Objective: To explore the Clinical value of real-time three-dimensional echocardiography (RT-3DE), two-dimensional speckle tracking imaging technology (2D-STI) combined with plasma free cell DNA (cf DNA) in evaluating right atrial(RA) volume changes and myocardial damage in patients with acute inferior myocardial infarction(AIMI) and right ventricular myocardial infarction(RVMI).Methods: Select 98 patients who were first diagnosed as AIMI in this hospital from January 2018 to January 2021. According to whether AIMI patients are combined with RVMI, they can be divided into AIMI group (50 cases) and AIMI+RVMI group (48 cases); another 38 cases are selected Healthy people on physical examination served as a control group. Routine two-dimensional echocardiography, RT-3DE, 2D-STI and plasma cf DNA testing were performed before surgery. Analyze the correlation between the RT-3DE and 2D-STI measurement indicators of AIMI and RVMI patients with RA, RV measurement indicators, and plasma cf DNA levels. To evaluate the diagnostic efficacy of RT-3DE, 2D-STI, and plasma cf DNA alone or in combination in the diagnosis of AIMI and RVMI.Results:There were no statistically significant differences between the AIMI group""s conventional two-dimensional echocardiography, RA""s RT-3DE and 2D-STI measurement indicators and the control group (P>0.05). The AIMI+RVMI group E/e"", RA RT-3DE measurement indicators (RAVmaxI, RAVminI, RAVpreI, TSVI, PSVI and ASVI) were significantly higher than the control group and AIMI group (P<0.05), while e"", TAPSE, The 2D-STI measurement indexes (LStot, LSpos) of PEF and RA were significantly lower than those of the control group and AIMI group (P<0.05). The plasma cf DNA level of AIMI+RVMI group was significantly higher than that of the control group and AIMI group (P<0.05), and the plasma cf DNA level of AIMI group was also significantly higher than that of the control group (P<0.05). The RT-3DE measurement indexes of RA in AIMI patients with RVMI (RAVmaxI, RAVminI, RAVpreI) were positively correlated with E/e"" and plasma cf DNA levels (P<0.05), but negatively correlated with TAPSE (P<0.05); AIMI The 2D-STI strain function measurement indexes (LStot, LSpos) of RA patients with RVMI were negatively correlated with E/e"" and plasma cf DNA levels (P<0.05), but positively correlated with TAPSE (P<0.05). The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of RT-3DE, 2D-STI combined with plasma cf DNA levels in the diagnosis of AIMI with RVMI were the highest (P<0.05).Conclusion: The combination of RT-3DE, 2D-STI and plasma cf DNA levels will help improve the diagnostic performance of AIMI with RVMI, and will help evaluate the changes in the volume of RA and myocardial damage in patients with AIMI and RVMI, and further provide clinical treatment The selection of the plan provides a basis for diagnosis.