I was wondering if it's left to right shunt that would make it a volume overload condition in the right side of the heart and thus dilation but also considering that maybe left chambers are also enlarged due to increased flow through the lungs?

2 Answers 2


The Ventricular Septal Defects represent 30% of all the congenital cardiac defects.

Important is to underline that the interventricular septum has a membranosus part (superior) and a muscular part (inferior).

There are also 4 types of VSD:

  • Perimembranosus: under aortic valve. gives a aortic insufficiency due to the prolapse of the right coronaric cuspid or of the non coronaric cuspid

  • In-let: in the upper-posterior part of the septum, under atrio-ventricular valves

  • Out-let: under aortic and pulmunar valvolar rings; this give a aortic insufficiency

  • Muscular-trabecular: (known also as swiss-cheese), because has more holes and is far from conduct pathways.

The shunt is always left to right, due to pressures of the venticulus. This creates a big difference between pulmonary and sistemic resistances, so the right ventricle is enlarged, but not the right atrius

Diagnostic part:

  • Xray: cardiomegaly

  • EKG: not specific signs of ventricular hypertrofy. The cild can be completely asintomatic, and have symptoms when make phisical activity

  • Heart Ultrasound: is the gold standard. This shows the discontinuity of the septum and with a flow examination it shows the left-to-right direction

I've read that you want references, and this is great. This is from my sudies and is actually on every Pediatric Manual. Also on Pubmed.



-my personal noted during internship

  • Please do add links as references. I appreciate that you added sources, but please add links to those sources so that the information is easier to find.
    – L.B.
    Mar 23, 2017 at 12:32
  • 1
    @L.B. Added references here too. Thanks to suggest me to put some references.
    – Backup
    Mar 23, 2017 at 14:21
  • The chamber receiving a diastolic volume load will dilate. Under normal circumstances, early in the course of exposrue to a VSD, this is the left ventricle.
    – Todd D
    Dec 7, 2017 at 5:50

With the Ventricular Septal Defects prior to Eisenmenger Syndrome the left to right shunt occurs because left atrial pressure exceeds right atrial pressure in systole and blood gets ejected directly into the Right Ventricular Outflow Tract and Pulmonary artery instead of the Right Ventricle. For this reason Right Ventricle does not dilate. However, increased flow through lungs does create a volume loading condition in the Left atrium and Left Ventricle. Hence the volume loading of the left side with the dilation and preserved integrity of the right side, as noted per the American College of Cardiology guidelines. http://www.acc.org/guidelines#sort=%40foriginalz32xpostedz32xdate86069%20descending&f:@fdocumentz32xtype86069=[guidelines]

  • Spelling out your acronyms on first use and a reference would make this a much better answer.
    – Carey Gregory
    Oct 20, 2016 at 3:50
  • I have edited the original answer per your instructions. Hope this helps.
    – John Doe
    Oct 20, 2016 at 20:35
  • Much better, but we still expect references on factual assertions. It doesn't have to be super rigorous, just something credible that confirms your statements.
    – Carey Gregory
    Oct 20, 2016 at 21:47
  • This answer contains many falsities. In a VSD, the shunt can be either Left to Right or Right to Left. The determinate of directionality is the pressure differential between the Left Ventricle and Right Differential- not the atria as suggested in @JohnDoe 's answer. In most early cases, the systemic pressure is higher than the pulmonary pressure and the shunt is left to right during systole. During diastole, pressure in the LV is usually higher than the RV resulting in a diastolic shunt from left to right. The net result is a predominant Left to Right shunt with LV volume overload.
    – Todd D
    Dec 7, 2017 at 5:49

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