Natural history of secundum atrial septal defect revisited in the era of transcatheter closure

Background: Several reports in the past have described the natural history of atrial septal defects, most dealing with a decrease in size or spontaneous closure of the defect. Some recent articles have also described an increase in size of the defect in a sizable number of cases which may be important in the current era of transcatheter closure. We analyzed the data of 52 consecutive cases diagnosed to have secundum atrial septal defect in the first year of life, seen over the last six years at our center. Methods and Results: All infants with a defect size of ≥4 mm on echocardiography were included. The first and the last echocardiographic images with a minimum interval of 6 months were used for analysis. Cases were divided into three groups depending upon the defect diameter (small: 4-5 mm, moderate: 6-8 mm and large: ≥ 9 mm). The age ranged from one day to 12 months (mean 2.9±3.2 months). On a follow-up of 0.7 to 7.0 years (mean 2.9±1.4 years), the septal defect reduced in size in 24 (46%) cases with complete closure in 14 of these. The size remained same in 13 (25%) and enlarged in 15 (29%) cases. The likelihood of closure was highest in small defect group as compared to the large defect group (p<0.05). Similarly, enlargement was more often seen in large defects. Conclusions: Small atrial septal defects of 4 mm to 5 mm are very likely to decrease in size or completely close on follow-up. Larger defects, on the other hand may remain large or enlarge further in a significant proportion of cases. A close observation is required for these cases if being considered for transcatheter closure.