Atrial Fibrillation: The Science behind Its Defiance

Abstract

Atrial fibrillation (AF) is the most prevalent arrhythmia in the world, due both to its tenacious treatment resistance, and to the tremendous number of risk factors that set the stage for the atria to fibrillate. Cardiopulmonary, behavioral, and psychological risk factors generate electrical and structural alterations of the atria that promote reentry and wavebreak. These culminate in fibrillation once atrial ectopic beats set the arrhythmia process in motion. There is growing evidence that chronic stress can physically alter the emotion centers of the limbic system, changing their input to the hypothalamic-limbic-autonomic network that regulates autonomic outflow. This leads to imbalance of the parasympathetic and sympathetic nervous systems, most often in favor of sympathetic overactivation. Autonomic imbalance acts as a driving force behind the atrial ectopy and reentry that promote AF. Careful study of AF pathophysiology can illuminate the means that enable AF to elude both pharmacological control and surgical cure, by revealing ways in which antiarrhythmic drugs and surgical and ablation procedures may paradoxically promote fibrillation. Understanding AF pathophysiology can also help clarify the mechanisms by which emerging modalities aiming to correct autonomic imbalance, such as renal sympathetic denervation, may offer potential to better control this arrhythmia. Finally, growing evidence supports lifestyle modification approaches as adjuncts to improve AF control.

Socioeconomic position and risk of atrial fibrillation: a nationwide Danish cohort study

“…However, only approximately 50% of AF cases are estimated to be explained on the basis of these risk factors, and the remaining causes are unknown or suggested to be, for example, alterations in the autonomic nervous system or genetics 6. The latter might especially be the case for younger adults with ‘lone AF’ 7. Accordingly, previous studies show inconsistent results which have varied with country of origin and different indicators of SEP 8.…”

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“…Cardiac remodeling by the ACE axis is a known driver of arrhythmia events. In the atria, AII promotes fibrosis that facilitates reentry, 115 and ACEIs and ARBs do provide some protection against the recurrence of atrial fibrillation after cardioversion in patients with left ventricular dysfunction. 48 AII promotes ventricular arrhythmias by prolonging QRS duration, and by promoting reentry through both fibrosis and slowed ventricular conductance.…”

Aging-Induced Biological Changes and Cardiovascular Diseases

“…The surgical ablation which involves various degrees of denervation of ANS has been shown to be efficient against AF [ 88 , 89 ]. The experimental procedures that target autonomic imbalance in animal models and human studies of AF have been developed [ 90 ]. Studies using a high frequency for sympathetic-mimicking atrial stimulation [ 91 ] and radiofrequency ablation of the cardiac autonomic ganglion plexus were acclaimed to be a good procedure for the abolishment of AF [ 92 ].…”