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A new predictive model for adverse outcomes after elective thoracoabdominal aortic aneurysm repair
A New Predictive Model for Adverse Outcomes After Elective Thoracoabdominal Aortic Aneurysm Repair Scott A. LeMaire, MD, Charles C. Miller III, PhD, Lori D. Conklin, MD, Zachary C. Schmittling, MD, Cu¨neyt Ko¨ksoy, MD, and Joseph S. Coselli, MD The Michael E. DeBakey Department of Surgery, Baylor College of Medicine, and The Methodist Hospital, Houston, Texas
Background. Recent recommendations have emphasized individualized treatment based on balancing a patient’s risk of thoracoabdominal aortic aneurysm rupture with the risk of an adverse outcome after surgical repair. The purpose of this study was to determine which preoperative risk factors currently predict an adverse outcome after elective thoracoabdominal aortic aneurysm repair. Methods. A single, composite end point termed adverse outcome was defined as the occurrence of any of the following: death within 30 days, death before discharge from the hospital, paraplegia, paraparesis, stroke, or acute renal failure requiring dialysis. A risk factor analysis was performed using data from 1,108 consecutive elective thoracoabdominal aortic aneurysm repairs.
Results. The incidence of an adverse outcome was 13.0% (144 of 1,108 patients); predictors included preoperative renal insufficiency (p ⴝ 0.0001), increasing age (p ⴝ 0.0035), symptomatic aneurysms (p ⴝ 0.020), and extent II aneurysms (p ⴝ 0.0001). These risk factors were used to construct an equation that estimates the probability of an adverse outcome for an individual patient. Conclusions. This new predictive model may assist in decisions regarding elective thoracoabdominal aortic aneurysm operations. For patients who are acceptable candidates, contemporary surgical management provides favorable results.
When I sit down with a patient to discuss risk of operation, I find that he or she is usually not too interested in all of the horrible things that can happen, but rather the probability of a good outcome. He is interested in the chances of getting out of this alive and in good shape. —R. Griepp [1]
doing well versus having an adverse outcome [1, 10, 11]. Such a model would allow estimation of a patient’s overall chance of surviving operation and leaving the hospital without neurologic deficits and without requiring hemodialysis. The purpose of this analysis of contemporary results was to determine which preoperative risk factors currently predict an adverse outcome after elective TAAA repair to enhance the risk– benefit decision-making process during preoperative assessment of individual patients.
A
s the results of surgical repair continue to improve, recent recommendations regarding thoracoabdominal aortic aneurysm (TAAA) management have emphasized individualized treatment based on balancing a patient’s risk of rupture with the risk of an adverse outcome after surgical repair [2–7]. To facilitate the first half of this fundamental risk versus benefit analysis, Juvonen and colleagues [8] developed a predictive model that estimates a patient’s risk of rupture in 1 year if the aneurysm is not repaired. To balance this model for rupture, we performed a retrospective analysis of 1,220 patients who had undergone TAAA repair and developed two predictive models focusing on the risk of operative mortality and paraplegia [9]. Recent trends in outcomes analysis, however, have supported the use of a single composite end point that reflects the probability of
Presented at the Forty-sixth Annual Meeting of the Southern Thoracic Surgical Association, San Juan, Puerto Rico, Nov 4 – 6, 1999. Address reprint requests to Dr Coselli, 6560 Fannin, #1100, Houston, TX 77030; e-mail: [email protected].
© 2001 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
(Ann Thorac Surg 2001;71:1233– 8) © 2001 by The Society of Thoracic Surgeons
Patients and Methods Patients Between January 1986 and December 1998, 1,220 consecutive patients underwent graft repair of TAAAs by a single surgeon (JSC). Of these, 112 patients (9.2%) had acute presentations, defined as acute pain, rupture, contained rupture, and complicated acute dissection [12]. Because nearly all patients with acute presentations undergo emergency operation and the need for a detailed decision analysis is essentially limited to elective cases, the 112 patients with acute presentations were excluded in the analysis and are not considered further in this study. A detailed analysis of these patients has been recently reported [13]. The characteristics of the remaining 1,108 patients who underwent elective TAAA repair are presented in Table 1. There were 659 men (59.5%) and 0003-4975/01/$20.00 PII S0003-4975(00)02678-3
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Table 1. Preoperative Characteristics of 1,108 Patients Undergoing Elective Thoracoabdominal Aortic Aneurysm Repair Characteristic Crawford extent Extent I Extent II Extent III Extent IV No dissection Chronic dissection Marfan syndrome Symptomatic aneurysms Preoperative paraplegia or paraparesis Concurrent aneurysm Prior aortic aneurysm repair Prior thoracic aortic aneurysm repair Ascending aorta and/or transverse aortic arch Elephant trunk Descending thoracic or thoracoabdominal aorta Diabetes Hypertension Coronary artery disease Prior coronary artery bypass or angioplasty Cerebrovascular disease Renal arterial occlusive disease Renal insufficiency Chronic obstructive lung disease Peptic ulcer disease
No. of Patients (%) 371 (33.5) 339 (30.6) 191 (17.2) 207 (18.7) 844 (76.2) 264 (23.8) 71 (6.4) 744 (67.1) 12 (1.1) 203 (18.3) 467 (42.1) 258 (23.3) 203 (18.3) 38 (3.4) 100 (9.0) 63 (5.7) 852 (76.9) 397 (35.8) 185 (16.7) 125 (11.3) 283 (25.5) 137 (12.4) 435 (39.3) 78 (7.0)
is, information available at the time of preoperative evaluation, were entered into the analysis. In addition to patient age and gender, the preoperative characteristics analyzed are listed in Table 1. The aneurysms were classified based on extent as defined by Crawford and colleagues [17] (Fig 1). Aneurysms associated with aortic dissection were considered chronic if operation was performed beyond 14 days after the onset of pain. Patients were considered symptomatic when any symptom (acute or chronic, severe or mild) related to the aneurysm was present, including pain, hoarseness, and dysphagia. Preoperative renal insufficiency was defined as serum creatinine exceeding 3.0 mg/dL or need for hemodialysis. Chronic obstructive lung disease was defined as the need for pharmacologic therapy for the treatment of chronic pulmonary compromise or a forced expiratory volume in 1 second of less than 75% of predicted value. Cerebrovascular disease was defined as a history of transient ischemic attack or stroke, documented carotid stenosis more than 50%, or a history of carotid endarterectomy or other cerebrovascular procedures. Coronary artery disease was defined as documented coronary stenosis more than 50% or a history of angina, myocardial infarction, or coronary artery angioplasty or bypass. Hypertension was defined as a history of high blood pressure (exceeding 140/90 mm Hg) or the need for antihypertensive medications. A single, composite end point termed adverse outcome was defined as the occurrence of any of the following: operative death, paraplegia, paraparesis, stroke, or acute
449 women (40.5%). Patient ages ranged from 18 to 88 years (mean, 65.3 years; median, 68 years). Extensive TAAAs (ie, Crawford extents I and II; Fig 1) were present in 64.1% of the patients.
Surgical Technique The details of the surgical technique have been recently described elsewhere [14]. With regard to spinal cord protection, a combination of moderate heparinization, permissive mild hypothermia, and aggressive reattachment of critical intercostal arteries (T8 to L1) was used consistently throughout the entire series. Left heart bypass (LHB) was used in 349 (31.5%) patients; no blood reservoir, heat exchanger, or oxygenator was incorporated in the bypass circuit [15]. Spinal-evoked potentials were not monitored. The use of cerebrospinal fluid drainage was limited to 44 patients (4%) who were enrolled in a randomized clinical trial that began in May 1997 [16].
Study Variables and Definitions All preoperative, intraoperative, and postoperative data were gathered prospectively over the 13-year period and entered into a database. In creating the predictive model for an individual patient’s risk of an adverse outcome, only factors relevant to the decision-making process, that
Fig 1. The Crawford classification of thoracoabdominal aortic aneurysms is based on the extent of aortic involvement. Extent I aneurysms begin above the sixth intercostal space (usually near the left subclavian artery) and extend down to encompass the aorta at the origins of the celiac axis and superior mesenteric arteries; although the renal arteries may also be involved, the aneurysm does not extend into the infrarenal segment. Extent II aneurysms also arise above the sixth intercostal space but extend distally into the infrarenal aorta, often to the level of the aortic bifurcation. Extent III aneurysms begin in the distal half of the descending thoracic aorta (below the sixth intercostal space) and extend into the abdominal aorta. Extent IV aneurysms generally involve the entire abdominal aorta from the level of the diaphragm to the bifurcation.
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Table 2. Results of Thoracoabdominal Aortic Aneurysm Repair in 1,108 Consecutive Elective Cases
Extent
No. of Patients
Operative Mortality
Paraplegia/ Paraparesisa
Renal Failure Requiring Dialysisb
Strokec
Adverse Outcome
I II III IV Total
371 (33.5%) 339 (30.6%) 191 (17.2%) 207 (18.7%) 1108 (100%)
23 (6.2%) 31 (9.1%) 8 (4.2%) 8 (3.9%) 70 (6.3%)
11 (3.0%) 21 (6.2%) 6 (3.2%) 2 (1.0%) 40 (3.6%)
8 (2.2%) 31 (9.3%) 11 (5.8%) 11 (5.4%) 61 (5.6%)
5 (1.3%) 7 (2.1%) 2 (1.0%) 1 (0.5%) 15 (1.4%)
39 (10.5%) 68 (20.1%) 21 (11.0%) 16 (7.7%) 144 (13.0%)
a Excludes 2 patients who died during operation and 7 patients with preoperative paraplegia. c 14 patients receiving preoperative dialysis. Excludes 2 patients who died during operation.
renal failure requiring dialysis. An operative death was defined as death occurring within 30 days or within the initial postoperative hospitalization [18]. All patients with postoperative neurologic deficits involving the lower extremities were included in the adverse outcome category, regardless of whether the deficit was paralysis (paraplegia) or weakness (paraparesis), immediate or delayed, transient or permanent. This included patients with unilateral lower extremity deficits, unless an associated deficit involving the ipsilateral upper extremity— indicating a stroke—was present. Stroke was defined as any new clinically evident brain injury present after operation, including focal and global deficits, and transient and permanent deficits. Postoperative renal failure was defined as an increase in serum creatinine to greater than 3.0 mg/dL (if normal preoperatively) or the need to initiate hemodialysis.
Statistical Analyses The statistical analysis was performed using the SAS (release 6.12; SAS Institute, Inc, Cary, NC) system for Windows. Risk factors were evaluated for association with adverse outcome using univariate analyses: categoric variables were analyzed using the 2 or Fisher’s exact test and continuous data were analyzed using Student’s t test. Risk factors that emerged with significance levels below 0.25 were analyzed by way of multiple stepwise logistic regression with confirmatory manual selection. Associations with outcomes were considered statistically significant when p was less than 0.05.
Results Overall Operative Morbidity and Mortality An adverse outcome occurred in 144 patients (13.0%). Two patients (0.2%) died in the operating room. There were 70 operative deaths (6.3%), including 48 30-day deaths (4.3%) and 69 in-hospital deaths (6.2%). The combined incidence of paraplegia/paraparesis was 3.6% (40 of 1,099 patients, excluding 7 patients with preoperative paraplegia and 2 patients who died during operation). Fifteen patients had paraplegia (10 immediate and 5 delayed); none of these patients recovered significant function before discharge. Of the 25 patients with paraparesis (14 immediate and 11 delayed), 6 (24%) had marked improvement in lower extremity strength by the
b
Excludes 2 patients who died during operation and
time of discharge. Renal failure developed in 9.6% of patients (105 of 1,094, excluding 14 patients receiving preoperative hemodialysis and 2 patients who died during operation); 61 of these 105 patients (58.1%) required hemodialysis. Fifteen patients (1.4%) suffered postoperative strokes (15 of 1,106, excluding 2 patients who died during operation). The overall incidence of adverse outcomes did not change significantly between the periods of 1986 to 1992 (26 of 170 patients, 15.3%) and 1993 to 1998 (118 of 938, 12.6%; p ⫽ 0.398). Stratified results based on aneurysm extent are listed in Table 2. Patients who underwent extent II repairs had the highest complication rates. With the exception of renal failure, extent IV repairs resulted in the lowest complication rates. The incidence of renal failure requiring dialysis was lowest after extent I repairs. Associations between TAAA extent and complications were significant for paraplegia/paraparesis (p ⫽ 0.011), renal failure (p ⬍ 0.001), and adverse outcome (p ⬍ 0.001). The trend toward higher mortality and stroke rates after extent II repairs did not reach statistical significance (p ⫽ 0.440 and 0.513, respectively).
Risk Analysis for Adverse Outcome After Elective Repair Univariate analysis revealed the following factors to be associated with an adverse outcome (Table 3): increasing age, extent II aneurysm, symptomatic aneurysm, hypertension, renal arterial occlusive disease, and renal insufficiency. Patients with extent IV aneurysms and previous thoracic aortic aneurysm repairs had a reduced risk of adverse outcome. Adverse outcomes occurred with similar frequencies regardless of site of previous thoracic aortic repair: 16 of 203 patients (7.8%) with prior ascending aortic or transverse aortic arch repairs, 8 of 100 patients (8%) with previous descending thoracic or TAAA repairs, and 3 of 38 patients (7.9%) with previous elephant trunk procedures. Only the former group, however, had a protective benefit that reached statistical significance (p ⫽ 0.022) when compared to patients without previous thoracic aortic repairs. On the basis of significant risk factors determined by multivariable analysis (Table 4), the probability of an adverse outcome after TAAA repair was predicted by: Risk ⫽ odds/(1 ⫹ odds), where odds ⫽ exp [(age ⫻ 0.0272) ⫹ (C2 ⫻ 0.8945) ⫹ (symptoms ⫻ 0.5504) ⫹ (renal ⫻
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Table 3. Results (p Values) of Univariate Analysis Regarding Factors Associated With Adverse Outcome After Thoracoabdominal Aortic Aneurysm Repair Adverse Outcome
Variable Age Gender Chronic dissection No dissection Extent I Extent II Extent III Extent IVa Marfan syndrome Symptomatic aneurysm Prior aortic aneurysm repair Prior thoracic aneurysm repaira Ascending aorta and/or transverse aortic archa Elephant trunk Descending thoracic or thoracoabdominal aorta Concurrent aneurysm Hypertension Diabetes mellitus Coronary artery disease Prior CABG or coronary angioplasty Renal arterial occlusive disease Renal insufficiency Hemodialysis Cerebrovascular disease Peptic ulcer disease Chronic obstructive pulmonary disease Preoperative paraplegia a
0.004 0.483 0.704 0.704 0.099 0.001 0.432 0.017 0.529 0.015 0.193 0.001 0.022 0.464 0.161 0.259 0.038 0.096 0.723 0.542 0.001 0.001 0.097 1.000 0.240 0.719 0.279
Factor associated with decreased risk.
CABG ⫽ coronary artery bypass grafting.
1.2612) ⫺ 4.6597], age ⫽ patient age in years, C2 ⫽ 1 for patients with an extent II aneurysm and 0 for patients with an extent I, III, or IV aneurysm, symptoms ⫽ 1 or 0, respectively, for patients with or without symptoms related to the aneurysm, and renal ⫽ 1 or 0, respectively, for patients with or without preoperative renal insufficiency. Risk stratification curves were constructed to allow rapid estimation of risk for any given patient (Fig 2). For Table 4. Results of Multivariable Analysis Regarding Adverse Outcome After Elective Thoracoabdominal Aortic Aneurysm Repair
Variable Intercept Age Extent II aneurysm Symptomatic Renal insufficiency
Parameter Estimate
p Value
Odds Ratio
95% Confidence Interval
⫺4.6597 0.0272 0.8945 0.5504 1.2612
0.0001 0.004 0.0001 0.02 0.0001
... 1.028/yr 2.446 1.734 3.350
... 1.009 –1.046 1.689 –3.543 1.130 –2.640 2.294 –5.430
Fig 2. Risk stratification curves to allow rapid estimation of the risk for an adverse outcome after elective surgical repair of a thoracoabdominal aortic aneurysm (A) is used for patients requiring an extent II repair and (B) is used for patients undergoing an extent I, III, or IV repair.
example, a 60-year-old patient with renal insufficiency and an asymptomatic extent III TAAA would have a 14% risk of an adverse outcome after operation. A secondary analysis was performed to evaluate the impact of LHB on adverse events. This adjunct did not significantly reduce the incidence of paraplegia, paraparesis, or adverse outcome in either extent I or II repairs (Table 5).
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Table 5. Secondary Analysis Regarding the Impact of Left Heart Bypass (LHB) on Paraplegia and Adverse Outcome in Patients Undergoing Elective Thoracoabdominal Aortic Aneurysm Repair
Extent I With LHB Without LHB p Value Extent II With LHB Without LHB p value
No. of Patients
Paraplegia/ paraparesis
Adverse Outcome
129 242
5 (3.9%) 6 (2.5%) 0.528
12 (9.3%) 27 (11.2%) 0.706
209 130
11 (5.3%) 10 (7.7%) 0.479
44 (21.1%) 24 (18.5%) 0.660
Comment The recent report regarding the risk of rupture for patients with degenerative thoracic aortic aneurysms (ie, without dissection) by Juvonen and colleagues [8] was the primary impetus for our initial analysis concerning elective cases. Unsatisfied with the usual method of assessing the risk of rupture— big aneurysm versus small aneurysm—the Mount Sinai group performed a multivariable analysis that included data from computergenerated three-dimensional computed tomographic reconstructions of the thoracoabdominal aorta. The resulting formula determines the probability of rupture within one year based on patient age, the presence of pain and chronic obstructive pulmonary disease, and the maximum true diameters of the descending thoracic and abdominal aortic segments. More recently, Juvonen and colleagues [19] have published a companion study focusing on the risk factors for rupture after distal aortic dissection. In either setting, by comparing the calculated risk of rupture with the calculated risk of an adverse outcome after operation, decisions regarding treatment could be supported with objective data. The risk analysis of our series was undertaken to balance the Mount Sinai models for risk of rupture with a complementary model that predicts operative risk based on contemporary results. Using the risk formula presented, the probability of an adverse outcome after TAAA repair can be directly calculated for an individual patient. Alternatively, the risk stratification curves can be used to rapidly obtain an estimation of this probability for any given patient (Fig 2) [8]. Increasing age and preoperative renal insufficiency have remained major risk factors for adverse outcomes, especially early mortality, throughout the history of TAAA repair. Both were among the predictive variables for early death determined by Svensson and associates’ [20] multivariable analysis of Crawford’s complete experience with TAAA repair in 1,509 patients treated between 1960 and 1991. The recent report by Acher and colleagues [6] confirmed that, along with acute presentation, age and elevated creatinine levels remain important predictors of early death. Although all patients with acute symptoms were ex-
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cluded, the presence of symptoms related to the aneurysm remained an important predictor of poor outcome. Similarly, Juvonen and coworkers [8] documented an increased risk of rupture in patients who had pain that experienced surgeons had characterized as being unrelated to the aneurysm. Along the continuum between truly asymptomatic aneurysms and ruptured aneurysms, the appearance of even mild symptoms seems to represent progression into a subacute phase that carries both an increased risk of rupture and increased perioperative mortality and morbidity rates. Therefore, the development of any symptoms—no matter how mild or uncharacteristic—in a patient with a TAAA demands immediate evaluation. The aneurysm must be considered the cause until proven otherwise. If the source of the problem remains unexplained, aneurysm repair should be considered. Extent II aneurysms also remain a major risk factor for adverse outcomes [6, 20]. Twenty percent of patients undergoing elective extent II repairs either died, had a neurologic complication, or required hemodialysis. This high-risk group of patients has benefited the most from evolving refinements in operative technique and innovations in spinal cord protection. A recent randomized clinical trial demonstrated that cerebrospinal fluid drainage markedly reduced the incidence of paraplegia/ paraparesis after extent I or II TAAA repairs [16]. We have also recently reported that the use of LHB in patients with extent II TAAAs has reduced the incidence of paraplegia from 13.1% to 4.8% (p ⫽ 0.007) [21]. In the current study, however, the secondary analysis regarding the impact of LHB (strictly in the setting of elective TAAA repair) did not reveal a significant reduction in either neurologic deficits or adverse outcome. The primary benefit of LHB may occur in nonelective cases. Because a consistent beneficial effect from LHB remains elusive, a clinical trial designed to assess its role during TAAA repair may be warranted. In conclusion, contemporary surgical management of TAAAs provides favorable results for patients who are acceptable candidates. When balanced with models predicting the probability of aneurysm rupture, the operative risk model presented may assist in decisions regarding elective aortic repair. The chief limitation of the model concerns its derivation from a single surgeon’s experience over a 13-year period. Whether or not the model will be applicable to future patients remains to be seen. The predictive accuracy of the formula will require validation through prospective evaluations. The authors gratefully acknowledge Autumn Jamison for providing database management, statistical analysis, and invaluable assistance with manuscript preparation.
References 1. Griepp RB. Mortality and paraplegia after thoracoabdominal aortic aneurysm repair: a risk factor analysis [Discussion]. Ann Thorac Surg 2000;69:414. 2. Coady MA, Rizzo JA, Elefteriades JA. Developing surgical
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intervention criteria for thoracic aortic aneurysms. Cardiol Clin 1999;17:827–39. Jacobs MJHM, Meylaerts SA, de Haan P, de Mol BA, Kalkman CJ. Strategies to prevent neurologic deficit based on motor-evoked potentials in type I and II thoracoabdominal aortic aneurysm repair. J Vasc Surg 1999;29:48–59. Kouchoukos NT, Rokkas CK. Hypothermic cardiopulmonary bypass for spinal cord protection: rational and clinical results. Ann Thorac Surg 1999;67:1940–2. Safi HJ, Subramaniam MH, Miller CC, et al. Progress in the management of type I thoracoabdominal and descending thoracic aortic aneurysms. Ann Vasc Surg 1999;13:457– 62. Acher CW, Wynn MM, Hoch JR, Kranner PW. Cardiac function is a risk factor for paralysis in thoracoabdominal aortic replacement. J Vasc Surg 1998;27:821–30. Svensson LG, Hess KR, D’Agostino RS, et al. Reduction of neurologic injury after high-risk thoracoabdominal aortic operation. Ann Thorac Surg 1998;66:132– 8. Juvonen T, Ergin MA, Galla JD, et al. Prospective study of the natural history of thoracic aortic aneurysms. Ann Thorac Surg 1997;63:1533– 45. Coselli JS, LeMaire SA, Miller CC III, et al. Mortality and paraplegia following thoracoabdominal aortic aneurysm repair: a risk factor analysis. Ann Thorac Surg 2000;69:409–14. Topouzis F, Yu F, Coleman AL. Factors associated with elevated rates of adverse outcomes after cyclodestructive procedures versus drainage device procedures. Ophthalmology 1998;105:2276– 81. Malley R, Inkelis SH, Coelho P, Huskins WC, Kuppermann N. Cerebrospinal fluid pleocytosis and prognosis in invasive meningococcal disease in children. Pediatr Infect Dis J 1998; 17:855–9. Acher CW, Wynn MM, Hoch JR, Popic P, Archibald J,
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Turnipseed WD. Combined use of cerebral spinal fluid drainage and naloxone reduces the risk of paraplegia in thoracoabdominal aortic aneurysm repair. J Vasc Surg 1994; 19:236– 48. Coselli JS, Rice DC, LeMaire SA, Schmittling ZC. Emergency surgery for thoracoabdominal aortic aneurysms with acute presentation. J Vasc Surg 2001; in press. Coselli JS, LeMaire SA. Surgical techniques: thoracoabdominal aorta. Cardiol Clin N Am 1999;17:751– 65. Coselli JS, LeMaire SA, Ledesma DF, Ohtsubo S, Tayama E, Nose´ Y. Initial experience with the Nikkiso centrifugal pump during thoracoabdominal aortic aneurysm repair. J Vasc Surg 1998;27:378– 83. Coselli JS, LeMaire SA, Ko¨ksoy C, et al. Cerebrospinal fluid drainage reduces paraplegia following thoracoabdominal aortic aneurysm repair: results of a clinical randomized trial. J Vasc Surg 2001; in press. Crawford ES, Crawford JL, Safi HJ, et al. Thoracoabdominal aortic aneurysms: preoperative and intraoperative factors determining immediate and long-term results of operation in 605 patients. J Vasc Surg 1986;3:389 – 404. Council of The Society of Thoracic Surgeons. Guidelines for data reporting and nomenclature for The Annals of Thoracic Surgery. Ann Thorac Surg 1988;46:260–1. Juvonen T, Ergin MA, Galla JD, et al. Risk factors for rupture of chronic type B dissections. J Thorac Cardiovasc Surg 1999; 117:776– 86. Svensson LG, Crawford ES, Hess KR, Coselli JS, Safi HJ. Experience with 1509 patients undergoing thoracoabdominal aortic operations. J Vasc Surg 1993;17:357–70. Coselli JS, LeMaire SA. Left heart bypass reduces paraplegia rates following thoracoabdominal aortic aneurysm repair. Ann Thorac Surg 1999;67:1931– 4.
Background. Recent recommendations have emphasized individualized treatment based on balancing a patient’s risk of thoracoabdominal aortic aneurysm rupture with the risk of an adverse outcome after surgical repair. The purpose of this study was to determine which preoperative risk factors currently predict an adverse outcome after elective thoracoabdominal aortic aneurysm repair. Methods. A single, composite end point termed adverse outcome was defined as the occurrence of any of the following: death within 30 days, death before discharge from the hospital, paraplegia, paraparesis, stroke, or acute renal failure requiring dialysis. A risk factor analysis was performed using data from 1,108 consecutive elective thoracoabdominal aortic aneurysm repairs.
Results. The incidence of an adverse outcome was 13.0% (144 of 1,108 patients); predictors included preoperative renal insufficiency (p ⴝ 0.0001), increasing age (p ⴝ 0.0035), symptomatic aneurysms (p ⴝ 0.020), and extent II aneurysms (p ⴝ 0.0001). These risk factors were used to construct an equation that estimates the probability of an adverse outcome for an individual patient. Conclusions. This new predictive model may assist in decisions regarding elective thoracoabdominal aortic aneurysm operations. For patients who are acceptable candidates, contemporary surgical management provides favorable results.
When I sit down with a patient to discuss risk of operation, I find that he or she is usually not too interested in all of the horrible things that can happen, but rather the probability of a good outcome. He is interested in the chances of getting out of this alive and in good shape. —R. Griepp [1]
doing well versus having an adverse outcome [1, 10, 11]. Such a model would allow estimation of a patient’s overall chance of surviving operation and leaving the hospital without neurologic deficits and without requiring hemodialysis. The purpose of this analysis of contemporary results was to determine which preoperative risk factors currently predict an adverse outcome after elective TAAA repair to enhance the risk– benefit decision-making process during preoperative assessment of individual patients.
A
s the results of surgical repair continue to improve, recent recommendations regarding thoracoabdominal aortic aneurysm (TAAA) management have emphasized individualized treatment based on balancing a patient’s risk of rupture with the risk of an adverse outcome after surgical repair [2–7]. To facilitate the first half of this fundamental risk versus benefit analysis, Juvonen and colleagues [8] developed a predictive model that estimates a patient’s risk of rupture in 1 year if the aneurysm is not repaired. To balance this model for rupture, we performed a retrospective analysis of 1,220 patients who had undergone TAAA repair and developed two predictive models focusing on the risk of operative mortality and paraplegia [9]. Recent trends in outcomes analysis, however, have supported the use of a single composite end point that reflects the probability of
Presented at the Forty-sixth Annual Meeting of the Southern Thoracic Surgical Association, San Juan, Puerto Rico, Nov 4 – 6, 1999. Address reprint requests to Dr Coselli, 6560 Fannin, #1100, Houston, TX 77030; e-mail: [email protected].
© 2001 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
(Ann Thorac Surg 2001;71:1233– 8) © 2001 by The Society of Thoracic Surgeons
Patients and Methods Patients Between January 1986 and December 1998, 1,220 consecutive patients underwent graft repair of TAAAs by a single surgeon (JSC). Of these, 112 patients (9.2%) had acute presentations, defined as acute pain, rupture, contained rupture, and complicated acute dissection [12]. Because nearly all patients with acute presentations undergo emergency operation and the need for a detailed decision analysis is essentially limited to elective cases, the 112 patients with acute presentations were excluded in the analysis and are not considered further in this study. A detailed analysis of these patients has been recently reported [13]. The characteristics of the remaining 1,108 patients who underwent elective TAAA repair are presented in Table 1. There were 659 men (59.5%) and 0003-4975/01/$20.00 PII S0003-4975(00)02678-3
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Table 1. Preoperative Characteristics of 1,108 Patients Undergoing Elective Thoracoabdominal Aortic Aneurysm Repair Characteristic Crawford extent Extent I Extent II Extent III Extent IV No dissection Chronic dissection Marfan syndrome Symptomatic aneurysms Preoperative paraplegia or paraparesis Concurrent aneurysm Prior aortic aneurysm repair Prior thoracic aortic aneurysm repair Ascending aorta and/or transverse aortic arch Elephant trunk Descending thoracic or thoracoabdominal aorta Diabetes Hypertension Coronary artery disease Prior coronary artery bypass or angioplasty Cerebrovascular disease Renal arterial occlusive disease Renal insufficiency Chronic obstructive lung disease Peptic ulcer disease
No. of Patients (%) 371 (33.5) 339 (30.6) 191 (17.2) 207 (18.7) 844 (76.2) 264 (23.8) 71 (6.4) 744 (67.1) 12 (1.1) 203 (18.3) 467 (42.1) 258 (23.3) 203 (18.3) 38 (3.4) 100 (9.0) 63 (5.7) 852 (76.9) 397 (35.8) 185 (16.7) 125 (11.3) 283 (25.5) 137 (12.4) 435 (39.3) 78 (7.0)
is, information available at the time of preoperative evaluation, were entered into the analysis. In addition to patient age and gender, the preoperative characteristics analyzed are listed in Table 1. The aneurysms were classified based on extent as defined by Crawford and colleagues [17] (Fig 1). Aneurysms associated with aortic dissection were considered chronic if operation was performed beyond 14 days after the onset of pain. Patients were considered symptomatic when any symptom (acute or chronic, severe or mild) related to the aneurysm was present, including pain, hoarseness, and dysphagia. Preoperative renal insufficiency was defined as serum creatinine exceeding 3.0 mg/dL or need for hemodialysis. Chronic obstructive lung disease was defined as the need for pharmacologic therapy for the treatment of chronic pulmonary compromise or a forced expiratory volume in 1 second of less than 75% of predicted value. Cerebrovascular disease was defined as a history of transient ischemic attack or stroke, documented carotid stenosis more than 50%, or a history of carotid endarterectomy or other cerebrovascular procedures. Coronary artery disease was defined as documented coronary stenosis more than 50% or a history of angina, myocardial infarction, or coronary artery angioplasty or bypass. Hypertension was defined as a history of high blood pressure (exceeding 140/90 mm Hg) or the need for antihypertensive medications. A single, composite end point termed adverse outcome was defined as the occurrence of any of the following: operative death, paraplegia, paraparesis, stroke, or acute
449 women (40.5%). Patient ages ranged from 18 to 88 years (mean, 65.3 years; median, 68 years). Extensive TAAAs (ie, Crawford extents I and II; Fig 1) were present in 64.1% of the patients.
Surgical Technique The details of the surgical technique have been recently described elsewhere [14]. With regard to spinal cord protection, a combination of moderate heparinization, permissive mild hypothermia, and aggressive reattachment of critical intercostal arteries (T8 to L1) was used consistently throughout the entire series. Left heart bypass (LHB) was used in 349 (31.5%) patients; no blood reservoir, heat exchanger, or oxygenator was incorporated in the bypass circuit [15]. Spinal-evoked potentials were not monitored. The use of cerebrospinal fluid drainage was limited to 44 patients (4%) who were enrolled in a randomized clinical trial that began in May 1997 [16].
Study Variables and Definitions All preoperative, intraoperative, and postoperative data were gathered prospectively over the 13-year period and entered into a database. In creating the predictive model for an individual patient’s risk of an adverse outcome, only factors relevant to the decision-making process, that
Fig 1. The Crawford classification of thoracoabdominal aortic aneurysms is based on the extent of aortic involvement. Extent I aneurysms begin above the sixth intercostal space (usually near the left subclavian artery) and extend down to encompass the aorta at the origins of the celiac axis and superior mesenteric arteries; although the renal arteries may also be involved, the aneurysm does not extend into the infrarenal segment. Extent II aneurysms also arise above the sixth intercostal space but extend distally into the infrarenal aorta, often to the level of the aortic bifurcation. Extent III aneurysms begin in the distal half of the descending thoracic aorta (below the sixth intercostal space) and extend into the abdominal aorta. Extent IV aneurysms generally involve the entire abdominal aorta from the level of the diaphragm to the bifurcation.
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Table 2. Results of Thoracoabdominal Aortic Aneurysm Repair in 1,108 Consecutive Elective Cases
Extent
No. of Patients
Operative Mortality
Paraplegia/ Paraparesisa
Renal Failure Requiring Dialysisb
Strokec
Adverse Outcome
I II III IV Total
371 (33.5%) 339 (30.6%) 191 (17.2%) 207 (18.7%) 1108 (100%)
23 (6.2%) 31 (9.1%) 8 (4.2%) 8 (3.9%) 70 (6.3%)
11 (3.0%) 21 (6.2%) 6 (3.2%) 2 (1.0%) 40 (3.6%)
8 (2.2%) 31 (9.3%) 11 (5.8%) 11 (5.4%) 61 (5.6%)
5 (1.3%) 7 (2.1%) 2 (1.0%) 1 (0.5%) 15 (1.4%)
39 (10.5%) 68 (20.1%) 21 (11.0%) 16 (7.7%) 144 (13.0%)
a Excludes 2 patients who died during operation and 7 patients with preoperative paraplegia. c 14 patients receiving preoperative dialysis. Excludes 2 patients who died during operation.
renal failure requiring dialysis. An operative death was defined as death occurring within 30 days or within the initial postoperative hospitalization [18]. All patients with postoperative neurologic deficits involving the lower extremities were included in the adverse outcome category, regardless of whether the deficit was paralysis (paraplegia) or weakness (paraparesis), immediate or delayed, transient or permanent. This included patients with unilateral lower extremity deficits, unless an associated deficit involving the ipsilateral upper extremity— indicating a stroke—was present. Stroke was defined as any new clinically evident brain injury present after operation, including focal and global deficits, and transient and permanent deficits. Postoperative renal failure was defined as an increase in serum creatinine to greater than 3.0 mg/dL (if normal preoperatively) or the need to initiate hemodialysis.
Statistical Analyses The statistical analysis was performed using the SAS (release 6.12; SAS Institute, Inc, Cary, NC) system for Windows. Risk factors were evaluated for association with adverse outcome using univariate analyses: categoric variables were analyzed using the 2 or Fisher’s exact test and continuous data were analyzed using Student’s t test. Risk factors that emerged with significance levels below 0.25 were analyzed by way of multiple stepwise logistic regression with confirmatory manual selection. Associations with outcomes were considered statistically significant when p was less than 0.05.
Results Overall Operative Morbidity and Mortality An adverse outcome occurred in 144 patients (13.0%). Two patients (0.2%) died in the operating room. There were 70 operative deaths (6.3%), including 48 30-day deaths (4.3%) and 69 in-hospital deaths (6.2%). The combined incidence of paraplegia/paraparesis was 3.6% (40 of 1,099 patients, excluding 7 patients with preoperative paraplegia and 2 patients who died during operation). Fifteen patients had paraplegia (10 immediate and 5 delayed); none of these patients recovered significant function before discharge. Of the 25 patients with paraparesis (14 immediate and 11 delayed), 6 (24%) had marked improvement in lower extremity strength by the
b
Excludes 2 patients who died during operation and
time of discharge. Renal failure developed in 9.6% of patients (105 of 1,094, excluding 14 patients receiving preoperative hemodialysis and 2 patients who died during operation); 61 of these 105 patients (58.1%) required hemodialysis. Fifteen patients (1.4%) suffered postoperative strokes (15 of 1,106, excluding 2 patients who died during operation). The overall incidence of adverse outcomes did not change significantly between the periods of 1986 to 1992 (26 of 170 patients, 15.3%) and 1993 to 1998 (118 of 938, 12.6%; p ⫽ 0.398). Stratified results based on aneurysm extent are listed in Table 2. Patients who underwent extent II repairs had the highest complication rates. With the exception of renal failure, extent IV repairs resulted in the lowest complication rates. The incidence of renal failure requiring dialysis was lowest after extent I repairs. Associations between TAAA extent and complications were significant for paraplegia/paraparesis (p ⫽ 0.011), renal failure (p ⬍ 0.001), and adverse outcome (p ⬍ 0.001). The trend toward higher mortality and stroke rates after extent II repairs did not reach statistical significance (p ⫽ 0.440 and 0.513, respectively).
Risk Analysis for Adverse Outcome After Elective Repair Univariate analysis revealed the following factors to be associated with an adverse outcome (Table 3): increasing age, extent II aneurysm, symptomatic aneurysm, hypertension, renal arterial occlusive disease, and renal insufficiency. Patients with extent IV aneurysms and previous thoracic aortic aneurysm repairs had a reduced risk of adverse outcome. Adverse outcomes occurred with similar frequencies regardless of site of previous thoracic aortic repair: 16 of 203 patients (7.8%) with prior ascending aortic or transverse aortic arch repairs, 8 of 100 patients (8%) with previous descending thoracic or TAAA repairs, and 3 of 38 patients (7.9%) with previous elephant trunk procedures. Only the former group, however, had a protective benefit that reached statistical significance (p ⫽ 0.022) when compared to patients without previous thoracic aortic repairs. On the basis of significant risk factors determined by multivariable analysis (Table 4), the probability of an adverse outcome after TAAA repair was predicted by: Risk ⫽ odds/(1 ⫹ odds), where odds ⫽ exp [(age ⫻ 0.0272) ⫹ (C2 ⫻ 0.8945) ⫹ (symptoms ⫻ 0.5504) ⫹ (renal ⫻
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Table 3. Results (p Values) of Univariate Analysis Regarding Factors Associated With Adverse Outcome After Thoracoabdominal Aortic Aneurysm Repair Adverse Outcome
Variable Age Gender Chronic dissection No dissection Extent I Extent II Extent III Extent IVa Marfan syndrome Symptomatic aneurysm Prior aortic aneurysm repair Prior thoracic aneurysm repaira Ascending aorta and/or transverse aortic archa Elephant trunk Descending thoracic or thoracoabdominal aorta Concurrent aneurysm Hypertension Diabetes mellitus Coronary artery disease Prior CABG or coronary angioplasty Renal arterial occlusive disease Renal insufficiency Hemodialysis Cerebrovascular disease Peptic ulcer disease Chronic obstructive pulmonary disease Preoperative paraplegia a
0.004 0.483 0.704 0.704 0.099 0.001 0.432 0.017 0.529 0.015 0.193 0.001 0.022 0.464 0.161 0.259 0.038 0.096 0.723 0.542 0.001 0.001 0.097 1.000 0.240 0.719 0.279
Factor associated with decreased risk.
CABG ⫽ coronary artery bypass grafting.
1.2612) ⫺ 4.6597], age ⫽ patient age in years, C2 ⫽ 1 for patients with an extent II aneurysm and 0 for patients with an extent I, III, or IV aneurysm, symptoms ⫽ 1 or 0, respectively, for patients with or without symptoms related to the aneurysm, and renal ⫽ 1 or 0, respectively, for patients with or without preoperative renal insufficiency. Risk stratification curves were constructed to allow rapid estimation of risk for any given patient (Fig 2). For Table 4. Results of Multivariable Analysis Regarding Adverse Outcome After Elective Thoracoabdominal Aortic Aneurysm Repair
Variable Intercept Age Extent II aneurysm Symptomatic Renal insufficiency
Parameter Estimate
p Value
Odds Ratio
95% Confidence Interval
⫺4.6597 0.0272 0.8945 0.5504 1.2612
0.0001 0.004 0.0001 0.02 0.0001
... 1.028/yr 2.446 1.734 3.350
... 1.009 –1.046 1.689 –3.543 1.130 –2.640 2.294 –5.430
Fig 2. Risk stratification curves to allow rapid estimation of the risk for an adverse outcome after elective surgical repair of a thoracoabdominal aortic aneurysm (A) is used for patients requiring an extent II repair and (B) is used for patients undergoing an extent I, III, or IV repair.
example, a 60-year-old patient with renal insufficiency and an asymptomatic extent III TAAA would have a 14% risk of an adverse outcome after operation. A secondary analysis was performed to evaluate the impact of LHB on adverse events. This adjunct did not significantly reduce the incidence of paraplegia, paraparesis, or adverse outcome in either extent I or II repairs (Table 5).
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Table 5. Secondary Analysis Regarding the Impact of Left Heart Bypass (LHB) on Paraplegia and Adverse Outcome in Patients Undergoing Elective Thoracoabdominal Aortic Aneurysm Repair
Extent I With LHB Without LHB p Value Extent II With LHB Without LHB p value
No. of Patients
Paraplegia/ paraparesis
Adverse Outcome
129 242
5 (3.9%) 6 (2.5%) 0.528
12 (9.3%) 27 (11.2%) 0.706
209 130
11 (5.3%) 10 (7.7%) 0.479
44 (21.1%) 24 (18.5%) 0.660
Comment The recent report regarding the risk of rupture for patients with degenerative thoracic aortic aneurysms (ie, without dissection) by Juvonen and colleagues [8] was the primary impetus for our initial analysis concerning elective cases. Unsatisfied with the usual method of assessing the risk of rupture— big aneurysm versus small aneurysm—the Mount Sinai group performed a multivariable analysis that included data from computergenerated three-dimensional computed tomographic reconstructions of the thoracoabdominal aorta. The resulting formula determines the probability of rupture within one year based on patient age, the presence of pain and chronic obstructive pulmonary disease, and the maximum true diameters of the descending thoracic and abdominal aortic segments. More recently, Juvonen and colleagues [19] have published a companion study focusing on the risk factors for rupture after distal aortic dissection. In either setting, by comparing the calculated risk of rupture with the calculated risk of an adverse outcome after operation, decisions regarding treatment could be supported with objective data. The risk analysis of our series was undertaken to balance the Mount Sinai models for risk of rupture with a complementary model that predicts operative risk based on contemporary results. Using the risk formula presented, the probability of an adverse outcome after TAAA repair can be directly calculated for an individual patient. Alternatively, the risk stratification curves can be used to rapidly obtain an estimation of this probability for any given patient (Fig 2) [8]. Increasing age and preoperative renal insufficiency have remained major risk factors for adverse outcomes, especially early mortality, throughout the history of TAAA repair. Both were among the predictive variables for early death determined by Svensson and associates’ [20] multivariable analysis of Crawford’s complete experience with TAAA repair in 1,509 patients treated between 1960 and 1991. The recent report by Acher and colleagues [6] confirmed that, along with acute presentation, age and elevated creatinine levels remain important predictors of early death. Although all patients with acute symptoms were ex-
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cluded, the presence of symptoms related to the aneurysm remained an important predictor of poor outcome. Similarly, Juvonen and coworkers [8] documented an increased risk of rupture in patients who had pain that experienced surgeons had characterized as being unrelated to the aneurysm. Along the continuum between truly asymptomatic aneurysms and ruptured aneurysms, the appearance of even mild symptoms seems to represent progression into a subacute phase that carries both an increased risk of rupture and increased perioperative mortality and morbidity rates. Therefore, the development of any symptoms—no matter how mild or uncharacteristic—in a patient with a TAAA demands immediate evaluation. The aneurysm must be considered the cause until proven otherwise. If the source of the problem remains unexplained, aneurysm repair should be considered. Extent II aneurysms also remain a major risk factor for adverse outcomes [6, 20]. Twenty percent of patients undergoing elective extent II repairs either died, had a neurologic complication, or required hemodialysis. This high-risk group of patients has benefited the most from evolving refinements in operative technique and innovations in spinal cord protection. A recent randomized clinical trial demonstrated that cerebrospinal fluid drainage markedly reduced the incidence of paraplegia/ paraparesis after extent I or II TAAA repairs [16]. We have also recently reported that the use of LHB in patients with extent II TAAAs has reduced the incidence of paraplegia from 13.1% to 4.8% (p ⫽ 0.007) [21]. In the current study, however, the secondary analysis regarding the impact of LHB (strictly in the setting of elective TAAA repair) did not reveal a significant reduction in either neurologic deficits or adverse outcome. The primary benefit of LHB may occur in nonelective cases. Because a consistent beneficial effect from LHB remains elusive, a clinical trial designed to assess its role during TAAA repair may be warranted. In conclusion, contemporary surgical management of TAAAs provides favorable results for patients who are acceptable candidates. When balanced with models predicting the probability of aneurysm rupture, the operative risk model presented may assist in decisions regarding elective aortic repair. The chief limitation of the model concerns its derivation from a single surgeon’s experience over a 13-year period. Whether or not the model will be applicable to future patients remains to be seen. The predictive accuracy of the formula will require validation through prospective evaluations. The authors gratefully acknowledge Autumn Jamison for providing database management, statistical analysis, and invaluable assistance with manuscript preparation.
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