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Mechanocardiographic assessment of systolic time intervals in normal children
Insights
This study establishes normal standards for systolic time intervals (STI) in children, identifying heart rate and body surface area as key influencing factors for accurate assessment.
Area of Science:
- Pediatric Cardiology
- Cardiovascular Physiology
- Biomedical Engineering
Background:
- Systolic time intervals (STI) are crucial indicators of left ventricular function.
- Establishing age- and size-specific normal values for pediatric STI is essential for accurate clinical interpretation.
- Previous studies have yielded conflicting results regarding factors influencing pediatric STI.
Purpose of the Study:
- To define normal standards for various left ventricular systolic time intervals in a large cohort of healthy children.
- To investigate the influence of physiological variables such as age, sex, and anthropometric measurements on pediatric STI.
- To develop regression equations for calculating normal STI values and prediction intervals.
Main Methods:
- Simultaneous electrocardiogram, phonocardiogram, and external carotid pulse recordings were obtained from 469 children (aged 5.0–16.9 years).
- Analysis included electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP), and others.
- Regression analysis was used to determine the impact of heart rate, body weight, body length (BL), and body surface area (BSA) on STI.
Main Results:
- Heart rate significantly influenced most STI, except for the upstroke time/LVET ratio (UT/LVET), which was independent.
- Body surface area (BSA) was a significant independent variable for QS2 and LVET.
- Body length (BL) independently influenced PEP, PEP/LVET, and QS1, aligning with echocardiographic findings but differing from older mechanocardiographic studies.
Conclusions:
- This study provides robust, regression-based normal standards for pediatric STI, incorporating key anthropometric variables.
- The developed equations allow for the calculation of normal STI and 95% prediction intervals, aiding in the detection of abnormalities.
- Findings emphasize the importance of considering individual developmental parameters (BSA, BL) alongside heart rate for accurate STI assessment in children.
Abstract:
Systolic time intervals (STI) were measured in 469 normal children, aged 5.0 to 16.9 years, using simultaneous recordings of the electrocardiogram, phonocardiogram and an external carotid pulse tracing. The data were analyzed to define the influence of sex, age, cardiac cycle length, body weight (BW), body length (BL), and body surface area (BSA) on the left ventricular STI. Regression, equations were evaluated for the calculation of normal standards for the following STI: electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP) systolic quotient (PEP/LVET), isovolumic contraction time (IVCT), electroacustical delay (QS1), and additionally for the so-called tension time (TT), upstroke time (UT), and the ascending index (UT/LVET) of the carotid pulse wave. Heart rate was found to influence all of the STI but the ratio UT/LVET, which revealed to be independent of any variable. Besides heart rate, BSA proved to be a second relevant independent variable for QS2 and LVET, respectively BL for PEP, PEP/LVET and QS1. These findings are in accordance to the results of comparable echocardiographic studies but disagree previous mechanocardiographic studies in smaller groups of children in whom age and not the above-mentioned parameters of the individual development seemed to influence the STI. A second set of equations was evaluated for the calculation of 95%-prediction intervals for the particular STI permitting to define abnormalities of the STI in individual children.