEE was utilized in all patients to assess the adequacy of the aortic root repair. Neurocerebral Monitoring NCM was used in 60% of patients. Forty percent of patients without NCM were done at night or at times when the dedicated neurology team was unavailable. Six (3.7%) patients underwent immediate therapeutic changes in the operation secondary to EEG changes after initiation of CPB. These EEG changes were due to malperfusion of arch branches leading to lack of adequate Fig 2. Using BioGlue instead of felt at the distal anastomosis (3-mm thick neo-media ). Fig 4. BioGlue is used to reinforce the sinus segment and obliterate the false lumen. Note the very careful application at the aortic root. Gauze is used inside the aorta to protect the valve leaflets and coronary ostia from any inadvertent spill.

4 Ann Thorac Surg AORTIC SURGERY SYMPOSIUM VIII BAVARIA ET AL S1851 Table 5. Neurocerebral Data Neurocerebral monitored patients 60% Changes in operating room due to EEG changes 3.7% Preoperative stroke 11 (7%) Postoperative stroke 5 (3%) Transient neurological deficit 9.8% so although the diagnosis was incorrect, the therapeutic procedure was necessary and similar. Fig 5. Completed dissection repair with resuspension and anastomotic application of BioGlue. cerebral blood flow. Prompt changes in circulatory management consisted of switching cannulation sites or cross-clamp release with direct temporary aortic arch fenestration. Results Neurologic Outcomes Of the 163 patients undergoing repair, 11 (7%) had sustained a preoperative CVA. Of note, 6 of 11 (55%) of these patients died in the hospital after successful repair of the dissection. Five patients out of the remaining 152 neurologically intact preoperative patients (3.3%) developed focal strokes postoperatively (Table 5). Diagnostic Intraoperative TEE was extremely useful and converted the diagnosis of four prior type A dissections to type B dissections, thereby avoiding median sternotomy. However, one case was misdiagnosed as a type A and was really a ruptured type B. This patient did poorly and died. Two cases were actually ruptured ascending aneurysms, Table 4. Reasons for Not Performing a Valve Resuspension 1. Marfan s syndrome 2. Sinus of valsalva aneurysm 3. Bicuspid valve or primary valve leaflet abnormality 4. Tear into sinus segment (not simply a dissection down to the annulus) Mortality Overall 30-day mortality was 14 of 163 (8.6%). The mortality for all those patients who died while in the hospital from their original surgery including 30-day mortality was 16 of 163 (9.8%). The relationship of patient CVA to mortality is demonstrated by the high mortality of those patients (6/11 [55%]) who presented with a focal stroke before successful repair of their type A dissections. Mortality in those patients who presented neurologically intact, but developed a perioperative stroke, was high as well (20%) (Table 6). In contrast, the mortality rate for patients who presented without focal neurologic deficits was only 10 of 152 (6.6%). Thus, an early, aggressive surgical intervention to attempt to prevent neurologic complications is warranted. Comment We have presented our results of a recent consecutive series of acute type A dissection presentations. Our earlier experiences with this disease, similar to other groups, revealed significant morbidity and mortality with the previous surgical approach to type A dissection. We felt that an integrated and standardized approach to this complicated disease could unify the entire surgical team towards accomplishing the goal of an alive, wellfunctioning patient postoperatively. We borrowed additional systems approaches from other surgical disciplines, especially our Level I Trauma service, and concentrated all expertise necessary for the successful outcome of this type of surgery with the surgical team. This includes intraoperative TEE performed by cardiovascular anesthesia and intraoperative EEG/SEP performed by dedicated operating room noninvasive, neurocerebral monitoring personnel accustomed to the Table 6. Mortality No. Overall 30-day mortality 14/163 (8.6%) In-hospital mortality (30-day mortality all 16/163 (9.8%) in-hospital deaths) In-hospital mortality with Preoperative CVA 6/11 (55%) New postoperative CVA 1/5 (20%) In-hospital mortality without preoperative 10/152 (6.6%) stroke

5 S1852 AORTIC SURGERY SYMPOSIUM VIII BAVARIA ET AL Ann Thorac Surg unpredictability and intensity of the operating room environment. We utilize rapid helicopter transport directly to the operating room whenever possible, bypassing the intensive care unit (ICU) entirely. The operating room then assumed the role of both the diagnostic and the therapeutic suite. Intraoperative TEE is utilized extensively for confirmation of the diagnosis as well as verification of proper circulation management and adequacy of preand postoperative valvular function. NCM is utilized whenever possible, as we believe this provides valuable information regarding dynamic brachiocephalic circulation changes that can occur after initiation of CPB, aortic cross-clamping, or ventricular fibrillation. Additionally, we use flatline EEG as the hard end point for termination of CPB before HCA,regardless of specific cooling time and absolute nasopharyngeal temperature. An open distal anastomosis allows for a more controlled reconstruction of the acutely dissected aorta. We prefer to perform a hemi-arch anastomosis routinely, but will complete a full arch (elephant trunk) if required (eg, significant arch tear), especially in a Marfan s or younger patient. During open arch dissection surgery, our circulation management protocol is to use RCP if arch reconstructive times are expected to be less than 40 to 50 minutes, and to use ACP if times are expected to be more than 40 to 50 minutes. Although focal stroke rates are reportedly equal when comparing ACP with RCP, temporary neurologic dysfunction has been shown to be significantly increased with RCP times more than 50 minutes [7]. We rarely use HCA alone. Aortic valve resuspension is generally preferred, as long as there is no antecedent aortic root pathology. However, we do not hesitate to perform an aortic root replacement if indicated. Recently, we have preferred to use the porcine stentless aortic root bioprosthesis (full root) as our aortic root conduit of choice, as this eliminates the need for coumadin. In addition, the 20-year life expectancy with a DeBakey type I dissection is poor. Meticulous reconstruction of the native aortic root and distally dissected aorta is extremely important to ensure a long-term repair that minimizes later reoperations on the residual aorta. To achieve this, we place geometrically fashioned strips of felt or BioGlue (or both) between the dissected layers of the aorta (Figs 1, 3). This creates an approximately 3-mm neo-media, which is strong and can accept sutures. We avoid felt strips placed on the intimal side or adventitial side of the aortic anastomosis. We have added BioGlue as an anastomotic adjunct during the repair of acute type A dissections since February At a mean of 14 months of follow-up (range, 1 to 38 months), we have no reoperations at the aortic root and two late distal aortic reoperations in the BioGlue subgroup (n 58). In summary, we believe that our standardized approach to the treatment of acute type A dissection has decreased our perioperative morbidity and mortality significantly compared with our previous experience between 1988 and 1994 [1]. Our present data, with a 55% mortality rate in those patients who present with a focal stroke, suggest that this subgroup may be candidates for aggressive medical therapy and possibly delayed surgery. This treatment algorithm could also be supported by recent data documenting a 42% 30-day survival in medically treated acute type A dissections [2]. Conversely, our 6.6% mortality for neurologically intact patients suggests aggressive and expeditious surgical intervention is warranted. This is evident in our protocol, as we bypass the ICU and radiology suites entirely, and directly admit acute type A dissections for the operating room. Finally, the treatment of acute type A dissections, a complex disease process, may benefit from a standardized surgical algorithm in regionally designated centers. References 1. Bavaria JE, Woo YJ, Hall RA, Wahl PM, Acker MA, Gardner TJ. Circulatory management with retrograde cerebral perfusion for acute type A aortic dissection. Circulation 1996; 94(Suppl 9):II 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: Fann JI, Smith JA, Miller DC, et al. Surgical management of aortic dissection during a 30-year period. Circulation 1995; 92(Suppl 9):II Coselli JS, Crawford ES, Beall AC Jr, Mizrahi EM, Hess KR, Patel VM. Determination of brain temperatures for safe circulatory arrest during cardiovascular operation. Ann Thorac Surg 1988;45: Bavaria JE, Woo YJ, Hall RA, Carpenter JP, Gardner TJ. Retrograde cerebral and distal aortic perfusion during ascending and thoracoabdominal aortic operations. Ann Thorac Surg 1995;60: Stecker MM, Cheung AT, Pochettino A, et al. Deep hypothermic circulatory arrest: I. Effects of cooling on electroencephalogram and evoked potentials. Ann Thorac Surg 2001;71: Bavaria JE, Pochettino A, Brinster DR, et al. New paradigms and improved results for the surgical treatment of acute type A dissection. Ann Surg 2001;234: