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Normal values for noninvasive estimation of left ventricular contractile state and afterload in children
R C Franklin1, R K Wyse, T P Graham
1Department of Pediatric Cardiology, Institute of Child Health, London, United Kingdom.
Insights
Assessing left ventricular function in children with congenital heart disease is crucial. This study provides a quantitative method to evaluate myocardial hypertrophy, afterload, and contractile state in children.
Area of Science:
- Pediatric Cardiology
- Echocardiography
- Cardiovascular Physiology
Background:
- Left ventricular function is critical for therapeutic interventions in children with congenital heart disease.
- Congenital heart disease alters loading conditions, complicating the assessment of ventricular contractility with standard load-dependent indexes.
Purpose of the Study:
- To establish a quantitative basis for assessing myocardial hypertrophy, afterload, and contractile state in children.
- To develop load-independent measures of left ventricular contractility in pediatric populations.
Main Methods:
- Utilized two-dimensional and M-mode echocardiography and arterial blood pressure measurements.
- Studied left ventricular morphometrics and contractility in 44 healthy children aged 2 to 12 years.
- Calculated load-independent indexes by correlating rate-corrected velocity of circumferential fiber shortening with end-systolic stress.
Main Results:
- Left ventricular dimensions and mass increased linearly with body surface area in normal children.
- Key contractility indexes like shortening fraction and ejection fraction remained constant.
- An inverse linear correlation was found between rate-corrected velocity of circumferential fiber shortening and end-systolic stress, establishing a load-independent contractile measure.
Conclusions:
- The study provides a quantitative framework for evaluating left ventricular function in children.
- Findings support the use of load-independent indexes for accurate assessment of contractility in pediatric congenital heart disease.
- This research aids in understanding myocardial hypertrophy, afterload, and contractile state in childhood cardiovascular conditions.
Abstract:
The outcome and suitability for therapeutic interventions in children with congenital heart disease depend frequently on left ventricular function. Congenital heart disease is characterized by changes in loading conditions, making it difficult to assess ventricular contractility using conventional load-dependent indexes. Two-dimensional and M-mode echocardiography and arterial blood pressure were used to study left ventricular morphometrics and contractility in 44 normal children, aged 2 to 12 years. Left ventricular end-systolic and end-diastolic length, diameter, wall thickness, volume and mass all showed linear increases with body surface area (p less than 0.001 in all). Shortening and ejection fractions, velocity of circumferential fiber shortening, morphometric ratios and endocardial meridional and circumferential stress (mean 46 and 115 g/cm2, respectively) all remained constant. A load-independent measure of the normal resting left ventricular contractile state was determined by relating the rate-corrected velocity of circumferential fiber shortening to end-systolic endocardial meridional and circumferential stress; there was an inverse linear correlation (r = -0.641 and -0.557 respectively, p less than 0.001). These data provide a quantitative basis for assessment of myocardial hypertrophy, afterload and contractile state in childhood.