Meta-Analysis of Individual Patient Data to Examine Factors Affecting Growth and Rupture of Small Abdominal Aortic Aneurysms

Abstract

INSTEAD trial and the known adverse affects of a patent false lumen after aortic dissection, studies such as this focusing on variables that can be identified after dissection as possible indicators for early endovascular therapy are clearly needed. Although patients with Marfan syndrome are not thought to be optimal candidates for endovascular treatments, non-Marfan patients with large proximal aortic tears and large aortas would seem to be two subgroups that would benefit from further study for "prophylactic" endovascular thoracic aortic repair after acute thoracic aortic resection. Meta-Analysis of Individual Patient Data to Examine Factors Affecting Growth and Rupture of Small Abdominal Aortic AneurysmsSweeting MJ, Thompson SG, Brown LC, et al; RESCAN collaborators. Br J Surg 2012;99:655-65. Conclusion: Risk factors differ for growth and rupture of small abdominal aortic aneurysms (AAAs). In addition to aneurysm diameter, diabetes and smoking may need to be considered in developing schedules for surveillance of small AAAs. No single drug for cardiovascular risk reduction has a pronounced affect on rupture or growth of small AAAs.Summary: It is now well established that screening for AAAs can reduce aneurysm-related mortality. Individual aneurysm and patient-specific factors affecting small AAA growth rate and rupture potential are not well established. Rupture of a small AAA is infrequent, and because most studies are small, there are little convincing data about factors that might affect risk of rupture of a small AAA. In addition, studies of growth rates of small AAAs have made minimal attempts to adjust for the multiplicity of potential risk factors in patients with AAA or to identify modifiers of aneurysm growth rate such as diabetes or smoking (Bergqvist D, Eur J Vasc Endovasc Surg 2011;41:663-1; and Powel JT et al, Br J Surg 2011;98:609-19; and Brady AR et al, Circulation 2004;110:16-21). In this report the authors used individual patient data from Ͼ15,000 people under follow-up for a small AAA to identify whether any of the common cardiovascular risk factors or classes of drugs used by patients with aneurysms influence growth and rupture rates of small AAAs. The authors requested individual patient data from corresponding authors of 25 studies that included Ͼ100 patients with a small AAA. Eighteen studies provided data to the RESCAN collaborators and 15,475 people were entered into the database. The effects of covariables (patient demographics, medical, and drug history) on AAA growth rate were summarized in an individual patient meta-analysis. Analysis used longitudinal random-affects modeling and survival analysis adjusted for aneurysm diameter. The mean AAA growth rate was 2.21 mm/y. AAA growth was independent of age and sex. The growth rate in smokers was increased by 0.35 mm/y, and the growth rate in patients with diabetes was decreased by 0.51 mm/y. Cardioprotective medications, mean arterial pressure, or use of antihypertensive medications had no significant effects on AAA growth. Calendar...

Morphological suitability for endovascular repair, non-intervention rates, and operative mortality in women and men assessed for intact abdominal aortic aneurysm repair: systematic reviews with meta-analysis

“…1 The decision to offer repair is made when the probable risk of rupture exceeds the risk of repair. Since the rate of rupture of small abdominal aortic aneurysm is four times higher in women than men at the same diameter, 2 women are often considered for repair at diameters smaller than 5·5 cm. Several studies 3,4 have suggested that the prognosis of individuals with abdominal aortic aneurysm is worse for women than men, with the operative mortality following repair of intact aneurysm being higher in women than men.…”

The association between body mass index and abdominal aortic aneurysm growth: a systematic review

“…Our most recent meta-analysis [6] of 19 studies demonstrated a statistically signifi cant slower growth rate in diabetic patients than in non-diabetic patients (unadjusted standardized MD (SMD), -0.32; 95% CI, -0.40 to -0.24; P < 0.00001; adjusted SMD, -0.29; 95% CI, -0.417 to -0.18; P < 0.00001). Taken together, diabetes is independently and negatively associated with both AAA presence [3,4] and growth [5,6], which suggests that decelerated mechanisms regarding the expansion of an existing AAA may be the same as those regarding the initial formation of an AAA. Further investigations are required to elucidate why BMI is not associated with AAA growth despite its trend toward a positive association with AAA presence.…”

“…When the data from six prospective cohort studies (OR, 0.54; 95% CI, 0.46 to 0.63; P < 0.00001), fi ve population screening studies (OR, 0.65; 95% CI, 0.57 to 0.75; p < 0.00001), and two casecontrol studies (OR, 0.27; 95% CI, 0.11 to 0.67; P = 0.005) were separately pooled, diabetes was also independently and signifi cantly associated with a lower prevalence of AAA (P for subgroup diff erences = 0.05) [4]. Furthermore, diabetes is also independently and negatively associated with AAA growth [5,6]. The RESCAN meta-analysis [5] of individual data from 6,268 patients from 10 studies (of the available 18 studies) demonstrated that diabetics had growth rates that were on average 0.51 (SE, 0.10) mm/year slower than those of non-diabetics, after adjustment for all demographics, medical history and drug history.…”

“…Furthermore, diabetes is also independently and negatively associated with AAA growth [5,6]. The RESCAN meta-analysis [5] of individual data from 6,268 patients from 10 studies (of the available 18 studies) demonstrated that diabetics had growth rates that were on average 0.51 (SE, 0.10) mm/year slower than those of non-diabetics, after adjustment for all demographics, medical history and drug history. Our most recent meta-analysis [6] of 19 studies demonstrated a statistically signifi cant slower growth rate in diabetic patients than in non-diabetic patients (unadjusted standardized MD (SMD), -0.32; 95% CI, -0.40 to -0.24; P < 0.00001; adjusted SMD, -0.29; 95% CI, -0.417 to -0.18; P < 0.00001).…”

“…Although abdominal aortic aneurysms (AAA) share many risk factors with occlusive vascular disease, there are some distinct features of both diseases, such as the disparate association between diabetes with atherothrombosis and AAA [1,2]. Type 2 diabetes, a state of relative insulin resistance, is negatively associated with both AAA presence [3,4] and growth [5,6]. These fi ndings suggest a protective role of obesity against AAA presence or growth [1], because one of the main mechanisms by which obesity has been implicated in vascular disease is insulin resistance [7].…”