The heart is richly innervated by afferent (sensory) and efferent (or visceromotor) nerves, the latter divided into sympathetic and parasympathetic. Their activity is finely integrated within a complex series of peripheral and central feedback circuits that allow the autonomic control of cardiac function. The entire autonomic nervous system (ANS) aims at maintaining cardiac homeostasis in the face of internal and external perturbations, ensuring appropriate and timely responses to stimuli. However, in pathological conditions such as myocardial infarction/ischaemia and heart failure, autonomic reflexes can become detrimental and lead to life-threatening arrhythmias and progression of myocardial dysfunction. In this section, we will first discuss the anatomy and then the basic physiology and pathophysiology of cardiac ANS, focusing both on the role of ANS in the genesis of ventricular arrhythmias (VA) and on the rationale for cardiac sympathetic blockade interventions for antiarrhythmic purposes.