Research on Dynamic Trajectory Changes of CMR T1 Mapping and Its Prognostic Value in Duchenne Muscular Dystrophy Cardiomyopathy

Background: LVEF in patients with Duchenne muscular dystrophy (DMD) typically declines progressively over time, eventually leading to heart failure. While higher LVEF is associated with longer survival, some patients exhibit features of subclinical myocardial injury even before LVEF deterioration. T1 mapping provides an objective measure of myocardial injury and can detect subtle structural changes such as fibrosis prior to LVEF reduction. This makes it a valuable tool for assessing subclinical myocardial damage in DMD cardiomyopathy. This study aims to characterize the longitudinal evolution of subclinical myocardial injury in DMD patients using global native T1 (Global Native T1) trajectories, stratify patients into subgroups based on these trajectories, and evaluate the predictive value of native T1 changes for LVEF decline, thereby facilitating early diagnosis and intervention.

Methods: This study included DMD patients diagnosed via genetic testing or skeletal muscle biopsy who underwent cardiac magnetic resonance (CMR) follow-up at our hospital between July 2018 and April 2025. Inclusion criteria required at least three CMR examinations and baseline LVEF >50%. Baseline characteristics, CMR functional parameters, and pre-contrast T1 mapping were collected. Functional parameters included LVEF, COi, and BSA-indexed LVEDVi, LVESVi, and LVSVi. Group-based trajectory modeling (GBTM) was applied to native T1 values to identify distinct myocardial injury progression patterns and patient subgroups. The primary endpoint was defined as LVEF ≤50% or a ≥10% decline from the previous measurement. Patients were categorized into endpoint and non-endpoint groups. Differences in native T1 and functional parameters were assessed using Student’s t-test, while trajectory subgroups were compared via one-way ANOVA or Kruskal-Wallis H test. Cox proportional hazards regression analyzed risk factors for endpoint events.

Results: Among 196 enrolled DMD patients (baseline LVEF >50%), 86 reached the endpoint (40 with LVEF ≤50%, 46 with ≥10% decline), while 110 did not. At endpoint occurrence, the endpoint group exhibited significantly lower LVEF (p< 0.001), and elevated global and segmental native T1 values (p< 0.001) compared to the non-endpoint group. Three trajectory subgroups were identified: low-level rising (L-rise, n=73, 37%), high-level rising (H-rise, n=38, 19%), and low-level stable (L-stable, n=85, 44%). Endpoint incidence was higher in the H-rise group (58%) than in the L-stable group (33%, p< 0.05). Multivariate Cox regression, adjusted for heart rate, LVSVi, and wheelchair use, showed both H-rise and L-rise groups had elevated endpoint risks, with HR of 1.89 and 1.74, respectively (p< 0.05).

Conclusion: Longitudinal Global Native T1 monitoring revealed three distinct trajectory patterns in DMD patients: L-rise, H-rise, and L-stable. The H-rise trajectory was an independent risk factor for cardiomyopathy progression, underscoring its prognostic utility in early risk stratification and intervention.