Fear of cold and heat in heart disease is mainly related to blood viscosity, blood flow rate, etc., increasing the risk of disease and morbidity. 1. Fear of cold: due to the drop in temperature skin surface stimulated by cold air, resulting in sympathetic nerve excitation, increased blood pressure, which will cause vasoconstriction, increase the oxygen consumption of cardiomyocytes, patients with heart disease will appear to be afraid of cold performance. The cold state will increase the patient’s blood viscosity, slowing down blood flow, promoting intravascular thrombosis, aggravating the condition. 2. Fear of heat (1) As the temperature rises, the body’s metabolism speeds up, which has an impact on the blood circulation system and requires the heart to pump more blood to fill the expanded blood vessels, thus increasing the burden on the heart. (2) Due to high temperatures, heart patients who sweat too much can easily lead to dehydration, while blood viscosity increases, may form blood clots, increasing the risk of myocardial ischemia. Therefore, for heart disease patients should choose a suitable living environment for themselves, avoid excessive cold and heat, and if there is any discomfort, it is recommended to seek medical treatment in a timely manner.