Cardiac autonomic regulation in patients undergoing pulmonary vein isolation for atrial fibrillation

Variability of baroreceptor reflex assessed by tilt table test in a patient undergoing pulmonary vein isolation

BACKGROUND

The autonomic nervous system (ANS) plays a significant role in atrial fibrillation (AF). Catheter ablation (CA) affects the ANS balance. The assessment of baroreceptor (BR) function is an established method to measure parasympathetic activity; however, it has been rarely used in patients undergoing CA of AF.

AIMS

This study is to assess changes in BR function caused by CA and to compare these changes between two different types of CA: point-by-point radiofrequency (RF) versus cryoballoon (CB).

METHODS

In this observational, prospective, single center study, 78 patients (25 females, mean age 58 ± 9) with paroxysmal AF and first CA were included: 39 patients (RF group) and 39 (CB group). The BR function was assessed non-invasively using tilt testing and three parameters: event count (BREC) depicting overall BR activity, slope mean depicting BR sensitivity (BRS), and BR effectiveness index (BEI).

RESULTS

The groups did not differ in clinical or demographic data. Before CA, tilting caused a marked decrease in BR function parameters in the whole study group (BREC (29 ± 14.0-50.0 vs 28 ± 9.0-44.0, p < 0.068), BRS (10.2 ± 7.1-13.2 vs 5.8 ± 4.9-8.5; p < 0.001), and BEI (52.9 ± 39.9-65.5 vs 39.6 ± 23.6-52.1; p < 0.001), supine vs tilting, respectively). These changes were similar in the both groups. After CA, BR function decreased in the whole group (BREC 12.0 ± 3.0-22.0 vs 6.0 ± 3.0-18.0, p = 0.004; BRS 4.8 ± 3.6-6.8 vs 4.0 ± 3.0-5.8, p = 0.014; BEI 18.7 ± 8.3-27.4 vs 12.0 ± 5.1-21.0, p = 0.009). BREC was significantly more decreased in the CB vs RF. Similar trend was noted for BRS and BEI.

CONCLUSIONS

CA significantly affects BR function. These changes were more pronounced following CB rather than RF CA.

Orthostatic Stress and Baroreflex Sensitivity: A Window into Autonomic Dysfunction in Lone Paroxysmal Atrial Fibrillation

The abnormal neural control of atria has been considered one of the mechanisms of paroxysmal atrial fibrillation (PAF) pathogenesis. The baroreceptor reflex has an important role in cardiovascular regulation and may serve as an index of autonomic function. This study aimed to analyze the baroreceptor reflex's role in heart rate regulation during upright tilt (HUT) in patients with lone PAF. The study included 68 patients with lone PAF and 34 healthy individuals who underwent baroreflex assessment. Parameters such as baroreflex sensitivity (BRS), number of systolic blood pressure (BP) ramps, and the baroreflex effectiveness index (BEI) were evaluated. The study found that PAF patients had comparable resting BPs and heart rates (HRs) to healthy individuals. However, unlike healthy individuals, PAF patients showed a sustained increase in BP with an upright posture followed by the delayed activation of the baroreceptor function with a blunted HR response and lower BEI values. This indicates a pronounced baroreflex impairment in PAF patients, even at rest. Our data suggest that together with BRS, BEI could be used as a marker of autonomic dysfunction in PAF patients, making it important to further investigate its relationship with AF recurrence after ablation and its involvement in cardiovascular autonomic remodeling.

The predictive value of heart rate variability indices tested in early period after radiofrequency catheter ablation for the recurrence of atrial fibrillation

INTRODUCTION

To explore the relationship between recurrence of atrial fibrillation (AF) and the autonomic nervous activity evaluated by heart rate variability (HRV) indices after radiofrequency catheter ablation (RFCA) in the early period.

METHODS

We enrolled 102 patients with paroxysmal AF and tested the HRV indices by the high-resolution Holter electrocardiogram the next morning after RFCA. The HRV indices were compared between the non-recurrence group (n = 85) and the recurrence group (n = 17).

RESULTS

The HRV indices included standard deviation of normal to normal intervals (SDNN), SDNN index, root-mean square successive differences (RMSSD), the proportion of normal to normal intervals differing by >50 millisecond (ms) (pNN50), high-frequency components (HF), low-frequency components (LF) and very low-frequency components were significantly higher in recurrence group than that in non-recurrence group, while no such difference was found for LF/HF. Based on the median value of the recurrent time (9 months), RMSSD (P = .012), pNN50 (P < .0001) and HF (P = .033) were lower in late recurrence group than that in early recurrence group. The Cox regression analyses indicated that higher values of RMSSD (P = .01), pNN50 (P = .02) and HF (P = .02) were associated with a higher risk of recurrence after adjusted for covariates. The receiver operating characteristic curves showed higher rates of clinical recurrence of AF after RFCA in patients with RMSSD ≥27.5 ms, pNN50 ≥4.5%, and HF ≥178.25 ms² .

CONCLUSIONS

Values of RMSSD, pNN50, and HF tested in the early period after RFCA could independently predict the recurrence of AF.