INFLUENCE OF DISEASE PHENOTYPE ON THE ACCURACY OF EJECTION FRACTION TO ESTIMATE CONTRACTILE PERFORMANCE: ASSESSMENT BY MULTI-DIRECTIONAL 3D GLOBAL AXIS-DEPENDENT AND PRINCIPAL STRAIN ANALYSIS

Abstract

Left Ventricular (LV) Ejection Fraction (EF) is a ubiquitously reported estimate of global contractile performance. While practical, the value of this marker across different geometric configurations has been challenged. With expanding availability of myocardial strain analysis techniques, opportunity exists to explore direct markers of tissue deformation. In this study we use 3-dimensional myocardial deformation analysis (3D-MDA) of cardiovascular magnetic resonance (CMR) cine images to calculate global circumferential, longitudinal, radial, and principal directions strain amplitude. This was performed across classified cohorts of ischemic cardiomyopathy (ICM), non-ischemic dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM) and healthy volunteers. Respective associations of LVEF to each strain-based marker of contractile performance were evaluated. Three-hundred-ninety-seven subjects underwent standard CMR imaging (3T) inclusive of multi-axial cine imaging. The study population included 78 with ICM, 86 with DCM, 85 with HCM, and 148 healthy controls. All cardiomyopathy states were confirmed by published criteria. LV volumes and LVEF were blindly calculated using commercial software. Axis dependent (circumferential, longitudinal, and radial) as well as principal strain (minimum, secondary, and maximum) amplitudes were computed by means of validated in-house software (3D-MDA) leveraging on short-axis and long-axis cine images. For the current analysis, association of global estimates of strain were reported and compared to LVEF using linear regression analysis. Mean age was 55.6±10.8 years (DCM: 58.4±11.3, ICM: 61.3±9.8, HCM: 50.1±11.2, normals: 54.0±8.8 years) with 134 (34%) female (DCM: 13%, ICM: 34%, HCM: 35%, normals: 40%). Mean LVEF was 50.5±21.2% (DCM: 26.5±8.3, ICM: 26.9±6.8%, HCM: 70.0±7.4%, normals: 65.6±5.5%). All associations of strain amplitude markers and LVEF are reported in Table 1. Across the entire population, strong associations were found between LVEF and all measures of strain amplitude (r=0.75 to r=0.92, p < 0.0001 for all). Performance was good in normal controls (r=-0.20 to r=-0.40, p < 0.005), although poor correlation was seen subepicardially for both minimum principal and circumferential directions of strain. Among diseased cohorts, associations were strongest for DCM (r=0.42 to r=0.60, p < 0.0001 for all). ICM patients maintained strong associations, although were objectively weaker with loss of significance for radial strain (wall thickening). HCM patients showed poor associations for LVEF across all strain-based parameters, statistical significance only maintained for subendocardial-based estimates of strain. Versus validated reference standards of myocardial deformation, LVEF is a sub-optimal measure of global contractile performance in patients with HCM and is associated with variable performance in patients with ICM.