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Ann Thorac Surg 2005;80:1290-1296
© 2005 The Society of Thoracic Surgeons
Department of Cardiothoracic and Vascular Surgery, The University of Texas Houston Medical School, Memorial Hermann Hospital, Houston, Texas
Accepted for publication February 3, 2005.
* Address reprint requests to Dr Safi, Department of Cardiothoracic and Vascular Surgery, The University of Texas Houston Medical School, 6410 Fannin St, Suite 450, Houston, TX 77030 (Email: hazim.j.safi{at}uth.tmc.edu).
Presented at the Fifty-first Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 4–6, 2004.
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Abstract |
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METHODS: Between February 1991 and September 2004, we repaired 355 descending thoracic aortic aneurysms. Excluded from analysis were 29 patients who required profound hypothermic circulatory arrest as a result of transverse arch involvement and 26 patients with aortic rupture, leaving a group of 300 patients for which outcomes were analyzed. Mean patient age was 67 years, and 102 (34%) of the patients were women. The adjunct group of distal aortic perfusion and cerebrospinal fluid drainage used in 238 (79.3%) patients was compared with a group of 62 patients who underwent simple cross-clamp with or without the addition of a single adjunct. Multivariable data were analyzed by Cox regression.
RESULTS: The incidence of neurologic deficit after all repairs was 2.3% (7 of 300 patients). The incidence of neurologic deficit (immediate and delayed) in the adjunct group was 1.3% (3 of 238 patients), and in the nonadjunct group was 6.5% (4 of 62 patients; p < 0.02). One case of delayed paraplegia occurred in each group. All neurologic deficits occurred in patients with aneurysmal involvement of the entire descending thoracic aorta (extent C; p < 0.02). Statistically significant predictors for neurologic deficit were the use of the adjunct (odds ratio [OR], 0.19; p = 0.02), previous repaired abdominal aortic aneurysm (OR, 7.0; p = 0.005), type C aneurysm (OR, 13.73; p = 0.02), and cerebrovascular disease history (OR, 4.7; p < 0.03). Thirty-day mortality was 8% (24 of 300 patients). Significant multivariate predictors of 30-day mortality were preoperative renal dysfunction (OR, 4.6; p < 0.01) and female sex (OR, 2.9; p < 0.03).
CONCLUSIONS: Repairs of the descending thoracic aorta using the adjunct of distal aortic perfusion and cerebrospinal fluid drainage can be performed with a low incidence of neurologic deficit and an acceptable mortality. The use of the adjuncts should be considered during elective repairs of the descending thoracic aorta.
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Introduction |
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Since 1991 we have used the combination of distal aortic perfusion and cerebrospinal fluid (CSF) drainage for repairs of the descending and thoracoabdominal aorta. The purpose of this study is to report our results with regard to early and late outcome for repairs of the descending thoracic aorta.
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Material and Methods |
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Surgical Technique
The details of our technique have been described previously [4], and will be reviewed briefly. All patients without free aneurysmal rupture were considered for the adjunct. Surgery was performed as follows.
After general anesthesia, the patient was positioned in the right lateral decubitus position and a CSF catheter was placed in the third or fourth lumbar space to allow CSF drainage and monitoring of CSF pressure. Cerebrospinal fluid drainage catheter insertion was attempted on all patients except those who had recently been on non–aspirin antiplatelet therapy (clopidogrel) or low-molecular-weight heparins, those who were coagulopathic, and those with a previous history of cerebral hemorrhage. Failure to obtain lumbar access has been encountered in patients with multiple previous lumber procedures. A neurophysiologist monitored somatosensory-evoked potentials. We used a modified thoracoabdominal incision, beginning in the abdomen 3 cm below the costal margin and continuing over the sixth rib before curving cephalad just posterior to the tip of the scapula. The lung was deflated, and the sixth rib was excised. We completed this incision by dividing the costal cartilage with heavy scissors. The diaphragm was partially incised circumferentially to improve exposure and to avoid traction injury to the phrenic nerve. A self-retaining retractor was then inserted, and the aorta was inspected. The pericardium was opened posterior to the phrenic nerve, and the patient was given 1 mg/kg body weight of sodium heparin. The left atrium was cannulated through the left pulmonary vein or the left atrial appendage. A BioMedicus (Minneapolis, MN) pump with an inline heat exchanger was attached to this cannula, and the arterial inflow was established through the left femoral artery or the descending thoracic aorta.
Distal aortic perfusion was begun as the cross-clamp was applied. For type A and type B aneurysms, the clamp was applied a few centimeters above and below the aneurysm to allow easy suturing of the anastomosis. For type C aneurysms, a sequential clamp technique was used. This allowed the important lower intercostal arteries to be perfused from below during construction of the proximal anastomosis and decreased the spinal cord ischemic time. The anesthesiologist carefully maintained a normal proximal aortic pressure during this time. The aorta was opened longitudinally and separated from the esophagus. Stay sutures were applied to the aneurysm wall, and hemostasis was obtained by oversewing any bleeding intercostal or bronchial arteries that were not to be reimplanted. Blood salvage was accomplished with a cell-saving device, and blood was reinfused using a rapid infuser system.
The amount of aorta that was replaced depended on what was identified as aneurysm at the time of exploration. Any aorta greater than 5 cm in diameter was replaced. In cases of dissection, extent of replacement depended on the acuity of the dissection. For acute dissection, we rarely replaced the entire descending thoracic aorta (type C) because of the difficulty in reattaching the intercostal arteries, unless it was enlarged greater than 5 cm. For chronic dissection, we would replace the entire diseased segments. In addition, we fenestrated the distal dissecting membrane before completing the distal anastomosis.
Once adequate hemostasis was obtained, an appropriately sized, woven Dacron tube graft was anastomosed to the proximal aorta with a running polypropylene suture. The graft was cut in a beveled fashion to accommodate the intercostal arteries. Reimplantation of patent, lower intercostal arteries (T8 through T12) was performed routinely except in cases of acute dissection or when technically impossible. The distal anastomosis was then performed, and the graft was flushed just before its completion. The aortic clamps were slowly removed, and suture lines were checked for hemostasis. The patient was weaned from left heart bypass once the rectal or bladder temperature reached 36°C. Protamine was administered, and the atrial and femoral cannulae were removed.
Postoperatively, the mean arterial pressure was maintained between 80 and 100 mmHg. Cerebrospinal fluid pressure was kept less than 10 mmHg for 3 days by draining up to 15 mL/h of CSF. As long as the patient was neurologically intact, no more than 15 mL/h of CSF fluid was drained. The CSF drain was removed before 3 days if it was nonfunctional or if bloody drainage was noted. If a delayed neurologic deficit appeared after removal of the drain, the CSF drain was immediately reinserted to decrease the CSF pressure. Usually, this led to the prompt resolution of the deficit [11].
Outcome Variables and Statistical Analysis
Operative mortality was defined as death occurring within 30 days of surgery, and in-hospital mortality was defined as death occurring during hospitalization. Patient characteristics analyzed in this study are listed in Table 1. Postoperative immediate neurologic deficit was defined as paraplegia or paraparesis observed after the patient awakened from anesthesia, regardless of severity. Delayed neurologic deficit is the development of paraplegia or paraparesis after the patient awakened and was noted to be neurologically intact as determined by a neurologist. Patients with stroke, identified by a thorough neurologic examination and computerized tomography scan of the head, were excluded from the neurologic deficit group, ie, neurologic deficit refers to paraplegia and paraparesis only. We considered aneurysms with dissection acute if surgery was performed in fewer than 14 days from the onset of pain, and chronic if after 14 days. Current smoking was tobacco use within 2 weeks of surgery. Cerebrovascular disease is defined as any previous history of cerebrovascular accident or having undergone intervention for carotid artery disease. Freedom from reoperation is defined as patients who did not require another distal aortic or aortic-related procedure.
Data were collected from chart reviews done by a trained nurse evaluator and were entered into a dedicated Microsoft Access (Microsoft Corp, Redmond, WA) database. Analysis was retrospective. Preoperative characteristics analyzed in this study are listed in Table 1. Patient follow-up was obtained by direct patient contact, telephone interview, or the Social Security Death Index (SSDI).
Data were managed under Health Insurance Portability and Accountability Act of 1996 confidentiality guidelines in a Microsoft Access database with encrypted patient identifiers. All analyses were conducted using SAS software version 8.2 (SAS Institute Inc, Cary, NC) running under Microsoft Windows XP Professional (Microsoft Corp). Univariate categorical data were analyzed by contingency table, with computation of common odds ratios (OR) and 
2 probability values. Continuous data were analyzed using logistic regression analysis. Long-term data were analyzed using Kaplan-Meier with log rank probability values, and by Cox regression. Multivariable short-term outcomes were analyzed by multiple logistic regression.
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Results |
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Thirty-day mortality was 7.3% (22 of 300 patients) with an in-hospital mortality of 8.0% (24 of 300 patients). Significant predictors associated with early mortality by univariate analysis were history of current smoking (OR, 4.27; p < 0.001) and renal dysfunction (OR, 4.71; p < 0.0008). Significant independent predictors of early mortality were preoperative renal dysfunction (OR, 4.6; p < 0.01) and female sex (OR, 2.9; p < 0.03; Table 2).
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Median follow-up was 97 months (range, 1 to 165 months). Survival follow-up was obtained in 96% (289 of 300 patients) of cases. The overall long-term survival was 79%, 76%, 64%, and 35% at 1, 2, 5, and 10 years, respectively (Fig 2). Freedom from aortic-related reoperation was 96.3% (289 of 300 patients; Fig 3). Eleven subsequent aortic-related procedures were performed on this study cohort: 6 patients for thoracoabdominal aortic aneurysm repair, 4 patients for abdominal aortic aneurysm repair, and 1 patient who had an aortobronchial fistula requiring a pneumonectomy.
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Comment |
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In the past, we have used multiple approaches for spinal cord protection during thoracic aortic aneurysm repair with varying results, but ultimately settled on the combination of distal aortic perfusion and CSF drainage [5]. The rationale for this approach has been presented previously [9]. Although distal aortic perfusion and CSF drainage form the crux of our approach to spinal cord protection, we admit that the reasons for our clinical results are more complex and are also the result of the overall system established specifically for aortic surgery. As with other aortic centers, the system that is established along with the experience of the surgeon and the operative team will provide an intangible that may not be obvious and ultimately is difficult to quantify when analyzing the operative results. Thus, trying to apply one approach, such as clamp and sew, may be applicable in one setting with good results, but may not be as reproducible in other settings. It was a goal from our study to provide evidence that the adjunct (distal aortic perfusion and CSF drainage) may improve outcomes but more importantly provide a technique that most others can apply. Of note, in previous reports aortic cross-clamp time remained a significant risk factor for paraplegia [1, 10], yet in this analysis, with the use of the adjunct, aortic cross-clamp time was not a risk factor for neurologic injury in either univariate or multivariate analysis. Moreover, four neurologic deficits were noted in patients with cross-clamp times greater than 30 minutes and three in patients with aortic cross-clamp times less than 30 minutes (p = 0.46). Thus, we found no correlation between aortic cross-clamp time and neurologic deficit in the current series.
In the current era of endovascular therapies, there has been increasing use of endovascular stenting for the descending thoracic aorta. With continuing evaluation of endovascular techniques, comparisons with open repair will be made. Recently, the results from the combined experience of EUROSTAR and the United Kingdom Thoracic Endograft registries have been published [12]. From this report, overall 30-day mortality was 5.4% for elective cases, and paraplegia was 4% after aneurysm stenting; 1-year follow-up was obtained for 45% (195 of 443 patients) of the entire cohort with an 80% survival for aneurysmal disease. Others have reported similar early results [13–18]. It remains striking that even with no aortic occlusion during endovascular stenting, neurologic deficit was still significant and has not been eliminated, ranging as high as 12% (with stroke as high as 7%) [13–17].
The correlation between aneurysm extent and patient outcome in thoracoabdominal aortic aneurysms has been recognized previously [19]. Descending thoracic aortic aneurysms have also been classified with prognostic significance [1]. In follow-up to our previous report [9], extent of repair as a risk factor (type C versus type A or B) became significant with regard to neurologic deficit. All cases of paraplegia were with repairs of the descending thoracic aorta type C (the entire descending thoracic aorta). As previously brought to our attention [14, 20], the extent of aneurysm exclusion performed during endovascular stenting now appears to be significant with regard to spinal cord injury.
The overall long-term survival was 79%, 76%, 64%, and 35% at 1, 2, 5, and 10 years, respectively (Fig 2), which is comparable to other series [1]. In addition, freedom from reoperation for distal aortic related condition was 96% at 13 years (Fig 3). Early (1 to 2 years) survival with endovascular stenting has been reported from 73% to 81% [13, 14] with freedom from reintervention at 54% at almost 4 years [13]. This report confirms that open repair for descending thoracic aortic repair remains durable for the long term and does not require multiple reinterventions.
Significant independent risk factors for mortality in this study were preoperative renal dysfunction and female sex. Renal dysfunction has previously been identified as a risk factor for both death and neurologic injury, but female sex is new for repairs of the descending thoracic aorta. Many recent studies with regard to outcomes in abdominal aortic aneurysm repairs in women [21–23] have been reported, but the reasons for this correlation for descending thoracic aortic repairs remains unclear.
This study must be viewed with certain limitations. Again, the statistical analysis in this study is retrospective, and will include inherent bias. Randomized prospective studies would be preferred but remain difficult to perform owing to the small overall numbers and varying management strategies used during repair. Because our adjunctive strategy is the combination of both distal aortic perfusion and CSF drainage, conclusions about each individual adjunct are difficult to make. In the past, others have reported the benefits of distal aortic perfusion and CSF drainage individually [24]. A recent meta-analysis does support the use of CSF drainage during thoracic aortic aneurysm repair [25]. In addition, the importance of determining CSF dynamics has been brought to our attention, and we are currently analyzing these data [26].
In our experience, repairs of the descending thoracic aorta using the adjunct of distal aortic perfusion and CSF drainage can be performed with a low incidence of neurologic deficit and an acceptable mortality. The use of the adjunct may be considered during elective repairs of the descending thoracic aorta.
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Discussion |
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Dr Estrera: When the aorta is opened, we simply inspect the intercostal arteries to see if they are patent. If they are patent, we will reattach them. We almost always reattach intercostal arteries number 8 through 12, if patent. If intercostal arteries number 8 through 12 are occluded, and changes are noted on neuromonitoring, somatosensory evoked potentials (SSEP), we will be more aggressive and reattach those patent intercostal arteries that are either higher or lower.
Dr D. Glenn Pennington (Johnson City, TN): You mentioned the question of the endograft. How many of these patients, I assume all in category A, perhaps, would be suitable candidates for endovascular grafting?
Dr Estrera: An interesting study recently published in the Journal of Vascular Surgery about endovascular stenting, the EUROSTAR study, reported a paraplegia rate of almost 5% and mortality from 8% to 10% for thoracic aortic stenting depending on the patient subgroup examined.
To specifically answer your question, patients with descending thoracic aortic aneurysms are candidates for stenting, but I still have some concerns about the durability of endovascular stenting. I don't know if we have the right graft yet based on what we have seen. Now, having said that, a large majority of our patients have intrinsic defects with the aortic wall, for example, acute and chronic dissection, Marfan's syndrome, and aneurysmal disease with medial degeneration, and if you stent the thoracic aorta in these patients and leave any abnormal aortic wall, the potential for complications still exists. Now, what are the indications for endovascular stenting? I think one good indication would be the traumatic aortic condition, either acute or chronic. In these cases, the aortic wall is pathologically normal, and it is an iatrogenic injury that caused that wall to dilate.
Dr Pennington: And have you actually done that?
Dr Estrera: We actually have a physician from Washington University who just joined our group who performs thoracic endovascular stenting.
Dr Pennington: You have done it?
Dr Estrera: I personally have not.
Dr Pennington: But it is being done at your institution?
Dr Estrera: Yes.
Dr John A. Kern (Charlottesville, VA): Very nice paper, and I think we all would agree that these adjunctive measures are becoming more and more standard for most of us. Basically I have two questions. In this retrospective review did you reimplant intercostals to the same degree in both your adjunctive and nonadjunctive groups, and then, did you see any complications at all from the use of cerebrospinal fluid (CSF) drainage?
Dr Estrera: Thank you, Dr Kern. Yes, there was no significant difference between the two groups, with regard to intercostal reattachment.
In terms of complications with the CSF drain, in this population of patients, descending thoracic aortic aneurysms, we did not see any complications. Now, we have seen complications using the CSF drain with thoracoabdominal aneurysm repairs. We are currently analyzing these data, but in over 1,200 cases, we have observed complications that have included spinal headaches after removal of the drain, CSF leak requiring a blood patch, cerebral hemorrhage (1 case), and spinal meningitis (1 case).
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Acknowledgments |
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