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Ann Thorac Surg 1995;59:1195-1199
© 1995 The Society of Thoracic Surgeons
Department of Cardiovascular Surgery, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo, Japan
Accepted for publication February 6, 1995.
| Abstract |
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| Introduction |
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We have performed surgical treatment of type A aortic dissection for more than 20 years [1012]. The purpose of this investigation is to evaluate the change in surgical results of type A aortic dissection with the introduction of retrograde cerebral perfusion.
| Material and Methods |
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In this investigation, the type of aortic dissection was classified according to the Stanford criteria [13, 14], and 102 cases were selected as Stanford type A aortic dissection involving the ascending aorta. With respect to the timing of operation, aortic dissection was defined as acute in patients who had received surgical treatment within 14 days after the onset of symptoms. Twenty-seven patients had acute type A dissection and 75 had chronic type A. Of 100 patients, 29 patients (29.0%) had Marfan's syndrome [15].
All patients gave informed consent, and the institutional committee on human research approved the present study protocol.
Intraoperative Circulatory Support
Concerning circulatory support during operation on aortic dissection, several types of assisted circulation have been used over the last 20 years [10, 11]. In patients with type A dissection, total cardiopulmonary bypass with simple aortic cross-clamp was performed in the initial years, and cardioplegia was introduced in 1977 [16]. In type A patients with an arch tear, temporary bypass between arch branches or hypothermic circulatory arrest was used by February 1985, antegrade selective cerebral perfusion [10] (Fig 1
) was applied since March 1985, and retrograde cerebral perfusion [17] (Fig 2
) was introduced in November 1990.
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Operative Techniques
In operations for type A aortic dissection, the ascending aorta to the aortic arch was exposed through a median sternotomy. Cardiopulmonary bypass with femoral arterial perfusion was performed under moderate (26° to 28°C) or deep (18° to 20°C; with aortic arch repair) systemic hypothermia. Since 1977, intermittent crystalloid cardioplegia (every 30 to 40 minutes), continuous coronary perfusion of cold blood (4°C), and topical cooling with ice slush were performed for myocardial protection during aortic cross-clamping. Composition of the cardioplegic solution was 50 g/L glucose, 20 U/L insulin, 20 mEq/L potassium chloride, 8.3 mEq/L sodium bicarbonate, and 4.4 g/L mannitol.
The ascending aorta was incised longitudinally, and the intimal tear, aortic wall dissection, both coronary orifices, and the aortic valve were examined closely. In standard cases without extended dissection beyond coronary orifices, the proximal aortic cuff just above the coronary orifices was oversewn with double-layered Teflon felts before the anastomosis was performed with a tubular woven Dacron graft. Shape and coaptation of the aortic valvular cusps were evaluated, and aortic valvuloplasty or aortic valve replacement was applied if necessary. If annuloaortic ectasia and aortic regurgitation were observed with aortic dissection, the whole aortic root was reconstructed with a composite graft by original or modified Bentall's procedure [18, 19].
In patients without aortic arch reconstruction, the distal aortic cuff at the end of ascending aorta was oversewn with double-layered Teflon felts and anastomosed to the tubular graft. For patients with an arch tear, aortic arch repair was performed under antegrade or retrograde selective cerebral perfusion with deep hypothermia. Low-flow perfusion of the lower body (20 to 30 mL/kg) was continued and open distal anastomosis [5, 20] with balloon occlusion of the descending aorta usually was applied. Major branches of aortic arch were reconstructed en bloc or separately according to the extension of the arch dissection.
In patients with major abdominal branches perfused from the false lumen of the aortic dissection, a fenestration technique or a double-barrel repair was applied at the position of the distal anastomosis [19].
Follow-up and Statistical Analysis
The follow-up interval of 84 operative survivors was from 0.2 to 21.6 years with a mean follow-up of 7.2 years. The information on all patients was confirmed by contacting the patients or their primary physicians in January 1994. No patient was lost during this follow-up period.
Any postoperative death in the hospital after operation for aortic dissection was considered an early death. Regardless of the cause of death, all late deaths were counted for analysis of the follow-up data.
We divided the patients into three period subgroups of type A aortic dissection according to the circulatory support techniques. Period I is from May 1972 to February 1985, before the introduction of selective cerebral perfusion techniques. Period II is between March 1985 and October 1990, when antegrade cerebral perfusion was used. Retrograde cerebral perfusion was performed from November 1990 to June 1993 (period III).
Statistical significance of differences between categoric parameters were evaluated by
2 contingency analysis. The average of continuous variable in each group was compared by analysis of variance and Student's t test. Postoperative survival was analyzed by the Kaplan-Meier actuarial method and compared among the subgroups by Cox-Mantel statistical analysis. A probability value less than 0.05 was considered to be statistically significant. Noted values are mean ± standard deviation.
| Results |
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In operations for type A aortic dissection, early mortality in period I was 12.1% in 33 chronic patients and 57.1% in 7 acute patients. In period II, the mortality was 11.1% in 27 chronic patients and 54.5% in 11 acute patients. There was no statistically significant difference between the two period subgroups in acute and chronic patients, respectively. In contrast, 1 of 15 chronic patients (6.7%) and none of 9 acute patients (0%) with retrograde cerebral perfusion died in period III, and the early mortality (4.2%) of this group was significantly lower than that of the period II group (p < 0.05).
Causes of early death are listed in Table 1
. Low cardiac output and bleeding were the main causes of death in period I; multiple organ failure, organ ischemia, and brain damage occurred in period II. In period III, only 1 patient with a residual descending aortic dissection of large false lumen and small true lumen showed perioperative organ ischemia.
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Figure 3
shows actuarial survival curves (including all deaths) of the three period subgroups of type A aortic dissection. The 5- and 10-year survival rates were 59.7% and 54.4% in period I and 63.2% and 58.9% in period II, respectively. This difference was not statistically significant. In period III, actuarial survival at the 3rd postoperative year was 91.7%, which was significantly higher than those in periods I and II (p < 0.05).
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| Comment |
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Hypothermic circulatory arrest is a valuable technique in aortic operations, but a safe duration of the arrest is considered to be less than 50 to 60 minutes [8, 21]. Current reports [21, 22] show that early postoperative mortality was 9% to 15% and the incidence of permanent brain damage was 3% to 7% after operation for thoracic aortic aneurysm or dissection with hypothermic circulatory arrest.
Selective cerebral perfusion with hypothermia has been introduced as one of the circulatory supports during aortic operations with arch repair [5]. Recently, antegrade selective cerebral perfusion [5, 10] or retrograde cerebral perfusion [9, 17] has been used in many medical centers mainly in Japan. According to these reports, the duration limit of antegrade selective cerebral perfusion was 2 hours or more, and that of the retrograde perfusion technique was about 80 to 90 minutes. In some patients in the present study with retrograde cerebral perfusion, symptoms and signs of temporary cerebral dysfunction were observed when the duration was more than 80 minutes. But all patients with retrograde cerebral perfusion recovered their consciousness and were discharged from the hospital except 1 patient with perioperative organ ischemia. In contrast, 3 of 38 patients (7.9%) with antegrade cerebral perfusion showed permanent brain damage due to stroke. Since its initial experience [9], retrograde cerebral perfusion has shown the advantage of reverse blood flow for removal of air and debris to avoid cerebral emboli.
Comparing antegrade and retrograde cerebral perfusion techniques, retrograde cerebral perfusion without cannulation of aortic arch branches provided an excellent operative view and made the time of arch repair shorter. Because the blood flow of retrograde cerebral perfusion is about 5 mL kg-1 min-1, half that of antegrade cerebral perfusion, and its distribution is different in each patient, profound hypothermia is considered to be necessary, and safe duration of the hypothermia might be extended with retrograde cerebral perfusion. Although the lower body including abdominal organs has a little longer time limit of hypothermic circulatory arrest, its ischemic injury would proceed as the arrest time is prolonged. Therefore, we have applied low-flow perfusion of the lower body during either antegrade or retrograde cerebral perfusion. However, 2 patients with antegrade cerebral and lower body perfusion for more than 2 hours suffered from postoperative multiple organ failure in period II.
With these recent techniques of circulatory support, extended surgical procedures [3, 19] were applied more for type A aortic dissection with an arch tear. In our current surgical strategy for aortic dissection, aortic arch repair with retrograde cerebral perfusion usually is performed for type A dissection with an arch tear or dissection of arch branches. Needless to say, recent advances in diagnostic tools, such as transesophageal echography, magnetic resonance imaging, and three-dimensional computed tomography, and progress in surgical materials, artificial grafts, membrane oxygenators, and so forth have made significant improvements in surgical strategies and results.
From the late results of this study, extended surgical repair of aortic arch with selective cerebral perfusion techniques reduced the incidence of rupture of residual aneurysms just distal to the graft replacement. The retrograde cerebral perfusion technique also significantly decreased the incidence of permanent complications with brain damage.
We conclude that overall surgical results of type A aortic dissection in this series improved with the introduction of retrograde cerebral perfusion and extended surgical procedures.
| Footnotes |
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| References |
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