Coldness of the heart while sleeping may be caused by improper insulation of the chest, myocardial ischemia, gastrointestinal diseases and other reasons. 1. Improper insulation of the chest: the coldness of the heart while sleeping may be related to the quilt or clothes not covering the heart area. 2. Myocardial ischemia: diseases such as coronary heart disease, myocarditis, heart failure, etc., can lead to abnormal function of the heart, which will easily cause myocardial ischemia. This leads to coldness in the heart when sleeping. 3. Gastrointestinal diseases: gastritis, gastric ulcer, enteritis and other gastrointestinal diseases, easily lead to indigestion. This may cause coldness in the heart while sleeping. It is recommended to go to the hospital for a checkup if you have a cold heart while sleeping.