People whose hearts sometimes beat too quickly can be treated with a device implanted under the skin that shocks the heart, which causes it to beat at a normal speed again. However, the shocks can be uncomfortable and alarming. Research suggests that people who receive more frequent and intense shocks are more likely to develop panic disorder, which arises as a conditioned fear in response to the automatic shocks (Godemann et al., 2001).
Dr. P. Marazzi/Science Source