Behaviour of the adrenergic cardiovascular drive in atrial fibrillation and cardiac arrhythmias

Aim: Animal studies have conclusively shown that the sympathetic nervous system plays a major role not only in regulating sinus node activity but also in promoting cardiac rhythm alterations. Less univocal and often circumstantial have been the evidences collected on this issue in humans. However, the introduction of the microneurographic technique in clinical research has allowed to gain new important insights on the role of neuroadrenergic factors in the pathophysiology of cardiac arrhythmias. Methods: The present paper will review the results of microneurographic studies performed by our group and others in the field of cardiac rhythm disturbances by addressing three specific issues. First it will examine the relationships between heart rate and muscle sympathetic neural outflow in a variety of cardiovascular diseases characterized by sympathetic activation. This will be followed by an analysis of the behaviour of the sympathetic nerve traffic responses to paroxysmal atrial fibrillation. Finally, the sympathetic adjustments to spontaneously occurring or artificially induced pre-mature ventricular contractions will be highlighted.