A few weeks back you learned about atrial septal defects, so now it’s time to look at how this same anomaly affects physiology when it occurs in the ventricles. A ventricular septal defect (VSD), is an abnormal opening between the right and left ventricles. It can vary in size, and when they’re small they can sometimes close on their own in that first year of life. It’s when they’re on the larger side that they start causing significant problems for our patients. They can actually be so large that it’s essentially as though the patient only has one ventricle. So, as you can imagine, the pathophysiology of a VSD is typically much more pronounced than an ASD. It’s also important to note that these patients often have other defects, so they can have a lot of problems and be very challenging. 

How does a VSD affect physiology?

So to think about how a ventral septal defect affects physiology, let’s go back to the blood flow through the heart and lungs. Let’s review that pathway again, shall we? 

  • Deoxygenated blood comes into the right atrium from the superior/inferior vena cava
  • Blood flows from right atrium to right ventricle
  • Right ventricle pumps blood into the pulmonary vasculature for gas exchange
  • Oxygenated blood enters the left atrium
  • Blood flows from left atrium into left ventricle
  • Left ventricle pumps oxygenated blood into the systemic circulation

Something to think about is the pressures in the heart. That right ventricle only has to pump blood into the lungs…but the left ventricles have to pump it all the way to the capillary bed out in the systemic circulation. So, which side is exerting higher pressure? If you said the left side, then you get a gold star! Good job! 

So now imagine that there’s a good-sized hole in the wall between those two ventricles. The left side pressures are higher than the right side pressures, so where’s that blood going to flow? It’s going to flow from the left side of the heart to the right side. Just like with ASD, this causes increased blood flow to the lungs, which can eventually lead to increased pulmonary vascular resistance and pulmonary congestion, leading to pulmonary edema. The right ventricle, with all that extra pressure exerted on it from the increased volume, is going to hypertrophy, meaning it gets enlarged. Any time the heart is enlarged, it doesn’t work as effectively, so this is just going to compound our patient’s problems. 

Some signs of a VSD in infants is pretty much the same as with an ASD…a baby that tires with eating, has “failure to thrive” or is not gaining weight, an increased respiratory rate, easy tiring in general, and baby will most likely have a murmur.

How is a VSD treated?

In a lot of cases, VSD may close on its own in that first year or be so minor that it doesn’t cause symptoms. If it does cause symptoms, then it is treated with surgery and this is usually done before the baby turns one year of age (though repair can occur at any time if a previously asymptomatic defect starts causing problems).

As with ASD, medications are designed to reduce the impact of symptoms. Namely the baby may get diuretics to decrease volume, which lowers the amount of fluid in the lungs. Medications to keep the heartbeat regular may also be used…common ones are digoxin and metoprolol.

What are the complications of a VSD?

In addition to the pulmonary congestion we just talked about a moment ago, a VSD (and an ASD) can cause pulmonary hypertension, which is actually one of the most common complications you’ll see. Pulmonary hypertension is essentially high blood pressure in the arteries of the lungs. This increased pulmonary pressure makes it difficult for blood to flow through the lungs, which in turn, makes the right side of the heart work harder. Eventually the right heart weakens and the patient goes into right heart failure. 

An additional complication of these septal defects is Eisenmenger syndrome. It occurs when that increased pressure in the lungs becomes so great that the direction of blood flow changes. So, instead of being a left-to-right shunt, it’s a right-to-left shunt. Take a moment and think about the implications of that. If the blood is being shunted from the right side of the heart to the left side, what does that mean for the patient? Remember, the blood on the right side of the heart is oxygen-poor. Usually that blood goes to the lungs to pick up oxygen, but in this case it’s being sent directly over into the left side of the heart and pumped out into systemic circulation without participating in gas exchange. This can cause a global hypoxia for the patient, and be fatal if left untreated.

Some more uncommon, but still possible complications are endocarditis (an infection in the heart) and problems with the valves. 

Over time, if not repaired, this defect can increase the risk for other complications, including heart failure, high blood pressure in the lungs (called pulmonary hypertension), irregular heart rhythms (called arrhythmia), or stroke.

I hope that helps you on your pediatric exams. What other topics about peds would you like to see?

Get this on Audio in Episode 73!


American Heart Association. (n.d.). Ventricular Septal Defect (VSD). Retrieved September 17, 2019, from Www.heart.org website: https://www.heart.org/en/health-topics/congenital-heart-defects/about-congenital-heart-defects/ventricular-septal-defect-vsd

CDC. (2019, January 22). Congenital Heart Defects—Facts about Ventricular Septal Defect | CDC. Retrieved September 17, 2019, from Centers for Disease Control and Prevention website: https://www.cdc.gov/ncbddd/heartdefects/ventricularseptaldefect.html

Chaudhry, T., Younas, M., & Baig, A. (2011). Ventricular septal defect (VSD)—Diagnosis and treatment—Mayo Clinic. 61(10), 1001–1004.

Fulton, D. R., & Saleeb, S. (2019, August). Isolated ventricular septal defects in infants and children: Anatomy, clinical features, and diagnosis. Retrieved from UpToDate website: https://www.uptodate.com/contents/isolated-ventricular-septal-defects-in-infants-and-children-anatomy-clinical-features-and-diagnosis