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

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 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.