Acyanotic heart disease - Ventricular septal defect.
Ventricular septal defect
The ventricular septal defect is the most common form of congenital heart disease with a prevalence of approximately 51 per 100 000 births. Patients usually present in the few months after birth, or in early adulthood, depending on the size of the defect.
Defects occur most frequently in the membranous portion of the ventricular septum. The size of the defect may be large in relation to the child at birth but, as the child grows, the size of the defect reduces proportionally.
Large ventricular septal defects allow blood to flow from the left to the right ventricle (left to right shunt), greatly increasing the flow in the pulmonary circulation. This may produce cardiac failure in the early months after birth. Significant defects are corrected in childhood, whilst less significant defects tend not to produce symptoms until early adult life. Increased pulmonary flow predisposes to pulmonary hypertension, and Eisenmenger's syndrome may also occur as a complication. Ventricular septal defects also predispose patients to endocarditis.
The uncomplicated ventricular septal defect is asymptomatic. When pulmonary hypertension develops, patients may present with shortness of breath, haemoptysis or syncope. On examination, the pulse pressure may be small, with evidence of right ventricular heave (right ventricular hypertrophy). A systolic thrill accompanied by pansystolic murmur may be evident. However, both are attenuated in the presence of pulmonary hypertension due to the reduced flow across the defect.
The ECG is normal in patients with an uncomplicated defect. In the presence of pulmonary hypertension, both right and left ventricular hypertrophy may be evident.
Similarly, a chest X-ray is normal in patients with an uncomplicated defect, with evidence of cardiomegaly due to ventricular hypertrophy in patients with large defects.
Echocardiography is a useful investigation to document the presence and estimate the size of a ventricular septal defect. Patients with large symptomatic defects will need to progress to left heart catheterization to quantify the severity of the left to right shunt and measure pulmonary artery pressures.
Asymptomatic patients with small defects do not require intervention and should be kept under regular surveillance.
Operation is advised for symptomatic patients when pulmonary-systemic flow ratios reach 2.0:1.0.
Most affected children have a relatively normal lifespan if they have survived the first few years. Patients with small defects lead a normal life. However, patients with large uncorrected defects are at risk of death, usually between the ages of 20 and 40.
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