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Non-contrast cardiac MRI for tissue characterization in patients with end stage renal disease
Journal of Cardiovascular Magnetic Resonance volume 18, Article number: P241 (2016)
End stage renal disease (ESRD) patients suffer high cardiovascular mortality rates with fibrosis-induced arrhythmia recognized as a leading contributor. Since ESRD patients are contraindicated to standard gadolinium-based fibrosis imaging, non-contrast cardiac magnetic resonance imaging (CMR) techniques could improve diagnosis and empower evaluation of emerging anti-fibrotic therapies. With remodeling and increased extracellular water volume, a corresponding and measurable loss of magnetization transfer (MT) occurs. We previously demonstrated the ability to identify tissue that enhances with gadolinium based on differences between pairs of differentially MT-weighted balanced steady state free precession (bSSFP) images1,2 (Figure 1A-C). In this study, we seek to apply non-contrast MT-based tissue characterization in ESRD patients.
ESRD patients on routine hemodialysis and healthy controls (n = 9/group to date) were imaged on a 1.5T Siemens Aera scanner. Pairs of prospectively gated cine bSSFP images were obtained at flip angles of 50 and 45° from base to apex [TR/TE=35.64/1.36 ms, FOV=260 × 260 mm2, Matrix=256 × 256, Thickness=8 mm, phases set to fill the cardiac interval]. Maps of ΔS/So were generated as ΔS/So=(S45-S5)/S5*100 (%), where Si is the signal intensity per voxel at flip angle i. We analyzed cardiac structure and global function. A custom feature tracking algorithm measured circumferential and longitudinal strains. The distribution of ΔS/So values across all controls was used to define a reference standard. To account for variations in heart size, this distribution was dynamically resized to simulate a cumulative distribution function of ΔS/So matching the number of voxels per individual heart. Each subject's observed ΔS/So distribution was compared to the appropriately-sized healthy standard using a one-sided Kolmogorov-Smirnov (KS) test.
While septal wall thickness was heightened in ESRD patients (Table 1), ejection fraction and peak circumferential and longitudinal strains were similar to controls. A sample ΔS/So map in an ESRD patient (Figure 1E) demonstrates scattered enhancement compared to a healthy control (Figure 1D). Corresponding ΔS/So distributions (Figure 1F) reveal a right skew in the ESRD patient, consistent with tissue remodeling. KS analysis revealed a trend toward greater rightward shift for ESRD patients (avg=13%, range: 3-48%) than controls (avg=4%: 0-12%, p = 0.12 vs. ESRD) when compared to the healthy standard. Four ESRD patients and only 1 control displayed ΔS/So distributions that diverged from the standard distribution by more than 10%.
MT-weighted bSSFP imaging revealed a promising trend towards elevated ΔS/So values in ESRD patients compared to controls, despite preserved contractile function. Analysis of ΔS/So distributions may provide a rapid and endogenous mechanism for myocardial tissue characterization in ESRD patients. Ongoing participant recruitment will increase sample sizes and may reveal additional pathologies in ESRD patients.
Stromp T, et al: Circulation. 2014, 130 A11915-
Stromp T, et al: JCMR Under review following revision.
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Stromp, T.A., Kaine, J.C., Andres, K.N. et al. Non-contrast cardiac MRI for tissue characterization in patients with end stage renal disease. J Cardiovasc Magn Reson 18, P241 (2016). https://doi.org/10.1186/1532-429X-18-S1-P241
- Longitudinal Strain
- Tissue Characterization
- Balance Steady State Free Precession
- Balance Steady State
- Septal Wall Thickness