Ventricular Septal Defect (VSD)

A ventricular septal defect (VSD) is a heart malformation present at birth. Any condition that is present at birth can also be termed a "congenital" condition. A VSD, therefore, is a type of congenital heart disease (CHD). The heart with a VSD has a hole in the wall (the septum) between its two lower chambers (the ventricles).

The most frequent types of congenital malformations affect the heart. It is estimated that approximately eight in 1,000 newborns have CHD. A VSD is the most frequent of the various types of CHD (25%-30% of all CHD). Approximately one infant in 500 will be born with a VSD.

The heart is made up of four separate chambers. The upper right chamber (atrium) receives blood back from the body with much of the oxygen extracted by the body organs and tissues. The blood is then pumped through a one-way valve into the lower right chamber (ventricle) from which it is pumped to the lungs to be again enriched with oxygen. This highly oxygenated blood then returns to the upper left-sided chamber (atrium) and next passes through a one-way valve into the lower left chamber (ventricle). From there, the oxygenated blood is pumped out into a large blood vessel (the aorta) and is distributed throughout the body through arteries.

The two upper chambers (right and left atria) are separated by a wall of muscle called the septum. Similarly, the two lower chambers (right and left ventricles) are also separated by a separate muscular septum. These septa (plural of septum) keep the lower oxygenated blood that has returned from the body from mixing with the highly oxygenated blood which has returned from the lungs.

A VSD is a hole in the ventricular septum.

The pressure generated during contraction by the left ventricle (LV) is higher than that generated by the simultaneous contraction of the right ventricle (RV). Blood will thus be pushed through the VSD (also called "shunted") from the left ventricle to the right ventricle. The right ventricle has to do extra work to handle the additional blood volume. It may have trouble expelling this larger volume of blood and compromise the ability to pump efficiently. In addition, the lungs receive too much blood under too much pressure. The arterioles (small arteries) in the lungs thicken in response to the excess blood under excess pressure. If this extra pressure persists, permanent damage can be done to the lungs.

It makes a considerable difference whether the size of the VSD is small or large. A larger VSD will allow more blood to be shunted from the higher-pressure LV to the lower pressure RV. As noted above, this will promote enlargement of the RV. It also promotes mixing of the highly oxygenated LV blood with the less oxygenated RV. This lower oxygenated blood is circulated throughout the body.

An infant with a VSD will generally not start to demonstrate abnormalities until 2 or 3 days of life. Common observations may include: (1) poor feeding (tires easily, poor suck); (2) rapid heart rate and respiratory rate; (3) unusual fussiness; and (4) pallor (paleness of the skin) and cyanosis (blue tinge of the skin). Should the presence of a VSD be missed, infants may demonstrate: (1) poor weight gain, (2) enlargement of the liver in association with congestive heart failure (inability to effectively pump blood); (3) shock and (4) possibly death.

The diagnosis of a VSD is usually suspected clinically by hearing a characteristic heart murmur. A murmur is a sound generated by abnormally turbulent flow of blood through the heart. This murmur is the result of blood being shunted through the VSD from the higher-pressure left ventricle into the lower-pressure right ventricle. At birth, this pressure imbalance is minimal and does not usually develop until later in the first week of life. As such, it is rare for a doctor to hear the murmur of a VSD until the baby is a few days of age.

The evaluation of a child with a possible VSD is designed to confirm the diagnosis but also to check for other anatomical defects in the heart and to estimate the size of the shunt of blood from the left to right ventricle.

Such an evaluation usually begins with an electrocardiogram (EKG, sometimes also abbreviated ECG) and possibly a chest X-ray. A soundwave test of the heart (echocardiogram) is used to define the anatomy and evaluate the characteristics (amount and pressures) of the shunted blood. With the advent of superb echocardiography, the previously required cardiac catheterization is rarely necessary.

The infant will commonly have reduced blood oxygen levels due to shunting of the LV blood into the RV. Most hospitals test for upper and lower blood oxygen levels (pulse oximetry) prior to discharging an infant from the hospital. Further studies and a consultation with a pediatric cardiologist should be undertaken prior to the infant being sent home.

Small defects (less than 0.5 square cm) are common. With a small VSD, there is minimal shunting of blood and the pressure in the right ventricle remains normal. Since the right ventricular pressure is normal, there is no damage to the lung arterioles. The heart functions normally. A prominent murmur heard through a stethoscope is usually the only sign that brings the VSD to attention. This murmur is commonly noted during the first week of life.

One-third to one-half of all small VSDs close spontaneously (on their own). This seemingly miraculous event occurs most often before the baby is 1 year old, almost always before age 4 (75% by 2 years of age). The closure is due to the small VSD being located between heart fibers that increase in size in time, thus encroaching upon the opening in the ventricular septum.

Even if a small VSD does not close spontaneously, surgical repair is usually not recommended. However, long-term follow-up is required.

With a large VSD (usually one greater than 1 cm²), there is significant shunting of blood from the left ventricle into the right ventricle. Thus extra blood volume puts a strain on the right ventricle and causes an increase in the blood pressure of the lungs called "pulmonary hypertension." The child may have labored breathing, difficulty feeding, poor growth, and have pallor.

Ultimately, the patient with a large VSD will need surgery to "patch the hole" in the ventricular septum. The timing of surgery is an individualized decision based upon several factors. These include

1. The extent and duration of increased pulmonary artery pressure are considered. Chronic pulmonary arteriolar pressure may become irreversible and put a strain on the right ventricle. These side effects may be treated with medications until surgery is appropriate.



 
2. A child with a large VSD often will not grow as robustly as his peers. The work of increased metabolic demands often requires additional calories when compared to children without such a cardiac defect. High-calorie dense supplements may be added to formula. Some infants may require nighttime continuous feedings using a tube that is passed through the nose to the stomach (nasogastric tube) to maximize growth. It is very rare to restrict fluid volumes in these children.



 
3. Infants with iron-deficiency anemia should receive iron supplements to maximize the oxygen carrying capacity of their blood. Blood transfusions to address such an anemia are rare.

There are two types of surgery available to correct a VSD: the intra-cardiac technique and the trans-catheter technique. The surgical technique is chosen based upon the nature of the VSD and associated side effects on the patient's heart and lungs. The intra-cardiac approach is the most common technique and is done while the patient is under cardiopulmonary bypass (a "heart-lung machine") and is an open-heart operation. This is the procedure of choice for most children and at most pediatric surgical centers. A second technique uses surgical instruments that are passed through catheters placed in the patient's large blood vessels into the heart. This "trans-catheter approach" is generally more difficult and should only be considered on select patients and at pediatric centers that have expertise in such a procedure.

After a successful surgical repair of the VSD, the two ventricles are entirely separate from each other and the circulation of the blood within the heart is normal. If the RV was enlarged, it can return to a more normal size. The high pressure in the pulmonary artery should also begin to resolve. If the child's growth had slowed, the child usually catches up within a year or two. Long-term follow-up is required. The long-term prognosis is usually excellent.

Complications with intra-cardiac VSD surgery are uncommon. Currently, most centers have an operative mortality rate of less than 1% if the VSD is the only defect and the heart is functioning normally. Major complications are rare (1%-2%) and include heart rhythm problems and incomplete closure of the VSD. Rarely, a pacemaker insertion or a second procedure to repair the defect may be necessary.

There are rare cases of VSD that may be harder to treat. These are most commonly VSDs which are associated with other cardiac defects (for example, Tetralogy of Fallot, coarctation of the aorta). Cases with multiple VSDs ("Swiss cheese" defects) are also harder to treat.

Repaired or not, whether small or large, a VSD creates an increased risk for infections of the heart walls and valves (endocarditis). Such an infection may be life-threatening. To help prevent endocarditis, a patient with a VSD (repaired or not) may need to take antibiotics before dental procedures, including cleaning and other dental care, and before surgical procedures on the mouth or throat. Long-term precautions should be discussed with the person's doctors. Previous recommendations for preoperative antibiotics before instrumentation of the urinary tract or lower intestinal tract were rescinded by the American Heart Association in 2007.