Hypoplastic Right Heart Syndrome (HRHS): A Reader's Query
Anonymous has left a new comment on your post "Amniocentesis Q & A":
Dear Dr. T,
Thank you very much for your informative blog. I am 33 years old, first pregnancy and I had excellent first trimester screening results as follows:
Draw date: 11 weeks 3 days
Free Beta hCG (MOM):0.78
PAPPA-A MOM: 1.39
NT (mm) 1.70
Down Syndrome Risk (after screening)= 1 in 7,195
Trisomy 18/13 Risk = 1 in > 10,000
I was very happy about those results, however, during my anatomy ultrasound at 19 weeks and 5 days, a serious congenital heart defect was identified on my baby girl's heart. She has a hypoplastic right heart. At this point, it was not possible to determine whether the tricuspid valve and/or pulmonary valve are partially/fully affected. The doctor assured me, however, that they could not see the blood flowing to the lungs. In addition, the doctor also saw a ventricular septum defect (VSD), which apparently is common in Down Syndrome babies but in my case it could also potentially be associated with the baby's complex heart condition, i.e.: tricuspid atresia. No other anomalies or markers were found on the ultrasound.
After talking to the genetic counselor, my risk was increased from 1 in 7,195 to 1 in 10, that is, a 10% chance of having a baby with a chromosomal problem. I then had an amnio 3 days ago - which went fine, no cramping, no bleeding, no fluid leaking, no fever so far. I got my FISH results yesterday indicating that the baby is chromosomally normal for the anomalies tested by FISH (T21, T13, T18, X, and Y). I was ready to celebrate when the genetic counselor said that FISH accuracy is 98% because there might have been some maternal cell contamination due to blood contained in the FISH sample. She also said that this is very unlikely but then why did she have to make such a remark?
Thus, I guess my questions to you are:
(i) How reliable are FISH results in this case?
(ii) How often is such a rare complex heart defect (Hypoplastic Right Heart Syndrome) found in Down Syndrome babies?
I am trying to have some piece of mind while I await for the final amnio results. I am hoping that my baby's heart problem is isolated and not linked to a chromosomal syndrome. I am scheduled for a fetal echocardiogram next week.
Thank you very much for your time and kind help.
Congenital heart defects occur in 0.8-1.1% of ALL pregnancies which reach delivery and about 10% of babies that undergo spontaneous abortion. At least 30 to 60% of these are not detected until after the birth of the baby despite repeated ultrasound evaluations during the course of the pregnancy. Fortunately mild abnormalities (such as isolated ventriculoseptal defects – VSDs) and even many complex congenital heart defects (such as hypoplastic left heart syndrome) are not associated with easily recognizable chromosomal abnormalities. Atrioventricular (endocardial cushion defects) defects are more commonly associated with chromosomal abnormalities (as seen in 30-50% of babies with Down syndrome – trisomy 21).
Hypoplastic right heart syndrome (HRHS) is actually one of the most rare complex congenital heart conditions occurring at about 1/4 the incidence of hypoplastic left heart syndrome. HRHS seems to most often be the consequence of the development of a very small (atretic or hypoplastic) pulmonary valve Which connects the right ventricle to the pulmonary artery), resulting in a small pulmonary artery beyond that valve (necessary for transporting blood from the heart to the lungs after birth) as well as a small ventricle, small tricuspid valve, and atrium on the right side of the heart as well. During development of the heart, good blood flow through all these structures is necessary for them to achieve normal size. So the severity of HRHS depends to some extent on both the timing and the degree of the insult to the pulmonary valve - the earlier and the more severe, generally the worse the HRHS.
Babies are able to survive in the uterus because they have two physiologic shunts for blood under normal circumstances – the foramen ovale (a large opening between the right atrium and the left atrium that assures the passage of the most highly oxygenated blood from the placenta into the left ventricle and subsequently to the brain) and, the ductus arteriosus which is a vascular connection between the aorta and the pulmonary artery. Both of these connections normally close shortly after delivery and, when the fetal heart anatomy is normal, this assures good blood flow to the lungs from the right ventricle as the lungs take over control of providing the most highly oxygenated blood to the left ventricle and out through the aorta into the systemic circulation. When these connections close in a new born with HRHS, there is inadequate blood flow to the lungs and the baby becomes blue (or cyanotic) as a consequece of inadequate oxgen for its tissues…
With regard to our reader’s questions, I would have the following comments:
The FISH results will pick up about 98% of the chromosomal abnormalities for which the laboratory is set up to screen. It will NOT pick up all chromosomal abnormalities and it is unlikely to pick up by itself subtle chromosomal abnormalities (microdeletions or additions) or isolated genetic defects. It is not very likely that your baby has Down syndrome. However, there does appear to be an increased risk for having another baby with a complex congenital heart defect and this may eventually lead your geneticists to seek some of these abnormalities in your baby and in you or your spouse.
Discussion of this is beyond my level of expertise, but examples of these include: isochromosome 5p (Paulick J, et al., Prenatal Diagn 2004;24 : 371–4); interstitial deletion of chromosome 5 (Gibbons, et al, Am J Med Genet 1999;86:289-93); interstitial deletion of chromosome 2 (Sharma J, et al., Int. J Cardiol 1997; 62:199–202); deletion 22q11 (Marino, et al Genet Med 2001;3:45-8); deletion of chromosome 22q11.2 associated with thymic hypoplasia (Chaoui, et al., Ultrasound Obstet Gynecol 2002;20:546-52).
Your greater challenge will be the weeks ahead if the diagnosis is confirmed and all I would suggest at this point is that you talk extensively with the Pediatric Cardiology and Surgery teams, members of the NICU and perhaps even other couples who have had a baby with HRHS. I wish you all the best….