Ventricular Septal Defect

VSD is categorised based on the location and the size of the defect. There are four types of ventricular septal defects, depending on their location. These may include:

1. Perimembranous Ventricular Septal Defect: In this condition, the defect occurs in the upper section of the ventricular septum. It is the most common type of VSD.
2. Inlet Ventricular Septal Defect: In this condition, the hole occurs just below the tricuspid valve in the right ventricle and the mitral valve in the left ventricle. This type of VSD may also be part of another heart defect known as an atrioventricular septal defect (AVSD).
3. Muscular Ventricular Septal Defect: This type of VSD occurs in the muscular part of the ventricular septum.
4. Conoventricular Ventricular Septal Defect: In this condition, the hole occurs below the pulmonary valve in the right ventricle and the aortic valve in the left ventricle, which connects the two chambers.

Depending on the size, VSDs can be categorised as small, medium or large.

The normal heart has four chambers, the lower two chambers, called the ventricles, are responsible for pumping the blood. In the normal course of events, blood low in oxygen returns to the right side of the heart. The right ventricle pumps blood into the lungs, where it is enriched with oxygen. This oxygen-rich blood returns to the left ventricle and pumps it to the whole body. A wall (ventricular septum) separates the right from the left side of the heart. A VSD will allow oxygen-rich blood to cross over (shunt) to the right, as the left-sided pressures are higher.

This leads to extra blood in the lungs and imposes an additional load on the heart. Depending on the size of the hole and hence, the shunt, varying degrees of symptoms can manifest in the child.

If the ventricular septal defect is small, signs may not appear until childhood. The symptoms and signs of the disease are often linked to the size of the hole and the type of VSD that occurs in the heart. Small defects may manifest only as an abnormal sound (murmur) on examination.

Infants with moderate to severe ventricular septal defect may exhibit the following symptoms:

• Sweating during feeding
• Slow weight gain
• Frequent respiratory infections
• Shortness of breath
• Fatigue

The larger the defect, the earlier and more severe the symptoms, and large defects usually present within a few weeks of the birth.

If the hole is small, it usually closes on its own, and the infant may not show any symptoms of the condition. The ventricular septal defect (VSD) diagnosis often starts with a physical examination. The doctor uses a stethoscope and hears a heart murmur during the exam. Next, the doctor may order the following tests to confirm the presence of VSD. These may include:

• Chest X-ray: The chest x-ray helps see the heart and lungs to seek evidence of the increased blood flow to the left side of the heart and lung.
• Pulse Oximetry: The test measures the amount of oxygen in blood.
• Electrocardiogram: The test is done to measure the duration and timing of the heartbeats. The test helps diagnose congenital disabilities or rhythm problems of the heart.
• Echocardiogram: Sound waves produce images of the heart and diagnose the ventricular septal defect. It also helps determine the condition's size, location, and severity. It is the mainstay of the diagnostic workup.
• Cardiac Catheterization: In this process, a catheter is inserted into a blood vessel and is guided to the heart. The doctor then releases a dye that helps identify congenital heart defects and check the severity of the condition. It gives information about the lung pressures, the quantum of shunt and associated defects. In late-presenting patients, it provides valuable information to help determine operability.
• Cardiac MRI: Cardiac MRI is fast becoming a valuable adjunct.

Infants born with smaller ventricular septal defects (VSD) generally don't require surgery. Instead, the doctor may observe the baby and treat the symptoms. At the same time, they wait to see if the defect closes independently. Infants with larger VSDs require medications to help treat the condition.

Medications 

On diagnosing a VSD, the paediatric cardiologist will initiate medication and give dietary advice. 

Medications are used to reduce the symptoms of the ventricular septal defect. The goal of therapy is to reduce risk of congestive heart failure, promote weight gain, help with sweating and fast breathing, development, and more. In addition, the doctor may use angiotensin-converting enzyme inhibitors to decrease the workload of the left ventricle. In contrast, Digoxin is used sparingly to support the heart muscles.

In patients with large VSD with poor growth and congestive heart failure not controlled with medication closure is indicated as soon as possible and preferably before 6 months of age. In patients with moderate VSD who are asymptomatic, closure by 2 years is indicated. If symptomatic earlier closure is advisable.

Any VSD associated with Aortic Valve Prolapse and leakage mandates closure.

Modes of VSD Closure 

Surgical Closure with a patch is the gold standard for VSD closure. Rarely, pulmonary artery banding may be considered a staging procedure for patients with multiple VSDs and patients with contraindications for cardiopulmonary bypass.

Some VSDs, like muscular VSD, can be closed non-surgically with a catheter-based device closure.

The outlook for patients with VSD Closure is excellent. Infective Endocarditis prophylaxis is recommended for 6 months after the procedure. However, all patients are also advised to maintain good oro-dental hygiene after this period.

If the hole is small, it usually doesn't cause any severe problems or complications. However, if the ventricular septal defect is medium or large and is left untreated, it may result in complications that may be life-threatening. These may include:  

• Heart failure
• Endocarditis infections inside the heart
• Progressive elevations of lung pressures, rendering the patient inoperable
• Irregular heart rhythms
• Lung problems
• Poor growth and development

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