Assessment of Diffuse and Focal Myocardial Fibrosis in Hypertrophic Cardiomyopathy Using Native T1 Mapping, Extracellular Volume, and Late Gadolinium Enhancement

Background: Hypertrophic cardiomyopathy (HCM) harbors both focal scar and diffuse interstitial fibrosis, which influence risk stratification. Conventional late gadolinium enhancement (LGE) detects macroscopic scar, whereas T1 mapping and extracellular volume (ECV) quantify diffuse fibrosis. This study evaluated the relationship between LGE, T1 mapping, and ECV in HCM. Methods: In this cross‑sectional analysis, 50 HCM patients underwent 1.5 T cardiac MRI including cine imaging, native and post‑contrast T1 mapping, and phase‑sensitive LGE sequences. ECV was computed from pre‑ and post‑contrast T₁ values adjusted for hematocrit. Segmental native T1, ECV, and LGE presence were recorded across 17 myocardial regions. Associations were tested by Fisher’s exact and logistic regression. Results: Cohort mean age was 42 ± 12 years (60% male); 56% had LV outflow tract obstruction. Global native T1 ranged 1004–1076 ms and mean ECV 26.7–31.9%. Only the basal anterolateral segment showed a significant LGE–ECV association (p = 0.024). Native T₁ predicted fibrosis in 13 of 16 segments (OR per ms increase 1.013–1.038, p < 0.01), with strongest effect in the mid inferoseptal wall. Conclusion: Native T1 mapping and ECV quantification provide sensitive and reproducible measures of diffuse interstitial fibrosis that complement LGE’s detection of focal scar in HCM. By demonstrating significant correlations across multiple myocardial regions—and identifying areas of subclinical fibrosis even in segments without overt LGE—these techniques enhance risk stratification and may guide more personalized management. Incorporation of T₁-based metrics into routine CMR protocols could improve prognostic accuracy and inform therapeutic decision‑making in hypertrophic cardiomyopathy.