 The autonomic nervous system is not unlike the electrical system in your car. Crisscrossing wires send electrical signals to speed this up or cool that down. The beating of your heart is controlled with clock-like precision by this complex electrical network. But a glitch can cause the heart to beat dangerously fast, putting the whole body at risk of shutting down. A recent study conducted by researchers from UCLA provides critical insights into a promising treatment option for this dangerous situation. They've shown that the best way to slow a fast-beating heart is by going straight to the source, the spinal cord. A healthy resting heart rhythm looks something like this, with a typical rate following between 60 and 100 beats per minute. An imbalance in the autonomic nervous system, however, can lead to a rhythm abnormality, termed an arrhythmia. Ventricular tachyarrhythmia is a faster-than-normal rhythm characterized by a rate above 100 beats per minute and originating in the lower chambers of the heart. Because excitation of heart muscles is controlled by nerves originating in the spinal cord, a therapeutic method called thoracic epidural anesthesia has been used to target this area. Thoracic epidural anesthesia is the delivery of numbing medication directly to the nerves in the upper-middle region of the spinal column. The idea is to inhibit the over-excited signal before it reaches the heart, though shown to be clinically effective, a complete understanding of its electrophysiological effects is lacking. Using pigs as a model, the research team strategically placed 56 electrodes on the animal's hearts, simulated the neural signals responsible for ventricular tachyarrhythmia, and administered epidural anesthesia. This allowed them to create high-resolution maps visualizing the effects of thoracic epidural anesthesia on heart rhythms. They found that this technique successfully suppresses the electrical signals sent by the autonomic nervous system and improves electrical wave stability in the heart. Importantly, the study suggests that this effect only occurs during over-excitation, not during normal resting conditions. These results further our understanding of the therapeutic effects of thoracic epidural anesthesia on ventricular tachyarrhythmia. By blocking the neural activity responsible for over-stimulation, this technique may help millions of people suffering from heart arrhythmias.