Association of heart rate variability and atrial fibrillation in patients with obstructive hypertrophic cardiomyopathy

Background Atrial fibrillation (AF) is surprisingly common in patients with obstructive hypertrophic cardiomyopathy (oHCM) and is associated with significant symptoms and poor survival. Globally accepted models for AF detection are yet to be established. We aimed to investigate the relationship between heart rate variability (HRV) and AF in patients with oHCM. Methods We enrolled 1112 consecutively recruited patients with oHCM, including 158 and 954 patients with and without AF, respectively. The HRV variables mainly included the standard deviation of the mean R-R intervals (SDNN), root mean squared successive difference (rMSSD), and percentage of cycles differing from the preceding one by > 50 ms (pNN50). The SDNN, rMSSD, and pNN50 were transformed into binary variables underlying the cutoff for AF detection (termed SDNN_cutoff, rMSSD_cutoff, and pNN50_cutoff, respectively). Results The mean age of this cohort was 48.94 ± 12.37 years, and 451 patients were females. The patients with AF were older, more likely to have palpitations, had a larger left atrial diameter and lower left ventricular outflow gradient, and a significantly higher SDNN, rMSSD, and pNN50 than those without AF. In multivariable logistic regression analysis, pNN50_cutoff was independently associated with AF (odds ratio: 7.86, 95% confidence interval [CI]: 4.25–14.7), while the model including pNN50_cutoff had the largest area under the curve (0.736; 95% CI: 0.690–0.782) and the lowest Akaike information criterion (774). Conclusion HRV was associated with a higher incidence of AF. Among the HRV variables, pNN50_cutoff (cutoff value = 43.5) may be a good predictor of AF in patients with oHCM.