Objective: To investigate the relationship between Ankle-Brachial Index (ABI) and renal function progression in patients with atrial fibrillation (AF). Design: Observational prospective multicentre cohort study. Setting: Atherothrombosis Center of I Clinica Medica of 'Sapienza' University of Rome; Department of Medical and Surgical Sciences of University Magna Græcia of Catanzaro; Atrial Fibrillation Registry for Ankle-Brachial Index Prevalence Assessment-Collaborative Italian Study. Participants: 897 AF patients on treatment with vitamin K antagonists. Main outcome measures: The relationship between basal ABI and renal function progression, assessed by the estimated Glomerular Filtration Rate (eGFR) calculated with the CKD-EPI formula at baseline and after 2 years of follow-up. The rapid decline in eGFR, defined as a decline in eGFR >5 mL/min/1.73 m2 /year, and incident eGFR2 were primary and secondary end points, respectively. Results: Mean age was 71.8±9.0 years and 41.8% were women. Low ABI (ie, ≤0.90) was present in 194 (21.6%) patients. Baseline median eGFR was 72.7 mL/min/1.73 m2, and 28.7% patients had an eGFR2. Annual decline of eGFR was -2.0 (IQR -7.4/-0.4) mL/min/1.73 m2/year, and 32.4% patients had a rapid decline in eGFR. Multivariable logistic regression analysis showed that ABI ≤0.90 (OR 1.516 (95% CI 1.075 to 2.139), p=0.018) and arterial hypertension (OR 1.830 95% CI 1.113 to 3.009, p=0.017) predicted a rapid eGFR decline, with an inverse association for angiotensin converting enzyme (ACE) inhibitors/angiotensin receptor blockers (OR 0.662 95% CI 0.464 to 0.944, p=0.023). Among the 639 patients with AF with eGFR >60 mL/min/1.73 m2, 153 (23.9%) had a reduction of the eGFR 2. ABI ≤0.90 was also an independent predictor for incident eGFR2 (HR 1.851, 95% CI 1.205 to 2.845, p=0.005). Conclusions: In patients with AF, an ABI ≤0.90 is independently associated with a rapid decline in renal function and incident eGFR2. ABI measurement may help identify patients with AF at risk of renal function deterioration. Trial registration number: NCT01161251.
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