Worse left ventricular strain assessed by novel CMR imaging reflects myocardial fibrosis in the general population

Both focal and diffuse myocardial fibrosis may impair myocardial contractility and cause mechanical alterations that can be measured by novel cardiac magnetic resonance (CMR) techniques like CMR feature tracking (CMR-FT) and strain encoded (fast-SENC) sequences. Associations between myocardial fibrosis and impaired strain have been shown in different cardiomyopathies. The relationship between focal and diffuse fibrosis and strain assessed by novel CMR imaging has not yet been studied in an elderly general population cohort.

To investigate the relationship between diffuse and focal myocardial fibrosis and left ventricular (LV) strain using state-of-the-art CMR imaging in an elderly general population cohort.

Two hundred community-dwellers born in 1950 without known coronary artery disease were recruited and examined with a 1.5-T Philips MRI scanner. Diffuse fibrosis was estimated by septal extracellular volume (ECV) fraction and focal fibrosis was quantified by late gadolinium enhancement (LGE). LV global longitudinal strain (GLS) and global circumferential strain (GCS) were obtained by both CMR-FT and fast-SENC. Fast-SENC was assessed as percentage of segments with strain ≤-17% (% normal myocardium). Linear models were used to assess the association between myocardial strain (CMR-FT and fast-SENC) and diffuse and focal fibrosis. Nonlinear associations were evaluated with restricted cubic splines with 3 knots. Likelihood Ratio Test was used to evaluate whether the fully adjusted models with splines provided a better fit than the linear model.

The median age was 69 (68.6-69.3) and 52% were male. Presence and volume of LGE was associated with GLS assessed by CMR-FT and fast-SENC % normal myocardium in all models. The association between LGE and GCS by CMR-FT was attenuated when adjusting for indexed LV end diastolic volume (LVEDVi). There was a significant non-linear association between ECV and both GLS and GCS (Table) with worsening strain at ECV values above 26 % (Figure). There were no significant associations between ECV and fast-SENC % normal myocardium (Table).

In an elderly general population cohort, focal myocardial fibrosis is associated with worse LV strain assessed by CMR-FT and fast-SENC % normal myocardium. The non-linear association between diffuse fibrosis and CMR-FT strain reveals worse cardiac function beyond a threshold value.