Heart bypass can cause hiccups, which is mainly caused by the stimulation of phrenic nerve during the surgery. Cardiac bypass grafting, also known as coronary artery bypass grafting, is a surgical procedure to treat coronary heart disease, which improves the blood supply to the heart muscle to alleviate the symptoms of angina pectoris and improve the cardiac function. The stimulation of the phrenic nerve during the procedure leads to spasm of the diaphragm muscle, which is shifted upward or deviated, and causes ergotism, resulting in hiccups, which is a normal reaction. If hiccups are caused after bypass surgery, medication can be applied appropriately, such as methylcobalamin tablets, etc., to improve the symptoms through the nutrition of nerves, and a light diet should be carried out after the surgery to avoid eating too hard and indigestible food, massage, and promotion of blood circulation, so as to avoid the recurrence of hiccups. If hiccups persist after the operation and the symptoms are not relieved, consult a doctor in time for treatment under the regular guidance of the doctor.