Fetal arrhythmia is a common abnormality during pregnancy, with an incidence of about 1 to 2% [1,2]. According to this projection, approximately 200,000 to 400,000 pregnant women are found to have fetal arrhythmias during routine antenatal examinations in China each year, which often causes great confusion and concern to the parents-to-be. For many perinatologists, pediatricians and cardiologists, clinical decision making and therapeutic monitoring guidance for fetal arrhythmias is a completely new field and a challenge for them. There is no doubt that without timely, accurate and effective therapeutic interventions, fetal arrhythmias will threaten fetal health and survival, and even involve neonatal, infant and child health problems, causing a series of family and social problems and economic burdens, which will have a serious negative impact on the development of maternal and child health in China. According to the statistics of different research centers, most of the fetuses visited for cardiac arrhythmias are transient sinus tachycardia, isolated supraventricular precontraction, transient irregular rhythm, etc. These fetal cardiac arrhythmias are benign processes during fetal heart development, which do not require emergency treatment and have good prognosis. Only about 10% of fetal arrhythmias are persistent, rapid or slow arrhythmias with secondary damage and irregular rhythms [3], but even so, 20,000 to 40,000 or more fetuses with clinically significant arrhythmias are diagnosed each year. Severe fetal arrhythmias are often associated with fetal heart failure and edema, and can even lead to fetal death. Timely and effective management often controls fetal arrhythmias and heart failure, and significantly reduces fetal vital organ damage due to hemodynamic changes, improves the prognosis of affected fetuses, and reduces the risk of fetal death secondary to “prenatal inaction”. It also improves the prognosis of the fetus and reduces fetal multi-system and multi-organ damage secondary to reduced perfusion of important organs due to “prenatal inaction”, such as reduced blood supply to the central nervous system due to intrauterine hemodynamic disorders or irreversible damage to the central nervous system due to further deterioration of severe postpartum arrhythmias, causing hypoxic-ischemic encephalopathy, polycystic encephalomalacia, intraventricular hemorrhage, etc. [4,5], thus improving the quality of life of the family and the child and reducing the economic, psychological and social burden of the family. family economic, psychological and social burden. At present, due to the social situation of late marriage and late childbirth in China, the age of first-time mothers is gradually increasing; the number of older mothers is increasing due to various social reasons; in recent years, due to the increasing incidence of infertility, the rate of in vitro fertilization is also gradually increasing, and the number of “precious” fetuses is gradually increasing. In these groups, the incidence of fetal arrhythmias is higher than in low-risk groups. The majority of fetal arrhythmias are diagnosed during prenatal examinations after 20 weeks of gestation, and without standardized clinical monitoring, screening, evaluation, and treatment to provide accurate and appropriate advice to the affected families for decision making, the maternal-fetal complex can suffer from preterm delivery [6] and even fetal and neonatal death [1-3] under stressful conditions such as arrhythmias and heart failure, and direct negative choices such as termination of pregnancy can be harmful to the fetus, the pregnant woman, and her family. When functional abnormalities of the fetal cardiovascular system are detected during prenatal diagnosis, the uncertainty of clinical referral, monitoring and treatment norms, and treatment effects (risk-benefit assessment) will cause great difficulties in decision-making for the parents and clinicians, and bring a great psychological burden to the pregnant women who choose to continue the pregnancy while waiting for delivery It is also detrimental to maternal and fetal health. Therefore, it is of great clinical and social importance to screen for fetal arrhythmias, to provide timely and appropriate intervention in severe cases, to provide accurate reference advice and psychological counseling to the affected families and parents-to-be, and to assist in making correct clinical decisions. Fetal echocardiography has become more and more widely used for early monitoring of clinical fetal conditions in recent years, because it can examine the structural and functional status of the fetal heart and help determine the nature of fetal arrhythmias [3,7,8], thus becoming the most valuable method for diagnosing fetal arrhythmias. The diagnosis, classification and management of fetal arrhythmias are based on the analysis of the electrophysiology and temporal sequence of the atria and ventricles. Although there are still difficulties in the diagnosis of some complex types of arrhythmias by fetal echocardiography, its validity and relative accuracy are sufficient to indicate prognosis and guide management. The use of M-mode ultrasound to evaluate arrhythmias is the most classical and commonly used method, which describes atrial motion by placing M-mode sampling lines in the direction through the atrial wall, atrioventricular valve, and ventricular wall, while recording the motion curves of all three to distinguish the source of abnormal contractions [8]; the use of spectral Doppler techniques to obtain blood flow spectra from multiple sites that respond to atrial motion is also a method that has been used more often in recent years (commonly used sampling With the development of Tissue Doppler Imaging (TDI), it is now possible to characterize the motion of the free edge of the atrioventricular valve [13] and also to simultaneously image the motion of tissue segments at different locations by tissue sizing. The motion of the fetal heart at different atrial levels can be characterized by simultaneous tracing of segmental motion at different locations by tissue sizing [14]. The normal fetal heart rhythm is regular with a heart rate of 120-160 beats/min. Fetal arrhythmia refers to irregular fetal heart rhythm or a fetal heart rate outside the normal range in the absence of contractions during routine prenatal examination [3,7]. A fetal heart rate of 20% of the low limit of normal heart rate is suggestive of bradycardia and 20% of the high limit of normal heart rate is tachycardia; both of which last more than 10 seconds. Pre-phase contraction is defined as at least 1 atrial or ventricular pre-phase contraction per 10 normal beats; the difference between supraventricular and ventricular tachycardia is that the former is stimulated by premature atrial beats and the latter by premature ventricular beats; in complete atrioventricular block, atrial and ventricular contractions do not coincide and do not correlate; the diagnosis of Ⅰ-Ⅱ AVB depends on the application of, in addition to the loss of correlation between the rhythm of the atrial and ventricular wall motion curves In addition to the loss of correlation between the rhythm of the atrial and ventricular wall motion curves, the diagnosis of I-II AVB relies on the application of simultaneous recording of the right pulmonary artery and right superior pulmonary vein spectrum, or the superior vena cava and ascending aorta flow spectrum, which can estimate the PR interval and thus diagnose I-II AVB and overt pre-excitation syndrome [15]; irregular heart rhythm refers to a heart rate in the normal range but the difference between the fastest and slowest heart rate is 25-30 beats/min. Each type of arrhythmia lasting <10 minutes is considered transient, and premature beats More than 10 beats per minute are considered frequent premature beats. Transient episodes of bradycardia, tachycardia and occasional premature beats are normal variants, which are functional changes of the immature heart. The diagnosis of fetal arrhythmia is usually made between 18-22 weeks of gestation, and partly at 16-20 weeks of gestation; therefore, prenatal examination in the middle of pregnancy should therefore be carefully performed with fetal heart auscultation to facilitate early detection of the problem and avoid delaying the best time for diagnostic management. In complete atrioventricular block, atrial contraction and ventricular contraction are inconsistent and uncorrelated; IºAVB refers to prolonged atrioventricular conduction resulting in prolonged PR interval, and IIºAVB refers to intermittent failure of atrial electrical impulses to travel down and periodic cessation of ventricular beats under regular atrial stimulation, and there are two types of such intermittent interruption of conduction, called Mo type I and Mo type II, the former refers to progressive prolongation of PR interval The former refers to a gradual prolongation of the PR interval and a gradual shortening of the RR interval until a missed heartbeat occurs, while the latter refers to a periodic interruption of atrioventricular conduction without a progressive prolongation of the PR interval; irregular heart rhythm refers to a heart rate in the normal range but with a difference of 25-30 beats/min between the fastest and slowest heart rates. The current status of fetal cardiac function evaluation is low in fetal myocardial tone, low T-tubular system, poorly organized myocardial fibers, low sarcoplasmic reticulum calcium uptake in cardiac myocytes, and low sympathetic nervous system. uptake is low, sympathetic distribution is low, cardiomyocytes are small, mitochondria, sarcoplasmic reticulum, myofilaments, α and β adrenergic receptors are few, non-contractile components are dominant (about 60%, while this proportion is only 30% in adult cardiomyocytes), fetal cardiomyocytes energy source is mainly glucose, while adult cardiomyocytes energy source is mainly fatty acids, myocardial workload increases when cardiac hypertrophy Fetuses may have cardiomyocyte replication, i.e., an increase in cardiomyocyte number, whereas in adults only an increase in cardiomyocyte volume, etc. These associated features reduce fetal myocardial compliance and contractility, resulting in a low fetal myocardial response to stress and a fetal heart more susceptible to cardiac insufficiency and heart failure when single or multiple factors are combined. Reliable noninvasive evaluation of fetal cardiac function is limited by many factors, including the small size of the heart in the fetal period, poor display of the ventricular endocardium, difficulty in standardizing the orientation of cardiovascular structures, and poor fetal motion and maternal abdominal wall acoustic window. It is well known that the ejection fraction (EF) and fractional shortening (FS), which are commonly used in conventional cardiac function evaluation, no longer reliably reflect the overall systolic function of the left ventricle when the ventricular morphology changes, and the analysis of mitral valve diastolic flow velocity curves is also affected by the rapid fetal heart rate. Therefore, the conventional methods used to assess LV function in adults and children are less likely to accurately evaluate fetal LV function. Given the irregular geometry of the right ventricle and the possible geometric changes in the right ventricle in fetal arrhythmias with abnormal cardiac function, it is more difficult to evaluate right ventricular function with existing imaging techniques and measurements, and the coexistence of systolic and diastolic abnormalities in fetal cardiac insufficiency makes a comprehensive evaluation of overall cardiac function more reasonable[16] . The Tei index is a recently used clinical index for the evaluation of ventricular function, which has many advantages, such as it is not affected by ventricular geometry and heart rate, it is not affected by gestational age during fetal life, it is easy to measure, and it is highly reproducible, so it is a practical method for evaluating fetal cardiac function [17,18]. isovolumetric contraction phase (ICT), isovolumetric relaxation phase (IRT), and ejection time (ET) are all important phases of the cardiac cycle, with ICT and IRT being particularly important because ATP utilization and Ca2+ ion inward and outward flow occur in these two phases. Studies applying the Tei index to the evaluation of fetal cardiac function have found that the Tei index can reliably evaluate fetal cardiac function in physiological or case-specific states. In cardiac insufficiency, both ICT and IRT are prolonged and ET is shortened, so the Tei index is increased in patients. christine et al [19] examined the left and right ventricular Tei index in 7 edematous and 23 normal fetuses, and the left and right ventricular Tei index in normal fetuses was 0. 41±0. 05, 0. 38±0. 04 , respectively, and was not affected by heart rate, while the left and right ventricular Tei index was significantly increased in edematous fetuses ( 0. 92±0. 06 vs. 0. 41±0. 05 Tsutsumi et al [20] studied 35 fetuses with intrauterine growth retardation, 30 fetuses whose mothers were diabetic, 50 normal fetuses and 20 normal infants and showed that the left ventricular Tei index decreased linearly with increasing gestational age in normal fetuses from 18 to 33 weeks of gestational age The Tei index decreases linearly with increasing gestational age. After 34 weeks of gestation, the decrease in Tei index accelerates. At 18 to 41 weeks of gestation, the right ventricular Tei index decreases mildly with increasing gestational age. The neonatal Tei index appears to be transiently elevated at birth and reaches stability after 24 h. The difference between Tei index of fetuses with intrauterine growth retardation and fetuses with diabetic mothers and normal fetuses was not significant from 18 to 26 weeks of gestation, while from 27 to 40 weeks of gestation, their Tei index was significantly higher than that of the normal group. The Tei index is a relatively independent Doppler index, and although the measured Doppler time intervals vary depending on the heart rate, a study of the left and right ventricular Tei indices in fetuses with different heart rates showed that the Tei index of the left and right ventricles was higher than that of the normal group. Tei index studies have shown that both left and right ventricular Tei indices are independent of heart rate [19,21,22].The limitations of Tei index are that the small size of the heart in early pregnancy makes the detection of fetal ventricular Tei index more difficult; the application of Tei index in patients with fetal arrhythmias is limited [22]. In recent years, James.C. Huhta [23,24] et al. proposed the cardiovascular profile score (CVPS) system as a multivariate scoring method for evaluating the status of fetal cardiac function, predicting the outcome of edematous fetuses and guiding their treatment, guiding and evaluating prenatal interventions for severe congenital cardiovascular anomalies, and also commonly used for the selection of the time frame for intrauterine treatment The CVPS system provides a semi-quantitative evaluation of multiple parameters related to poor fetal prognosis measured by 2D Doppler ultrasound, including fetal edema, heart/thorax area ratio, atrioventricular regurgitation, umbilical artery flow spectrum, umbilical vein and venous catheter flow spectrum, each with a score of two out of 10, i.e., cardiac function. The CVPS is an important guide to the clinical management of fetal arrhythmias/heart failure. It is generally accepted that intervention should be performed once the CVPS is reduced; CVPS ≥ 7 points, treatment for the etiology is often effective; 7 points > CVPS ≥ 5 points, treatment is controversial, and dynamic changes are mostly observed after treatment; CVPS