Ventricular Septal Defect

Morphology

Ventricular septal defects are an abnormal communication at the ventricular level. They can be located in either inlet, trabecular, or outlet portion of the ventricular septum. The inlet portion includes perimembranous and inlet muscular ventricular septal defect, trabecular ventricular septal defect may be midmuscular, multiple, or apical, while the outlet portion includes subpulmonary or doubly committed ventricular septal defect.

Pathophysiology & natural history

The magnitude of the shunting is dependent on the size of the defect and the relative ratio of pulmonary vascular resistance to systemic vascular resistance. Pulmonary vascular resistance is high at birth and falls during the first few weeks of life, resulting in an increase in pulmonary blood flow during the first few weeks of life. As resistance falls there is progressively more pulmonary blood flow usually resulting in symptoms at approximately 4 to 6 weeks of life for unrestricted ventricular septal defect. A not insignificant number of ventricular septal defect become smaller (60 - 70%), and undergo spontaneous closure.

Diagnosis

There are three distinct clinical presentations of patients requiring surgical treatment of ventricular septal defect. These groups correspond approximately to the patients less than 6 months of age, between 6 and 18 months of age, and those over 18 months of age. Young infants present with congestive heart failure and failure to thrive, and constitute the highest risk group. Those between 6 and 18 months typically have increased pulmonary vascular resistance so are not in congestive failure, and require prompt operative closure to prevent irreversible pulmonary vascular obstructive disease. Their operative risk, depends on the degree of pulmonary vascular obstructive disease. Patients over 18 months, children, and adults require repair for complications of ventricular septal defect such as infundibular stenosis, aortic insufficiency, recurrent endocarditis, aneurysm of sinus of Valsalva, and tricuspid insufficiency.

Operative closure of ventricular septal defect is indicated in infants who have heart failure, failure to thrive, or a rising pulmonary vascular resistance (above 8 wood units). Operative closure of all ventricular septal defect is indicated by the second year of age, symptoms or not, as the risk for irreversible pulmonary vascular obstructive disease rises substantially thereafter. Pulmonary artery banding is reserved for cases with multiple ventricular septal defect and in symptomatic patients with concomitant medical conditions such as RSV pneumonia or intracerebral hemorrhage.