systolic to diastolic duration ratio in children with normal cardiac function and its relation to heart rate, age and body surface area

ABSTRACT

We have shown the ratio of systole to diastole to be a valuable global index of ventricular dysfunction in pediatric dilated and restrictive cardiomyopathy and also of ventricular function of the single systemic right ventricle in children who have undergone Norwood procedure for hypoplastic left heart. As this index may be a valuable indicator of ventricular performance in other conditions, normal reference values need to be established. The purpose of this study was to establish normal values for the S/D ratio in children and to investigate its relation to heart rate, age and body surface area. We reviewed 179 echocardiograms of healthy children and young adults [mean 70.18 months, SD +/- 65.12 months, range 0.02 months to 19 years] and measured the average duration of the holosystolic tricuspid regurgitant jet [systolic interval]. The remainder of the cardiac cycle [i.e the period between 2 tricuspid regurgitant jets] was defined as the diastolic interval. We evaluated the relation between the S/D ratio and heart rate, age and body surface area by univariate and multivariate linear regression analysis. Ranges, mean values and standard deviations are reported from age 0.02 months to 19 years [70.18 +/- 65.12 months], BSA 0.11 to 2.51m[2] [0.85 +/- 0.55] and heart rate 50 to 156 bpm [96.72 +/- 23.19]. The systolic period ranged between 208.5 to 467 msec [314.08 +/- 52.57] and the diastolic period between 166.5 to 809 msec [341.34 +/- 129.61] yielding a S/D ratio between 0.397 to 1.62 [0.995 +/- 0.23]. The S/D ratio correlated positively with heart rate [y = 0.0073x+0.2969, r = 0.72]. However, in multivariate analysis there was no significant correlation with age and body surface. Heart rate had a greater effect on shortening the diastolic period, in an exponential fashion [y = 130679x -1.3232, r = -0.88] than on systolic period which responded in linear fashion [y = -1.9228x + 500.05, r = -0.85]. We provide normal reference values for the S/D ratio across a wide range of heart rates in children, adolescents and young adults