Ventricular Septal Defects

Pediatric echocardiographers, both physician and sonographers, will tell you that everything you know about adult echocardiography must be suspended as you begin to understand the weird world of Pediatric Cardiology.

It’s true that there is slight enmity between the two groups and it derives from 1) as a sonographer for adults, you will probably rarely see the complicated fetal and newborn cardiovascular systems and the myriad complexes that are part of congenital heart disease, and 2) you can’t tell a baby what to do.


Taking the first issue, because it is simpler, VSDs are seen in adults with congenital defects but their compensatory mechanisms have allowed them to thrive with mild-to-moderate limitations.  The other instance, for adults, occurs after a myocardial infarction involving the interventricular septum.  The damaged or necrotic tissue fails to support the IVS in its normal activities and requires immediate surgery.

Taking the second issue, the pediatric sonographer has to take great and imaginative strides to get a child to cooperate to make a standard, by adult criteria, request and the patient perform as you have asked.

I walked into the Medical College of Georgia’s (currently called Georgia's Children's Hospital, in Augusta, Georgia) pediatric cardiology lab and it seemed to me to be in utter chaos.  Parents with their child, waiting for the examination, looked as wide-eyed as I looked.  The waiting room was full of toys, children running around screaming and laughing, and I wondered how could anything get done?  I learned how.

It’s a child’s world.  In order to do a standard adult exercise stress test, the sonographer has to come up with ways to produce the same results.  That was the answer to the children running around.   Instead of it being seen as some bad behavior, they were involved in producing an equivalent exam.  The sonographer told the child to run up and down the hall screaming and then jump back on the examination bed for a prize.  The test I was seeing was to detect or monitor the effects of a VSD.

Can you imagine telling an adult to run up and down the halls, screaming, might be a little strange for a stress test?

The ventricular septal defect (VSD) is a communication – a hole – between the left and right sides of the heart.  A VSD is found frequently in congenital heart disease and it brings along its friends; Tetralogy of Fallot, Truncus Arteriosus, Eisenmengers Syndrome, Tricuspid Atresia, and even the Univentricular Heart.  There are a nearly impossible numbers of configurations of the heart as nature strives for survival.  The pediatric cardiologist and sonographer work closely together to get an understanding of each child’s circulatory configuration and how to test in real-life terms the identity, the limitations, and the possible need for palliative and corrective surgeries needed for the child to cope with daily demands of physical growth for that particular child.

Our hats off to the congenital heart disease warriors for their difficult, and sometimes heart breaking, tasks.

A simple VSD, being a congenital communication between left and right sides of the heart, comes in many flavors.  They are mostly defined by their location, their size, their numbers (yes, there can be more than one), and the effect it has on the ability to thrive.  This is usually detected in patients early on if there are signs observed during ob/gyn or fetal ultrasound. 

With a newborn, that first breath, that first cry, the inhalation of O2 triggers a phenomenal cascade of events in the heart and the rest of the circulatory system.  Temporary pathways shut down or shrivel up. A one way door closes. It’s as if a massive turnpike suddenly re-routes itself, or an astronaut stepping out of the protective environment of the International Space Station and turning on their individual life-support system, which they hope, is functional and operating.

That first breath of 21% oxygen causes chemoreceptors in certain vessels, like the ductus arteriosus, to constrict, the alveoli in the lungs to puff up like popcorn,  blood pressures in the left heart rise, the foramen ovale closes, and blood flow is forced through the lungs. 

Fetal Circulatory System Infant Circulatory System
Fetal Circulatory System Newborn Circulatory System

All in that first breath.  Normally.

The newborn may show signs of congenital heart disease by their activities, general anatomy, congenital defects that include, Down Syndrome, Cri du chat syndrome, fetal alcohol syndrome,  Edward’s syndrome (Trisomy 18), Apert syndrome (craniosynostosis and syndactyly), and a whole spectrum of birth defects that involve the heart.

Probably the most important criteria for assessment of a VSD is how it affects the oxygenation of blood entering the systemic circulation.  The conditions are typically cyanotic, lack of optimal oxygenation, and acyanotic where perfusion has compensated for maintaining the bodies demand.  These are easily described as “Blue” – cyanotic,  and “Pink” – acyanotic.  And, they both are related to the flow patterns occurring in the heart and lungs.

Types of ventricular septal defects begin with their location.  This diagram shows the location of the defect from the right side of the heart.  The terminology varies from resource to resource.



So generally, these are:

  • Inlet – below the tricuspid valve, RVIT.
  • Outlet – supracristal, RVOT
  • Perimembranous – the membranous septum
  • Trabecular – in the trabecular web
  • Muscular – the mid-portion of the interventricular septum

The degree of the severity depends on many factors, which include, left and right heart pressures, pulmonary vascular resistance, oxygen saturations, compensatory mechanisms, and the presence of any other congenital birth defects affecting the cardiovascular system.

Some of these may become reduced as the patient grows, particularly the muscular types, but many may persist and cause problems to develop which must be monitored. 

A particular concern with a large VSD is when the right heart nears the pressures generated in the left heart where flow was moving from left to right as a shunt, high pressures in the right heart contribute to increasing damage in the pulmonary vascular bed which increases vascular resistance so that a flow reversal occurs and deoxygenated blood moves through the right to left shunt which is called Eisenmengers’s syndrome, and symptoms of long term cyanosis may result in heart failure.

While this article was intended just to inform you of the intricacies of the ventricular septal defect, the new course we are preparing introduces you to the signs and symptoms, auscultation, the electrocardiogram, cardiac imaging, catheterization lab hemodynamic results, and how echocardiography is used in detecting and treating those with cardiovascular disease. We hope that you will enjoy it.

Richard K. H. Duncan


Resources:
National Institute of Health - https://ghr.nlm.nih.gov/condition
Terry Reynolds' "The Echocardiographer’s Pocket Reference”, 4th Edition, and “The Pediatric Echocardiographer’s Pocket Reference”, 1st Edition.  Congenital Heart Disease in Adults.
Genetics Home Reference - https://ghr.nlm.nih.gov/condition
Congenital Heart Defects.com - http://www.congenitalheartdefects.com/typesofCHD.html
Koenig, Peter, Ziyad Hijazi, and Frank Zimmerman. Essential Pediatric Cardiology. New York: McGraw-Hill Medical Pub. Division, 2004. Print.
Ammash, Naser M. "Ventricular Septal Defects in Adults." Annals of Internal Medicine Ann Intern Med 135.9 (2001): 812. Web.
"Ventricular Septal Defect." Wikipedia. Wikimedia Foundation, 2 May 2016. Web. 17 May 2016
Image: Patrick Lynch – Wikipedia Commons – CC 2016




 

 


 
 
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