Regional myocardial strain by cardiac magnetic resonance feature tracking for detection of scar in ischemic heart disease

Background: Although cardiac magnetic resonance (CMR) can accurately quantify global left ventricular strain using feature tracking (FT), it has been suggested that FT cannot reliably quantify regional strain. We aimed to determine whether abnormalities in regional strain measured using FT can be detected within areas of myocardial scar and to determine the extent to which the regional strain measurement is impacted by LV ejection fraction (EF). Methods: We retrospectively studied 96 patients (46 with LVEF <= 40%, 50 with LVEF > 40%) with coronary artery disease and a late gadolinium enhancement (LGE) pattern consistent with myocardial infarction, who underwent CMR imaging (1.5T). Regional peak systolic longitudinal and circumferential strains (RLS, RCS) were measured within LGE and non-LGE areas. Linear regression analysis was performed for strain in both areas against LVEF to determine whether the relationship between strain and LGE holds across the LV function spectrum. Receiver-operating curve (ROC) analysis was performed in 33 patients (derivation cohort) to optimize strain cutoff, which was tested in the remaining 63 patients (validation cohort) for its ability to differentiate LGE from non-LGE areas. Results: Both RLS and RCS magnitudes were reduced in LGE areas: RLS = -10.4 +/- 6.2% versus - 21.0 +/- 8.5% (p < 0.001); RCS = -10.4 +/- 6.0% versus -18.9 +/- 8.6%, respectively (p < 0.001), but there was considerable overlap between LGE and non-LGE areas. Linear regression revealed that it was partially driven by the natural dependence between strain and EF, suggesting that EF-corrected strain cutoff is needed to detect LGE. ROC analysis showed the ability of both RLS and RCS to differentiate LGE from non-LGE areas: area under curve 0.95 and 0.89, respectively. In the validation cohort, optimal cutoffs of RLS/EF = 0.36 and RCS/EF = 0.37 yielded sensitivity, specificity and accuracy 0.74-0.78. Conclusion: Abnormalities in RLS and RCS within areas of myocardial scar can be detected using CMR-FT; however, LVEF must be accounted for.