Diabetes-associated diffuse myocardial fibrosis assessed by native T1 mapping: Adverse cardiac phenotype and modest...

Diabetes mellitus (DM) promotes myocardial remodeling through advanced glycation end-products, interstitial fibrosis, and microvascular dysfunction. We investigated whether native T1 mapping captures this adverse phenotype and provides incremental prognostic information beyond established clinical risk factors in a real-world population.

Patients undergoing CMR were enrolled in a prospective single-center all-comer registry. CMR parameters were compared between groups, adjusted for LV end-diastolic volume index and major fibrosis-inducing comorbidities. Prognostic significance for the composite endpoint of all-cause mortality, heart failure hospitalization, and appropriate ICD shock therapy was assessed using Cox regression. Incremental value was evaluated by likelihood-ratio testing, IDI, and NRI.

Among 3614 patients (DM n = 635, 18%), DM patients showed higher native T1 and impaired GLS (1137 ms [1134-1139] vs. 1147 ms [1141-1153], p < 0.001; -16.05% [-16.2 to -15.9] vs. -13.8% [-14.2 to -13.4], p < 0.001). The T1 difference persisted after adjustment for fibrosis-inducing comorbidities. In the multivariable model (N = 2426, 82 events), native T1 and lower LVEF were independently associated with outcomes. GLS was independently prognostic only when replacing LVEF. DM patients with T1 > 1123 ms showed the poorest prognosis. Adding native T1 improved global model fit (LR χ² = 7.94, p = 0.0048), discrimination (C-index 0.758 → 0.771), reclassification (NRI = 0.113, p = 0.013).

Patients with DM exhibit distinct structural and functional myocardial phenotypes. Native T1 captures diffuse myocardial alterations associated with adverse outcomes and provides modest incremental prognostic information beyond established clinical risk factors within the observed follow-up period, supporting comprehensive CMR phenotyping for risk stratification in DM.