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Ann Thorac Surg 2007;83:S805-S810
© 2007 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, National Cardiovascular Center, Osaka
b Department of Thoracic Surgery, Fujita Health University, Aichi, Japan
* Address correspondence to Dr Sasaki, Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan. (Email: hmsasaki{at}hsp.ncvc.go.jp).
Presented at Aortic Surgery Symposium X, New York, NY, April 2728, 2006.
| Abstract |
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METHODS: Between 2000 and 2005, 305 patients underwent elective total arch replacement for arch or distal arch aneurysm using a Dacron (DuPont, Wilmington, DE) quadrifurcated prosthesis through a median sternotomy. There were 34 dissecting and 271 nondissecting aneurysms. Brain protection was standardized using antegrade selective cerebral perfusion with right axillary artery cannulation at 20° to 28°C. Risk factors for early mortality and neurologic complications were investigated using multivariate logistic regression analyses.
RESULTS: The durations of hypothermic circulatory arrest, myocardial ischemia, selective cerebral perfusion, cardiopulmonary bypass, and surgery were 60.9 ± 16.8, 125.2 ± 39.3, 150.1 ± 39.0, 229.8 ± 91.4, and 466.4 ± 175.8 minutes, respectively. Seven patients died, for a 2.3% early mortality. Permanent neurologic dysfunction developed in 5 patients (1.6%), and temporary neurologic dysfunction in 20 (6.6%). The mid-term survival rate was 94.6% ± 1.5% at 3 years. On multivariate analyses, prolonged surgery was a risk factor for early mortality. Preoperative cerebral hypoperfusion was a significant determinant for temporary neurologic dysfunction and male gender for permanent neurologic dysfunction.
CONCLUSIONS: Integrated total arch replacement using antegrade selective cerebral perfusion with right axillary artery cannulation yields a favorable outcome with low mortality and cerebral morbidity rates.
| Introduction |
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| Patients and Methods |
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Surgical Techniques and Brain Protection
All aneurysms were approached through a median sternotomy and replaced using a quadrifurcated Dacron (DuPont, Wilmington, DE) prosthesis with open distal anastomosis.
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Systemic circulation is resumed using a branch of the arch graft. The left subclavian artery is initially reconstructed using a branch graft, and the patient is slowly rewarmed to 30°C. The proximal aortic anastomosis follows, above the sinotubular junction, using 4-0 polypropylene running suture. Coronary circulation is initiated by unclamping the aorta. The other two arch vessels are finally reconstructed with branch grafts.
Definition of Neurologic Deficits and Other Variables
Permanent neurologic dysfunction (PND) was defined as the presence of permanent neurologic deficits either focal or global in nature, persisting at discharge. Transient neurologic dysfunction (TND) was defined as the occurrence of postoperative confusion, agitation, delirium, or prolonged obtundation [12]. Cerebral hypoperfusion was defined as the preoperative presence of more than 50% stenosis of the arch vessels or the intracranial vessels, or both, on echo or magnetic resonance angiography study, or hypoperfusion on acetazolamide-loading cerebral flow scintigraphy.
Data Collection and Statistical Analysis
Medical records were reviewed for clinical variables including preoperative status, intraoperative data, postoperative complications, and mid-term survival. Follow-up was 100% complete. The mean follow-up period was 31.0 ± 19.6 months. We retrospectively reviewed the overall outcome of TAR and investigated risk factors for hospital mortality and cerebral morbidity by multivariate logistic regression analyses.
Statistical analysis was done with SPSS software (SPSS Inc, Chicago, IL). Values are expressed as the mean ± standard deviation or medians (range), with values of p < 0.05 considered significant. Logistic regression was used to investigate risk factors for mortality and cerebral morbidity. Kaplan-Meier estimates were used to calculate survival rates.
| Results |
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| Comment |
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With SCP, however, atheromatous cerebral emboli remain a major concern. A variety of embolic phenomena are caused by systemic CPB perfusion through the ascending aorta across the arch aneurysm or by retrograde femoral artery perfusion. Arch vessel cannulation also carries a risk of cerebral embolization [17, 18]. For these reasons, an alternative perfusion pathway using the right axillary artery has been routinely used for both CPB and SCP [9].
The right axillary artery can easily be exposed and cannulated and is less atherosclerotic than the arch. Unfortunately, in Japanese patients, particularly small women, the axillary artery is too small to accept larger-size cannulae, so that additional cannulation through the femoral artery or the ascending aorta is necessary for systemic CPB flow. Femoral artery cannulation was previously performed. Retrograde femoral artery perfusion was useful not only for flushing out debris in the descending aorta but also to check for bleeding from the key distal anastomosis in the descending aorta.
The combination of right axillary artery and femoral artery perfusion was used for approximately 3 years, between 2000 and 2002, and we have previously reported its advantages [9]. With this combination, downstream flow through the right axillary artery can compete with retrograde femoral artery perfusion in the descending aorta and may prevent cerebral emboli. However, in the absence of atherosclerosis, ascending aorta cannulation, which yields antegrade CPB flow, has become our first choice rather than femoral artery perfusion [19].
We believe that right axillary artery cannulation is of use even with ascending aorta cannulation because the switch from systemic perfusion by way of CPB to SCP is easy, with no discontinuity, and cannulation-induced emboli from the brachiocephalic artery can be avoided. We have therefore been able to increase core temperature to 28°C [20]. If the ascending aorta is atherosclerotic, however, the femoral artery is chosen as an alternative site of cannulation.
We have thus continued integrated TAR using SCP with right axillary artery perfusion in the last 6 years. In this study, the early and mid-term outcomes were reviewed, with assessment of significant determinants for mortality and cerebral morbidity. Our integrated TAR yielded a satisfactory 2.3% early mortality rate, even with difficult surgery including a two-stage repair of extensive thoracic aortic aneurysms involving the arch, and even for elderly individuals with a median age of 73 years. The current outcome is comparable or superior to those described in previous reports [2123].
Multivariate analysis demonstrated that only prolonged surgery was an independent determinant of early death. In contrast, Kazui and colleagues [3] reported that chronic renal failure, long CPB time (>300 minutes), participation in an early series, and shock were risk factors for death in their first study, and PND in a more recent study [4]. No other factors such as age, coexisting coronary artery disease, reoperative surgery, dissection, neurologic comorbidities, postoperative neurologic complications, or concomitant surgery including coronary artery bypass or root surgery were significant predictors of early mortality.
Preoperatively, 30.2% of the patients had coexisting coronary artery disease. The strategy for treatment of coronary artery disease associated with arch aneurysms is still controversial. Cardiologists tend to suggest safer catheter intervention before TAR because TAR has a high mortality risk and most patients who need TAR are old. Conversely, prompt performance of combined TAR with coronary artery bypass grafting (CABG) is recommended by surgeons because CABG is can be performed concomitantly with a low risk. In the present series, TAR and CABG were performed together in 62 patients, 3 of whom died, yielding a mortality rate of 4.8%. The causes of death were unrelated to coronary artery disease: bowel necrosis in 2 patients and mediastinitis in 1. We therefore believe that use of combined TAR with CABG is justified.
Ergin and colleagues [12, 18] reported that postoperative cerebral morbidity after TAR remains a major problem resulting in mortality and serious morbidity. The present study did not yield similar results. Multivariate analysis revealed preoperative cerebral hypoperfusionincluding old cerebral infarctionto be a risk factor for TND, although it was not an independent predictor for PND. This finding was expected. TND is considered to be due to cerebral hypoperfusion during CPB, or HCA with selective or retrograde cerebral perfusion [12]. Conversely, most strokes are considered due to embolism originating from hematoma or atheroma in the aorta or in the arch vessels [12]. For patients with cerebral hypoperfusion before surgery, our strategies were modified to include higher CPB perfusion pressure (>60 mm Hg), more profound hypothermia (20° to 22°C), and higher SCP flow rates, with increases in SCP pressure of 20% to 30%. These refinements yielded good outcomes empirically.
On multivariate analysis, male gender was the only significant determinant of PND. As mentioned, the cause of PND is believed to be emboli caused by atheroma in the ascending aorta/aortic arch and in the arch vessels, particularly under well-established brain protection, whether in conjunction with RCP or SCP [12]. In the present series, 78.0% of the 305 patients were men, and all patients who sustained PND were men. Male gender is widely considered a risk factor for atherosclerotic change in all arteries. This finding was therefore also expected.
The degree of atheromatous change was not assessed in this study, although atherosclerotic aneurysm was evaluated as a potential risk factor. It is of interest that the Mt. Sinai group [7] assessed clot/atheroma as a risk factor for adverse outcome including cerebral complications; however, it is difficult to quantitatively evaluate the degree or amount of atheromatous lesions.
For patients with severe atheromatous lesions in the arch vessels or their orifices, adequate brain protection technique is still controversial. RCP has been criticized because prolonged HCA results in cerebral morbidity [5, 6, 1315], whereas SCP theoretically has a longer cerebral safety margin [24]. However, SCPrequiring cannulation of the arch vesselshas the potential for cerebral embolism, which has been considered its worst shortcoming [8, 12].
In our strategy involving right axillary artery cannulation, we can avoid cannulation of the brachiocephalic artery, which sometimes exhibits atheromatous change. Fortunately, the left common carotid artery is generally less atheromatous, making its cannulation easy and safe. Cannulation of the left subclavian artery is sometimes dangerous because it often has the most severe atheromatous changes of the three arch vessels. In these situations, cannulation must be carefully performed, or patients must be cooled to below 22° to 23°C and the left subclavian artery left uncannulated.
Atheroma in the ascending aorta and the aortic arch is another potential source of emboli to the brain. Atheromatous change in the ascending aorta and the arch should be assessed by preoperative computed tomography or epiaortic echo examination, and ascending aortic cannulation for CPB should be carefully performed. The impact of right axillary artery perfusion on cerebral safety in TAR has been elucidated in this study.
In addition, since 2000 we have used a unique stepwise technique for easy and secure anastomosis [11, 12]. With this technique, distal anastomosis has become much easier, with good exposure of the anastomosis site even in difficult aneurysms extending distally. In TAR through a median approach, the distal anastomosis is a key aspect. One shortcoming of the stepwise anastomosis is the need for another graft-to-graft anastomosis, but this normally takes only 5 to 10 minutes. Another is the possibility of dislodgement of atheroma in the descending aorta. One patient who experienced bowel necrosis a few days after surgery required resection of the gut. However, we believe the stepwise anastomosis technique is useful and safe overall, particularly for aneurysms extending distally, and consequently will improve the overall outcome of integrated TAR with SCP and right axillary artery perfusion. The recent outcome of integrated TAR using SCP with right axillary artery cannulation was satisfactory, with low hospital mortality and cerebral morbidity rates.
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