Effects of VSD

thumbThe severity of a VSD is primarily related to its size, and to some extent, its location within the ventricular septum:

  1. Perimembranous VSDs are the most frequent type; they involve the membranous septum, bordered by the AV valve, and may extend into one of the other regions (confluent); the tricuspid valve is often abnormal, valve leaflets or extra tissue may herniate, prolapse or occlude the defect; aortic valve commissure abnormalities may coexist; the defects may coexist with malalignement of the outlet septum, typically as part of a more complex congenital heart disease.
  2. Muscular VSDs are the second most common form of VSDs; they are completely surrounded by muscle. There can be multiple openings, in which case they are called “Swiss-cheese” defects.
  3. Inlet/Atrioventricular canal VSDs. Located on the area of the septum formed by endocardial cushion tissue (also called atrioventricular (AV) septum), immediately inferior to the tricuspid valve; associated with anomalies of the AV valves, considered part of atrioventricular septal defects (AVSDs).
  4. Outlet/Conoseptal VSD occurs below the pulmonary valve (subpulmonary), overlying the outlet septum; one of the aortic valve leaflets may prolapse through the defect, resulting in the development of a left ventricular outflow tract gradient, functional closure of the defect or aortic insufficiency ( Rolo, 2015).

Small defects often close spontaneously with no long-term harm. However, large defects can significantly impact the heart and lung function (Webb et al., 2019).

graphic A large VSD creates a pressure difference between the left and right ventricles, causing a left-to-right shunt (Park, 2019).This means oxygenated blood is pumped from the high-pressure left ventricle, through the VSD, into the lower-pressure right ventricle, and then back to the lungs. This recirculation of oxygenated blood through the lungs instead of being delivered to the systemic circulation makes the heart pump inefficiently (Park, 2019; Webb et al., 2019). The increased blood flow to the lungs leads to pulmonary overcirculation and congestion (Webb et al., 2019). To compensate, the heart must work against higher pressures, eventually leading to heart failure when the workload becomes too great and the heart cannot meet the body's metabolic demands (Webb et al., 2019). Clinical signs of a large VSD and heart failure in infants may include failure to thrive, tachypnea, tachycardia, increased work of breathing, and frequent respiratory infections (Park, 2019). A characteristic holosystolic heart murmur is also typically auscultated (Park, 2019).

In some cases, the pulmonary blood vessels react to the increased blood flow and higher pressures by constricting. This initial vasoconstriction is an attempt to protect the lungs by limiting the amount of blood flow. However, over time, this sustained constriction and high pressures cause irreversible structural changes in the developing pulmonary vasculature, a process called pulmonary vascular remodeling (Warnes et al., 2001; Webb et al., 2019). This can lead to pulmonary hypertension (Webb et al., 2019). Figure 2 demonstrates the significant reduction in small pulmonary vessels in a child with pulmonary hypertension compared to the normal lung vasculature shown in Figure 1, severely limiting gas exchange capacity. If the left-to-right shunt persists and pulmonary hypertension can become severe, it can eventually lead to a reversal of the shunt (Eisenmenger syndrome), where deoxygenated blood flows from the right ventricle to the left ventricle, causing cyanosis (Baumgartner et al., 2020; Warnes et al., 2001).

Individuals with VSDs also have an increased risk of infective endocarditis (Baumgartner et al., 2020; Warnes et al., 2001). Depending on the VSD location, there can also be an association with the development of aortic valve regurgitation over time (Webb et al., 2019). Management of large VSDs often involves surgical repair to close the defect, along with medical management of HF symptoms (Park, 2019; UpToDate, n.d.)."

References:

Baumgartner, H., De Backer, J., Babu-Narayan, S. V., Budts, W., Chessa, M., Diller, G. P., ... & Mulder, B. J. (2020). ESC Guidelines for the management of adult congenital heart disease. European Heart Journal, 42(6), 563-645.

Park, M. K. (2019). Park's Pediatric Cardiology for Practitioners (7th ed.). Elsevier.

Rolo, V. (2015). Ventricular septal defects . Anaesthesia Tutorial of the Week. https://resources.wfsahq.org/atotw/ventricular-septal-defects/

UpToDate. (n.d.). Ventricular septal defect: Clinical manifestations and diagnosis. Retrieved April 22, 2025, from [Insert UpToDate Link Here if Possible, otherwise omit the link]

UpToDate. (n.d.). Ventricular septal defect: Management. Retrieved April 22, 2025, from [Insert UpToDate Link Here if Possible, otherwise omit the link]

Warnes, C. A., Williams, R. G., Bashore, T. M., Child, J. S., Driscoll, D. J., Gersony, W. M., ... & Webb, G. D. (2001). ACC/AHA 2001 guideline for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Adults With Congenital Heart Disease). Journal of the American College of Cardiology, 37(5), 1169-1200.

Webb, G. D., Smallhorn, J. F., Therrien, J., & Redington, A. N. (2019). Nadas' Pediatric Cardiology. Elsevier.

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