Background: Color Doppler echocardiography greatly facilitates the diagnosis of isolated muscular ventricular septal defect with a small shunt.

Data sources: Original research articles were collected from database, including PubMed and Google scholar. Relevant articles about muscular ventricular septal defect were included.

Results: The frequency of isolated muscular ventricular septal defect is 5.7% in preterm infants and 1.1-5.3% in term infants. Spontaneous closure in muscular ventricular septal defect occurs with higher frequency and earlier than in perimembranous ventricular septal defect. Approximately 80-90% of isolated muscular ventricular septal defect closes spontaneously by 12 months of age. Midventricular muscular ventricular septal defect is spontaneously closed earlier in the short term, but no site difference is found in the long term. The spontaneous closure mechanism is regarded as aposition of the muscle tissue or fibrous tissue formation in the right ventricular side, but in rare cases involves aneurysm formation of the fibrous tissue. Regarding spontaneous closure of isolated muscular ventricular septal defect diagnosed for the fetus, further studies are needed. Chromosomal microarray analysis of fetuses with isolated muscular ventricular septal defect has revealed that it is not a severe risk factor of chromosomal abnormalities.