Effects of acute hydration changes on cardiovascular magnetic resonance native T1 and T2 mapping

Changes in hydration status may affect myocardial native T1 and T2 values and influence the clinical interpretation. We aimed to assess the impact of acute preload augmentation on native T1 and T2. Cardiovascular magnetic resonance (CMR) native T1 and T2 mapping were performed twice on the same day in 20 healthy participants before and after an acute preload augmentation by a 2-liter intravenous infusion of isotonic sodium chloride (0.9%). Test-retest reproducibility was evaluated in 30 healthy participants with two consecutive CMR examinations on the same day. Sixteen participants were included in both substudies. In the 20 healthy participants undergoing acute preload augmentation (55% males, mean age (interquartile range [IQR]) 43 [29-51] years), native T1 increased with 17 ms (95% confidence interval [CI] 7 to 26; p = 0.001), T2 with 1.7 ms (95% CI 0.8 to 2.4; p < 0.001), and blood T1 with 46 ms (95% CI 28 to 65; p < 0.001). Test-retest variability in 30 healthy participants (47% males, median age 43 [28-52] years) showed 95% limits of agreement (LOA) of ± 26 ms for native T1, ± 2.1 ms for T2, and ± 57 ms for blood T1. In the 16 participants included in both substudies, the mean differences in changes post-infusion versus test-retest were 22 ms (95% CI 8 to 36; p = 0.01) for native T1, 1.9 ms (95% CI 0.9 to 2.9; p = 0.001) for T2, and 62 ms (95% CI 32 to 91; p < 0.001) for blood T1. Native T1 and T2 values increased following acute preload augmentation. However, the changes were within the 95% LOA of the test-retest reproducibility.