Impact of Obesity on the Atrial Substrate is Compounded by Age

Abstract

Introduction: Obesity is a recognised risk factor of human atrial fibrillation (AF) and its prevalence has been projected to increase perhaps concomitantly with the AF epidemic. The impact of the aging population on the effects of obesity on the atria is not known. Methods: Intracellular membrane potential recordings were obtained from the isolated right atria of Zucker lean (n = 12) and obese rats (n = 12) aged 3, 7 and 12 months respectively (n = 4 per age group). An aluminosilicate glass electrode (100 MΩ, filled with 3 M KCl) was used to record intracellular action potential parameters during atrial pacing. Atrial orientation and pacing site and glass electrode position were kept consistent throughout each experiment. Results: Obese animals were significantly heavier than age-matched lean animals across all age groups (p < 0.01). Blood pressure was significantly higher in obese animals aged >7 months (p < 0.0001) compared to lean animals, and further increased with age (p < 0.05). In lean animals, APD demonstrated a gradual decrease and plateau with age alone. In contrast, in obese animals there was a progressive increase in APD (p < 0.05). At each pacing cycle length (200, 300 and 400 ms), the APD was significantly longer in obese rats aged 7 and 10 months compared to their age-matched lean rats (p < 0.001). Conclusion: The impact of obesity on the substrate for AF is greater with increasing age. These findings have significant implications to the consequences of the obesity epidemic in an aging population.