The Combined Effect of Renin Angiotensin System Blockade and Metformin on Abdominal Aortic Aneurysm Growth Rate in People with Diabetes Mellitus-A Propensity-Matched Retrospective Cohort Study.

BACKGROUND

Identification of a safe and effective medical therapy for abdominal aortic aneurysm (AAA) remains a significant unmet clinical need. This study evaluated the associations between commonly prescribed medications in type 2 diabetes mellitus (T2DM), HbA1c measurements, and AAA growth over a 14-year surveillance period.

METHODS

A retrospective cohort study including all patients enrolled in the AAA screening and surveillance program at Norfolk and Norwich University Hospital NHS Foundation Trust. Records of AAA size, risk factors, medications, outcomes, complications, and mortality were analyzed. A 1:1 propensity matching was undertaken to validate results.

RESULTS

The study comprised 986 patients (84.7% male), of whom 199 had T2DM. The mean initial AAA diameter did not differ significantly between groups (39.3 mm [standard deviation (SD) 7.2] in T2DM versus 39.4 mm [SD 6.9] in non-T2DM; P = 0.68). Patients with T2DM had a significantly lower mean AAA growth rate (2.2 mm/year [SD 3.1] vs. 2.7 mm/year [SD 2.9]; P = 0.042). The mean follow-up duration was longer in the T2DM group (5.2 years [SD 3.6] vs. 4.6 years [SD 3.3]; P = 0.03). Use of metformin and angiotensin-converting enzyme inhibitor/angiotensin II receptor type I blocker therapy was independently associated with reduced AAA growth rates (1.40 mm/year, 95% confidence interval [CI] 1.05-1.88; and 1.67 mm/year, 95% CI 1.52-1.83, respectively). Combined therapy was associated with the greatest reduction (1.19 mm/year, 95% CI 0.97-1.47) compared with neither medication (1.94 mm/year, 95% CI 1.78-2.12). These findings remained significant after 1:1 propensity score matching.

CONCLUSION

Metformin and ACEi/angiotensin II receptor type I blocker therapy are associated with reduced AAA growth rates, with the greatest protective effect observed in patients receiving combined therapy.