Background: The presence of myocardial fibrosis is associated with worse clinical outcomes in hypertrophic cardiomyopathy (HCM). Cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) sequences can detect regional, but not diffuse myocardial fibrosis. Post-contrast T(1) mapping is an emerging CMR technique that may enable the non-invasive evaluation of diffuse myocardial fibrosis in HCM. The purpose of this study was to non-invasively detect and quantify diffuse myocardial fibrosis in HCM with CMR and examine its relationship to diastolic performance.
Methods: We performed CMR on 76 patients - 51 with asymmetric septal hypertrophy due to HCM and 25 healthy controls. Left ventricular (LV) morphology, function and distribution of regional myocardial fibrosis were evaluated with cine imaging and LGE. A CMR T(1) mapping sequence determined the post-contrast myocardial T(1) time as an index of diffuse myocardial fibrosis. Diastolic function was assessed by transthoracic echocardiography.
Results: Regional myocardial fibrosis was observed in 84% of the HCM group. Post-contrast myocardial T(1) time was significantly shorter in patients with HCM compared to controls, consistent with diffuse myocardial fibrosis (498 ± 80 ms vs. 561 ± 47 ms, p < 0.001). In HCM patients, post-contrast myocardial T(1) time correlated with mean E/e' (r = -0.48, p < 0.001).
Conclusions: Patients with HCM have shorter post-contrast myocardial T(1) times, consistent with diffuse myocardial fibrosis, which correlate with estimated LV filling pressure, suggesting a mechanistic link between diffuse myocardial fibrosis and abnormal diastolic function in HCM.