Apparent hypoxic changes in pulmonary arterioles and small arteries in infancy.

The pulmonary arterioles and small arteries were studied and their musculature and its nuclei were quantified in 90 neonates, infants, and young children who had suffered from a variety of clinical and hypoxic conditions immediately before death. Among the 90 cases investigated in this study, 30 were of sudden infant death syndrome (SIDS). No evidence was found to support the view that cases of SIDS are subjected to chronic hypoxia before death as significantly more medial muscle tissue in the pulmonary arterioles and small arteries was found in the chronic hypoxic group compared to the SIDS, non-hypoxic, and acute hypoxic groups. Furthermore, there was no statistically significant difference in the amount of medial muscle tissue of the pulmonary vessels as between the SIDS, non-hypoxic, and acute hypoxic groups. With other signs of acute hypoxia found at the necropsy of SIDS, the results of this study could be considered to support the view that cases of SIDS succumb as a result of an acute episode of hypoxia, or possibly repeated short-duration episodes of acute hypoxia which do not produce pulmonary vascular changes.

Fibrosis of the conducting tissue in infancy.

The conducting tissue of the heart was studied in a group of 38 cases of the sudden infant death syndrome and in a control group of 28 children dying of known causes. A variable amount of fibrous tissue was found in the atrioventricular complex in almost every case. There was a statistically significant increase in fibrous tissue with age in both groups and there was also significantly more fibrosis in the sudden infant death group compared with the controls. Possible explanations for these findings are discussed and it is suggested that the results might be of aetiological significance in the sudden infant death syndrome.