Heart rate variability and early recurrence of atrial fibrillation after electrical cardioversion

OBJECTIVES The study evaluated the role of the autonomic nervous system in atrial fibrillation (AF) recurrence. BACKGROUND Early recurrence of AF after cardioversion (CV) is attributed to electrical remodeling. The possibility that an abnormal autonomic modulation might contribute to this phenomenon has not yet been adequately tested. METHODS We analyzed short-term heart rate variability (HRV) in 93 patients with persistent AF and on chronic amiodarone treatment, after restoration of sinus rhythm by electrical CV. RESULTS Two weeks later, 25 patients presented with AF. Spectral analysis of HRV revealed that patients with AF recurrence were characterized by significantly greater low/high (LF/HF) frequency ratio in comparison to those in sinus rhythm (5.8 ± 6.86 vs. 1.1 ± 1.7). At univariable analysis, no clinical parameter differentiated the two groups. Using logistic regression analysis, LF/HF ratio was significantly associated with AF recurrence, with an odds ratio of 1.97 (95% confidence interval [CI] 1.33–2.94). By using a cutoff value of ≥2, LF/HF ratio presented a sensitivity and a specificity of, respectively, 76% and 90%. AF recurred in 9% of the patients with LF/HF ratio <2 compared with 73% of those with an LF/HF ratio >2. No correlation was observed between LF/HF ratio and late AF recurrences. CONCLUSIONS These data indicate that signs of increased sympathetic and reduced vagal modulation of sinus node characterized patients with an early AF recurrence and suggest that an abnormal autonomic control may contribute to electrical remodeling by facilitating intracellular calcium overload.