INCREASING INCIDENCE OF VENTRICULAR SEPTAL-DEFECTS CAUSED BY IMPROVEDDETECTION 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 incide nce was significantly higher in the cohort of children born during the 6-year period from 1986 to 1991 than among those born in the precedin g 4-year period, 1982-1985 (6.5 and 4.0 per 1000 respectively; p < 0.0 5). The increase was caused entirely by an increased detection rate of small defects in the muscular part of the interventricular septum aft er introducing echocardiography as a standard method for investigating suspect congenital heart defects in the neonatal period. This also ex plained entirely an increase in the total incidence of congenital hear t 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 ch ildren 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 s eptum closed spontaneously. Small defects in the muscular part of the interventricular septum with spontaneous closure in early life may rep resent the tail of a normal developmental process, and not defects in the sense of malformations.