Lifeline Registry Update: Expansion to an Outcomes Registry
An overview of the progress to date and expanding initiatives for the near future.
The Lifeline Registry of Endovascular Aneurysm Repair was established in 1998 by the Lifeline Foundation (now American Vascular Association Foundation), the nonprofit foundation of the Society for Vascular Surgery (SVS), as a mechanism to collect long-term safety, efficacy, and outcome data on endovascular graft recipients. Financial support for the Lifeline Registry is provided by Boston Scientific Corporation, Cook Incorporated, Edwards Lifesciences LLC, Endologix Incorporated, W. L. Gore & Associates, Guidant Corporation, Medtronic AVE, and TriVascular. The Registry database is managed and analyzed by New England Research Institutes, Inc., in Watertown, Massachusetts.
At the June 2004 Annual Conference of the Society for Vascular Surgery, Christopher Zarins, MD, on behalf of the Registry Publications Committee, presented the results of primary outcome measures (all-cause mortality, aneurysm-related mortality, rupture, surgical conversion) at 6 years.
The Registry contains data from the Guidant Ancure, Medtronic AneuRx, Gore Excluder, and Endologix PowerLink IDE abdominal aortic aneurysm (AAA) clinical trials with corresponding surgical controls, as well as postmarket commercial data from patients treated with Guidant Ancure, Medtronic AneuRx, Gore Excluder, Medtronic Talent (Investigator IDE), and Cook Zenith devices. With the coordination of Andrew Hill, MD, the Canadian Society for Vascular Surgery also participates in the registry by providing data on commercially available endovascular grafts. There are currently 2,908 endovascular graft patients and 334 surgical control patients in the Lifeline Registry database. This robust collection of safety, efficacy, and outcomes provides unbiased reporting of data.
Because the basic tenet of the Lifeline Registry is to evaluate long-term safety and efficacy of endovascular grafts in general, all data analyses are performed by pooling results from multiple endovascular grafts. It is the position of the Registry that through pooling of results, the most reliable data regarding the utility of a new technology will be uncovered. Given the variability in the devices, including the experience of the surgeon, device improvements, device features, and patient compliance, device-specific analyses are not currently performed.
Overall, patients receiving endovascular grafts were older and had more cardiac comorbidities compared to surgical controls (ie, open repair), but there was no difference in the primary endpoints of all-cause mortality, AAA death, or aneurysm rupture between the endovascular graft and surgical control groups up to 3 years. In general, analyses of endovascular graft data obtained from clinical trials (ie, manufacturer IDE) compared with commercially available grafts (ie, postmarket surveillance) showed no statistically significant differences in either baseline characteristics or outcomes. Kaplan-Meier analysis of all endovascular graft recipients at 6 years revealed 99% freedom from rupture and 98% freedom from aneurysm-related death. Results of endovascular aneurysm repair are favorable even in elderly, higher-risk populations who are not appropriate candidates for surgery. Women have a higher risk of rupture and surgical conversion than men, but no difference in AAA death rate. It was concluded that endovascular grafts can be a safe, effective, and durable treatment of infrarenal AAAs. Appropriate patient selection and follow-up are necessary to optimize results. These data demonstrate safety, effectiveness, and long-term durability of endovascular grafts in the treatment of patients with infrarenal aneurysms.
The Registry has published two reports regarding its design and content; however, the first detailed report of primary outcomes was submitted in December 2004 to the Journal of Vascular Surgery for publication. In addition to the impending publication, the Registry is working closely with the FDA and industry to provide a pool of surgical control patients, currently 334 patients, in a standard report format to model more efficient phase II clinical trials for premarketing approval.
Using the extensive experience with the Lifeline Registry, the SVS has the platform and the experience to establish and provide outcome analyses on thoracic aortic aneurysms (both endovascular graft recipients and open repair surgical controls). The Society is also developing a carotid stent/carotid endarterectomy registry to encompass both an extensive analysis of required postapproval studies and pending broad-label trials. In addition, the SVS is developing a program with the American College of Surgeons to initiate a carotid outcomes registry based on the National Surgical Quality Improvement Program (NSQIP) database. The effort to expand into a vascular outcomes registry is the new priority for the newly reorganized AVA/SVS.
Incidence of AAAs in CABG Patients
The purpose of the Epics I study is to identify the prevalence of unanticipated abdominal aortic aneurysms in patients with a history of coronary artery bypass grafting.
By Carlo A. Dall'Olmo, MD, for the Epics I Investigators: Allan L. Ippolito, MD; John M. McIlduff, MD; Wayne K. Kinning, MD; Gregory J. Fortin, MD;
Scott A. Garner, MD; Robert G. Molnar, MD; Brad M. Sweda, MD;
Thomas A. Shuster, DO; Russell W. Becker, DO; Brenda S. Buckle, ANP, bc;Joanne e. Drago, RVT; and Ann M. Inskeep, RVT
The validity, need, cost effectiveness, and benefits of screening for abdominal aortic aneurysms (AAAs) have been clearly established.1-6 Several large population-based, randomized screening trials have reported an AAA prevalence of 3.6% to 7.6% in men and 1% to 1.3% in women.7-13 In all but two studies, the enrollment age for subjects was 65 years and older.8-12 In those two studies, one in men and one in women, the enrollment age was 50 years of age and older, and the prevalence of AAAs was 3.6% for men and 1% for women.7,13 Little has been written, however, about the prevalence of AAAs in the subset of the population undergoing coronary artery bypass grafting (CABG).
Recently, Monney et al studied the prevalence of AAAs in a group of male patients, 60 years of age and older, who had undergone CABG.14 In 395 consecutive CABG patients, they found 40 AAAs, for a prevalence of 10.1%. Because this represents an increase in the prevalence of AAAs versus that reported in the studies of the population at large, we believed it was important to gather more data on this subset and initiated the Evaluation of Unsuspected Abdominal Aortic Aneurysms in Patients Who Have Undergone Coronary Artery Bypass Grafting (Epics I) study.
As a result, we decided to screen for AAAs in 750 subjects (both men and women), who had undergone CABG. Women were included to see if the prevalence of AAAs in this subset was greater than what is reported in the population at large.12,13 All subjects were 60 years of age and older. Excluded were subjects with either a known AAA or a history of AAA that had been surgically treated in the past. Data regarding the subject's smoking history and the presence or absence of hypertension and diabetes were obtained. The diagnosis of AAA was based on an ultrasound measurement of the abdominal aorta of 30 mm or greater in either a transverse or an anterior-posterior diameter.15 Screening was performed by registered vascular technologists in our vascular laboratory using a 2-MHz to 3.5-MHz probe on HP (Palo Alto, CA), GE Healthcare (Salt Lake City, UT), Philips Medical Systems (Best, The Netherlands), and Siemens Medical Solutions (Malvern, PA) Duplex machines. Eligible patients were enrolled after being referred by their cardiac surgeons or by self-referral when informed of the study in our office. All confidentiality guidelines were honored.
The study was initiated in September 2004 and as of January 4, 2005, we have screened 502 subjects: 339 men and 163 women. The following represents the preliminary results in the initial 502 subjects.
Table 1 represents the total number of male and female subjects, the number in whom an ultrasound could not be performed, the number screened, the number of AAAs found, and the prevalence of AAAs in each group. Obesity was the main reason for inadequate ultrasound examinations. Table 2 represents the subject age distribution and the AAAs found, and Table 3 gives a breakdown in AAA size for each group.
Table 4 represents the smoking history of men and women, divided into three categories: nonsmokers, previous smokers, and current smokers, and the prevalence of AAAs found in each group.
Table 5 lists the number of diabetics (type 1 or 2), nondiabetics, the number of subjects with a history of hypertension, and the prevalence of AAAs in each group.
The preliminary findings in this study indicate that male subjects 60 years of age and older with a history of CABG had a prevalence of unsuspected AAAs of 6.6%, whereas in women aged 60 years and older with a history of CABG, the prevalence was 3.2%. Although the prevalence of AAAs in our study for men was not as high as the 10.1% reported in the series of Monney et al, it is equal to or greater than the prevalence of 3.6% to 7.6% reported in a number of large randomized AAA screening trials.7-11,14
When comparing the prevalence of AAAs in men identified in these large screening trials, one notices the age selected for the subject's enrollment differs from study to study. Whereas our study and that of Monney et al enrolled men beginning at age 60, most studies used age 65 years and older as the enrollment age.8-11,14 Only one study used 50 years of age as the enrollment age; in this study, the prevalence of AAAs was 3.6% for men.7 Because age has been reported as an independent risk factor for the development of AAAs with their prevalence increasing with age, it is not surprising that the study enrolling men at a younger age had the lowest prevalence rate (3.6%).7,16,17 Although the enrollment age for men in our study was 60 years of age, the 6.6% prevalence rate was at the upper end of the 4% to 7.6% reported in studies enrolling men 65 years and older, suggesting that the prevalence of AAAs may be higher in the subset of male subjects with a history of CABG. Because our study design was to uncover “unsuspected” AAAs, 11 men with a history of CABG were excluded because they had a known history of AAA or had been treated for an AAA in the past. Had they been included, the prevalence of AAAs in this subset of men would have been 9.2%. No women were excluded because of a known or previously treated AAA.
One unexpected finding in the female group screened for AAAs was the 3.2% prevalence. Previous series reported a prevalence of unsuspected AAAs in women of 1%.12,13 We realize our sample size is small, but these preliminary findings suggest that this is an area that merits further investigation.
Age has been reported as an independent risk factor in the prevalence of AAAs, and our findings in both men and women as shown in Table 2 are in keeping with this.16,17
Smoking has been reported to be the single most preventable risk factor for AAAs. As reported in multiple studies, current smokers are 7.6 times more likely to have an AAA than nonsmokers, and exsmokers are three times more likely to have an AAA than nonsmokers.17-20 Our findings in men (Table 4) reveal that the majority of AAAs (21 of 22) were identified in current and former smokers. Interestingly, in the female group, two of the five aneurysms were found in nonsmokers, and the remaining three were found in former smokers. We look forward to gaining more smoking-related data as the study unfolds in this subset of patients.
Hypertension was defined by history as those subjects formerly or currently on antihypertensive medication. All five AAAs found in women were in the hypertensive group of 133 women, whereas 16 AAAs were found in 254 hypertensive men. Six AAAs were found in normotensive men. The use of antihypertensive medication, ever or current, was reported to increase the risk of AAAs in both men and women and our findings reflect this.16
From our preliminary findings, in subjects 60 years of age and older with a history of CABG screened for unsuspected AAAs, men had a prevalence of 6.6%, whereas women had a prevalence of 3.2%, three times that reported in population-based studies. These findings suggest that there is a higher than expected prevalence of AAAs in those individuals with a history of CABG and that screening for AAAs in this subset of patients has merit.
Age, male gender, smoking, and hypertension contribute to the prevalence of AAAs, whereas diabetes has a negative correlation.
Carlo A. Dall'Olmo, MD, is a vascular surgeon at The Michigan Vascular Center, and McLaren Regional Medical Center. He and fellow investigators Allan L. Ippolito, MD; John M. McIlduff, MD; Wayne K. Kinning, MD; Gregory J. Fortin, MD; Scott A. Garner, MD; Robert G. Molnar, MD; Brad M. Sweda, MD; Thomas A. Shuster, DO; Russell W. Becker, DO,Brenda S. Buckle, ANP, BC; Joanne E. Drago, RVT; and Ann M. Inskeep, RVT, have no financial interest in this study. It is supported by a grant to the Michigan Vascular Research Center by Medtronic, Inc. IRB approval for this study was obtained from McLaren Regional Medical Center on July 16, 2004. Dr. Dall'Olmo may be reached at (810) 732-1810; Carlodall@aol.com.
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