The impact of visit-to-visit heart rate variability on all-cause mortality in atrial fibrillation

Objective: We aimed to investigate the association between visit-to-visit heart rate variability (VVHRV) and all-cause mortality in patients diagnosed with atrial fibrillation (AF). Previous studies have shown a positive correlation between VVHRV and several adverse outcomes. However, the relationship between VVHRV and the prognosis of AF remains uncertain.Methods: In our study, we aimed to examine the relationship between VVHRV and mortality rates among 3983 participants with AF, who were part of the AFFIRM study (Atrial Fibrillation Follow-Up Investigation of Rhythm Management). We used the standard deviation of heart rate (HRSD) to measure VVHRV and divided the patients into four groups based on quartiles of HRSD (1st, <5.69; 2nd, 5.69-8.00; 3rd, 8.01-11.01; and 4th, >= 11.02). Our primary endpoint was all-cause death, and we estimated the hazard ratios for mortality using the Cox proportional hazard regressions.Results: Our analysis included 3983 participants from the AFFIRM study and followed for an average of 3.5 years. During this period, 621 participants died from all causes. In multiple-adjustment models, we found that the lowest and highest quartiles of HRSD independently predicted an increased risk of all-cause mortality compared to the other two quartiles, presenting a U-shaped relationship (1st vs 2nd, hazard ratio = 2.28, 95% CI = 1.63-3.20, p < .01; 1st vs. 3rd, hazard ratio = 2.23, 95% CI = 1.60-3.11, p < .01; 4th vs. 2nd, hazard ratio = 1.82, 95% CI = 1.26-2.61, p < .01; and 4th vs. 3rd, hazard ratio = 1.78, 95% CI = 1.25-2.52, p < .01).Conclusion: In patients with AF, we found that both lower VVHRV and higher VVHRV increased the risk of all-cause mortality, indicating a U-shaped curve relationship.