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Left ventricular wall stress and thickness in complete transposition of the great arteries. Implications for surgical
Insights
Left ventricular pressure loading thickens walls in transposition of the great arteries, but wall stress remains constant. Early surgery is recommended for left ventricle systemic work.
Area of Science:
- Cardiology
- Pediatric Cardiology
- Cardiac Physiology
Background:
- Transposition of the great arteries (TGA) presents unique challenges for left ventricular (LV) development and function.
- Understanding LV adaptation to pressure and volume loads is crucial for managing TGA patients.
Purpose of the Study:
- To investigate the impact of volume and pressure loading on LV posterior wall thickness and wall stress in TGA.
- To determine optimal timing and strategies for surgical interventions involving LV systemic support.
Main Methods:
- Combined echocardiography and cardiac catheterization data analysis.
- Assessment of LV posterior wall thickness and calculation of LV wall stress using a radius/wall thickness ratio, adjusted for ventricular geometry and pressure.
Main Results:
- Pure volume loading caused minimal LV posterior wall thickening (0.52 mm/log month).
- Pressure loading above half of right ventricular pressure induced significant thickening (2.80–3.89 mm/log month).
- LV walls are thinner in low-pressure TGA ventricles compared to high-pressure ones by 1-3 months of age.
Conclusions:
- LV wall stress is constant in TGA when accounting for geometry and pressure, similar to normally related great arteries.
- Surgical interventions like the arterial switch operation for LV systemic work should be performed within the first month of life.
- Preparatory operations should aim to load the LV to >50% of systemic pressure before definitive surgery.
Abstract:
The effects of volume and pressure loading of the left ventricle on posterior wall thickness and left ventricular wall stress in transposition of the great arteries were studied by combining echocardiographic and cardiac catheterization data. Pure volume loading with low left ventricular pressure resulted in little or no thickening of the left ventricular posterior wall (0.52 mm/log month). Pressure loading to levels above half of the right ventricular pressure was associated with thickening (2.80 to 3.89 mm/log month); however, further increase in pressure or volume load did not significantly alter the rate of thickening. Estimates of ventricular wall stress using a simple radius/wall thickness ratio may be misleading. However, if allowance is made for variable ventricular geometry and pressure, estimated wall stress is constant in transposition and is approximately equal to that reported previously in patients with normally related great arteries. The walls of low-pressure left ventricles in patients with transposition are demonstrably thinner than those of high-pressure left ventricles by age 1 to 3 months (2.67 versus 3.52 mm). Surgical procedures to use the left ventricle for systemic work, such as the arterial switch operation, should be performed in the first month of extrauterine life. Preparatory operations, if necessary prior to arterial switch, should load the left ventricle to greater than half systemic pressure.