Does the angiotensin-converting enzyme (ACE) gene polymorphism affect rate of abdominal aortic aneurvsm expansion?

Objectives: the tissue renin-angiotensin system (RAS), which plays an important role in vascular structure and function, is regulated in part by an insertion-deletion polymorphism of the angiotensin converting enzyme (ACE) gene. We hypothesised that ACE genotype might affect rate of AAA expansion via modulating long-term structural changes associated with RAS activation. Methods: fifty-eight patients (50 M, mean age 70 years, mean initial aneurysin size 4.3cm) with current or previous AAA and serial (>3) annual ultrasound measurements of antero-posterior AAA size provided a sample of leucocyte DNA for ACE genotyping. AAA expansion rate (cm per year) for individual subjects was calculated by linear regression. Results: median AAA expansion rate was 0.28 cm/year (range 0-1.8 cm/year), and the genotype distribution included DD (n = 14), DI (n 29) and 11 (n = 15). Corresponding median AAA expansion rates for each of the three genetic subgroups were 0.22, 0,32 and 0,30 cm/year, respectively (p = 0.6, nonparametric). Conclusions: the wide inter-individual variability in AAA expansion rate is likely to reflect complex genetic and environmental interactions, but the lack of any relationship with ACE genotype suggests that differences in vascular ACE activity in aortic tissue are not major determinants of the variability in rate of AAA dilatation.