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Regional non-uniformity of wall dynamics in normal left ventricle
Insights
Left ventricular myocardial wall dynamics differ regionally in children. Systolic thickening is greatest near the papillary muscles, indicating non-uniform function and structure in the normal heart.
Area of Science:
- Pediatric Cardiology
- Cardiac Physiology
- Echocardiography
Background:
- Understanding regional myocardial function is crucial for diagnosing pediatric cardiac conditions.
- M-mode echocardiography provides insights into left ventricular wall dynamics.
Purpose of the Study:
- To compare myocardial wall dynamics across different regions of the normal pediatric left ventricle.
- To investigate regional variations in systolic thickening and movement.
Main Methods:
- M-mode echocardiograms were performed on 31 healthy children.
- Tracings were recorded at three distinct left ventricular levels: mitral valve ring, leaflet tips, and papillary muscles.
- Data were digitized to analyze fractional shortening, wall thickening, and movement.
Main Results:
- Fractional shortening increased from the base to the apex.
- Systolic posterior wall thickening varied significantly, increasing from 55% at the base to 106% near the papillary muscles.
- Peak posterior wall thinning rate also increased from base to apex.
- Epicardial movement and septal dynamics showed distinct regional patterns.
Conclusions:
- The normal pediatric left ventricle exhibits significant regional differences in myocardial function.
- These functional variations correlate with underlying structural differences in myocardial fiber arrangement.
- Non-uniformity is a key characteristic of normal left ventricular mechanics.
Abstract:
M-mode echocardiograms were performed in 31 normal children in order to compare myocardial wall dynamics in different regions of the left ventricle. Tracings were recorded at the level of the mitral valve ring (level 1), near the tips of the mitral valve leaflets (level 2), and in the region of the papillary muscles (level 3) and were digitised. Fractional shortening increased from 31.7 per cent at level 1 to 36.5 per cent at level 3. Peak VCF and minor dimension lengthening rate were the same at all three levels, as were end-diastolic posterior wall thickness and peak systolic wall thickening rate. Striking regional differences, however, were seen in the extent of systolic posterior wall thickening which increased from 55 per cent at the base to 106 per cent at the papillary muscles, and in peak posterior wall thinning rate, which increased from 6.4 cm/s at the base to 10.0 cm/s at the papillary muscles. There was greater systolic inward movement of epicardium at level 1 than at levels 2 and 3. The septum thinned and thickened more slowly than did the posterior wall and did not show major differences between levels. Systolic reduction in minor dimension thus occurs largely by thickening of the wall at level 3 and by sphincter-like inward movement of the entire wall at level 1. These regional differences can be explained by a circumferential arrangement of myocardial fibres at the base of the heart and a more prominent longitudinal component towards the apex. Thus, non-uniformity of function is a prominent feature of the normal left ventricle and may reflect regional variation in its structure.