Objectives  This study sought to assess the rate of progression of fibrosis by 2 consecutive cardiac magnetic resonance (CMR) examinations and its relation with clinical variables.

Background  In hypertrophic cardiomyopathy (HCM) myocardial fibrosis, detected by late gadolinium enhancement (LGE), is associated to a progressive ventricular dysfunction and worse prognosis.

Methods  A total of 55 HCM patients (37 males; mean age 43 ± 18 years) underwent 2 CMR examinations (CMR-1 and CMR-2) separated by an interval of 719 ± 410 days. Extent of LGE was measured, and the rate of progression of LGE (LGE-rate) was calculated as the ratio between the increment of LGE (in grams) and the time (months) between the CMR examinations.

Results  At CMR-1, LGE was detected in 45 subjects, with an extent of 13.3 ± 15.2 g. At CMR-2, 53 (96.4%) patients had LGE, with an extent of 24.6 ± 27.5 g. In 44 patients, LGE extent increased significantly (≥1 g). Patients with apical HCM had higher increments of LGE (p = 0.004) and LGE-rate (p < 0.001) than those with other patterns of hypertrophy. The extent of LGE at CMR-1 and the apical pattern of hypertrophy were independent predictors of the increment of LGE. Patients with worsened New York Heart Association functional class presented higher increase of LGE (p = 0.031) and LGE-rate (p < 0.05) than those with preserved functional status.

Conclusions  Myocardial fibrosis in HCM is a progressive and fast phenomenon. LGE increment, related to a worse clinical status, is more extensive in apical hypertrophy than in other patterns.