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muscular ventricular septal defects
Recently, our facility has been picking up more muscular VSDs than ever during our anatomy scans regardless of age at the time of referral (many are in the second even third trimester when we see them for the first time and no heart defect has been reported or suspected). I can only speculate that this is due to our facilities continued effort to improve our detection rate of congenital heart defects and the scanning talent and dedication of our sonographers. Although we do not perform an "official" fetal echocardiogram, nor do we charge for one, we have made significant improvements in the quality of our prenatal cardiac evaluation using the AIUM guidelines as our reference for images to be obtained or attempted during the scan. In addition, I believe that the significant improvement in the ultrasound systems, the superb resolution, and the amazing color Doppler applications have allowed us to obtain images and detect anomalies that were not previously obtainable on older systems. Having said this, and due to the nature of muscular VSDs and their potential to close spontaneously in utero, when are they clinically significant? A few of the patients that we detected/suspected a muscular VSD went for a formal fetal echo two to three weeks later and the exam was reported out as normal. So the assumption is either it had closed spontaneously in the interim or it was not real to begin with. Of those that have been confirmed by fetal echocardiography, the patients are essentially counseled that this type of VSD is usually hemodynamically insignificant and most close spontaneously and no further prenatal fetal echocardiography follow-up is necessary. Of course, postnatal evaluation is recommended. So my question to the experts is when are they significant if an isolated finding. How do you counsel your patients. Obviously, any anxious parent will be devastated at the news that their unborn child has a congenital heart defect however minor it may be.
I will attach a clip of a case I scanned today. There was a muscular VSD in the apical portion of the muscular septum at 28 weeks. She was referred for AMA, first visit with our group. Was not visible without color Doppler.
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Replies to This Discussion
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Permalink Reply by Joe Kreeger on -
Lisa,
We (in pediatric cardiology) typically say that when a VSD diameter (in its largest dimension) is more than 10% of the overall length of the ventricular septum in the fetal four-chamber view, and by third trimester, then it will be significant enough postnatally to warrant therapy and close/regular followup until it either closes spontaneously or needs surgical intervention. Keep in mind that multiple small (~1mm each) muscular defects can create a collectively large shunt in the postnatal period, making management difficult as well. As you may know, it is uncommon for most subarterial defects to close spontaneously, so the parents are always counseled accordingly.
Hope that helps,
Joe Kreeger -
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Permalink Reply by Lisa M. Allen on -
Thanks, that is very helpful. I am working out of an MFM practice, not pediatric cardiology so I rarley get the postnatal follow-up on these cases.
oe Kreeger, RDCS, RCCS, FASE said:
Lisa,
We (in pediatric cardiology) typically say that when a VSD diameter (in its largest dimension) is more than 10% of the overall length of the ventricular septum in the fetal four-chamber view, and by third trimester, then it will be significant enough postnatally to warrant therapy and close/regular followup until it either closes spontaneously or needs surgical intervention. Keep in mind that multiple small (~1mm each) muscular defects can create a collectively large shunt in the postnatal period, making management difficult as well. As you may know, it is uncommon for most subarterial defects to close spontaneously, so the parents are always counseled accordingly.
Hope that helps,
Joe Kreeger -
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Permalink Reply by Dr.Haissam Aref.DMS on -
i think it depends upon the size of the VSD and of course the site
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Permalink Reply by Lisa M. Allen on
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The "in-plane" view is looking at the entire interventricular septum usually viewed from the right ventricle, also referred to as en face. If performing 3D/4D STIC, you can manipulate the initial image of acquisition to take a slice of the interventricular septum by various methods specific to each vendor and isolate the interventricular septum to evaluate for VSDs. I will forward an article that demonstrates this view later. There is a very nice article entitled The 'in-plane' view of the inter-ventricular septum. A new approach to the characterization of ventricular septal defects in the fetus. Prenat Diagn. 2006 Jan;26(1):90-1; PMID: 16378315
I also just posted this on a comment wall...
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Permalink Reply by David N Jackson on -
Lisa,
Once again you have been at the vanguard of stimulating an important discussion. You asked several key questions:
1) Is a small, isolated VSD significant?
2) What is the sensitivity of an obstetrical screening ultrasound in identifying VSD?
3) How many will become undetectable at delivery?
4) Does a screening sonogram that detects VSD warrant a detailed fetal echo?
Our own experience is to follow second trimester, isolated small vsd's in our own center. We are typically very reassuring regarding prognosis. Patients accept the embryologic reality that VSD's are often apparent early and then spontaneously resolve. Any VSD's that appear subjectively "large" or that persist into the third trimester we refer for pediatric consultation. The purpose is to give the patient antepartal contact with the pediatric providers that will see the child after delivery. Joe's response of an attempt to quantify clinical significance based upon a % of ventricular length is intriguing and worthy of study and publication.
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Permalink Reply by Lisa M. Allen on
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Thank you for your comments. As a follow-up, two of the cases that we had detected (that did receive a confirmatory formal prenatal fetal echo) have since delivered. One was a small apical muscular VSD and the other a large mid muscular VSD. Both babies had postnatal fetal echocardiography exams and went home with mom and are being followed by pediatric cardiology. The larger mid muscular VSD's postnatal report also describes irregular aortic arch isthmus, patent ductus arteriosus (small) with small bidirectional arterial shunt at the ductal level consistent with systemic level pulmonary artery systolic hypertension, patent foramen ovale, and biatrial enlargement (R>L). I will try to continue to follow that one.
I do believe the sensitivity of detecting the isolated VSDs depends on the experience of the examiner and the quality of the ultrasound system (and color Doppler settings). There will always be the technical limitations we encounter such as maternal obesity, gestational age and fetal position, etc. The importnat thing is that I think we are getting better at the detection of CHD which is our goal!! At least the nursery will have the "heads up" and can pursue postnatal management accordingly.
David N Jackson said:
Lisa,
Once again you have been at the vanguard of stimulating an important discussion. You asked several key questions:
1) Is a small, isolated VSD significant?
2) What is the sensitivity of an obstetrical screening ultrasound in identifying VSD?
3) How many will become undetectable at delivery?
4) Does a screening sonogram that detects VSD warrant a detailed fetal echo?
Our own experience is to follow second trimester, isolated small vsd's in our own center. We are typically very reassuring regarding prognosis. Patients accept the embryologic reality that VSD's are often apparent early and then spontaneously resolve. Any VSD's that appear subjectively "large" or that persist into the third trimester we refer for pediatric consultation. The purpose is to give the patient antepartal contact with the pediatric providers that will see the child after delivery. Joe's response of an attempt to quantify clinical significance based upon a % of ventricular length is intriguing and worthy of study and publication.
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