Abstract 2713: Comparison of MRI Myocardial Tissue Tagging and Tissue Doppler Imaging for Assessment of Mechanical Dyssynchrony
Background: Echocardiographic (EC) indices of mechanical dyssynchrony (MD) are based largely upon longitudinal strain, whereas magnetic resonance imaging myocardial tissue tagging (MRI-MT) assessment is based on circumferential strain, the latter being the primary direction of myocardial contraction.
Methods: We sought to compare cardiac MRI studies with an EC protocol using 2D imaging, tissue Doppler imaging (TDI), and M-mode in 32 subjects. Absolute strain, time to peak strain in 6 segments, TDI septal-to-lateral delay (SLD; MD if ≥ 70 ms), and M-mode septal-to-posterior wall motion delay (SPWMD; MD if ≥ 130 ms) were measured and compared to the MRI-MT-based CURE (circumferential uniformity ratio estimate, CURE; 0 –1, 0 = asynchrony, 1 = perfect synchrony; MD if < 0.75), which recently has been shown to predict clinical CRT response.
Results: The 8 control subjects (normal QRSd; CURE 0.975 ± 0.01; SLD 26 ± 27 ms) had less MD by MRI-MT (p = 0.0001) and TDI (p = 0.04) as compared to 24 subjects with ejection fraction ≤ 35% (QRSd 135 ≤ 35 ms; CURE 0.695 ± 0.17; SLD 59 ± 39 ms). There was a moderate correlation between TDI and MRI-MT (R = 0.62), with a discordance rate of 22% overall and 25% in cardiomyopathy subjects, in some cases due to abnormal CURE with normal SLD and, in others, normal CURE with abnormal SLD. The M-mode assay (SPWMD) could not be assessed in 10 patients with septal akinesis (AK), although there was MD by TDI and MRI-MT in most of these subjects. In the patients without AK, the discordance rate between TDI and M-mode was 33%.
Conclusions: MRI-MT assessment of circumferential strain and MD is complementary to TDI with a good correlation, but also a significant discordance rate.