Asian Cardiovasc Thorac Ann 2004;12:300-305
© 2004 Asia Publishing EXchange Ltd
Surgical Outcome of Subtypes of Aortic Arch Dissection
Kaan Kirali, MD,
Hasan Ardal, MD,
Vedat Erentu
, MD,
Denyan Mansurolu, MD,
Nilgün U Bozbua, MD,
Cevat Yakut, MD
Department of Cardiovascular Surgery, Ka
uyolu Heart and Research Hospital, Istanbul, Turkey
For reprint information contact: Kaan Kirali, MD Tel: 90 216 326 6969 Fax: 90 216 339 0441 Email: imkkirali{at}yahoo.com Department of Cardiovascular Surgery, Kouyolu Heart and Research Hospital, Kadiköy, Istanbul 81020, Turkey.
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ABSTRACT
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This study was conducted to investigate if the site of primary intimal tear involving the aortic arch and the surgical approach affect the early and late results of total aortic arch replacement. Between 1993 and November 2001, 42 patients underwent graft replacement of the total aortic arch for aortic dissection. Their mean age was 51.9 ± 9.8 years, and 38 of them were male. All operations were performed under hypothermic circulatory arrest with retrograde cerebral perfusion. Hospital mortality was 28.6% (12 patients). There were 2 late deaths. Multivariate analysis showed that chronic obstructive pulmonary disease and ascending aortic replacement with or without valve replacement were significant independent determinants of early death. Patients with the intimal tear originating in the ascending aorta showed a tendency towards lower 7-year survival rates than those with a tear at other aortic sites or with multiple tears, while the presence of chronic obstructive pulmonary disease adversely affected early and late outcomes. We conclude that the primary site of an intimal tear that involves the aortic arch affects early and late survival, but concomitant non-cardiac diseases play an even more important role in the early outcome as they increase the complexity of the operation.
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INTRODUCTION
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The goal of radical reconstruction for aortic dissection involving the aortic arch is to re-establish continuity of the true lumen through distal anastomosis. Approaches to total arch replacement include the elephant trunk technique, in which the arch vessels are resected together with an island of arch tissue and then implanted into the tube graft; the semiarch technique, in which the peninsula-shaped aortic arch is anastomosed to the graft; and the isolated total arch replacement. With refinement in thoracic aortic surgery, various cerebral protection methods and aortic arch repair techniques have been developed. The choice of techniques can influence the operative outcome.1–6 Continuous retrograde cerebral perfusion (RCP) via the superior vena cava as an adjunct to hypothermic circulatory arrest (HCA) has the main advantages of allowing adequate time for the precise repair of arch lesions and avoiding cerebral embolism. The safe limit for circulatory arrest is approximately 60 minutes, however we have shown previously that the longer RCP time required for the elephant trunk procedure does not increase early or late mortality.1 On the other hand, the subtypes of acute aortic dissection show different outcomes, with type A dissection involving the arch showing the worst long-term results.7 The aim of this study was to determine the effects that subtypes of aortic arch dissection and the operative procedures have on immediate and long-term surgical outcome.
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PATIENTS AND METHODS
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Patients with intrathoracic aortic dissection scheduled to undergo aortic arch replacement were included in this study. Those who received hemiarch replacement were excluded, as well as cases of aortic dissection not requiring aortic arch replacement, and patients with previous aortic surgery. Patients with type B dissection were referred for surgery only if they fulfilled all of these criteria: intractable pain, rapid or clear enlargement of the aorta, aortic arch dissection with a ruptured or unruptured pseudoaneurysm exceeding 5 cm in size, transient cerebral ischemia, and unsuturable tissue in the aortic arch in hemiarch replacement.
A total of 42 patients undergoing total aortic arch replacement for aortic dissection involving the aortic arch between 1993 and November 2001 were included in this study. There were 38 male (90.5%) and 4 female patients (9.5%) with a mean age of 51.9 ± 9.8 years (range, 33 to 71 years). Diagnosis was confirmed by computed tomography, magnetic resonance imaging, echocardiography, angiography, or a combination of these tools. Acute aortic dissection occurred in 22 patients (52.4%) (group A) and chronic dissection in 20 (47.6%) (group B). The primary site of the intimal tear was as follows: ascending aorta, 18 cases; arch, 5 cases; proximal descending aorta (within 5 cm from the origin of the left subclavian artery), 15 cases; multiple tears, 4 cases (Table 1
).
All patients were operated through a median sternotomy. Femoral arterial cannulation and bicaval cannulation were used routinely. When there was a risk of incision into the aorta upon sternotomy, femorofemoral cannulation and systemic cooling were instituted before sternotomy. Systemic cooling was maintained at between 15°C and 18°C. Barbiturates were administered immediately before the initiation of deep HCA. RCP flow was maintained at 300 mL·min–1 or less and proximal venous pressure at approximately 25 mm Hg to prevent cerebral edema during HCA. After distal anastomosis of the elephant trunk graft to the proximal descending aorta, the aortic arch island containing the brachiocephalic vessels was attached to the graft. When the descending aorta was not involved, only the arch and the ascending aorta or the arch alone was replaced. The brachiocephalic vessels were again preserved with an island of arch tissue, and they were reimplanted after end-to-end distal anastomosis of the graft to the proximal edge of the descending aorta had been made. Replacement of the aortic root with the ascending aorta was performed using modifications of the Bentall procedure (button and flanged techniques), while isolated ascending aortic dissection was treated by supracoronary replacement of the ascending aorta. The surgical procedures performed are listed in Table 2. Mean aortic crossclamp time was 116.7 ± 26.5 minutes (range, 73 to 197 minutes), mean cardiopulmonary bypass time was 179.4 ± 44.0 minutes (range, 112 to 325 minutes), and RCP time was 63.7 ± 16.7 minutes (range, 22 to 109 minutes).
Postoperatively, all patients had echocardiography or magnetic resonance imaging performed annually over a period ranging from 0.6 to 7.4 years (mean, 2.5 ± 2.3 years).
Data were statistically analyzed using SPSS for Windows version 10.0 (SPSS, Inc., Chicago, IL, USA). Continuous data are expressed as mean ± standard deviation. The chi-squared test and Student’s t test were employed for univariate analysis, and forward stepwise logistic regression for multivariate analysis. Independent risk factors of early and late outcome were examined by univariate and multivariate analyses. Survival was estimated by the Kaplan-Meier method, and the differences between survival curves were tested with a log-rank test. Event-free rates are presented as mean ± standard error of the estimate. Statistical significance is defined as p < 0.05.
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RESULTS
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The overall hospital mortality rate was 28.6%, or 12 patients (Table 3). The last 3 patients died in the intensive care unit in the first 60 days. Death occurred in 5 of 13 patients (38.5%) who underwent the elephant trunk procedure and supracoronary ascending aortic replacement, 3 of 15 patients (20%) who had the elephant trunk graft without ascending aortic replacement, 2 of 5 patients (40%) who received isolated aortic arch replacement, and 2 of 5 patients (40%) who received a composite graft of the ascending aorta with a valve. Hospital mortality rates were similar in both groups (27.3% in group A, 30.0% in group B), but they were significantly different among the dissection subtypes (ascending aorta, 44.4% mortality; descending aorta and arch, 20.0%; multiple tears, 0%; p < 0.05). Hemodynamic instability, chronic obstructive pulmonary disease (COPD), and renal insufficiency were preoperative risk factors for early death (Table 4). Patients without these risk factors (n = 23) had significantly better outcome than those with these risk factors (n = 19) (8.7% versus 52.6% mortality, p = 0.002). Stepwise logistic regression analysis showed that COPD and ascending aortic replacement were significant predictors of hospital mortality (Table 5).
There were 2 late deaths (6.7%), both in group A (Table 3
). The 1st patient was operated on for type A aortic dissection and the whole thoracic aorta was replaced with an elephant trunk graft. Infective endocarditis developed at the anastomotic site between the distal ascending aorta and the prosthetic graft 3 years after the operation. The main finding was a steep gradient in the ascending aorta. He died during urgent re-operation. The 2nd patient died from rupture of a newly developed descending aortic aneurysm. Univariate analysis showed hemodynamic instability ( p < 0.001) and graft infection ( p < 0.03) as significant predictors of late mortality. Actuarial survival for all patients was 62.3% ± 8.6% at 5 years (mean, 4.9 ± 0.5 years; 95% confidence interval, 3.9 to 6.0 years).
Comparisons of survival at 7 years were not significantly different between acute and chronic dissection (57.8% ± 12.1% versus 70.0% ± 10.2%), having and not having elephant trunk procedure (58.3% ± 9.7% versus 80.0% ± 12.6%), having and not having ascending aortic replacement (48.5% ± 12.2% versus 80.0% ± 8.9%), and elective and urgent operation (32.0% ± 17.0% versus 75.0% ± 7.6%). Survival at 7 years of patients with the primary intimal tear in the ascending aorta (34.7% ± 13.9%) was lower than those with the tear in the descending aorta (80.0% ± 10.3%) or the aortic arch (80.0% ± 17.9%) or those with multiple tears (100%), but the difference between the first group and the others did not reach statistical significance (Figure 1). Moreover, patients with COPD had significantly worse early and late outcomes (Figure 2).
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Figure 1. Actuarial freedom from death according to the location of the intimal tear in the aorta (log-rank, p = 0.06).
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Figure 2. Acturial freedom from death in the presence or absence of chronic obstructive pulmonary disease (COPD) (log-rank, p = 0.003).
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Postoperatively, 33 patients showed signs of normal awakening from anesthesia within 8 hours after surgery, while 9 patients (21.4%) experienced neurologic complications. One of the cases (2.4%) was fatal, while 2 were temporary cerebral events and 6 were minor neurologic events. There were 2 cases of delayed awakening and difficulty in comprehension. Another 2 patients had vocal cord paralysis. Univariate analysis determined that diabetes mellitus ( p = 0.03), RCP time ( p = 0.04), and COPD ( p = 0.06) were important predictors of early neurologic events. Stepwise logistic regression analysis revealed that diabetes mellitus ( p = 0.06) and RCP time ( p = 0.05) were important risk factors for early neurologic events (Table 5).
Eight patients (19.0%) had postoperative pulmonary complications. Three (7.1%) of them had adult respiratory distress syndrome and all died. Nonfatal pulmonary complications developed in the other 5 patients (11.9%), which healed without any sequelae. Univariate and stepwise logistic regression analyses showed that COPD was a significant risk factor for early pulmonary complications (Table 5).
Other early complications were renal failure in 4 patients (9.5%), 2 of whom died, and low cardiac output syndrome in 7 patients (16.7%), 6 of whom died.
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DISCUSSION
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The most useful classifications of aortic dissection were developed by DeBakey and the Stanford group, but both are inadequate for defining the treatment approach and outcome in terms of the intimal tear site. Often it is assumed that the tear is above the commissura in type A dissection and in proximity to the left subclavian artery in type B dissection, but other patterns are also common.7 The DeBakey classification does not include a category for a tear in the arch, and the Stanford system is independent of the location of the tear. Perhaps a new classification should be described for aortic dissection involving the aortic arch to define risk factors and surgical strategies. A new subclassification under the Stanford system has been reported, but it is used only for acute type A dissection.7 We have modified this new subclassification adapting it for aortic arch dissection requiring total arch replacement. We have found that the aortic arch is frequently involved in ascending or descending aortic dissection, whereas isolated arch dissection is less common.
In the present study, we observed that ascending aortic dissection involving the arch had the lowest survival rate, but the type of surgical procedure performed did not significantly affect long-term survival. Recent technical improvements have made concomitant procedures safer for patients with extended aortic dissection.3 However, a patent distal false lumen is still the main reason for re-operation in aortic dissection.8 The reported early mortality rates for acute aortic dissection range from 6.2% to 25%.3,9–12 Kazui and associates13 reported that in patients with significant preoperative risk factors early mortality increased to 60%–70%. It is clear that the severity of the dissection and concomitant noncardiac diseases before the operation affect surgical outcome. Our overall operative mortality (28.6%) was higher than reported rates, but patients without preoperative risk factors had a significantly better outcome than those with these risk factors (8.7% versus 52.6%).
Ascending aortic replacement and COPD could both be risk factors for cardiac failure and pulmonary insufficiency, which were the main causes of early death in this study. Although COPD or smoking was not shown to be a risk factor for rupture of thoracic aortic aneurysm,14 COPD was found to be a significant risk factor for coronary bypass surgery or reintubation.15,16 Moreover, while most studies show several preoperative risk factors for surgery on acute aortic dissection, pulmonary complications are usually observed to be a significant postoperative risk factor for mortality or morbidity.17 Okita and associates6 found COPD a risk factor for mortality after aortic arch operations, and in the present study COPD was a significant risk factor for early and late outcome after total arch replacement for dissection. The introduction of COPD as a variable may have obscured the significance of smoking, and therefore we still urge patients with aneurysm or risk factors (Marfan syndrome, medial degeneration, and hypertension) to stop smoking. We have reported recently that extensive aortic surgery in patients with Marfan syndrome did not negatively affect the outcome.18 In this study, we did not find Marfan syndrome a risk factor.
The most important complication of aortic arch surgery is neurologic dysfunction, which occurs in 25% to 30% of patients operated under HCA or RCP. Age, duration of HCA, and atherosclerotic aneurysms were shown to be risk factors for neurologic impairment.5,6 In recent years, the use of RCP has generally produced favorable results. The advantages of this technique include diffuse cerebral cooling, flushing out of metabolites, prevention of potential embolism, and allowing a much longer time for aortic arch surgery. However, it is clear that RCP does not meet the metabolic demand of the brain. Nevertheless, it allows the extension of HCA time. The temperature of the central nervous system is a more important factor for improved outcome after aortic arch operations. While some studies reported that prolonged HCA and RCP (> 60 minutes) were not risk factors for mortality or stroke in patients undergoing aortic arch surgery,6,19 another study revealed that longer RCP time (between 60 and 90 minutes) was of marginal significance in determining mortality.20 We did not find that prolonged RCP (> 60 minutes) during aortic arch surgery affected early survival, but it increased early neurologic events, confirming our earlier findings.1 Shorter RCP time (< 60 to 65 minutes) is thus recommended.
In summary, aortic arch dissection of ascending aortic origin adversely affects surgical outcome, and associated complications also raise the surgical risk. Preoperative risk factors must be investigated carefully in all patients undergoing aortic arch replacement, and specific attention should be paid to the pulmonary system as preoperative pulmonary dysfunction can cause serious complications after such complex surgical procedures.
Presented at the 51st International Congress of the European Society for Cardiovascular Surgery, Helsinki, Finland, June 28–July 1, 2002, and the 8th Aortic Surgery Symposium, New York, May 2–3, 2002.
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ABSTRACT
INTRODUCTION
