A ventricular septal defect (VSD) is a hole in the wall or septum of the heart that separates the left and right lower chambers, called ventricles. This hole allows blood to flow from the left ventricle into the right ventricle instead of flowing into the aorta, the main artery that sends oxygenated blood to the rest of the body. Blood from the right ventricle is pumped into the lungs.
VSDs are the most common congenital cardiac anomalies. They are found in 30-60% of all newborns with a congenital heart defect, or about 2-6 per 1000 births. Congenital VSDs are frequently associated with other congenital conditions, such as Down syndrome.
During heart formation, when the heart begins life as a hollow tube, it begins to partition, forming a septa. If this does not occur properly it can lead to an opening being left within the ventricular septum. It is debatable whether all those defects are true heart defects, or if some of them are normal phenomena, since most of the trabecular VSDs close spontaneously on their own.
A VSD can also form a few days after a myocardial infarction (heart attack) due to mechanical tearing of the septal wall, before scar tissue forms, when macrophages start remodeling the dead heart tissue.
Small ventricular septal defects rarely cause problems. A physician usually discovers these holes by noticing an extra heart sound called a murmur on a routine physical exam. This murmur is often not present in the first few days of life. Most of these holes will close on their own, particularly if they are in the muscular portion of the septum. Even if these holes do not close, they will rarely cause any health problems. Rarely, these holes can be associated with the development of other heart issues that with time can become important. Therefore, if the small ventricular septal defect does not close, the child should continue to be seen by a cardiologist for occasional checkups.
Large ventricular septal defects can cause problems, often developing gradually in the first few months of life.
Before birth, the pressure on the right side of the heart is equal to pressure on the left side of the heart. As soon as the baby takes its first breath, the pressure in the lungs and the right side of the heart starts to decrease. This process is slow and usually takes about 2-4 weeks for the pressure in the lungs to reach normal level. In the first 1 to 2 weeks of life, babies with large ventricular septal defects may do very well. But as the pressure in the right side of the heart decreases, blood will start to flow to the path of least resistance (i.e., from the left ventricle through the ventricular septal defect to the right ventricle and into the lungs). This will gradually lead to symptoms of congestive heart failure and must be treated.
Medium or moderate ventricular septal defects are more challenging to predict. Sometimes babies born with moderate ventricular septal defects will have problems with congestive heart failure like babies with large ventricular septal defects. Others will have no problems at all and just need to be watched.
Symptoms of a large ventricular septal defect occur from the increased workload on the heart. If the hole in the ventricular wall is large, symptoms may include:
- Heart murmur
- Shortness of breath
- Continuous fast breathing
- Enlarged heart
- Pulmonary hypertension
- Failure to thrive
- Difficulty maintaining a normal weight gain in the first few months of life
- A fast heart rate
Ventricular septal defects never get bigger and sometimes get smaller or close completely. This is why when a baby is diagnosed with a ventricular septal defect, most cardiologists will not recommend immediate surgery but will closely observe the baby and try to treat symptoms of congestive heart failure with medication to allow time to determine if the defect will close on its own.
Many times observation is the only treatment needed, with regular checkups with the cardiologist. This may be as infrequent as every two to three years in older children with small ventricular septal defects to weekly in babies with large ventricular septal defects.
Babies who have shown some signs of congestive heart failure will typically be placed on medication, usually a diuretic to help get rid of extra fluid in the lungs. Sometimes digoxin will be added to help increase the strength of the heart. Sometimes a medication to lower the blood pressure will also be added to relieve the workload of the heart.
In babies who are failing to thrive because it is too difficult for them to eat, a high calorie formula or fortified breastmilk will be added to help the baby grow. Sometimes babies get so worn out with feeding that a small tube through the nose and to the stomach is temporarily necessary to deliver the food. The goal is to control the signs of heart failure to allow the baby time to grow. In the meantime, the ventricular septal defect can get smaller and cause fewer problems, in which case the infant will not require surgery and will eventually stop needing medications.
When the symptoms of a ventricular septal defect are hard to control with medicines or there is persistent evidence that the heart is doing too much work, surgical closure of the defect is often recommended. Surgical closure of isolated ventricular septal defects is uncomplicated in 99 percent or more of cases.
In cases necessitating surgical intervention, a heart-lung machine is required and a median sternotomy is performed.
Percutaneous endovascular procedures are less invasive and can be done on a beating heart, but are only suitable for certain patients. They consist of accessing the heart through a needle puncture in the skin rather than open heart surgery. Repair of most VSDs is complicated by the fact that the conducting system of the heart is in the immediate vicinity.
If large ventricular septal defects are diagnosed and managed appropriately, a child with a ventricular septal defect will have a normal length of life with no restrictions.