Ventricular septal defect (VSD) is another common congenital heart defect, accounting for approximately 10%-20% of adult congenital cardiovascular diseases. It can occur as an isolated defect or in combination with other anomalies.
Pathological Anatomy
The ventricular septum consists of three parts: the membranous portion, the infundibular portion, and the muscular portion. Based on the location of the defect, VSD can be classified into:
- Membranous defect: The most common type
- Infundibular defect: Further divided into subarterial and intracristal types
- Muscular defect
Pathophysiology
VSD inevitably results in a left-to-right shunt at the ventricular level. The hemodynamic effects include:
- Increased pulmonary blood flow
- Increased left ventricular volume load
- Decreased systemic blood flow
- Development of Eisenmenger syndrome in late stages
Clinical Manifestations
The clinical presentation depends on the degree of hemodynamic impact and the severity of symptoms. VSD is classified into small, moderate, and large defects:
Small VSD
Patients are typically asymptomatic. A grade IV-VI pansystolic murmur with a thrill can be heard along the left sternal border at the 3rd-4th intercostal spaces. The pulmonic second heart sound (P2) may exhibit mild splitting but no significant accentuation.
Moderate VSD
Some patients may experience exertional dyspnea. Auscultation reveals a pansystolic murmur with a thrill along the left sternal border and a mid-diastolic regurgitant murmur at the apex. P2 may be mildly accentuated.
Large VSD
Severe hemodynamic effects make survival into adulthood rare. Patients may develop right-to-left shunting, resulting in cyanosis, along with dyspnea and reduced exercise capacity. The systolic murmur along the left sternal border may decrease in intensity to grade III, and P2 becomes accentuated. A diastolic murmur caused by secondary pulmonary valve regurgitation may sometimes be heard.
Auxiliary Examinations
Electrocardiography (ECG)
ECG may be normal or show left axis deviation. Larger defects may show left ventricular or biventricular hypertrophy.
Chest X-ray
Increased pulmonary vascular markings and a slightly enlarged cardiac silhouette can be seen. Large defects may show marked dilation of the pulmonary artery and its primary branches, with a sudden reduction in vascular markings in the outer third of the lung fields.
Echocardiography
Echocardiography demonstrates a continuous interruption in the ventricular septum.
Diagnosis and Differential Diagnosis
A typical VSD can be diagnosed based on clinical manifestations and echocardiography. Differential diagnoses include pulmonary valve stenosis and hypertrophic cardiomyopathy. In cases with pulmonary hypertension, differentiation from primary pulmonary hypertension and tetralogy of Fallot is necessary.
Treatment
The treatment options include interventional therapy and surgical treatment.
Patients with significantly elevated pulmonary artery pressure and pulmonary vascular resistance >7 Wood units are not suitable for surgery.
Prognosis
Patients with small defects generally have a good prognosis. However, those with large defects and severe pulmonary hypertension have a poor prognosis.