A heartbeat of 110 to 120 beats per minute after chemotherapy is tachycardia, which is dangerous, and the causes of post-chemotherapy tachycardia vary. The causes of post-chemotherapy tachycardia mainly include infection, bone marrow suppression and toxic side effects of drugs. 1. Infection: After chemotherapy, patients’ immunity decreases, which may easily cause infection. Infection often leads to higher body temperature and faster heart rate, which may be manifested as a heartbeat of 110-120 beats/minute. As long as the infection is controlled, the body temperature will be lowered, and the heart rate of the patient will be reduced to the normal level, and the danger will not be great. 2. Bone marrow suppression: chemotherapy drugs can cause bone marrow suppression, leading to a decrease in the hematopoietic function of the bone marrow, resulting in anemia. Anemia can lead to tachycardia, which can be manifested as a heartbeat of 110 to 120 beats per minute. This situation is usually less dangerous, timely blood transfusion, the patient’s heart rate will be reduced to normal levels. 3. Toxic side effects of drugs: chemotherapeutic drugs such as pyranamphenicol and epothilone have certain toxic side effects on the heart, which can cause arrhythmia, which can be manifested as 110~120 beats/min or even higher, and cardiac arrest or sudden death may also occur in some patients. This situation is more dangerous, usually need to stop using this kind of chemotherapy drugs and symptomatic treatment, otherwise need to stop chemotherapy. If a heartbeat of 110-120 beats occurs after chemotherapy, you should inform your doctor to find out the cause and take appropriate solutions.