About Single Ventricle Heart Disease (SVHD) | Mezzion

About SVHD

Single Ventricle Heart Disease explained

What is SVHD?

SVHD stands for Single Ventricle Heart Disease. This means that a person is born with a heart where one of the two lower chambers (ventricle) does not develop properly. In a normal heart, each ventricle does a separate job; the right ventricle pumps blood without oxygen (blue blood) to the lungs and the left ventricle pumps blood with oxygen (red blood) around the body.1

People with SVHD are left with just one ventricle large enough to pump all the blood and do its job. Because of this, the blue blood and red blood (which are supposed to stay separate) mix together. This means there is a smaller amount of blood with oxygen getting to the rest of the body causing the person’s skin to appear blue (cyanosis).1

A heart with SVHD


How many people are affected by SVHD?

Single ventricle heart defects are rare – they happen to around 5 of every 10,000 children born and are usually diagnosed at birth. The cause is unknown in most cases and they don’t tend to run in families; normally the defect occurs randomly.1

SVHDs are not all the same; there are several kinds and some are linked to defects in the valves and blood vessels as well:1

  • Hypoplastic left heart syndrome (HLHS):
    This is where the left ventricle, mitral valve, aortic valve and aorta (a blood vessel) are all too small.
  • Double outlet right ventricle:
    This is where both the aorta and the pulmonary artery (blood vessels) come out of the right ventricle. This means the left ventricle doesn’t develop properly.
  • Tricuspid atresia:
    This is where the tricuspid valve fails to develop. This means that the right ventricle doesn’t develop properly.
  • Double inlet left ventricle:
    This is where both of the top chambers of the heart connect to the left ventricle. This means that the right ventricle doesn’t develop properly.

What does SVHD mean for the person affected?

Every child and adult with SVHD is affected differently, but there are lots of similarities in how they will be treated and managed.

Most people with SVHD will experience:1

  • At least three surgeries to help re-route the blood through their heart
    • Many are stable after the surgeries are completed with symptoms appearing slowly as they age
  • Difficulty exercising
  • Blueish color of the skin, nails and tongue (cyanosis)
  • Swollen tummy (ascites)
  • Life-threatening complications
    • Including liver problems, blood clots and heart failure
  • Irregular heart beats
  • Lower life expectancy

What treatments are currently available?

Treatment of single ventricle heart defects usually involves three surgeries – the first is performed as few days after birth, the second surgery happens around 4 - 12 months old and the third is performed between 18 months and 3 years.2 The aim of the surgeries is to re-route the blood to help the body get more and more oxygen. This is done in three stages to help put less stress on the heart. The final stage is called the Fontan procedure.1

The Fontan procedure

The Fontan procedure re-routes the connections of the blood vessels in the heart and allows the blue blood and red blood to stay separate. The ventricle which is large enough to do a normal job is used to do the harder job of pumping blood to the body. This means the job of getting blood to the lungs has to be done without a ventricle to pump, using a channel from the blood vessel into the top chamber of the heart.1

Ongoing treatments

People with SVHD may need to take some medications regularly, for example blood thinners, and many may have more surgery or a heart catheter as they grow to help improve the function of their heart. Very rarely, a heart transplant may be necessary.3 New treatment options are currently being explored to help improve a person with SVHD’s ability to exercise.

The Fontan operation



  1. Adult Congenital Heart Association (ACHA). Single Ventricle Defects and the Fontan. Available at: https://www.achaheart.org/your-heart/health-information/single-ventricle-defects-and-the-fontan/ (accessed June 2018).
  2. American Heart Association. Single Ventricle Defects. http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Single-Ventricle-Defects_UCM_307037_Article.jsp#.Wx50LIpKiUk (accessed June 2018).
  3. Children’s Hospital of Philadelphia. Single Ventricle Heart Defects. http://www.chop.edu/conditions-diseases/single-ventricle-heart-defects (accessed June 2018).


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