The morbidity and mortality rates associated with the. Outcome of Surgical Treatment in Patients With Acute Type B Aortic Dissection

Outcome of Surgical Treatment in Patients With Acute Type B Aortic Dissection Tomoki Shimokawa, MD, Kazutaka Horiuchi, MD, Naomi Ozawa, MD, Kenu Fumimoto, MD, Susumu Manabe, MD, Tetsuya Tobaru, MD, and Shuichiro Takanashi, MD Departments of Cardiovascular Surgery and Cardiology, Sakakibara Heart Institute, Tokyo, Japan Background. Surgery for acute type B aortic dissection is associated with significant mortality and morbidity. The purpose of this study was to assess the clinical outcome of surgical management of complicated acute type B aortic dissection. Methods. During the last 5 years, 112 patients were admitted for acute type B aortic dissection. Of these patients, 24 consecutive patients were enrolled who underwent surgical management during the acute or subacute stage. The mean age was 66.7 9.1 years; 8 patients were female. Indications for surgery were rupture in 10 patients, impending rupture in 7, and malperfusion in 7. Fifteen patients were transferred from another hospital. The overall clinical outcome including morbidity, aortarelated events, and death were retrospectively assessed. Results. The mean duration from the time of onset to surgery was 7.1 9.0 days. Graft replacement of the aorta included the total aortic arch with cerebral perfusion in 6 patients, and replacement of the distal aortic arch or descending aorta with left heart bypass in 12. The remaining 6 patients underwent peripheral bypass for ischemia. Significant complications occurred in 7 patients (24.8%). The operative mortality rate was 8.3% (2 of 24); 5.6% (1 of 18) with central operation and 16.7% (1 of 6) with peripheral operation. The 5-year survival rate was 82.6 7.9% and freedom from aorta-related events at 1 and 5 years were 95.2% 4.7% and 68.0% 16.6%, respectively. Conclusions. Surgical management of patients with complicated acute type B dissection has an acceptable perioperative risk and survival. This study suggests earlier surgery with left heart bypass may be beneficial for appropriate patients. (Ann Thorac Surg 2008;86:103 8) 2008 by The Society of Thoracic Surgeons The morbidity and mortality rates associated with the surgical management of acute type B aortic dissection (AD) still remain high, despite improved surgical techniques and perioperative care [1 3]. For this reason, the optimal initial management, especially in complicated cases of acute type B AD, has been unclear. Thus, the purpose of this study was to report early and intermediate surgical outcomes for acute type B AD. Patients and Methods Accepted for publication Feb 29, 2008. Address correspondence to Dr Shimokawa, Department of Cardiovascular Surgery, Sakakibara Heart Institute, 3-16-1 Asahicho, Fuchu City, Tokyo, 183-0003, Japan; e-mail: tshimokawa-circ@umin.ac.jp. Between January 2002 and March 2007, 112 symptomatic patients with type B acute AD were treated at Sakakibara Heart Institute. Of these patients, 24 consecutive patients (24%) were enrolled who were treated surgically during the acute or subacute stage (within 8 weeks after the onset of pain) [4]. Patients with chronic dissection or retrograde type A dissection were excluded. The overall clinical outcome data were recorded in a database, and the main endpoints were morbidity, aorta-related events, and death. Data analysis was approved by the Institutional Review Board, and the Board waived the need for patient consent. Aortic dissection was classified as type B according to the Stanford classification if the dissection did not involve the ascending aorta [4]. Intramural hematoma was defined as a dissecting membrane without any degree of patency of the false lumen. All patients had medical therapy to reduce blood pressure after hospitalization as part of our standard protocol. Patients were treated in the cardiovascular care unit with continuous arterial pressure monitoring, central venous access for administration of intravenous antihypertensive medications, and urine output monitoring through a bladder catheter. To obtain adequate blood pressure control with the goal of systolic blood pressure less than110 mm Hg, -blockers, calcium-channel blockers, and nitroglycerin were used intravenously. Pain resolved with blood pressure control and analgesia in most cases. Surgery was considered if there was rupture, impending rupture, or malperfusion, based on serial clinical evaluations and computed tomographic (CT) scans in the immediate or subacute phase. Signs of impending rupture included recurrent intractable pain, CT evidence of rapid aortic expansion ( 55 mm), or the presence of a new ulcerlike projection despite medical therapy. Malperfusion of an aortic branch was 2008 by The Society of Thoracic Surgeons 0003-4975/08/$34.00 Published by Elsevier Inc doi:10.1016/j.athoracsur.2008.02.098

104 SHIMOKAWA ET AL Ann Thorac Surg ACUTE TYPE B AORTIC DISSECTION SURGERY OUTCOME 2008;86:103 8 Table 1. Preoperative Findings Central (n 18) Peripheral (n 6) Age (years) 66.2 8.5 68.2 9.1 Sex (male/female) 13/5 3/3 DeBakey type IIIa 7 0 IIIb 11 6 Intramural hematoma 9 0 Operative indication Rupture 10 Impending rupture 7 Ischemia leg 4 Renal and leg 1 1 Superior mesenteric 1 artery and leg Duration from onset to operation (days) 9.3 9.5 (0 30) 0.7 1.1 (0 1) Table 2. Operative Findings in Patients With Central Value Entry site Arch 1 Distal arch 13 Descending aorta 1 Unknown 3 Rupture site 4T 1 8T 1 Unknown 8 Procedure Arch replacement 6 Distal arch and descending replacement 10 Descending replacement 2 Proximal clamp Ascending aorta 1 Arch 10 Distal arch 2 No 5 Distal clamp Descending aorta 12 No 6 Table 3. Operative Findings in Patients With Peripheral Value Procedure Abdominal aorta fenestration 2 Abdominal aorto both external iliac bypass 3 Axillo both femoral bypass 1 Femorofemoral bypass 2 Superior mesenteric artery bypass 1 (saphenous vein graft) defined by clinical abnormalities detected by clinical symptoms, physical examination, or imaging studies. The mean patient age was 66.7 9.1 years (range, 47 to 79), and 8 (33.3%) were women. After diagnosis of AD on CT scan, 15 patients (62.5%) were transferred from another hospital. Twelve patients (50.0%) were admitted within 3 hours after the onset of symptoms, and 18 (75.0%) were admitted within 6 hours. Indications for surgery were rupture in 10 patients (41.7%), impending rupture in 7 (24.8%), and malperfusion in 7 (24.8%). In the rupture patients, CT scan on admission revealed mediastinal hematoma in 9 patients and hemothrax in 7 (left in 5, bilateral in 2). One patient was intubated, and 3 were in cardiogenic shock with a systolic blood pressure of 80 mm Hg or less. The remaining patient had severe chest pain and hemothrax 9 days after hospitalization. In the impending rupture patients, serial CT scan revealed rapid aortic expansion in 3 patients with a mean aortic diameter 58.3 2.5 mm and presence or marked extension of ulcerlike projection in 4 during the medical therapy. In the malperfusion patients, severe leg pain without a peripheral pulse occurred at the time of onset in 4 patients and after hospitalization in 2. The remaining patient had acute renal failure and lower limb ischemia on admission. The CT scan showed a narrowing of the true lumen caused by thrombosed dissected lumen at proximal descending aorta. Surgery was performed during the acute stage (within 2 weeks after the onset of pain) in 19 (79.2%) and the subacute stage (from 2 to 8 weeks) in 5 (20.8%). Twenty procedures were performed emergently, 3 were performed urgently, and 2 were considered elective. Preoperative patient characteristics are shown in Table 1. Operative Techniques In patients with rupture, impending rupture, or central ischemia, the graft replacement between the distal aortic arch and descending thoracic aorta was performed through a left thoracotomy. Left heart bypass with lowdose heparin was performed as circulatory support during aortic cross-clamping. The flow rate was maintained at 2.0 to 3.0 L/min with a mean pressure in the femoral artery greater than 60 mm Hg; activated coagulation time was controlled to approximately 250 to 300 s with a core temperature of 34 C. In all patients, the proximal clamp was placed between the left carotid artery and left subclavian artery or nondissected descending aorta. The proximal aortic stump just beneath the left subclavian artery was anastomosed to a woven Dacron (C.R. Bard, Haverhill, PA) graft with reinforcement using Teflon (Impra Inc, subsidiary of L.R. Bard, Tempe, AZ) felt, and the distal end of the graft was anastomosed to the true lumen with reinforcement using Teflon felt. Normally, intercostal arteries were sacrificed from T3 to T7 and preserved from T8 to T12. The patients who had a ruptured distal aortic arch on CT scan were indicated for total aortic arch replacement. Most of these patients were

Ann Thorac Surg SHIMOKAWA ET AL 2008;86:103 8 ACUTE TYPE B AORTIC DISSECTION SURGERY OUTCOME cooled to a core temperature of 22 to 25 C. After institution of antegrade cerebral perfusion, a separate elephant trunk graft was fixed to the true lumen using Teflon felt just distal to the site of intimal tear and rupture without distal clamping. Subsequently, a fourbranched arch graft was anastomosed to the stump with the elephant trunk graft, arch vessels, and proximal nondissected aorta. In patients with leg ischemia, anatomical bypass or extra-anatomical bypass was indicated depending on the patient s condition. After the operation, the blood pressure was controlled in all surgical patients. Follow-Up and Statistical Analysis Follow-up was 96% because data on 1 patient were lost during the follow-up period. Computed tomography studies were obtained before discharge, 6 months after surgery, and annually thereafter. Analysis was complete for patients to an endpoint of either death or completion of the study (November 30, 2007). The mean follow-up time was 28.1 14.8 months (range, 10.3 to 68.1). All statistical analyses were performed using a statistical software program (SPSS Inc, Chicago, IL). The Kaplan- Meier method was used to calculate the cumulative survival rate. Continuous data are expressed as the mean standard deviation. Results Operative Findings The mean duration from the time of symptom onset to surgery was 7.1 9.0 days (range, 0 to 30). Graft replacement of the thoracic aorta was performed in 18 patients; for rupture in 10, impending rupture in 7, and ischemia in 1. Resection of the aorta included the total aortic arch in 6, distal aortic arch and descending aorta in 10, and descending aorta in 2. Concomitant procedures were reconstruction of the left subclavian artery in 1 and intercostal artery in 1. According to preoperative CT scan, intraoperative transesophageal echocardiography, and surgical findings, the entry site was identified in 15 patients (83.3%). The location of the entry was in the aortic arch in 1 patient, distal aortic arch in 13, and descending aorta in 1. However, the site of rupture was identified in only 2 of the 10 patients with aortic rupture. All patients had blood transfusion. Operative findings in the central operation patients are shown in Table 2. The remaining 6 patients underwent surgical intervention for ischemia, extra-anatomical bypass in 3, and infrarenal aortoiliac bypass in 3. In 2 patients, aortic fenestration at the infrarenal abdominal aorta did not improve limb ischemia, and therefore an additional graft bypass was performed. All patients recovered from ischemia. Operative findings in the peripheral operation patients are shown in Table 3. Early Morbidity and Mortality The average stay in the intensive care unit and hospital after surgery was 2.9 2.2 days and 28.3 20.8 days, Table 4. Outcome and Follow-Up Computed Tomography Study Central Peripheral Complication Respiratory failure 2 Mediastinitis 1 Dialysis 1 Paraparesis 1 Bleeding 1 Rupture 1 Outcome In-hospital death 1 1 Late death 2 Aorta-related event Thoracoabdominal aorta 1 replacement Distal arch replacement 1 State of aorta on computed tomography Patent false lumen 6 4 Normal aorta 9 105 respectively. Significant complications occurred in 7 patients (24.8%): pulmonary failure (defined as need for mechanical ventilation for more than 48 hours postoperatively) in 2 patients (8.3%), renal failure (defined as need for hemodialysis) in 1 (4.2%), bleeding requiring operation in 1 (4.2%), paraparesis in 1 (4.2%), mediastinitis in 1 (4.2%), and wound infection in 2 (8.3%). There were 2 in-hospital deaths, 1 of mediastinitis within 4 months and 1 of rupture within 12 days of surgery. The operative mortality rate was 8.3% (2 of 24); 5.6% (1 of 18) among patients with central operation and 16.7% (1 of 6) among patients with peripheral operation. Early outcomes are shown in Table 4. Survival and Late Follow-Up There were 2 late deaths. One patient who had emergent distal arch replacement using left heart bypass for rupture and was discharged without complications died suddenly 3 months after surgery. Postoperative CT scans at 1 week and 2 months after surgery showed a residual patent false lumen in the distal descending aorta, and the maximum aortic diameter was 37 mm. However, because a significant problem was not found at the site of anastomosis, we classified this death as aorta-related. The other patient died owing to bleeding of a gastric ulcer 1 month after surgery. The 5-year survival rate was 82.6% 7.9%. Two patients required aorta-related reoperations: expanding distal thoracoabdominal aorta (9T to aortic bifurcation) at 2 years and expanding distal aortic arch at 2 years. Freedom from aorta-related events at 1 and 5 years were 95.2% 4.7% and 68.0% 16.6%, respectively. The survival and freedom from aortarelated events are shown in Figure 1. Follow-up CT scans or magnetic resonance imaging scans were available in 20 patients. In patients with central operation, a patent

106 SHIMOKAWA ET AL Ann Thorac Surg ACUTE TYPE B AORTIC DISSECTION SURGERY OUTCOME 2008;86:103 8 Fig 1. (A) Survival and (B) freedom from aorta-related events. false lumen was identified in 6 patients with a mean diameter 37.8 4.7 mm. The remaining patients had a normal distal aorta. In patients with peripheral operation, all patients had a patent false lumen with a mean diameter 38.3 6.6 mm. Late outcomes and the results of CT scan during follow-up are shown in Table 4. Comment For uncomplicated acute type B AD patients, medical management is currently the preferred method of treatment, with a very low mortality rate of 0% to 7.4% [1 3]. Complicated patients, however, including those with rupture, impending rupture (persistent symptoms, rapidly expanding false lumen, new ulcerlike projection), or malperfusion often require more aggressive approaches. Although this study was performed as a singleinstitution series with a small number of patients, the results indicate that surgical management is associated with acceptable outcomes for complicated acute type B patients. This study provides current data for surgical management, and it is important to compare these results with the results of alternative treatment strategies in this cohort. In 384 patients with acute type B AD in the International Registry of Acute aortic dissection (IRAD), inhospital mortality was 13%, with most deaths occurring within the first week [5]. A risk prediction model controlling for age and sex identified hypotension/shock, absence of chest/back pain on presentation, and branch vessel involvement to be associated with an increased risk of in-hospital mortality. In our experience with all acute type B AD patients, overall hospital mortality was 3.6% (4 of 112): 2.3% (2 of 88) when medical management was maintained. According to another IRAD report that analyzed 82 patients who required surgery for acute type B AD, the overall in-hospital mortality was 29.3% [6]. Independent predictors of surgical mortality were age greater than 70 years and preoperative shock/ hypotension. The report concluded that different indications for surgery produce different operative results, and preoperative evaluation of type B patient permits an assessment of surgical risk, similar to type A dissections. In this study, the overall operative mortality rate was 8.3%; 10.0% with rupture, 0% with impending rupture, and 14.3% with malperfusion. These findings suggest that early surgery is appropriate for selected patients in the acute and subacute phase of type B dissection. There is still controversy concerning the optimal surgical method. Currently, we perform distal arch replacement with left heart bypass or total arch replacement with antegrade cerebral perfusion as a central operation. In this study, there were no operative deaths in patients after graft replacement with left heart bypass. The use of low-dose heparin and left heart bypass with mild hypothermia may have reduced the incidence of fatal complications in the present study. Trimarchi and coworkers [6] noticed that hypothermic circulatory arrest may have been helpful in improving surgical results and recommended the avoidance of aortic clamping between the left common carotid artery and left subclavian artery, which is not safe in cases of fragile acute aortic dissection. However, their data confirmed that a longer hypothermic circulatory arrest time was correlated with a poor outcome, and cerebral perfusion showed a trend for improved outcome. Lansman and colleagues [7] reported their series of 34 consecutive patients undergoing surgery for acute type B AD with no operative mortality and a low incidence of paraplegia. Hypothermic circulatory arrest was employed in only 16 patients during proximal clamping. We believe that the proximal clamp can be safely placed in most patients with acute type B AD when dissection does not involve the aortic arch. Previous studies support our experience that arteriosclerosis in patients with AD is less common than in patients with aortic aneurysm [8]. Total aortic arch replacement was indicated in patients with retrograde dissection and limited rupture of the distal arch. However, particular attention should be paid to distal clamping because in most cases the clamp is placed at the dissected distal descending aorta. Although Lai and coworkers [9] showed no difference in outcome with cross-clamping versus open distal repair with deep hypothermic circulatory arrest after repair of acute type

Ann Thorac Surg SHIMOKAWA ET AL 2008;86:103 8 ACUTE TYPE B AORTIC DISSECTION SURGERY OUTCOME A AD, further follow-up investigation will be necessary to justify our belief. To restore limb perfusion, aortic grafting, aortic fenestration, or extra-anatomic bypass can be selected. However, because the pulse was sometimes restored spontaneously, optimal surgical management remains controversial. Panneton and coworkers [10] reported the effectiveness of aortic fenestration for organ or limb ischemia. However, in 2 of our patients undergoing open fenestration, perfusion of the limb did not recover. Thus, we performed further graft bypass. We speculate that if the pseudolumen was thrombosed at the stenotic portion, proximal abdominal fenestration did not resolve the limb malperfusion. Anatomical or extra-anatomical bypass provided good results in such patients. However, Hsu and associates [1] reported that 3 of 8 patients undergoing extra-anatomic bypass died of central aortic rupture. Thus, medical management is also important in all surgical patients. For patients presenting with life-threatening complications, percutaneous catheter-based techniques of fenestration or stent-grafting have been reported to have potential advantages over surgery [11]. However, complications of stent implantation, such as occlusion of the left subclavian artery, inadequate device placement, and proximal type 1 endoleak, have been documented [12]. Despite a difference in in-hospital mortality rates with different management strategies (32% with surgery, 7% with endovascular techniques, and 10% with medical therapy alone), the IRAD confirmed that the in-hospital management strategy did not appear to impact long-term survival rates in patients discharged from the hospital [13]. We did not perform endovascular procedure for acute AD because of technical limitation. There are a few limitations of this study. The size of the cohort was relatively small and the follow-up period was short. Moreover, this study was a single-institution retrospective study and there was no control group. Further randomized, controlled studies are needed to address the best therapeutic strategy for complicated acute type B AD and factors associated with optimal short- and longterm outcomes. In summary, this study reviewed our recent 5-year experience with surgical treatment of acute type B AD. Surgical management in patients with complicated acute type B dissection has an acceptable perioperative risk and survival. This study suggested earlier surgery with low-dose heparin and left heart bypass under mild hypothermia may be beneficial in appropriate patients. This study could not have been performed without the support and cooperation of the medical and nursing staff of the intensive care and cardiovascular care units of Sakakibara Heart Institute. The authors also thank Dr Yusuke Watanabe for contributions to this study. References 107 1. Hsu RB, Ho YL, Chen RJ, Wang SS, Lin FY, Chu SH. Outcome of medical and surgical treatment in patients with acute type B aortic dissection. Ann Thorac Surg 2005;79: 790 4. 2. Estrera AL, Miller CC III, Safi HJ, et al. Outcomes of medical management of acute type B aortic dissection. Circulation 2006;114(Suppl):I384 9. 3. Nienaber CA, Eagle KA. Aortic dissection: new frontiers in diagnosis and management: part II: therapeutic management and follow-up. Circulation 2003;108:772 8. 4. Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections. Ann Thorac Surg 1970;10:237 47. 5. Suzuki T, Mehta RH, Ince H, et al. Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD). Circulation 2003;108(Suppl 1):II312 17. 6. Trimarchi S, Nienaber CA, Rampoldi V, et al. Role and results of surgery in acute type B aortic dissection: insights from the International Registry of Acute Aortic Dissection (IRAD). Circulation 2006;114:357 64. 7. Lansman SL, Hagl C, Fink D, et al. Acute type B aortic dissection: surgical therapy. Ann Thorac Surg 2002; 74(Suppl):1833 5. 8. Silence J, Collen D, Lijnen HR. Reduced atherosclerotic plaque but enhanced aneurysm formation in mice with inactivation of the tissue inhibitor metalloproteinase-1. Circ Res 2002;90:836 7. 9. Lai DT, Robbins RC, Mitchell RS, et al. Does profound hypothermic circulatory arrest improve survival in patients with acute type an aortic dissection? Circulation 2002;106: I218 28. 10. Panneton JM, Teh SH, Cherry KJ Jr, et al. Aortic fenestration for acute or chronic aortic dissection: an uncommon but effective procedure. J Vasc Surg 2000;32:711 21. 11. Dake M, Kato N, Mitchell RS, et al. Endovascular stent-graft placement for the treatment of acute aortic dissection. N Engl J Med 1999;340:1524 31. 12. Tailor PR, Gaines PA, McGuinness CL, et al. Thoracic aortic stent graft early experience from two centres using commercially available devices. Eur J Vasc Endovasc Surg 2001; 22:70 6. 13. Tsai TT, Fattori R, Trimarchi S, et al. Long-term survival in patients presenting with type B acute aortic dissection. Insights from the International Registry of Acute Aortic Dissection. Circulation 2006;114:2226 31. INVITED COMMENTARY The authors [1] assessed the clinical outcome of surgical management of complicated acute type B aortic dissections. This is a valuable report, especially because endovascular therapy ostensibly has emerged as the therapy of first choice for this particular acute aortic syndrome. One of the major messages that this report adds to our understanding is that conventional therapy of complicated acute type B dissections is an indispensable part of the surgeon=s armentarium for managing this complex entity. As shown in this report, the logistics of the operation have been standardized, and because deep hypothermic circulatory arrest is no longer a prerequisite, the major concerns of conventional therapy have been attenuated. 2008 by The Society of Thoracic Surgeons 0003-4975/08/$34.00 Published by Elsevier Inc doi:10.1016/j.athoracsur.2008.04.037