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Systolic time intervals in children: normal standards for clinical use
Insights
This study establishes reliable standards for assessing left ventricular performance in children using systolic time intervals. Regression equations based primarily on heart rate provide practical clinical tools for pediatric cardiology.
Area of Science:
- Pediatric Cardiology
- Cardiovascular Physiology
Background:
- Accurate assessment of left ventricular performance is crucial in pediatric cardiology.
- Establishing reliable reference standards for systolic time intervals in children is necessary for clinical evaluation.
Purpose of the Study:
- To derive regression equations for systolic time intervals in normal children.
- To establish reliable clinical standards for assessing left ventricular performance in pediatric patients.
Main Methods:
- Measurement of systolic time intervals in 253 normal children.
- Utilized stepwise regression analysis to identify relevant variables (heart rate, age).
- Developed regression equations for electromechanical systole (QS2), left ventricular ejection time (LVET), and pre-ejection period (PEP).
Main Results:
- Heart rate was the primary determinant for QS2 and LVET in both sexes.
- Heart rate was the main determinant for PEP in males; age had a minor influence in females.
- The PEP/LVET ratio was largely independent of heart rate and age, with a consistent mean value (0.30 ± 0.04).
Conclusions:
- Regression equations based on heart rate offer practical clinical standards for pediatric systolic time intervals.
- The PEP/LVET ratio can be used universally across children, independent of age and heart rate.
- The described methods are practical for routine clinical use in children, providing a reliable basis for assessment.
Abstract:
Systolic time intervals were measured in 253 normal children, with careful attention to precise recording and measuring techniques, to derive regression equations which could be used as reliable standards for clinical assessment of left ventricular performance in this age group. Using stepwise regression analysis, a highly significant correlation was found for electromechanical systole (QS2) and for left ventricular ejection time (LVET) with heart rate alone in both males and females, and age was not found to be a relevant variable. Similarly, for the preejection period (PEP) in males, heart rate was the only relevant variable. PEP in females showed a small but significant influence of age in addition to heart rate; in practice, this small influence can be neglected. Regression equations relating each of the systolic time intervals to heart rate alone were therefore derived for clinical use. The PEP/LVET ratio was found to be only weakly correlated with heart rate in males and with age in females, and in practice can be considered to be independent of these variables. The mean value of the PEP/LVET ratio and its standard deviation (0.30 +/- 0.04) can therefore be used for all children. We found that satisfactory recording of systolic time intervals can be obtained with little difficulty in almost all children using the techniques described. The method is therefore practical for clinical use in children, as it is in adults, and the normal standards derived in this study can serve as a reliable basis for its application.