Abstract
Objective: The outcome of thoracoabdominal aortic aneurysm repair after operations for descending thoracic or infrarenal abdominal aortic aneurysm was investigated. Methods: Between May 1982 and July 2000, 102 patients underwent thoracoabdominal aortic aneurysm repair. Of these patients, 36 had previously undergone operations for descending thoracic or abdominal aortic aneurysm. To evaluate the influence of previous descending thoracic or infrarenal abdominal aortic aneurysm repair on the results of TAAA replacement, patients were divided into two groups: one group of patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group I, n=36) and one group of patients who had not previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group II, n=66). Results: Patients with previous descending thoracic or infrarenal abdominal aortic aneurysm repair had more chronic dissection and extensive thoracoabdominal aortic aneurysm. The distal aortic perfusion time and total aortic clamp time were both longer in group I. The total selective visceral and renal perfusion time and operation time did not differ significantly between the two groups. In 30-day mortality rates were 5.5% in group I and 13% in group II. Major postoperative complications included paraplegia in 14% of patients in group I and 3.1% in group II, renal failure requiring hemodialysis in 22% of patients in group I and 19% of patients in group II, respiratory failure in 36% of patients in group I and 30% of patients in group II, postoperative hemorrhage in 11% of patients in group I and 16% of patients in group II. Conclusion: The presence of a previous descending thoracic or infrarenal abdominal aortic aneurysm did not adversely affect the outcome of thoracoabdominal aortic aneurysm repair.
1 Introduction
The long-term results of most thoracic or abdominal aortic aneurysm reconstructions are satisfactory. However, some patients require a reoperation for a separate aneurysm after the original aortic reconstruction. Thus, in cases of thoracic or abdominal aortic aneurysms there is quite a high risk of development of multiple aortic aneurysms. Crawford and Cohen [1] reported that 59.6% of patients who originally presented with aortic aneurysms involving the ascending, transverse arch, or descending segments developed multiple aneurysms, whereas multiple aneurysms developed in only 12% of patients who initially had abdominal aortic aneurysms. Carrel et al. [2] reported that new or recurrent aortic aneurysms accounted for 36 of the 130 (27.7%) thoracic aortic reoperations in 120 patients. Most of the reports on surgical treatment of recurrent and multiple aneurysms present results of more proximal aortic operations after infrarenal abdominal aortic aneurysm repair [3]. Mortality rates in previous reports range from 12.2% to 28.6% [4–7].
There are few reports on thoracoabdominal aortic aneurysm (TAAA) repair in patients with previous thoracic aortic aneurysm repair. Of the 1509 patients in Crawford's complete TAAA experience, reported by Svensson and colleagues [8], 181 (12%) had previously undergone a proximal aortic operation, and this group of patients was characterized by a lower 30-day mortality rate compared to the group of patients who had not previously undergone thoracic aortic aneurysm repair (4% in the group with previous thoracic aortic aneurysm repair versus 9% in the group without previous thoracic aortic aneurysm repair, P=0025). Furthermore, Coselli and colleagues [9] reported that previous thoracic aortic aneurysm repair did not adversely affect the outcome of thoracoabdominal aortic aneurysm repair.
The reported outcomes of surgical repair of multilevel and recurrent aortic aneurysms vary widely. Therefore, the safety of TAAA repair in patients with previous thoracic or abdominal aortic aneurysm repair remains uncertain. Since 1982, we have used selective visceral and renal perfusion during thoracoabdominal aortic repair [10]. We retrospectively evaluated our experience with TAAA repair to compare results in patients who had undergone and those who had not undergone previous descending thoracic or infrarenal abdominal aortic aneurysm repair.
2 Materials and methods
2.1 Patients
Between May 25, 1982 and August 2, 2000, 102 consecutive patients underwent thoracoabdominal aortic aneurysm repair. We collected retrospective data from the hospital records of these patients who were entered in our departmental registry after receiving surgical treatment. The 102 patients include 74 men (73%) and 28 women (27%). Patients’ ages ranged from 29 to 91 years (median, 62 years). There were 11 patients (11%) with Marfan's syndrome. Aortic dissection was present in 41 patients (40%) and nondissecting aneurysm in 62 (60%). Eight of the patients presenting with dissection had Marfan's syndrome. Mean aneurysm size was 66±16 mm. Ninety-five of the aneurysms (93%) had been repaired electively and seven (6.9%) had been repaired nonelectively. Associated risk factors included hypertension in 54 patients (53%), chronic renal insufficiency (serum creatinine ≫1.5 mg/dl) in 12 patients (12%), and diabetes in six patients (5.9%). According to the TAAA extent classification of Crawford et al. [11], 23 (23%) aneurysms were extent I, 28 (27%) were extent II, 35 (34%) were extent III, and 16 (16%) were extent IV.
Of the 102 patients, 36 (35%) had previously undergone operations for descending thoracic or infrarenal abdominal aortic aneurysm. Detail of previous surgical procedures performed in these patients are given in Table 1 . To evaluate the influence of previous descending thoracic or infrarenal abdominal aortic aneurysm repair on the results of TAAA replacement, patients were divided into two groups: one group of patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group I, n=36) and one group of patients who had not previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group II, n=66). The characteristics of the patients in the two groups are shown in Table 2 . Of the 36 patients in group I, 23 (64%) had dissection (P≪0.003). Eight of the 11 patients with Marfan's syndrome (73%) were in group I. Deep hypothermic circulatory arrest for spinal cord protection was used on four patients each in groups I and II after 1995.
Classification of previous descending thoracic or infrarenal abdominal aortic aneurysm repair
Comparison of preoperative characteristics in both patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair and in those had not
2.2 Surgical procedure
The patients were treated according to a previously reported procedure [12]. Briefly, under double-lumen endotracheal–tube anesthesia, a left thoracoabdominal incision was made with circumferential division of the left hemidiaphragm. Dissection was performed along the extraperitoneal plane. After dissection was completed, a femoro-femoral bypass was started with full heparinization. The lower body blood pressure we maintained at more than 50 mmHg. A clamp was placed proximal to the aneurysm. The aorta was transected above the aneurysm and anastomosed proximally in an end-to-end fashion to a woven Dacron graft. While the proximal end was being anastomosed, segmental, visceral and renal arteries were perfused by placing a distal clamp at the mid-thoracic level. Next, the distal clamp was moved to the supra celiac level, and patent intercostal arteries at the T4 to T8 level were oversewn, and segmental arteries below the T9 level, if patent, were reconstructed using the inclusion button technique. After implantation of the segmental arteries, the proximal clamp was moved below those, allowing perfusion of the lower intercostal and lumbar arteries. Visceral and renal arteries were also reimplanted as a large Carrel patch or preserved in a bevelled distal aortic anastomosis. During reconstruction, selective visceral and renal perfusion with 10–12 F balloon cannulas was performed by clamping the outflow tubing to the lower extremities. Each artery was perfused at a flow rate of 200–300 ml/min. After completion of the anastomosis of the visceral and renal arteries, the balloon cannulas were removed from the origins of those arteries, and the clamp was placed across the graft distal to the reimplanted arteries, thereby restoring flow to the reimplanted arteries. The distal end of the graft was sutured to the aortic bifurcation or the common iliac arteries.
We had been operating on patients using the above-described surgical procedure for 17 years. However, we had not been able to reduce the occurrence of spinal cord ischemia to levels lower than 10%. In an effort to reduce the occurrence of postoperative neurologic complications, we therefore modified the surgical procedure [13]. In the modified procedure, a prosthesis is prepared by suturing 8-mm grafts to an aortic graft. Small tubular grafts are used as interposition grafts for reattachment of individual intercostal or lumbar arteries. Proximal anastomosis is performed in the usual fashion. After completion of anastomosis, the proximal clamp is positioned on the graft, and the distal clamp is placed at a level between T8 and T9. Before T8 arteries are reattached to the side-arm grafts, the intercostal arteries above the T7 level are oversewn. After the reconstruction of T8 arteries, the proximal clamp is moved caudally below the reconstructed side-arm grafts while maintaining perfusion to the reimplanted arteries. The distal clamp is then moved to a level between T9 and T10. In the same fashion, patent segmental arteries are reconstructed segment-by-segment from the T9 level to the L1 level. The reason for reimplanting all patent arteries between T8 and L1 is that the blood supply to the spinal cord in 91% of cases is provided by some arteries from T8 through to L1 and the arteria radicularis magna does not always originate from the larger segmental arteries [14]. The segment-by-segment reattachment technique is used to shorten the ischemic time as much as possible. The mean time required for reconstruction of the individual arteries is less than 10 min. The non-used side-arm grafts are occluded and sutured. When the diameter or quality of the aorta does not allow the segment-by-segment reattachment technique to be performed, hypothermic circulatory arrest is used. Femoro-femoral bypass is performed using a heparin-coated perfusion apparatus that includes a centrifugal pump (Carmeda Closed Chest Support System; Medtronic, Anaheim, CA). This heparin-coated cardiopulmonary bypass apparatus has allowed us to reduce the dose of heparin [15]. Flow rates are adjusted to keep the mean distal aortic pressure above 50 mmHg. Visceral and renal perfusion is carried out in conjunction with distal aortic perfusion. Each flow depends upon visceral or renal vessel resistance, and ranges from 80 to 220 ml/min (mean flow, 155 ml/min). Blood flow is considered appropriate when the patient's urine output is 0.5 ml/min [16].
2.3 Statistical analysis
Data were processed using Stat View J-5.0 software (Abacus Concepts Inc, Berkeley, CA). Variables in group I and II were compared using χ2 test, Fisher's exact test, and Mann–Whitney U-test. Data for times and age are presented as means±SD.
3 Results
The overall 30-day and in-hospital mortality rates for the 102 patients treated with TAAA repair were 9.8% (10 patients) and 20% (20 patients), respectively. There were two intraoperative deaths (2.0%) due to hemorrhage secondary to rupture, and these two patients were excluded when calculating and analyzing morbidity rates. Rates of mortality, paraplegia or paraparesis, renal failure, pulmonary complication, postoperative bleeding, stroke rates are summarized in Table 3 . Overall, the incidence of paraplegia or paraparesis was 6.9% (seven patients). Fourteen patients (14%) were returned to the operation room due to postoperative bleeding. Postoperatively, 32 patients (31%) developed pulmonary complications, six patients (5.9%) had stroke, and 20 patients (20%) had renal failure, which required temporary or chronic hemodialysis. There were no statistically significant differences between group I and group II. Although the differences did not reach statistical significance, postoperative paraparesis/paraplegia rates tended to be higher in the patients who had undergone previous descending thoracic or infrarenal abdominal aortic aneurysm repair. However, there was not a significance difference between in-hospital mortality rates in the two groups. There was also no differences between the causes of in-hospital mortality for patients who had undergone and those who had not undergone previous descending thoracic or infrarenal abdominal aortic aneurysm repair (Table 4) .
Comparison of postoperative results in both patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair and in those had not
Comparison of causes of in-hospital deaths in both patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair and those who had not
With regard to intraoperative techniques (Table 5) , the distal aortic perfusion time was longer in group I. The total selective visceral and renal perfusion time, total aortic clamp time and operation time did not differ significantly between the two groups.
Comparison of intraoperative variables in both patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair and in those had not
Deep hypothermic circulatory arrest was used on eight patients (four patients in each group) in TAAA repair after 1995. The mortality rate was 50% in both groups. The incidences of pulmonary complications were 100% in group I and 75% in group II.
The variables found to be associated with in-hospital mortality in univariate analyses are presented in Table 6 . There was a greater incidence of pulmonary complication and postoperative hemodialysis in group I. Graft infection was a significant variable associated with in-hospital mortality in both patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair and in those had not.
Univariate analysis in both patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair and in those had not
4 Discussion
In contrast to the patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group I), those who had not previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group II) were older and did not have a significant difference in co-morbid disease. The larger proportion of patients with Marfan's syndrome in the former group undoubtedly contributed to these differences in age and coexisting disease. The more extensive aneurysms and higher prevalence of dissection in group I explain the longer distal aortic perfusion times. Despite having less extensive aneurysms and shorter clamp and perfusion times, the 30-day mortality and in-hospital mortality rates in patients in group II tended to be higher. However, there was no significant difference the 30-day mortality and in-hospital mortality rates between the two groups. An intrinsic selection bias for group I may have contributed to the lower 30-day mortality rate in this group. Careful medical follow-up after the initial operation may have resulted in risk factor prevention. In addition, because some patients who would have needed future TAAA repair did not survive their initial aortic operation, several patients with significant co-morbid disease may have been automatically eliminated from group I. Therefore, by surviving the previous operation, the group of patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair may have been inherently more likely to be able to tolerate the TAAA repair compared with those who had not previously undergone descending thoracic or infrarenal abdominal aortic repair.
There was no significant difference between complication rates or mortality rates in the two groups. In group I patients, there was a greater risk of lung damage during thoracotomy due to lung adhesion, and it was thought that there would be a higher incidence of postoperative respiratory complications in this group, but a significant difference between incidences of pulmonary complications in the two groups was not found. The fact that there were more Crawford type I cases in group II may been the cause of the higher incidence of pulmonary complications in group II.
More patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group I) had Marfan's syndrome than did patients who had not previously undergone such aneurysm repair (group II), and an increase in chronic dissection accounted for 64% of the causes of TAAA in group I (P=0.003). However, the fact that there was no significant difference between complications in the two groups suggests that chronic dissection has no effect on the probability of paraplegia or other postoperative complications occurring. Coselli et al. [17] reported that chronic aortic dissociation is not a risk factor for postoperative paraplegia in cases of TAAA. Although no significant differences were found between incidences of postoperative paraplegia in the two groups in the present study, a high incidence of paraplegia was found in the patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair. However, Coselli et al. [9] reported a low rate of paraplegia in patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair.
Many recent studies have shown that CSF drainage is useful for protection of the spine. We have been using CSF drainage since 1999, but we have not yet accumulated sufficient data from cases to be able to conclude whether CSF drainage is effective or not. We have also come to be able to identify the artery of Adamkiewicz on MRA, and identification of this artery has provided useful preoperative information. The artery of Adamkiewicz is identifiable in about 70% of patients, and identification of this artery provides useful information for reconstruction of intercostal arteries and the lumbar artery in TAAA as well as enabling surgery time to be reduced.
Deep hypothermic circulatory arrest in repair of TAAA was used on eight of the patients in the present study after 1995 (four patients in each group). These results suggest that repairs of TAAA using deep hypothermic circulatory arrest can not be performed with acceptably low overall mortality and morbidity rates. The role of deep hypothermic circulatory arrest during distal aortic surgery remains controversial. Several recent studies have shown that there are high associated mortality and morbidity rates. Safi et al. [18], for example, reported that six of 21 patients who underwent hypothermic circulatory arrest due to failure to obtain proximal aortic control died within 30 days (28.6%). Excluding two intra-operative deaths, paraplegia developed in 10.5% of the patients and stroke occurred in 31.6% of the patients. Crawford et al. [19] reported that major drawbacks of the deep hypothermia technique through left thoracotomy are lung injury secondary to manipulation of the left lung and blood coagulation disorders [19]. Considering the high rates of hospital mortality and postoperative complications, it seems that deep hypothermia should be limited to patients in whom segmental aortic clamping can not be performed.
In conclusion, the presence of a previous descending thoracic or infrarenal abdominal aortic aneurysm repair did not adversely affect the outcome of TAAA repair. Therefore, we recommend at least biannual computed tomography scanning of the chest and abdomen for follow-up in patients who had an initial aortic aneurysm repair.
Dr Kirsch (Paris, France): Did you assess the risk factor of time in your analysis between both groups? I expect that your reinterventions were much more frequent in your more recent experience, which might account for the good results in your reinterventions.
Dr Kawaharada: Unfortunately, I did not statistically evaluate the risk factor of time in our study. However, re-operation cases have not been more frequent in recent cases. The number of first-time operation cases and the number of re-operation cases have remained almost the same over the past 10 years.
