Objective:To investigate the application of cardiac magnetic resonance (CMR) quantitative techniques in evaluating myocardial involvement differences between new onset and longstanding systemic lupus erythematosus (SLE) patients.Methods:From August 2020 to April 2023, 14 new onset and 15 longstanding SLE patients treated at the First Affiliated Hospital of Anhui Medical University were prospectively included as the study group. Additionally, 18 age-, gender-, body surface area-, and body mass index-matched healthy volunteers were included as the control group. Clinical baseline data, electrocardiograms, and CMR results including left ventricular ejection fraction (LVEF), left ventricular end-systolic volume index (LVESVI), left ventricular end-diastolic volume index (LVEDVI), cardiac index (CI), left ventricular stroke volume index (LVSVI), left ventricular mass index (LVMI), myocardial strain, native T 1 values, and T 2 values were collected. One-way analysis of variance (ANOVA) or Kruskal-Wallis H test was used to compare the quantitative parameters among the three groups. Bonferroni correction was applied for pairwise group comparisons. Results:The native T 1 values [1 114.50 (1 089.33, 1 150.39) ms, 1 085.32 (1 051.31, 1 129.75) ms] and T 2 values [(55.9±3.4) ms, (53.3±1.5) ms] of new onset and longstanding SLE patients were higher than those of the healthy control group [native T 1 values 1052.62 (1024.75, 1077.59) ms, H=17.72, P<0.001; T 2 values (51.2±1.3) ms, F=18.70, P<0.001]. The T 2 values of the new onset SLE group was higher than that of the longstanding SLE group ( P<0.05). The LVEDVI[86.87 (80.80, 93.55) ml/m 2], LVSVI [54.63 (50.42, 59.03) ml/m 2], and LVMI [48.39 (41.65, 53.26) g/m 2] of the new onset SLE group were higher than those of the control group [LVEDVI: 71.11 (65.80, 81.28) ml/m 2, Z=3.02, P=0.003; LVSVI: 42.17 (40.36, 51.33) ml/m 2, Z=2.76, P=0.006; LVMI: 38.48 (35.22, 43.83) g/m 2, Z=3.10, P=0.002]. The LVEDVI and LVSVI of the new onset SLE group were also higher than those of the longstanding SLE group [LVEDVI: 73.30 (69.87, 84.71) ml/m 2, Z=1.97, P=0.048; LVSVI: 45.53 (42.28, 50.98) ml/m 2, Z=2.34, P=0.020]. Conclusion:Myocardial involvement is more severe in new onset SLE patients, whereas acute myocardial injury is alleviated in longstanding SLE patients. Therefore, early detection of cardiac involvement in SLE patients is crucial for improving prognosis.