Systolic and Diastolic Time Intervals Measured from Doppler Tissue Imaging: Normal Values and Z-score Tables, and Effects of Age, Heart Rate, and Body Surface Area

Abstract

The aim of this study was to develop normal values, including Z-score tables when appropriate, for systolic time (St) and diastolic time (Dt) intervals measured by Doppler tissue imaging (DTI) and to determine the effects of age, heart rate (HR), and body surface area on DTI-derived time intervals in children. We studied 593 children with normal echocardiogram results. Developmental factors ranged from age 1 day to 18 years, HR 46 to 182/min, and body surface area 0.08 to 2.80 m(2). A total of 7 DTI-derived time interval parameters were studied. Five time interval parameters were measured from DTI: isovolumic contraction time (IVCT), isovolumic relaxation time (IVRT), ejection time, St, and Dt. In addition, we calculated the Tei index (TX) and St/Dt. We sampled longitudinal directed DTI waves from 3 sites: mitral annulus, basal interventricular septum, and tricuspid annulus from an apical 4-chamber view. Parameters were measured in each case from a single echocardiogram during times of hemodynamic stability. By univariate analysis all 7 time intervals at each of the 3 sampling sites correlated with age, HR, and body surface area (P < .001-P < .003), except the mitral annulus TX (P = .1). The following results are all based on multivariate analysis. IVCT, IVRT, and TX correlated best with age at all 3 sites (P < .001). However, when we corrected for HR by dividing by square root(R)-R interval, both corrected IVCT and corrected IVRT became constants at all 3 sites. The change in TX with age was very small and not clinically significant. Therefore, for practical clinical purposes, corrected IVCT, corrected IVRT, and TX were constant at all 3 sites. Ejection time, St, Dt, and St/Dt correlated best with HR at all 3 sites (P < .001). Ejection time, St, and Dt all decreased at faster HRs, whereas St/Dt increased at faster HRs.