Ventricular Septal Defect

Ventricular septal defects are the most common congenital heart defects found in children. The defect is a simple communication in the muscle between the two lower chambers of the heart. A report published in 2002 by Hoffman and Kaplan in the Journal of the American College Cardiology estimated the incidence of VSD to be approximately 2 to 5 percent of all live births. Fortunately 85 to 90 percent of these defects will close spontaneously.
When this defect is present in an infant, the effect is variable. In the vast majority of cases a loud murmur is present. This is often the first clue that the defect is present. VSD can be seen with other defects, and is associated with other congenital defects affecting the mitral, tricuspid or aortic valve. If these structures are involved, the effect may be more profound, especially in an infant.
Blood flows through a VSD from the left side of the heart to the right side. The low pressure associated with the right side of the heart easily allows blood to move across the VSD with minimal resistance. The flow via a VSD is transmitted directly to the pulmonary circulation. If the defect is small, there is very little long-term consequence. In large defects, the lungs are eventually overloaded with the increased flow, and pulmonary hypertension will develop. As this resistance increases in the right heart, the flow across the VSD will decrease. If the lung pressure becomes severely elevated, the flow will change direction, and the patient will develop a drop in systemic oxygen levels and turn blue (known as cyanosis).
The most common finding with a VSD is a murmur. Patients with a small defect will have a loud murmur with essentially no symptoms. Large defects will often present in adolescence or adulthood with shortness of breath and cyanosis if they have gone undiagnosed. A murmur might be present but it will be related to the defect.
Treatment of VSD depends on the size of the defect and the pulmonary pressures. Surgical closure of the defect is the most common treatment, but newer catheter-based methods to place occluder devices across the defects are possible if the anatomy is acceptable. If the lung pressures are excessively high, treatment of the defect is contraindicated.
A special subset of VSD is the post myocardial infarction VSD. This rare condition is seen in the first 24 to 48 hours after a heart attack. The damage to the heart is so extensive that the muscle between the left and right chambers ruptures or tears. The flow of blood into the right side of the heart across the VSD results in shock. The condition is almost 100 percent fatal if not repaired. Unfortunately the risk of surgery after a large heart attack complicated by VSD is also very high. In fact, the operative mortality can be as high as 50 percent.
Catheter-based treatment of post MI VSD is becoming widely accepted as a safe and effective method to stabilize a patient to help bridge him to surgery or as a definitive procedure to repair the VSD. If an umbrella device or occluder is implanted, the hemodynamic derangements caused by the tear can be reversed, and many patients can fully recover.