A population-based analysis of endovascular versus open thoracic aortic aneurysm repair

Article Outline

• Abstract
• Methods
• Results
• Discussion
• Conclusions
• Author contributions
• Acknowledgment
• References
• Copyright

Objective

The perioperative outcomes of open surgical and endovascular repair of intact thoracic aortic aneurysms (TAAs) during the last 3 months of 2005 were compared using a national administrative database.

Methods

The Nationwide Inpatient Sample was used to identify patients undergoing open aneurysm repair (OAR) or endovascular TAA repair (TEVAR) from October 1 to December 31, 2005. Patient demographic data, length of stay, hospital charges, patient disposition, and mortality were examined. Where appropriate, univariate tests of association used the χ² test, and multiple logistic regression analysis was used to determine predictors of in-hospital mortality, complications, and discharge status.

Results

A total of 1030 patients underwent open TAA repair and 267 underwent TEVAR. There was no significant difference in mortality between OAR and TEVAR (adjusted odds ratio [OR], 1.2; 95% confidence interval [CI], 0.73-2.12), although OAR patients were more likely to have cardiac, respiratory, and hemorrhagic complications. Patients undergoing TEVAR were more likely to be discharged to home (adjusted OR, 6.37; 95% CI, 2.93-13.70) and had a decreased length of stay (5.7 days vs 9.9 days; P = .0015). The differences in hospital charges and costs were not significant.

Conclusion

Although further study is warranted, this study of a national sample suggests that endovascular TAA repair is safe in the short-term, associated with fewer cardiac, respiratory, and hemorrhagic complications, and requires a shorter hospital stay.

An open surgical approach to thoracic aortic aneurysm (TAA) repair has been the method of treatment for 50 years. Open aneurysm repair (OAR) is associated with significant complications, however, including intraoperative and postoperative myocardial infarction, renal insufficiency, hemorrhage, postoperative pneumonia, lower extremity ischemia, stroke, and paralysis. These risks are compounded because aneurysm patients frequently have multiple cardiovascular comorbidities, protracted hospital stays, and poor long-term survival.¹ Despite this, these risks are frequently outweighed by the threat of aneurysm rupture, estimated to be 50% to 75% for large, untreated aneurysms, and its incumbent high mortality rate.², ³, ⁴

The last 20 years has witnessed the rapid development of a number of catheter-based approaches for the treatment of vascular pathologies since Parodi first established the feasibility of endovascular stent grafting.⁵ In the mid-1990s, the endovascular paradigm was first applied to aneurysms of the thoracic aorta.⁶, ⁷ Short-term results appear promising, but there remains a dearth of evidence on the success of this approach, in no small part due to the relatively rare occurrence of TAA compared with abdominal aortic aneurysm (AAA). TAA is estimated to occur in 6/100,000 person-years, compared with 36.5/100,000 person-years for AAA.⁴, ⁸ To date, no prospective, randomized trial has compared the two approaches, and the current published reports are plagued with significant limitations.⁹ Single-institution studies often display sampling bias and the effects of institutional learning curves. Case series are frequently weakened by small patient sample sizes and heterogeneous patient populations.

In late 2005, an International Classification and Diagnosis, Ninth Revision (ICD-9), procedure code unique to endovascular thoracic aortic aneurysm repair (TEVAR) was introduced.¹⁰ This allows for an analysis of data comparing OAR and TEVAR that provides a “snapshot” of the current state of practice in the United States (US). A literature search reveals that this is the first study comparing OAR and TEVAR patient outcomes from a large, unselected sampling that represents nearly the entire scope of unruptured TAA repairs in the country.

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Methods 

All data were abstracted from the Nationwide Inpatient Sample (NIS)¹¹ from October 1, 2005, through December 31, 2005. The NIS, the largest all-payer inpatient care database, is sponsored by the Agency for Healthcare Research and Quality¹² and contains data from >8 million hospital discharges annually from 1054 hospitals in 37 states, representing 90% of all US hospital discharges. The database contains patient and hospital demographic data, ICD-9 diagnosis and procedure codes, mortality information, and hospital charges.

Patients with an ICD-9 primary diagnosis code for TAA without mention of rupture (441.2) and with a primary procedure code for endovascular implantation of a graft in the thoracic aorta or resection of a vessel with replacement, specifically any thoracic vessel involvement (39.73 and 38.45, respectively) were selected for analysis.

Exclusion criteria included age <50 years, concurrent ICD-9 procedure codes for both OAR and TEVAR, and ICD-9 diagnosis codes for congenital anomalies such as gonadal dysgenesis, Marfan syndrome, and Turner syndrome, as well as the diagnosis of polyarteritis nodosa (758.6, 759.82, 446). Patients with abdominal or thoracoabdominal aneurysm diagnosis codes (441.1, 441.5, 441.4, 441.0, 441.6, 441.7) were excluded, as were those with procedure codes for the repair of these pathologies (39.71, 38.44).

Outcomes assessed included in-hospital mortality, postoperative complications, length of stay, hospital charges, hospital costs, patient disposition after discharge, and patient demographics such as age, gender, race, and number of cardiovascular comorbidities. The ICD-9 coding system has specific codes for complications resulting from a procedure, and these were used to determine the complication rates. The number of comorbidities was determined by the presence of ICD-9 diagnosis codes for diabetes mellitus, hypertension, preoperative renal insufficiency, chronic obstructive pulmonary disease, ischemic heart disease, cerebrovascular occlusive disease, and peripheral arterial disease.

Statistical analysis was performed using SAS 9.1 software (SAS Institute, Cary, NC). Descriptive statistics for baseline patient characteristics and in-hospital mortality were obtained. Where appropriate, univariate tests of association used the χ² test, and multiple logistic regression analyses were used to determine predictors of in-hospital mortality, complications, and discharge status. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. Values of P < .05 were considered statistically significant.

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Results 

During the last quarter of 2005, 1030 intact, unruptured TAAs were repaired (Table 1). Of those, 267 (26%) were repaired by TEVAR, and the remaining 763 (74%) were repaired by OAR.

Table I. Demographic and cardiovascular comorbidity data for open versus endovascular thoracic aortic aneurysm repair

Variable	Total	OAR	TEVAR	P
Patients, No.(%)	1030(100)	763(74.0)	267(26.0)
Age, mean ± SD, y	67.1 ± 21.4	66.1 ± 21.3	69.9 ± 20.9	.01
Sex, No.(%)
Male	689(66.9)	504(66.1)	185(69.2)
Female	341(33.1)	259(33.9)	82(30.8)	.35
Race, No.(%)
White	661(85.1)	533(89.0)	128(71.8)
Nonwhite	116(14.9)	66(11.0)	50(28.2)	<.0001
Pre-op comorbidities
Number, No.(%)
0-1	490(47.6)	407(53.3)	83(31.2)
2-3	483(46.9)	330(43.3)	153(57.3)
<4	57(5.5)	26(3.4)	31(11.6)	<.0001
Cardiovascular
Diabetesa	104(10.1)	84(11.0)	20(7.6)	.12
Hypertensionb	694(67.4)	490(64.3)	204(76.2)	.0004
Renal insufficiencyc	150(14.6)	97(12.7)	53(20.0)	.0036
COPDd	204(19.8)	138(18.1)	66(24.8)	.02
Ischemic heart diseasee	397(38.5)	282(36.9)	115(43.1)	.07
CVODf	91(8.8)	41(5.3)	50(18.8)	<.0001
PADg	75(7.3)	25(3.3)	50(18.7)	<.0001

COPD, Chronic obstructive pulmonary disease; CVOD, cerebrovascular occlusive disease; OAR, open aneurysm repair; PAD, peripheral arterial disease; TEVAR, thoracic endovascular aneurysm repair.

The average ages were 66 years for OAR patients and nearly 70 years for TEVAR (P = .01). Data on race were unavailable for 253 patients (24.6%). Of the remaining patients, almost 15% were nonwhite, and 43% of these underwent TEVAR compared with 19% of white patients (P < .0001). Women comprised one-third of the sample size (n = 341) and were as likely as men to undergo TEVAR (24% vs 27%; P = .35).

TEVAR patients tended to have a higher burden of cardiovascular comorbidities (P < .0001). Although TEVAR and OAR patients were similar in their rates of diabetes mellitus (P = .12) and ischemic heart disease (P = .07), the TEVAR patients were significantly more likely to have hypertension, renal insufficiency, chronic obstructive pulmonary disease, cerebrovascular occlusive disease, and peripheral artery disease (Table 1).

In-hospital mortality did not differ between the two repair approaches (Table II): OAR patients had a 6.4% mortality rate compared with 7.7% for TEVAR patients (P = .49). OAR patients had a higher overall complication rate (33% vs 20%; P < .0001). The two approaches were equivalent in their rates of iatrogenic cerebrovascular accident; however, hematoma development, postoperative infections, and cardiac, respiratory, and hemorrhagic complications were more likely to develop in OAR patients (Table III).

Table II. Clinical outcomes after open vs endovascular thoracic aortic aneurysm repair

Variable	OAR	TEVAR	P
Total patients, No.(%)	763(74.0)	267(26.0)
Death, No.(%)	49(6.4)	21(7.7)	.49
Complication, No.(%)
Any	253(33.1)	55(20.4)	<.0001
Cardiac	144(18.9)	15(5.7)	<.0001
Length of stay, d
Median±SD	9.9±20.3	5.7±10.2	.0015
Median	7	5	.0011
Disposition, No.(%)
Home	601(78.8)	242(90.3)
Institution	112(14.7)	5(2.0)	<.0001

OAR, Open aneurysm repair; SD, standard deviation; TEVAR, thoracic endovascular aneurysm repair.

Table III. Postoperative complications after open versus endovascular thoracic aortic aneurysm repair

Variable	OAR	TEVAR	OR	95% CI
Iatrogenic CVAa	0.034	0.019	1.84	0.70-4.84
Complication from a procedure
Cardiacb	0.189	0.057	3.85	2.23-6.66
Respiratoryc	0.072	0	41.81	2.57-679.21
Urinaryd	0.014	0.076	0.17	0.08-0.36
Complication during a procedure
Hemorrhagee	0.064	0.018	3.70	1.43-9.50
Hematomaf	0.077	0.089	0.85	0.52-1.40
Other postoperative infectiong	0.014	0	7.73	0.45-132.16

CI, confidence interval; CVA, cerebrovascular accident; OAR, open aneurysm repair; OR, odds ratio; TEVAR, thoracic endovascular aneurysm repair.

On average, TEVAR patients had hospital stays that were approximately half as long as OAR patients (P = .0015) and were more likely to be discharged to home rather than to an extended-care facility (P < .0001; Fig). Most TEVAR patients are discharged from the hospital within the first few days of their procedure, and a significantly higher number of OAR patients had prolonged hospitalizations (>10 days) than did TEVAR patients.

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• Fig 1. 

  Inpatient length of stay for open (dark bars) and endovascular (gray bars) thoracic aortic aneurysm repair.

TAA repair had an average hospital charge to the patient or insurer of $119,932 and an average cost to the hospital of $50,285, with no significant difference between the two approaches (data not shown). A subgroup analysis of patients who were free of complications found that the TEVAR approach was associated with a $10,000 reduction in cost (P = .0331), but no difference in hospital charges.

Multivariate analysis used the type of repair, age, gender, and the number of comorbidities to predict death, the development of a complication, and discharge to home (Table IV). OAR and an increased comorbidity burden were significant predictors of death. The type of repair and age predicted the development of a complication, and the repair type, age, gender, and comorbidity burden all predicted discharge to home.

Table IV. Multivariate analysis of independent predictors of adverse outcomes

Outcome	OR	95% CI	P
Death
Repair type (OAR vs TEVAR)	3.5	1.2-10.4	.03
Age (vs 50-64 years)
65-79	2.4	0.4-14.1	.53
≥80	1.6	0.2-12.3
Sex (male vs female)	0.8	0.4-1.9	.68
Comorbidities (vs 0-1)
2-3	1.4	0.6-3.3	<.0001
4-5	14.1	4.9-40.7
Complication
Repair type (OAR vs TEVAR)	1.5	1.0-2.3	.04
Age (vs 50-64 years)
65-79	2.7	1.6-4.7	.001
≥80	2.9	1.4-6.0
Sex (male vs female)	1.0	0.7-1.4	.92
Comorbidities (vs 0-1)
2-3	1.0	0.7-1.4	.18
4-5	0.4	0.2-1.1
Discharge to home
Repair type (OAR vs TEVAR)	0.1	0.1-0.3	<.0001
Age (vs 50-64 years)
>65-79	0.4	0.1-1.1	.04
≥80	0.2	0.1-0.7
Sex (male vs female)	3.4	2.1-5.5	<.0001
Comorbidities (vs 0-1)
2-3	0.4	0.3-0.7	<.0001
4-5	0.0	0.0-0.1

CI, Confidence interval; EVAR, endovascular aneurysm repair; OAR, open aneurysm repair; OR, odds ratio; TEVAR, thoracic endovascular aneurysm repair.

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Discussion 

Although our study demonstrated no difference in mortality rates between TEVAR (95% CI, 5.2%-11.7%) and OAR (95% CI, 4.9%-8.4%), TEVAR was associated with a significantly shorter hospital stay, fewer cardiac, respiratory, and hemorrhagic complications, and a higher likelihood of discharge to home rather than an extended-care facility.

Multivariate analysis revealed that women are less likely to be discharged to home than men. Overall, women undergoing TAA repair were older than their male counterparts (P = .0270), and this was generally true when broken down by repair type and the number of comorbidities present. No women with four or more comorbidities underwent TEVAR. Women undergoing TAA repair tended to be older and sicker, which may explain why female gender predicts discharge to an extended-care facility rather than to home.

Based on our data, OAR is currently performed approximately three times as often as TEVAR. If the experience with AAA is mirrored, it is entirely likely that the proportion of TAA repairs performed with an endovascular approach will increase. Stent grafts are designed and simulation-tested to be durable for 10 years, and in the coming years, more evidence will become available about the in vivo longevity of these grafts.⁹ If the data are favorable, many more patients, particularly younger patients, will become candidates for TEVAR. As the technology proliferates and the collective clinical experience with TEVAR increases on an individual practitioner and an institutional level, the mortality rate associated with endovascular repair for TAAs may decrease just as it has for endovascular AAA repair.¹³, ¹⁴

Our study demonstrated equivalent in-hospital costs and charges for the two types of repair. Although this information is useful in informing health care economists, policy decisions must be based on in-hospital as well as long-term financial data. That TEVAR patients are more often discharged to home rather than to an extended-care facility may favor this approach in the short-term, although this information must be tempered by the fact that many well-recognized complications of EVAR—namely endoleak, stent migration, and stent fracture—are known to occur more frequently after hospital discharge. In addition, TEVAR patients currently require life-long computed tomography surveillance, a cost that is not captured by the NIS. Further study comparing the late costs of both approaches using different data sources is needed.

Analysis of data for those patients who were free of complications revealed that the length of stay was shortened by approximately 1 day for both types of repair and costs and charges were decreased. The decrease in costs favored TEVAR.

Analysis of patient demographics reveals that this is one of the few examples in medicine of patients who belong to a minority racial group being more likely to receive the cutting edge care (ie, TEVAR). Prima facie, it may suggest that nonwhite patients are recipients of better, more technologically advanced care. A more likely explanation, however, is that minority patients tend to come to medical attention much later than white patients and with more cardiovascular comorbidities, making them poorer candidates for OAR. Certainly, this explanation would be more consistent with the previously published reports on disparities in cardiovascular health care.¹⁵, ¹⁶, ¹⁷

This investigation does present limitations associated with studies that use large administrative databases. Owing to the nature of the NIS, only in-hospital events, including mortality, can be captured. Because hospital admissions are not linked, readmissions are counted as separate events and cannot be linked to the original hospitalization. Accordingly, the NIS is not an appropriate data source for assessing late complications associated with TEVAR.

Furthermore, limited clinical information is available, making it impossible to garner more specific details such as aneurysm size or morphology. It is also not possible to evaluate all of the clinically important outcomes of TAA repair with the NIS, including postoperative paraplegia, which is a well-known and feared complication of TAA repair. The complication code for iatrogenic cerebrovascular accident refers specifically to ischemic or hemorrhagic stroke complicating a procedure. Although the code may include postprocedural paralysis, it is secondary to cerebral damage as the mechanism of injury, rather than spinal cord injury, which is a major concern in the repair of TAA but, regrettably, cannot be assessed using the NIS database.

The limited granularity of the database precludes its use in ascertaining more detailed information about the exact surgical methods used. Certain techniques for open surgical repair have become outmoded, but the database does not distinguish those cases in which they are used from the ones in which the most up-to-date, preferred surgical methods are used. This analysis includes all of those cases.

In addition, it is important to be cognizant that all TAA repairs fitting the inclusion criteria were included in this study, irrespective of surgeon and hospital volume. The literature does suggest that increased hospital volume—and especially surgeon volume—are important determinants of patient outcomes, particularly in major procedures such as TAA repair.¹⁸, ¹⁹

Only in-hospital events were captured, so it is possible that the TEVAR mortality rate is underestimated because these patients are released from the hospital more quickly than OAR patients; however, the equivalent mortality rates are consistent with single-institution series comparing the two approaches.²⁰, ²¹ On the other hand, OAR patients are more likely to be discharged to an extended-care facility. Deaths that occur at these secondary facilities are not captured in the NIS database, which may cause the OAR mortality rate to be underestimated as well. Studies of midterm follow-up for TEVAR show that the real concern for death lies in the immediate perioperative period before hospital discharge,²², ²³, ²⁴ suggesting that our mortality rate accurately captures the bulk of repair-related deaths.

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Conclusions 

This study demonstrates that endovascular repair is equivalent to open surgical repair for TAA repair in terms of in-hospital mortality, and is favorable in the development of cardiac, respiratory, and hemorrhagic complications, hospital length of stay, and discharge to home. Additional long-term study of the clinical and economic outcomes, as well as select immediate postoperative outcomes, such as paraplegia, between the two approaches is warranted.

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Author contributions 

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We thank Zhaohui Fan and Vivek Sharma for their assistance in analysis of the NIS database.

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References 

1. Leurs LJ, Bell R, Degrieck Y, Thomas S, Hobo R, Lundbom J, et al. Endovascular treatment of thoracic aortic diseases: Combined experience from the EUROSTAR and United Kingdom Thoracic Endograft registries. J Vasc Surg. 2004;40:670–679
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (190 KB)
   • CrossRef
2. Johansson G, Markstrom U, Sweedenborg J. Ruptured thoracic aortic aneurysms: a study of incidence and mortality rates. J Vasc Surg. 1995;21:985–988
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (354 KB)
   • CrossRef
3. McNamara JJ, Pressler V. Natural history of arteriosclerotic thoracic aneurysms. Ann Thorac Surg. 1978;26:468–473
   • View In Article
   • MEDLINE
   • CrossRef
4. Bickerstaff LK, Pairolero PC, Hollier LH, Melton LJ, Van Peenen HJ, Cherry KJ, et al. Thoracic aortic aneurysm: a population based approach. Surgery. 1982;92:1103–1107
   • View In Article
   • MEDLINE
5. Parodi J, Palmaz J, Barone H. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg. 1991;5:494–499
   • View In Article
6. Dake MD, Miller DC, Semba CP, Mitchell RS, Walker PJ, Liddell RP. Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med. 1994;331:1729–1734
   • View In Article
   • MEDLINE
   • CrossRef
7. Mitchell RS, Dake MD, Semba CP, Fogarty TJ, Zarins CK, Liddel RP, et al. Endovascular stent-graft repair of thoracic aortic aneurysms. J Thorac Cardiovasc Surg. 1996;111:1054–1062
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (1969 KB)
   • CrossRef
8. Melton LJ, Bickerstaff LK, Hollier LH, Van Peenen HJ, Lie JT, Pairolero PC, et al. Changing incidence of abdominal aortic aneurysms: a population-based study. Am J Epidemiol. 1984;120:379–386
   • View In Article
   • MEDLINE
9. Svensson LG, Kouchoukos NT, Miller DC. Expert consensus document on the treatment of descending thoracic aortic disease using endovascular stent-grafts. Ann Thorac Surg. 2008;85:S1–S41
   • View In Article
   • CrossRef
10. International Classification of Diseases; Rev 9. Washington, DC: Department of Health and Human Services; 1991;
    • View In Article
11. HCUP Nationwide Inpatient Sample (NIS). Healthcare Cost and Utilization Project (HCUP). Rockville, MD: Agency for Healthcare Research and Quality; 2005;www.hcup-us.ahrq.gov/nisoverview.jsp
    • View In Article
12. HCUP Nationwide Inpatient Sample (NIS). Healthcare Cost and Utilization Project (HCUP) (What is the NIS?). Rockville, MD: Agency for Healthcare Research and Quality; 2005;http://www.hcup-us.ahrq.gov/nisoverview.jsp#Whatis
    • View In Article
13. Cowan JA, Dimick JB, Henke PK, Rectenwald J, Stanley JC, Upchurch GR. Epidemiology of aortic aneurysm repair in the United States from 1993 to 2003. Ann N Y Acad Sci. 2006;1085:1–10
    • View In Article
    • MEDLINE
    • CrossRef
14. Dimick JB, Stanley JC, Axelrod DA, Kazmers A, Henke PK, Jacobs LA, et al. Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age. Ann Surg. 2002;235:579–585
    • View In Article
    • MEDLINE
    • CrossRef
15. Kressin NR, Petersen LA. Racial differences in the use of invasive cardiovascular procedures: review of the literature and prescription for future research. Ann Intern Med. 2001;135:352–366
    • View In Article
    • MEDLINE
16. Huber TS, Wang JG, Wheeler KG, Cuddeback JK, Dame DA, Ozaki CK, et al. Impact of race on the treatment for peripheral arterial occlusive disease. J Vasc Surg. 1999;30:417–425
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (82 KB)
    • CrossRef
17. Feinglass J, Rucker-Whitaker C, Lindquist L, McCarthy WJ, Pearce WH. Racial differences in primary and repeat lower extremity amputation: results from a multihospital study. J Vasc Surg. 2005;41:823–829
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (130 KB)
    • CrossRef
18. Birkmeyer JD, Siewers AE, Finlayson EV, Stukel TA, Lucas FL, Batista I, et al. Hospital volume and surgical mortality in the United States. N Engl J Med. 2002;346:1128–1137
    • View In Article
    • CrossRef
19. Birkmeyer JD, Stukel TA, Siewers AE, Goodney PP, Wennberg DE, Lucas FL. Surgeon volume and operative mortality in the United States. N Engl J Med. 2003;349:2117–2127
    • View In Article
    • CrossRef
20. Ellozy SH, Carroccio A, Minor M, Jacobs T, Chae K, Cha A, et al. Challenges of endovascular tube graft repair of thoracic aortic aneurysm: midterm follow-up and lessons learned. J Vasc Surg. 2003;38:676–683
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (496 KB)
    • CrossRef
21. Najibi S, Terramani TT, Weiss VJ, Mac Donald MJ, Lin PH, Redd DC, et al. Endoluminal versus open treatment of descending thoracic aortic aneurysms. J Vasc Surg. 2002;36:732–737
    • View In Article
    • Abstract
    • Full-Text PDF (77 KB)
    • CrossRef
22. Tespili M, Banfi C, Valsecchi O, Aiazzi L, Ricucci C, Guagliumi G, et al. Endovascular treatment of thoracic aortic disease: mid-term follow-up. Catheter Cardiovasc Interv. 2007;70:595–601
    • View In Article
    • CrossRef
23. Fattori R, Napoli G, Lovato L, Grazia C, Piva T, Rocchi G, et al. Descending thoracic aortic diseases: stent-graft repair. Radiology. 2003;229:176–183
    • View In Article
    • MEDLINE
    • CrossRef
24. Sandroussi C, Waltham M, Hughes CF, May J, Harris JP, Stephen MS, et al. Endovascular grafting of the thoracic aorta, an evolving therapy: ten-year experience in a single centre. ANZ J Surg. 2007;77:974–980
    • View In Article
    • CrossRef