Increasing incidence of ventricular septal defects caused by improved detection rate.

In a population-based study in children born alive during the 10-year period from 1982 to 1991 (n = 22,810), ventricular septal defects (VSDs) were diagnosed in 127 cases, an incidence of 5.6 per 1000. The incidence was significantly higher in the cohort of children born during the 6-year period from 1986 to 1991 than among those born in the preceding 4-year period, 1982-1985 (6.5 and 4.0 per 1000 respectively; p < 0.05). The increase was caused entirely by an increased detection rate of small defects in the muscular part of the interventricular septum after introducing echocardiography as a standard method for investigating suspect congenital heart defects in the neonatal period. This also explained entirely an increase in the total incidence of congenital heart defects to 10.6 per 1000 in the last period from 8.4 per 1000 in the first, although this increase was not significant (p > 0.05). More children born in 1986-1991 had spontaneous closure of their VSDs (75.5%) than those born in 1982-1985 (51.5%) (p < 0.05). In 69.3% of patients the VSDs closed during the first year of life. For the cohort born in 1986-1991, 84.6% of the defects located in the muscular part of the septum closed spontaneously. Small defects in the muscular part of the interventricular septum with spontaneous closure in early life may represent the tail of a normal developmental process, and not defects in the sense of malformations.