Cardiac function class I is not considered heart failure. Cardiac function class I means that the patient has cardiac insufficiency but does not have related clinical manifestations; cardiac function class I is the evaluation of the mildest degree of cardiac insufficiency, which means that when doing light activities, it does not affect physical labor, and after that, there will not be chest tightness, shortness of breath, panic, and other uncomfortable symptoms. However, symptoms such as decreased endurance, chest tightness, shortness of breath, and panic may occur during strenuous exercise, such as racing, heavy lifting, and heavy physical labor. Heart failure is a syndrome of cardiac insufficiency caused by various heart diseases, most of which are symptomatic manifestations caused by a decrease in myocardial contractility and an inability of cardiac blood output to meet the metabolic demands of the body. Therefore, cardiac function class I is not considered heart failure. Although the first level of cardiac function is the lightest degree of evaluation of cardiac insufficiency, but if the situation of cardiac insufficiency, it is recommended to choose early to seek medical treatment, improve the examination to clarify the cause of targeted treatment.