Swollen feet are found in a large proportion of patients with grade 3 and 4 heart failure. Also, swollen feet are a sign of right heart failure or total heart failure; left heart failure alone does not cause swollen feet. Swollen feet are not necessarily a sign of heart failure, but can also be caused by other conditions, such as sprained ankles, adverse drug reactions, and hypothyroidism. According to the New York Heart Association’s Heart Failure Classification, when heart failure grade 3 or 4 is reached, the patient’s condition is more serious, and if there is a right heart failure or total heart failure, there will be subcutaneous edema, which will appear from the low hanging parts of the body first, and it is common in the ankles and lower limbs, and then gradually develops upward. If the patient has left heart failure alone, he or she will not have swollen feet even if the heart failure is grade 3 or 4. Swelling of the feet is not unique to heart failure, but may also occur if the patient has a sprained ankle, hypothyroidism, or has been taking antihypertensive drugs such as diphenhydramine for a long period of time, so be careful to differentiate. If the patient has swollen feet, it is recommended to go to the hospital for a clear diagnosis and appropriate treatment.