Functional heart disease is not subject to sudden death from a medical theory point of view. This is because there are no underlying pathological changes in the heart and there is no problem with plaque from atherosclerosis and there is no problem with vasospasm. In the case of functional heart disease, there is a special situation in which sudden death can occur, i.e., overexertion, and if care is not taken, critical situations can occur beyond what the heart can withstand, such as when the whole person’s circulatory system is affected by hypotension, which affects the perfusion of various organs and can lead to critical situations such as cerebral underperfusion and coma. Therefore, for functional heart disease, although the risk of sudden death is low, measures need to be taken to prevent sudden death from occurring.