The impact of age on the atrial substrate: insights from patients with a low scar burden undergoing catheter ablation of persistent atrial fibrillation.

Background: Advancing age is a strong risk factor for the development of atrial fibrillation (AF). However, its impact on the left atrial (LA) substrate in patients is not well defined.

Methods: Forty-seven patients underwent catheter ablation of persistent AF. Bipolar electrograms from the LA were recorded for voltage analysis. The AF cycle length was determined by averaging the cycle lengths of ten fibrillatory ("f") waves on lead V(1). The mean amplitude of the same ten "f" waves was also determined. The ablation strategy consisted of pulmonary vein isolation, electrogram guided, and linear ablation.

Results: There was an inverse relationship between the mean bipolar LA voltage and age (R = -0.58; P < 0.0001). There was a direct relationship between AF cycle length and age (R = 0.74; P < 0.0001). There was an inverse relationship between amplitude of the "f" waves and age (R = -0.62; P < 0.0001). Areas of scar were found in 15 of the 47 patients (32%). AF cycle length was longer in patients with vs. those without scar (183 ± 20 vs. 151 ± 15 ms; P < 0.0001). Advancing age was the only predictor of LA scar (OR, 1.32; 95% CI, 1.11-1.58; P < 0.01). Forty patients (85%) remain arrhythmia-free without antiarrhythmic medications after a mean follow-up of 18 ± 10 months. Neither age nor LA scar was associated with outcome.

Conclusions: In patients undergoing ablation of persistent AF, advancing age makes for a complex LA substrate that is characterized by areas of low voltage/scar, and yet is associated with a lower AF frequency. LA scar did not seem to impact outcome in this small study.