A 30-year-old pregnant woman was found to have an abnormal heart rhythm during her maternity checkup in her third month of pregnancy, and the checkup ECG suggested atrial flutter with a heart rate at 155 beats/min, twice the normal rate. The doctor at the local hospital did not propose a specific treatment plan because of her pregnancy, but only reminded the patient of regular checkups, and 1 month ago the patient developed significant bilateral lower limb edema, which the local hospital did not know how to handle and suggested she be referred to Nanjing for treatment. The patient came to another hospital in Nanjing at first, and the doctor also found it tricky and suggested transferring her to our hospital for treatment, considering the limited technical conditions and the possibility of aggravation of her condition by continuing to wait. The diagnosis of atrial flutter was very clear and lasted for at least 3 months, and the heart was already significantly enlarged and the lower limbs were already swollen. But such a serious atrial flutter, it is best to promptly convert within 48 hours of discovery, more than 48 hours need to be converted after at least 3 weeks of anticoagulation, otherwise rash conversion, there may be a risk of thromboembolism, but do not convert, so fast heart rate will lead to increased burden on the heart, a long time will lead to tachycardia cardiomyopathy, heart enlargement, heart failure, especially especially pregnant women are still in the process of pregnancy, the heart If not treated in time, the pregnant woman will definitely not be able to wait until 32-34 weeks, and her life will be in danger. Considering Ms. Li’s special situation, we immediately discussed the treatment plan with the obstetrics and anesthesiology departments to ensure the safety of the pregnant woman while preserving the fetus. In order to protect the safety of Ms. Li and the fetus in pregnancy, every step of the operation was very careful. The director of the cardiac ultrasound room, who was also the first time to perform esophageal ultrasound on a pregnant woman, was careful in every step and very successfully excluded the left atrial thrombus, and the timely implementation of cardiac electro-rhythm became possible. At the same time, the type and dosage of anesthetic drugs were confirmed with the chief of anesthesiology, and the whole process of cardioversion was monitored by the chief obstetrician so that any problems could be dealt with immediately. After ruling out left atrial thrombus and 5 days of anticoagulation with low molecular heparin, Ms. Li underwent cardioversion surgery. Due to the preliminary argumentation and adequate preparation, Ms. Li’s surgery was successful. The heart beat rate was about 100 per minute after the electric cardioversion, and the normal sinus rhythm was restored, and the fetal heart was completely normal when we listened to the fetal heart at that time after the electric cardioversion, so our hanging heart was finally relieved. After the follow-up treatment, it became possible for the pregnant woman to continue her pregnancy. However, according to the available literature, cardioversion is the safest method for both the pregnant woman and the fetus in this pregnancy. Moreover, because of the small size of the fetal heart, the threshold of ventricular fibrillation is relatively high and does not lead to fetal heart damage. The success of this procedure was due to the fact that there were no ready-made cases to follow, which came from our extensive literature review and good communication with the patient, on the one hand, and the cooperation and trust of the patient and his family on the other. If the patient and the patient hesitate, it is difficult for us to come to do such a thing in the current medical environment in this case. Therefore, we would like to remind all pregnant women in particular that heart problems are not trivial, especially during pregnancy, when the heart burden is already higher than normal, and it will get heavier as the pregnancy progresses. Therefore, if you find heart discomfort or detected heart problems during pregnancy, you must seek timely consultation and treatment, not to have the fluke mentality of having a baby and then treating it, delaying treatment may cause very serious consequences for the pregnant woman and the fetus.