Modulation of Autonomic Nervous Activity in the Termination of Paroxysmal Atrial Fibrillation

Ventricular response as a predictor of the termination of sustained paroxysmal atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common sustained atrial arrhythmia. Accurate detection of the timing and possibility of AF termination is vital for optimizing rhythm and rate control strategies. The present study evaluated whether the ventricular response (VR) in AF offers a distinctive electrocardiographic indicator for predicting AF termination.

METHODS

Patients experiencing sustained paroxysmal AF for more than 3 h were observed using 24-h ambulatory Holter monitoring. VR within 5 min before AF termination (VR 0-5 min, BAFT) was compared with VR observed during the 60th to 65th min (VR 60-65 min, BAFT) and the 120th to 125th min (VR 120-125 min, BAFT) before AF termination. Maximum and minimum VRs were calculated on the basis of the average of the highest and lowest VRs across 10 consecutive heartbeats.

RESULTS

Data from 37 episodes of paroxysmal AF revealed that the minimum VR0-5 min, BAFT (64 ± 20 bpm) was significantly faster than both the minimum VR120-125 min, BAFT (56 ± 15 bpm) and the minimum VR60-65 min, BAFT (57 ± 16 bpm, p < .05). Similarly, the maximum VR0-5 min, BAFT (158 ± 49 bpm) was significantly faster than the maximum VR120-125 min, BAFT (148 ± 45 bpm, p < .05). In the daytime, the minimum VR0-5 min, BAFT (66 ± 20 bpm) was significantly faster than both the minimum VR60-65 min, BAFT (58 ± 17 bpm) and minimum VR120-125 min, BAFT (57 ± 15 bpm, p < .05). However, the mean and maximum VR0-5 min, BAFT in the daytime were similar to the mean and maximum VR120-125 min in the daytime, respectively. At night, the minimum, mean, and maximum VR0-5 min, BAFT were similar to the minimum, mean, and maximum VR120-125 min, respectively.

CONCLUSIONS

Elevated VR rates during AF episodes may be predictors for the termination of AF, especially during the daytime and in patients with nondilated left atria. These findings may guide the development of clinical approaches to rhythm control in AF.

Autonomic modulation before and after paroxysmal atrial fibrillation events in patients with ischemic heart disease

BACKGROUND

The autonomic activity plays a critical role in generating paroxysmal atrial fibrillation (PAF). This study aimed to evaluate the changes in the autonomic nerve activity before and after PAF events in patients with and without ischemic heart disease (IHD).

METHODS

The study included 49 patients (71.43 ± 12.24 years old, 26 males) with PAF events lasting more than 30 s during 24-hr ambulatory Holter monitoring. The 20-min intervals before and after PAF events were divided into eight segments of 5 min each. Heart rate variability (HRV) analyses of the time and frequency domains were applied to each time segment.

RESULTS

Patients with IHD had significant increases in the root mean square successive differences (r-MSSD, p = .008) and HF component (p = .04), followed by a significant increase in the LF/HF ratio (p = .02) preceding the onset of PAF. Patients without IHD had only a significant increase in the r-MSSD (p = .045) preceding the onset of PAF. During the termination of PAF events, patients in both the IHD and control groups had a significantly decreased r-MSSD and HF, respectively.

CONCLUSION

Ischemic heart disease causes a sympathovagal imbalance in the initiation of PAF. Decreased parasympathetic activity regulated the termination of PAF in both the IHD and control groups. The modification of the autonomic nervous system (ANS) activity should be individualized due to the autonomic complexity in AF arrhythmogenesis and termination.

Human Heart Cardiomyocytes in Drug Discovery and Research: New Opportunities in Translational Sciences

In preclinical drug development, accurate prediction of drug effects on the human heart is critically important, whether in the context of cardiovascular safety or for the purpose of modulating cardiac function to treat heart disease. Current strategies have significant limitations, whereby, cardiotoxic drugs can escape detection or potential life-saving therapies are abandoned due to false positive toxicity signals. Thus, new and more reliable translational approaches are urgently needed to help accelerate the rate of new therapy development. Renewed efforts in the recovery of human donor hearts for research and in cardiomyocyte isolation methods, are providing new opportunities for preclinical studies in adult primary cardiomyocytes. These cells exhibit the native physiological and pharmacological properties, overcoming the limitations presented by artificial cellular models, animal models and have great potential for providing an excellent tool for preclinical drug testing. Adult human primary cardiomyocytes have already shown utility in assessing drug-induced cardiotoxicity risk and helping in the identification of new treatments for cardiac diseases, such as heart failure and atrial fibrillation. Finally, strategies with actionable decision-making trees that rely on data derived from adult human primary cardiomyocytes will provide the holistic insights necessary to accurately predict human heart effects of drugs.

Time-dependent cervical vagus nerve stimulation and frequency-dependent right atrial pacing mediates induction of atrial fibrillation

Objective:

This study aimed to investigate the effects of right cervical vagus trunk simulation (RVTS) and/or right atrial pacing (RAP) on the induction of atrial fibrillation (AF).

Methods:

Twenty-four healthy adult dogs were randomly divided into four groups: RAP groups comprising RAP₅₀₀ (RAP with 500 beats/min) and RAP₁₀₀₀ (RAP with 1000 beats/min) and RVTS groups comprising RVTS and RAP₅₀₀+RVTS. All dogs underwent 12-h intermittent RAP and/or RVTS once every 2 h. The AF induction rate, AF duration, atrial effective refractory period (ERP), and dispersion of ERP (dERP) were compared after every 2 h of RAP or/and RVTS.

Results:

All groups had successful AF induction. The RAP₁₀₀₀ group had the highest AF induction rate and the longest AF duration. The RAP₁₀₀₀ group also had a shortened ERP in comparison to the other groups as well as the maximum dERP. Compared to the RAP₅₀₀ group, RAP₅₀₀+RVTS had an increased capacity to induce AF as measured by the AF induction rates, AF duration, ERP, and dERP.

Conclusion:

Increased tension in the vagus nerve and the intrinsic cardiac autonomic nervous system plays an important role in AF induction through different potential mechanisms. Interventions involving the vagus nerve and/or intrinsic cardiac autonomic nervous system can be a future potential therapy for AF.