Authonomic nervous system and heart activity. old and new (review) [sistema nervoso autonomo e attività cardiaca. vecchie e nuove acquisizioni]

The autonomic nervous system plays an important role in the modulation of cardiac electrophysiology and arrhythmo-genesis. The mechanisms by which autonomic activation is arrhythmogenic or antiarrhythmic are complex and different for specific arrhythmias. In atrial fibrillation, simultaneous sympathetic and parasympathetic activations are the most common trigger. In contrast, in ventricular fibrillation in the setting of cardiac ischemia, sympathetic activation is proar-rhythmic, whereas parasympathetic activation is antiarrhythmic. In inherited arrhythmia syndromes, sympathetic stimulation precipitates ventricular tachyarrhythmias and sudden cardiac death except in Brugada and J-wave syndromes where it can prevent them. Heart rate variability (an index of myocardial temporal dispersion), analyzed with QT variability index (QTVI), specifics segment of QT interval (QT peak-end) or intra-QT phase spectral coherence, may be considered a possible tool in stratifying the arrhythmic susceptibility in patients at risk of FV and sudden cardiac death (SCD). Moreover, direct nerve activity recordings (stellate ganglion and vagal nerve) in diseased animal models have provided insights into the understanding of the role of cardiac ANS in arrhythmogenesis. The identification of specific autonomic triggers in different arrhythmias has brought the idea of modulating autonomic activities for both preventing and treating these arrhythmias.