[Congenital heart defects in Iceland 1990-1999.]

About 1% of live born children have congenital heart defects (CHD). Knowledge of the true incidence of CHD is important because of the risk of bacterial endocarditis in patients with heart defects. This knowledge could also serve as a basis for research on the etiology of CHD. The aim of our study was to investigate the incidence of CHD in children born in Iceland during a ten year period, from 1990 to 1999. A similar study on CHD was carried out in Iceland for children born 1985-1989. The incidence of CHD in the present study was compared to the previous and to similar studies from other countries.

Information about the patients were obtained from medical records from two hospitals covering the whole country, a private clinic of pediatric cardiologists, echocardiography database, autopsy reports and death certificates. Distribution of specific heart defects, age at diagnosis, symptoms leading to the diagnosis, referral pattern, treatment and quality of life was investigated. Other congenital defects, chromosomal defects and syndromes in the patients were studied. Premature children with patent ductus arteriosus (PDA) and children with patent foramen ovale (PFO) or atrial septal defect (ASD) smaller than four millimeters were excluded. We also studied the incidence of bicuspid aortic valve (BAV). All diagnoses were confirmed with echocardiography and in some cases cardiac catheterization.

Between 1990 and 1999 there were 44,013 live births in Iceland, 740 children were diagnosed with a CHD or 1.7% of live born children. Yearly incidence varied from 1.04% of live births in 1991 to 2.34% in 1997. Male/female ratio was 1/1. The distribution of the defects was following: ventricular septal defect (VSD) 338 (45.7%), ASD 90 (12.2%), PDA 85 (11.5%), valvar pulmonal stenosis 48 (6.5%), BAV 38 (5.1%), coarctation of the aorta 28 (3.8%), tetrology of Fallot 22 (3.0%), transposition of the great arteries 14 (1.9%), aortic stenosis 11 (1.5%), common atrioventricular septal defect 10 (1.4%), mitral valve regurgitation 9 (1.2%), sub-aortic stenosis 7 (0.9%) and hypoplastic left heart syndrome 5 (0.7%). Other defects were less frequent. About 47% of children with CHD were diagnosed either before birth or before discharge from the delivery institution. A cardiac murmur on examination was the most common symptom leading to the diagnosis of CHD, 631 patients (85.3%). Extracardiac anomalies were seen in 89 patients (12.0%). Chromosomal abnormalities were seen in 36 patients of whom 28 had Down's syndrome. The majority or 499 patients have no symptoms but are still in follow-up, 20 patients have daily symptoms and/or receive medical treatment and 27 patients have died. Conslusions: Annual incidence of patients diagnosed with a CHD has increased during the study period. This is observed in minor CHD but the incidence of major defects does not alter. This yearly incidence (1.7%) is higher than in the previous study, where it was 1.1%. The difference can partly be explained by the BAVs, which were excluded in the 1985-1989 study. But the number of CHD diagnosed each year has increased, this being most pronounced in the last three years. The annual incidence in our study is also higher than in other population studies. The most likely explanation for the higher incidence in our study is the fact that access to pediatric cardiologists is very good in Iceland. Diagnosis, registration and follow-up is conducted by only a few cardiologists for the whole nation and takes place at a single pediatric cardiology center. Of 740 patients diagnosed with CHD in the study period 713 are alive. The outcome of the therapy is good and the majority of the patients has no symptoms.