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Myocardial changes in immature infants requiring prolonged ventilation
Insights
Prolonged oxygen ventilation in premature infants can cause cardiac hypertrophy and myocardial damage. This study suggests these heart lesions result from ongoing hypoxia and coronary circulation issues, posing a risk to infant therapy.
Area of Science:
- Neonatal Cardiology
- Pediatric Pathology
- Respiratory Medicine
Background:
- Premature infants requiring prolonged mechanical ventilation and high oxygen concentrations are at risk for cardiopulmonary complications.
- Bronchopulmonary dysplasia is a known complication, but associated cardiac pathology is less understood.
- Cardiac hypertrophy and myocardial lesions have been observed in infants with severe bronchopulmonary dysplasia.
Purpose of the Study:
- To investigate the nature and potential causes of cardiac lesions in infants with prolonged ventilation and high oxygen exposure.
- To compare findings in ventilated infants with a control group of stillbirths and neonatal deaths.
- To elucidate the relationship between respiratory support, hypoxia, and cardiac pathology in immature infants.
Main Methods:
- Necropsy examination of 14 infants with prolonged ventilation (≥14 days) and high oxygen concentrations.
- Histopathological analysis of cardiac tissue, including assessment of heart weight, valves, septum, and intramural vessels.
- Comparison with cardiac findings in 100 control infants (50 stillbirths, 50 neonatal deaths) of comparable gestational age.
Main Results:
- 11 out of 14 infants exhibited cardiac hypertrophy (heart weight >2 SD above mean), primarily in immature neonates with severe bronchopulmonary dysplasia.
- Cardiac hypertrophy involved ventricles and septum, showing necrosis and fibroelastotic scarring, with intimal thickening in intramural vessels.
- Intravascular and endocardial platelet thrombi were found in the youngest infants with hypertrophy; myocardial necrosis was present in 19/100 control infants.
Conclusions:
- Prolonged high-concentration oxygen ventilation in immature infants is associated with significant cardiac hypertrophy and myocardial damage.
- These cardiac lesions appear to be a consequence of ongoing hypoxia and coronary circulation compromise.
- Myocardial damage represents a serious potential complication, impacting therapeutic strategies for immature, asphyxiated infants.
Abstract:
Fourteen infants who had required prolonged ventilation with high concentrations of oxygen for 14 days or more, were studied at necropsy. 11 infants of immature gestation at birth had gross cardiac hypertrophy, defined as a heart weight greater than 2 SD above the mean for their age. No congenital malformation of valves or septum was found, and in the 7 youngest infants with hypertrophy, the ductus arteriosus was anatomically patent. 3 of these 7 infants had an accompanying nurmur. All 11 infants had severe bronchopulmonary dysplasia. The cardiac hypertrophy affected both ventricles and septum in an irregular fashion and was associated with areas of necrosis, progressing to coarse fibroelastotic scars. The intramural vessels showed marked intimal thickening but the main coronary vessels were normal. The 2 youngest infants with cardiac hypertrophy showed the presence of intravascular and endocardial platelet thrombi. In the 3 infants without cardiac hypertrophy less severe zones of necrosis and scarring were present, and only occasional bundles of hypertrophied muscle fibres were seen. In an attempt to understand these hitherto undescribed lesions, a group of 50 fresh stillbirths and 50 first-week neonatal deaths of comparable gestational age were studied. In 19 of these infants foci of myocardial fibre necrosis were present. It is suggested that the lesions in the older infants represent a more advanced and continuing stage of that seen in the younger infants, and that the foci of necrosis are the result of continuing hypoxia and related problems to a failing coronary circulation. The possibility of myocardial damage represents a serious hazard to the successful therapy of the immature asphyxiated infants.