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a Division of Thoracic and Cardiovascular Surgery, University of Florida College of Medicine, Gainesville, Florida
b Division of Biostatistics, Department of Epidemiology and Health Policy Research, University of Florida College of Medicine, Gainesville, Florida
c Division of Vascular and Endovascular Therapy, University of Florida College of Medicine, Gainesville, Florida
Accepted for publication August 6, 2010.
* Address correspondence to Dr Beaver, Division of Thoracic and Cardiovascular Surgery, University of Florida, PO Box 100129, Gainesville, FL 32610-0129 (Email: thomas.beaver{at}surgery.ufl.edu).
| Abstract |
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Methods: Retrospective review of thoracic aneurysm repair rates for 2000 to 2007 and analysis of patient characteristics and complications for 2006 and 2007 cohorts uses the National Inpatient Sample. International Classification of Diseases, 9th Revision codes were used to identify unruptured descending thoracic aneurysm cases undergoing either thoracic endovascular aortic repair (39.73) or open repair (38.45).
Results: Thoracic aneurysm open repair averaged 3.3 per million from 2000 to 2002 and increased to 5.6 per million in 2003 with introduction of 16 slice computed tomographic scanners. In 2005 endovascular repair was 1.2 repairs per million, which increased dramatically to 6.1 repairs per million in 2006. In 2007, endovascular repair decreased to 4.8 repairs per million while the open repair rate was 3.1 repairs per million. The 2006 and 2007 open repair cohorts had more favorable baseline characteristics compared with the endovascular cohort. Open repair mortality was significantly greater than endovascular mortality in 2006 (estimated relative risk, 8.48; 95% confidence interval 3.03 to 23.75), but not in 2007 (estimated relative risk, 0.71; 95% confidence interval 0.12 to 4.24). Length of stay was greater for open repair in 2006 and 2007.
Conclusions: Thoracic endovascular aortic repair has been rapidly adopted in the United States resulting in increased treatment of thoracic aortic aneurysms. Despite older age and comorbidities, endovascular repair had better outcomes and shorter hospital stays.
| Introduction |
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| Dr Martin discloses that he has a financial relationship with Terumo Corporation.
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In 2005 the United States Food and Drug Administration (US FDA) approved the first thoracic aortic endograft for descending thoracic aneurysm repair (TAG device; W. L. Gore and Assoc, Flagstaff, AZ) in the US. In May and June of 2008, the FDA approved two more thoracic endografts, Zenith TX2 (Cook Incorporated, Bloomington, IN) and Talent (Medtronic Vascular, Santa Rosa, CA). After introduction of these devices our institution witnessed increased utilization of thoracic endovascular aneurysm repair (TEVAR), which prompted this review of thoracic aneurysm repair trends using the National Inpatient Sample (NIS). The TEVAR is reported to offer benefits such as lower early morbidity and mortality [1–8], shorter operating times, decreased blood loss, and decreased hospital length of stay [3, 6, 9]. However, peripheral vascular complications, paralysis, and endoleaks (inadequate seal of the endografts) are associated with TEVAR [1, 2]. The TEVAR patients require rigorous life-long surveillance with computed tomographic (CT) scans for endoleaks and stent-graft migration.
Unlike Europe, the US does not have a thoracic endovascular stent registry. Consequently, national practice patterns, long-term outcomes, and patient characteristics in US clinical practice environment are largely unknown. This lack of data raises questions about current trends in thoracic aortic aneurysm repair. This report examines national TEVAR and open repair utilization trends, changes in utilization rates, and implications for the management of thoracic aortic disease.
| Material and Methods |
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The International Classification of Diseases, 9th Revision (ICD-9) codes were used to identify cases included in the analysis. We used previously described NIS exclusion criteria to identify descending thoracic aneurysm repairs [12]. Briefly, patients were ages 18 years and older, underwent thoracic aneurysm repair (38.45 and 39.73), and had an unruptured thoracic aneurysm diagnosis (441.2). Cases with both endovascular and open repair codes, ruptured thoracic aneurysms (441.1), or thoracoabdominal aneurysms (441.6 and 441.7) were excluded. Ruptured thoracic aneurysms were excluded because inclusion would distort outcome analysis of elective repairs. Annual repair rates were calculated by adjusting annual repair volume using annual 18+ population estimates provided by the US Census Bureau [13]. Comparisons for age, gender, race, and disposition after discharge with respect to repair type were examined for all included cases. Trends for abdominal aneurysm repair (38.44 and 39.71), unruptured thoracic aneurysm diagnosis (441.2), and thoracic CT scans (87.41) were analyzed by recording number of primary procedure or primary diagnosis codes and adjusting for annual population estimates [14].
Comorbidities, complications, and mortality were analyzed separately for 2006 and 2007 cohorts. Comorbidities and complications were identified using ICD-9 codes (Table 1). Random effects meta-analyses of yes or no events (comparing use to nonuse of the procedure) provided an overall estimate of the relative risk of open repair: TEVAR, 95% confidence limits, and a two-sided p value [15]. To control for institution, which we believed represented the most important confounder, only those hospitals performing both TEVAR and open repairs were included. Institution was the sampling unit, not the individual. Due to the small size of the subject pool available in matched institutions, statistical analysis examining gender and race as additional control variables was not possible. The same basic method, adjusting for institution, was used to compare age and length of stay using a mean of means analysis [16]. Results were similar whether including or excluding centers performing only one of the two procedures. We also performed a fixed effects meta-analysis using the Cornfield-Mantel-Haenszel method for in-hospital mortality; that analysis agreed with the above and is not reported.
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| Results |
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| Comment |
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Orandi and colleagues [11] and Schwarze and colleagues [10] hypothesized, and we agree, that TEVAR trends are mirroring EVAR trends showing increased endovascular and decreased open repair utilization. This study adds evidence that elderly patients are more likely to receive endovascular repair for both thoracic and abdominal aneurysms [10, 11]. The current findings support earlier results [11] showing that despite increased comorbidities for TEVAR patients, perioperative mortality and complications as well as length of stay are lower for TEVAR than open repair.
Orandi and colleagues [11] reported no significant differences for in-hospital mortality for TEVAR (7.7%) versus open repair (6.4%) for the 2005 cohort (p = 0.49). Although our 2007 hospital-matched analysis showed the mortality for open repair was also similar to that of TEVAR (1.35% vs 1.91%, respectively), the 2006 matched analysis showed a higher mortality with open repair. The reason for this discrepancy in mortality is unknown. The discrepancy between the 2006 and 2007 in-hospital mortality in the matched analysis may be influenced by hospital volume and (or) surgeon volume. Neither hospital nor surgeon volume were assessed in the matched analysis due to small sample sizes that were inadequate to perform the analysis.
Reasons for Increased UDTAA Repair
Overall increases in UDTAA repairs may be related to an increased pool of patients as it appears TEVAR was offered to older patients who previously may have been judged inoperable because the risk-to-benefit ratio of the procedure was not considered acceptable. The 2007 NIS cohort analysis revealed that TEVAR patients were older with more comorbidities than open repair patients. Alternatively, increased UDTAA repair rates may reflect the use of TEVAR in smaller aneurysms, although we could not directly investigate aneurysm size using NIS data. The literature for small AAA repair using EVAR is still developing with limited consensus on whether EVAR is appropriate for small AAA [17]. Additional research for long-term outcomes and incidence of repair for small aneurysms is needed for both TEVAR and EVAR.
Advances in CT technology may be another contributing factor related to the increased repair of UDTAA. In 2002, the 16-slice CT scanner became available. In 2003 increases in UDTAA diagnosis and UDTAA repair paralleled increased utilization of thoracic CT scans (Figs 1; 2). Similarly, in the 1970s and 1980s advances in two-dimensional echocardiography and the introduction of CT were associated with increases in the diagnosis of UDTAA [18]. In 2007 another rise in CT scan utilization was noted [19] and may reflect postoperative surveillance CT scans for TEVAR, but more likely reflects increased emergency room use of the so called "triple rule out" CT scan (for pulmonary embolus, coronary artery disease, and thoracic aortic disease).
The Implications of Increased TEVAR Utilization
The implications of increased TEVAR utilization must be considered carefully. The use of thoracic endografts is relatively new. It is prudent to examine data and concerns raised from the EVAR experience. Although TEVAR has rapidly been adopted into clinical practice, long-term data are lacking which is a concern in light of the EVAR experience. The European registry (European collaborators on stent-graft techniques for abdominal aortic aneurysm repair [EUROSTAR]) results reveal a small risk of late ruptures and aneurysm-related deaths after EVAR, raising concerns that similar risks may apply to TEVAR [20]. The FDA has issued a warning expressing similar concerns regarding lack of long-term EVAR outcomes data [21].
In addition to possible late ruptures, endoleaks and graft failure are important outcomes which necessitate the need for vigilant monitoring after endovascular intervention. The EVAR data have shown higher complication rates when follow-up is less than recommended. Patient compliance with follow-up may be more important for TEVAR than EVAR; the rate of type I proximal seal endoleaks are reported to occur more frequently after TEVAR than EVAR due to anatomic differences in the thoracic aorta [22]. Logistic difficulties regarding long-term patient follow-up in clinical practice must be acknowledged. Even in the setting of the Gore TAG thoracic stent clinical trial [2], which reported that late endoleaks occurred in 4% of trial subjects, patient follow-up was less than anticipated.
Given the lack of data currently available, TEVAR should only be used in anatomically appropriate patients who understand the importance of long-term follow-up and are willing to be compliant with surveillance recommendations. Younger patients requiring repair of thoracic aneurysms should be explicitly informed about the need for annual CT scan surveillance for endoleaks and may be better served with open repair as mortality rates for open repair have improved dramatically in recent years. A 2008 expert consensus panel reported a 4.8% 30 day open repair mortality at centers of excellence [23]. However, for elderly patients who may be considered unfit for open repair, TEVAR appears a viable option, at least in the short term [3, 24–26].
Off-Label Use of TEVAR
According to NIS data, 3,257 TEVARs were performed in the US in 2007. However, based on exclusion criteria in this study it appears only 1,103 TEVARs were used for UDTAA. This discrepancy illustrates the use of stent grafts for hybrid procedures and other aortic pathology in addition to UDTAA. Given the rapid adoption of TEVAR, future comparative effectiveness research focusing on patient outcomes from actual clinical practice including off-label utilization is warranted.
Public Health Implications
Epidemiologic data for thoracic aortic disease is limited and continued monitoring of the trends in UDTAA repair is warranted. Prior studies have shown the incidence of UDTAA is increasing with our growing elderly population, including patients with many comorbidities [18, 27]. Data from clinical trials are limited by restrictive inclusion criteria, small study populations, and use of historic controls, which may not reflect the typical clinical practice [1, 4, 9]. An additional consideration is the cost of open versus endovascular thoracic aneurysm repair. Data on short-term costs indicate that inpatient hospital costs are greater for open repair than TEVAR despite much higher endograft costs for TEVAR [28]. Additional research on the long-term outcomes, costs and quality of life are needed to determine the best surgical option for these patients.
Limitations
The results and conclusions which can be drawn from analyzing the NIS data are limited because the NIS does not collect data on clinical variables. The main limitation of this study is that results from the matched institution analysis may not be generalizable to hospitals that do not perform both TEVAR and open repair. The ICD-9 codes were used to identify descending thoracic aneurysms only because thoracic endografts are currently only FDA approved for UDTAA. Thus, ascending aneurysm repairs were not assessed in this study.
Conclusion
In summary, a dramatic shift in treatment of thoracic aortic disease is occurring in the United States toward TEVAR with an overall increase in thoracic aortic repair. Thoracic endovascular aortic repair is being offered to older patients with more comorbidities. Further comparative effectiveness research is required to understand the long-term clinical and financial implications of the choice of repair for patients with thoracic aortic disease.
| Acknowledgments |
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