516Ventricular septal defect (VSD) is the most common congenital heart malformation and can be detected during the prenatal and postnatal period, in childhood, and in adulthood. Spontaneous closure of VSD can be determined through a variety of methods-echocardiography, Doppler color flow imaging, angiography, auscultation, and cardiac catheterization-and can be proven by pathological evidence at necropsy. There are two major types of VSD, membranous and muscular, as well as the perimembranous variety, which comprises variable portions of the adjacent muscular septum but lacks the membranous septum. VSD appears either as an isolated cardiac defect without other abnormalities or with several complex malformations. It has long been recognized that VSD can close spontaneously, but the incidence of spontaneous VSD closure is still uncertain. Since necropsy study of the hearts with VSD has rarely been reported, information on morphological features of spontaneous VSD closure remains limited. In addition, the mechanisms for spontaneous VSD closure are not fully understood. Herein, we present a brief review of the incidence of spontaneous VSD closure, morphological characteristics of the closure, and the main mechanisms responsible for the closure.
INCIDENCE OF SPONTANEOUS VSD CLOSURETh e incidence of spontaneous ventricular septal defect (VSD) closure varies greatly, depending on the age and gender of subjects at spontaneous closure, the size and site of the defect, the types of defect, as well as the population studied, methods employed, and length of follow-up period. Table 1 presents available data on the incidence of spontaneous VSD closure.Age and gender. Age has been found to have a significant infl uence on the incidence of spontaneous VSD closure, whereas gender seems less likely to aff ect the incidence. Although spontaneous VSD closure can occur at any agegestation, infancy, childhood, adolescence, and adulthood (1)-it occurs most commonly during the fi rst 6 months of life (2), during the fi rst year (3, 4), or soon after the fi rst year of life (5). Afterward, the occurrence of closure declines progressively and occurs less commonly after the age of 10 (5). It has been documented that the incidence of the close increases with age, from 24% at 18 months of age to 50% at 48 months and 75% at 120 months (6). However, in older children, at 3.5 years old, the incidence declines sharply to 44% and then rises to 66% at 7 years and 75% at 10.5 years (6). A similar trend has been found in other reports, which showed 57% (109/190) of cases closed before 3 years of age, 89% (169/190) closed before 8 years of age (7), and 4% to 10% closed after the age of 17 (8, 9). During adulthood, the incidence of spontaneous VSD closure remarkably declines. One study showed that of 188 adults with VSD, 19 patients' (10%) VSD closed spontaneously between the age of 17 and 45 years, and the incidence of closure was greater in the 17-to 24-year age group than the 25-to 34-year group, the 35-to 44-year group, and the ≥45-year group (8)...