1025 Global strain rate do not reduce biological variability compared to S", and do not normalize for body size

Abstract

Abstract Background As the Left ventricular (LV) apex is stationary, and maximum velocities are in the mitral plane, peak systolic annular velocity (S") normalized for wall length (WL) is a measure of peak systolic strain rate (Fig. 1), as is strain rate measured by tissue Doppler. As the normalization presumably corrects for the size of the heart (and thus body), this should reduce biological variability, but this assumption has previously been shown to be faulty for annular displacement (MAPSE) vs global longitudinal strain. Methods The HUNT study examined 1266 subjects without evidence of heart disease, from a mixed urban / rural population of North Tøndelag county in Norway. Annular systolic velocity was measured by pulsed-wave Tissue Doppler in the septal, lateral, anterior and inferior points, and averaged. Wall lengths was measured in a straight line in the same points, and S" was normalized (S"/WL) and averaged. Segmental systolic strain rate was also measured by combined speckle tracking / Tissue Doppler and averaged to a global value (GLSR). Results are given in table 1. All three measures declined with increasing age (R was -0.23, -0.29 and -0.29, respectively, all p < 0.001) The over-all relative standard deviations were similar for S", normalized S" and global strain rate. Both S"/WL and GLSR correlated negatively with BSA, R was - 0.22 and 0.17, respectively (p < 0.001), while S" showed a modest positive correlation; R = 0.13, (p < 0.001) Conclusion Normalizing peak systolic mitral annular velocity for length do not reduce biological variability, and introduces a systematic error in the body size relation, due to the one-dimensional nature of the normalisation, and the three-dimensional nature of LV deformation. This is in accordance with what has previously been shown for global longitudinal strain vs. annular plane displacement. Table 1 Age (years) S" (cm/s) S"/WL (/s) GLSR (/s) < 40 9.1 (1.2) 0.93 (0.13) 1.08 (0.12) 40 - 60 8.3 (1.3) 0.86 (0.13) 1.03 (0.12) > 60 7.7 (1.3) 0.81 (0.14) 0.98 (0.14) All 8.4 (1.4) 0.87 (0.14) 1.03 (0.13) Relative SD (%) 16.7 16.1 12.6 Mitral annular velocity (S"), normalised velocity (S"/WL) and Global strain by age groups. (Standard deviations in parentheses) Abstract 1025 Figure. Fig. 1