A population-based study relevant to seasonal variations in causes of death in children undergoing surgery for congenital cardiac malformations

AIMS: Our objectives were, first, to study seasonal distribution of perioperative deaths within 30 days after surgery, and late death, in children undergoing surgery for congenitally malformed hearts, and second, to study the causes of late death. METHODS: We analysed a retrospective cohort of 1,753 children with congenital cardiac malformations born and undergoing surgery in the period from 1990 through 2002 with a special focus on the causes of late death. The data was obtained from the registry of congenital cardiac malformations at Rikshospitalet, Oslo, and the Norwegian Medical Birth Registry. The mean follow-up from birth was 8.1 years, with a range from zero to 15.2 years. RESULTS: During the period of follow-up, 204 (11.6%) of the children died having undergone previous surgery. Of these 124 (7.1%) died in the perioperative period, and 80 (4.5%) were late deaths. There were 56 late deaths during the 6 coldest months, compared with 24 during the 6 warmest months (p < 0.01). There was no significant seasonal variation in perioperative deaths. Respiratory infection was the most common cause of late death, and occurred in 25 children, of whom 24 died during the 6 coldest months. Of the 8 sudden late deaths, 7 occurred during the 6 coldest months. There was no seasonal variation for the other causes of death. CONCLUSIONS: In children undergoing surgery for congenital cardiac malformations in Norway, there is a seasonal variation in late death, with a higher proportion occurring in the coldest months. Death related to respiratory infections predominantly occurs in the winter season, and is the overall most common cause of late death.