The impact of infarct size on regional and global left ventricular systolic function: a cardiac magnetic resonance imaging study

Myocardial infarction (MI) results in myocardial scarring which can have an impact on left ventricular (LV) stiffness and contractile function, ultimately leading to reduced LV systolic function and LV remodelling, However some concerns about the relation between scar extension and segmental wall motion contractility is not enough clear. Thus, the association between myocardial scar, LV regional and global function and LV remodeling should be investigated. We studied the relationship between scar extension, wall motion score index (WMSI), LV dimensions and systolic function in a group of patients with previous MI by cardiac magnetic resonance (CMR). 133 patients with previous (>6 month) MI were retrospectively enrolled in the study. Indexed end-systolic volume (ESVi), indexed end-diastolic volume (EDVi), LV ejection fraction (EF), stroke volume (SV), LV mass were measured using CMR. WMSI and sum scar score (SSS) were also measured following AHA\ACC criteria giving an arbitrary cut-off to distinguish larger from restricted late gadolinium enhancement (LGE) area. A total of 2261 segments were studied: regional wall motion abnormalities were present in 1032 segments (45 %) and 724 (32 %) showed presence of MI (LGE). WMSI correlated significantly with EF (r = −0.87, p < 0.0001) in all patients and in both patients with EF ≥ 40 % (r = −0.77, p < 0.0001) and EF < 40 % (r = −0.68, p < 0.0001). WMSI also correlated significantly with SSS (r = 0.57, p < 0.0001). The correlation between WMSI and SSS was more significant in patients with transmural MI (WMSI 2.1 ± 0.5 and SSS 17 ± 8; r = 0.55, p < 0.0001) than with non transmural MI (WMSI 1.6 ± 0.7 and SSS 6 ± 4; r = 0.34 and p = 0.02). A significant correlation was also found between EF and SSS (r = −0.55 and p < 0.0001) and between SSS and LV indexed volumes (EDVi; r = 0.44, p < 0.0001 and ESVi; r = 0.51, p < 0.0001). Infarct transmurality and extension as expressed as SSS assessed with cardiac MRI has an impact on global and regional systolic function. A multi-parametric score measuring WMSI scar transmurality and extension, could better identify an increased cardiac remodeling after coronary event.