Background: It has been shown that the ratio of systolic duration to diastolic duration (S/D) is a valuable global index of ventricular dysfunction in pediatric dilated and restrictive cardiomyopathy and is also a valuable index of the ventricular function of single systemic right ventricles in children who have undergone palliation of hypoplastic left-heart syndrome. The purposes of this study were to establish normal values for the S/D ratio in children without heart disease and to investigate its variation with heart rate (HR), age, and body surface area.
Methods: Of 752 children found to have functional murmurs by clinical means, 179 (24% of the total database) had trace holosystolic tricuspid regurgitation. These patients ranged in age from 0.02 months to 19 years. For this study, the diastolic interval was defined as the period of right ventricular filling (ie, the period between 2 tricuspid regurgitant jets) and the systolic interval as the remainder of the cardiac cycle corresponding to the duration of holosystolic tricuspid regurgitation, including the periods of isovolumic contraction and relaxation. The relations between the systolic and diastolic periods and their ratio (S/D ratio) and HR, age, and body surface area were evaluated using univariate and multivariate linear regression analysis.
Results: Patient's age ranged from 0.02 months to 19 years (mean, 70.18+/-65.12 months), body surface area from 0.11 to 2.51 m2 (mean, 0.85+/-0.55 m2), and HR from 50 to 156 beats/min (mean, 96.72+/-23.19 beats/min). The systolic period ranged from 208.5 to 467 ms (mean, 314.08+/-52.57 ms) and the diastolic period from 166.5 to 809 ms (mean, 341.34+/-129.61 ms), yielding a S/D ratio ranging from 0.397 to 1.62 (mean, 0.995+/-0.23). Systolic period duration showed a linear negative decrease with increasing HR (y=1.9228x+500.05, r=-0.85). Diastolic duration decreased in an exponential fashion as HR increased (y=130,679x(-1.3232), r=-0.88). The S/D ratio correlated positively with HR (y=-1.656+0.0265 HR-0.000954 HR2, r=76). On multivariate analysis, no significant correlations of S/D ratio with age or body surface area were found.
Conclusions: The results of this study provide useful reference values for the S/D ratio across a wide range of HRs in children, adolescents, and young adults.