Work

Native left ventricular myocardial T1 spatial heterogeneity in non-ischemic dilated cardiomyopathy

Year: 2016

Type: article

Abstract: Myocardial fibrosis is involved in the pathology of non-ischemic dilated cardiomyopathy (NICM). Recently, the application of native (non-contrast) myocardial T 1 measurement has been proposed as an imaging biomarker of cardiac remodeling. However, spatial heterogeneity in T 1 measurements has been observed across different segments and slices. Furthermore, T 1 values measured with current T 1 mapping sequences are influenced by myocardial T 2 values. The objective of this study was to 1) assess the spatial heterogeneity of T 1 measurements across different segments and slices in healthy subjects and patients, and 2) determine the association of native T 1 with myocardial structure and function. We prospectively studied 39 NICM patients (LVEF≤50% without evidence of prior infarction by CMR) and 30 subjects with normal LV systolic function without known cardiovascular disease. CMR was performed using a 1.5-T MRI scanner (Philips Achieva). Native T 1 mapping was performed using slice-interleaved T 1 mapping sequence (STONE) [ 1 ]. T 2 mapping was performed using slice-interleaved T 2 mapping [ 2 ]. Voxel-wise T 1 and T 2 were estimated using a 2-parameter and 3-parameter model [ 3 ]. All images were corrected for motion [ 4 ]. T 1, T 2, and extra-cellular volume (ECV) measurements were measured using a 16 segments AHA model across the base, mid, and apical LV. NICM participants (57 ± 15 years) were predominantly male (74%). By design, all had a reduced LV ejection fraction (mean LVEF 34 ± 10%). Figure 1 shows native T1, T2, and ECV in two patients with a NICM. Parametric maps to the right in each panel demonstrate full ventricular coverage. The regional distribution of native myocardial T 1 was similar in patients with and without NICM[RN1], as shown in Figure 2 . Relative to subjects without NICM, subjects with NICM had a higher native T 1 (1131 ± 51 vs. 1070 ± 28 msec; p < 0.0001), a higher ECV (0.28 ± 0.04 vs. 0.25 ± 0.02, P = 0.001) and a longer myocardial T 2 (52 ± 8 vs. 47 ± 5 msec; P = 0.01). After multivariable adjustment, a lower global native T 1 time was associated with a higher LVEF (b = -0.59, P = 0.0003), higher right ventricular ejection fraction (b = -0.47, P = 0.006), and lower left atrial volume index (b = 0.51, P = 0.001). (A) Images from a 47-year-old woman with a NICM with moderate reduction in LV function (LV ejection fraction 30%) . (B) Images from a 39-year-old heathy male (LV ejection fraction 61%). Variability in segmental native T 1 across all 16 myocardial segments in individuals with normal LV function (red) and study participants with NICM (blue) . The error bars represent standard error of the mean. In NICM, native myocardial T 1 is elevated in a homogeneous manner, suggesting a global (not regional) abnormality in myocardial tissue composition. This low variability is similar between healthy and NICM patients across different segments. For subjects with NICM, native T 1 is associated with biventricular systolic function and left atrial volume, and may represent a non-contrast marker of tissue remodeling in this cohort.

Source: Journal of Cardiovascular Magnetic Resonance

DOI: 10.1186/1532-429x-18-s1-q41