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== Hypoplastic left heart syndrome ==
{{Short description|Congenital heart defect}}
{{Use dmy dates|date=October 2023}}


{{Infobox medical condition (new)
'''Hypoplastic left heart syndrome''' (HLHS) is a rare [[congenital heart defect]] in which the left side of the heart is underdeveloped. This condition affects normal blood flow through the heart, as the left side of the heart is unable to effectively pump blood to the body.
| name            = Hypoplastic left heart syndrome
| synonyms        = Cyanotic heart disease - hypoplastic left heart<ref>{{cite web |title=Hypoplastic left heart syndrome: MedlinePlus Medical Encyclopedia |url=https://medlineplus.gov/ency/article/001106.htm |website=medlineplus.gov |accessdate=28 May 2019 |language=en}}</ref>
| image          = Hlhs-web.jpg
| caption        = Illustration of heart suffering from hypoplastic left heart syndrome
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'''Hypoplastic left heart syndrome''' ('''HLHS''') is a rare [[congenital heart defect]] in which the left side of the heart is severely underdeveloped. It may affect the [[left ventricle]], [[aorta]], [[aortic valve]], or [[mitral valve]].<ref>{{cite journal |year=2006 |title=The nomenclature, definition and classification of hypoplastic left heart syndrome |journal=Cardiology in the Young |volume=16 |issue=4 |pages=339–368 |pmid=16839428 |doi=10.1017/s1047951106000291|last1=Tchervenkov |first1=C. I |last2=Jacobs |first2=J. P |last3=Weinberg |first3=P. M |last4=Aiello |first4=V. D |last5=Béland |first5=M. J |last6=Colan |first6=S. D |last7=Elliott |first7=M. J |last8=Franklin |first8=R. C |last9=Gaynor |first9=J. W |last10=Krogmann |first10=O. N |last11=Kurosawa |first11=H |last12=Maruszewski |first12=B |last13=Stellin |first13=G |doi-access=free }}</ref>


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==Anatomy and Pathophysiology==
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In HLHS, several structures on the left side of the heart are affected, including the [[left ventricle]], [[mitral valve]], [[aortic valve]], and [[aorta]]. The left ventricle is typically small and non-functional, the mitral and aortic valves may be stenotic or atretic, and the ascending aorta is often underdeveloped.
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==Signs and symptoms==
The underdevelopment of these structures leads to a reliance on the [[right ventricle]] to pump blood to both the lungs and the rest of the body. Blood flow to the body is dependent on a patent [[ductus arteriosus]], a fetal blood vessel that connects the pulmonary artery to the aorta, which normally closes shortly after birth.
[[File:HLHS.jpg|thumb|Infant with cyanosis due to hypoplastic left heart syndrome]]
Closing of the [[ductus arteriosus]] in a heart that is severely underdeveloped on the left results in [[cyanosis]] and respiratory distress which can progress to [[cardiogenic shock]] and death. The first symptoms are cyanosis that does not respond to oxygen administration or poor feeding. Peripheral pulses may be weak and extremities cool to the touch.<ref name=":12">{{Cite web |url=https://www.uptodate.com/contents/hypoplastic-left-heart-syndrome |title= Hypoplastic left heart syndrome |last=Fulton |first=David R.|date=October 26, 2017 |website= Up To Date |access-date= 2017-11-30}}</ref>


HLHS often co-occurs with low birth weight and premature birth.<ref name=":12" />
==Clinical Presentation==
Newborns with HLHS may appear normal at birth but can rapidly develop symptoms as the ductus arteriosus begins to close. Symptoms include:
* Cyanosis (bluish skin color)
* Rapid breathing
* Poor feeding
* Lethargy
* Cold extremities


In neonates with a small atrial septal defect, termed "restrictive", there is inadequate mixing of oxygenated and deoxygenated blood. These neonates quickly decompensate and develop [[acidosis]] and cyanosis.<ref name=":12" />
Without intervention, HLHS is usually fatal within the first few days or weeks of life.
 
On EKG, right axis deviation and right ventricular hypertrophy are common, but not indicative of HLHS. Chest x-ray may show a large heart ([[cardiomegaly]]) or increased pulmonary vasculature. Neonates with HLHS do not typically have a [[heart murmur]], but in some cases, a pulmonary flow murmur or [[Tricuspid insufficiency|tricuspid regurgitation]] murmur may be audible.<ref name=":12" />
 
Co-occurring tricuspid regurgitation or right ventricular dysfunction can cause [[hepatomegaly]] to develop.<ref name=":12" />
 
==Causes==
[[Image:Hypoplastic left heart syndrome.svg|thumb|upright=1.5|Diagram of a healthy heart and one with hypoplastic left heart syndrome]]
There is no known cause in the majority of HLHS cases.<ref name="Barron2009">{{cite journal |author=Barron, D. J., Kilby, M. D., Davies, B., Wright, J. G., Jones, T. J., & Brawn, W. J. |year=2009 |title=Hypoplastic left heart syndrome |journal=The Lancet |volume=374 |issue=9689 |pages=551–564 |pmid=19683641 |doi=10.1016/s0140-6736(09)60563-8}}</ref> Some cases may have a genetic component, as HLHS has been shown to be heritable and associated with specific gene mutations.<ref>{{cite journal |author=Hinton, R. B., Martin, L. J., Tabangin, M. E., Mazwi, M. L., Cripe, L. H., & Benson, D. W. |year=2007 |title=Hypoplastic left heart syndrome is heritable |journal=Journal of the American College of Cardiology |volume=50 |issue=16 |pages=1590–1595 |pmid=17936159 |doi=10.1016/j.jacc.2007.07.021}}</ref><ref name="pmid11470490">{{cite journal |vauthors=Dasgupta C, Martinez AM, Zuppan CW, Shah MM, Bailey LL, Fletcher WH |title=Identification of connexin43 (alpha1) gap junction gene mutations in patients with hypoplastic left heart syndrome by denaturing gradient gel electrophoresis (DGGE) |journal=[[Mutat. Res.]] |volume=479 |issue=1–2 |pages=173–86 |year=2001 |pmid=11470490 |doi= 10.1016/S0027-5107(01)00160-9}}</ref>
 
 
Not all, but some, cases of aortic stenosis in a fetus can put stress on the left ventricle ''in utero,'' that can eventually lead to decreased perfusion and stop the growth of the left ventricle. <ref name=":4">{{Cite journal|last=Schidlow|first=David N.|last2=Freud|first2=Lindsay|last3=Friedman|first3=Kevin|last4=Tworetzky|first4=Wayne|date=2017|title=Fetal interventions for structural heart disease|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/echo.13667|journal=Echocardiography|language=en|volume=34|issue=12|pages=1834–1841|doi=10.1111/echo.13667|issn=1540-8175}}</ref>
 
=== Environmental causes ===
In a retrospective analysis of over 1,300 newborns (born between 1996 and 2006) from 24 children’s hospitals in the United States, researchers at Cincinnati Children’s Hospital in Ohio found that babies with HLHS were more likely to be born in summer months, suggesting that seasonality and environmental factors may play a significant role in causation.<ref>{{cite journal |vauthors=Eghtesady P, Brar A, Hall M |title=Seasonality of hypoplastic left heart syndrome in the United States: a 10-year time-series analysis |journal=J. Thorac. Cardiovasc. Surg. |volume=141 |issue=2 |pages=432–8 |date=February 2011 |pmid=20817208 |doi=10.1016/j.jtcvs.2010.06.060 }}</ref>
 
===Genetics===
Genetic loci associated with HLHS include [[GJA1|GJA1 (connexin 43)]], [[HAND1]], [[NKX2-5 (gene)|NKX2.5]], 10q22, and 6q23.<ref name=":1" /><ref name="HLHS Review 2012 Feinstein">{{cite journal|last1=Feinstein|first1=JA|last2=Benson|first2=DW|last3=Dubin|first3=AM|last4=Cohen|first4=MS|last5=Maxey|first5=DM|last6=Mahle|first6=WT|last7=Pahl|first7=E|last8=Villafañe|first8=J|last9=Bhatt|first9=AB|last10=Peng|first10=LF|last11=Johnson|first11=BA|last12=Marsden|first12=AL|author12-link=Alison Marsden|last13=Daniels|first13=CJ|last14=Rudd|first14=NA|last15=Caldarone|first15=CA|last16=Mussatto|first16=KA|last17=Morales|first17=DL|last18=Ivy|first18=DD|last19=Gaynor|first19=JW|last20=Tweddell|first20=JS|last21=Deal|first21=BJ|last22=Furck|first22=AK|last23=Rosenthal|first23=GL|last24=Ohye|first24=RG|last25=Ghanayem|first25=NS|last26=Cheatham|first26=JP|last27=Tworetzky|first27=W|last28=Martin|first28=GR|title=Hypoplastic left heart syndrome: current considerations and expectations|journal=Journal of the American College of Cardiology|date=3 January 2012|volume=59|issue=1 Suppl|pages=S1–42|pmid=22192720|pmc=6110391|doi=10.1016/j.jacc.2011.09.022}}</ref><ref>{{cite journal |author=Hinton, R. B., Martin, L. J., Rame-Gowda, S., Tabangin, M. E., Cripe, L. H., & Benson, D. W. |year=2009 |title=Hypoplastic left heart syndrome links to chromosomes 10q and 6q and is genetically related to bicuspid aortic valve |journal=Journal of the American College of Cardiology |volume=53 |issue=12 |pages=1065–1071 |pmc=2703749 |doi=10.1016/j.jacc.2008.12.023 |pmid=19298921}}</ref> There is a slight risk of recurrence in future pregnancies, estimated to be 2-4%, which increases to 25% in families with two affected children.<ref name="Barron2009"/> This is thought to be mediated by genetic mutations with [[incomplete penetrance]].<ref name=":1" />
 
HLHS is also associated with several genetic syndromes, including [[trisomy 13|trisomy 13 (Patau syndrome)]], [[trisomy 18|trisomy 18 (Edwards syndrome)]], [[Partial Trisomy 9|partial trisomy 9]], [[Turner's syndrome|Turner's syndrome (XO)]], [[Jacobsen syndrome|Jacobsen syndrome (11q deletion syndrome)]], [[Holt-Oram Syndrome|Holt-Oram syndrome]], and [[Smith-Lemli-Opitz Syndrome|Smith-Lemli-Opitz syndrome]].<ref name=":1" /><ref name="HLHS Review 2012 Feinstein" />
 
=== Risk factors ===
Presence of a [[cystic hygroma]] increases the risk of HLHS in a fetus.<ref name=":2">{{Cite book|chapter-url=http://accessmedicine.mhmedical.com/content.aspx?aid=1102100362|title=Williams Obstetrics|last=Cunningham|first=F. Gary|last2=Leveno|first2=Kenneth J.|last3=Bloom|first3=Steven L.|last4=Spong|first4=Catherine Y.|authorlink4=Catherine Y. Spong|last5=Dashe|first5=Jodi S.|last6=Hoffman|first6=Barbara L.|last7=Casey|first7=Brian M.|last8=Sheffield|first8=Jeanne S.|date=2013|publisher=McGraw-Hill Education|edition=24|location=New York, NY|chapter=Fetal Imaging}}</ref>
 
== Pathophysiology ==
At birth, the [[ductus arteriosus]] is still open, and there is higher than normal resistance to blood flow in the lungs. This allows for adequate oxygenation via mixing between the atria and a normal appearance at birth. When the ductus begins to close and pulmonary vascular resistance decreases, blood flow through the ductus is restricted and flow to the lungs is increased. <ref name=":12" />
 
In typical anatomy, the left side of the heart receives [[oxygen]]-rich blood from the lungs and pumps it to the rest of the body. In people with HLHS, the [[aorta]] and [[left ventricle]] are underdeveloped (beginning ''in utero''),<ref>{{cite journal|author=Galindo, A., Nieto, O., Villagrá, S., Grañeras, A., Herraiz, I., & Mendoza, A.  |year=2009 |title=Hypoplastic left heart syndrome diagnosed in fetal life: associated findings, pregnancy outcome and results of palliative surgery |journal=Ultrasound in Obstetrics & Gynecology |volume=33 |issue=5 |pages=560–566 |pmid=19367583 |doi=10.1002/uog.6355}}</ref> and the [[aortic valve|aortic]] and [[mitral valve|mitral]] valves are either too small to allow sufficient blood flow or are atretic (closed) altogether.<ref>{{Cite web |url= http://www.pted.org/?id=hypoplasticleft1 |title= Hypoplastic Left Heart Syndrome {{!}} Congenital Heart Disease - Cove Point Foundation {{!}} Johns Hopkins Children's Hospital |last=Burns |first=Paul Burns and Jasper |website= www.pted.org |access-date= 2017-11-30}}</ref>  As [[blood]] returns from the [[lung]]s to the [[left atrium]], it cannot be pumped to the rest of the body by the left ventricle. The neonate is reliant on blood flowing through an [[atrial septal defect]] to mix oxygenated and deoxygenated blood, and on a [[patent ductus arteriosus]] to allow blood to reach the aorta and the systemic circulation via the right ventricle. This is what defines HLHS as a "single ventricle" defect.<ref name=":1" />
 
Due to the underdevelopment of the left side of the heart ''in utero'', the increased afterload causes hypertension of the left atrium, pulmonary edema, and therefore lung damage to the fetus before birth. <ref name=":4" />


==Diagnosis==
==Diagnosis==
Hypoplastic left heart syndrome can be diagnosed prenatally or after birth via echocardiography. Typical findings include a small left ventricle and aorta, abnormalities of the mitral and aortic valves, retrograde flow in the transverse arch of the aorta, and left-to-right flow between the atria. It is often recognized during the second trimester of pregnancy, between 18 and 24 weeks' gestation.<ref name=":12" />
HLHS can be diagnosed prenatally using [[fetal echocardiography]]. Postnatal diagnosis is typically confirmed with an [[echocardiogram]], which can visualize the underdeveloped structures of the heart. Additional tests may include [[chest X-ray]] and [[electrocardiogram]] (ECG).


==Management==
==Treatment==
Treatment for HLHS involves a series of surgeries or, in some cases, a [[heart transplant]]. The surgical approach, known as the Norwood procedure, is typically performed in three stages:


===Medical===
===Stage 1: Norwood Procedure===
Without life-prolonging interventions, HLHS is fatal, but with intervention, an infant may survive. A [[cardiothoracic surgeon]] may perform a series of operations or a full [[heart transplant]]. While surgical intervention has emerged as the standard of care in the United States, other national health systems, notably in France, approach diagnosis of HLHS in a more conservative manner, with an emphasis on termination of pregnancy or compassionate care after delivery.<ref name="pmid22397767">{{cite journal |vauthors=Noseda C, Mialet-Marty T, Basquin A | title = Hypoplasies sévères du ventricule gauche : soins palliatifs après un diagnostic prénatal | journal = [[Archives de pediatrie]] | volume = 19 | issue = 4 | pages = 374–380 |date=April 2012 | pmid = 22397767 | doi = 10.1016/j.arcped.2012.01.022 }}</ref>
This surgery is performed shortly after birth. It involves reconstructing the aorta and connecting it to the right ventricle, allowing the right ventricle to pump blood to the body.


Before surgery, the ductus must be kept open to allow blood-flow using medication containing [[prostaglandin]]. Air with less oxygen than normal is used for infants with hypoplastic left heart syndrome. These low oxygen levels increases the [[pulmonary vascular resistance]] (PVR) and thus improve blood flow to the rest of the body due to the greater pressure difference between the lungs and body.  Achieving oxygen levels below atmosphere requires the use of inhaled nitrogen.<ref name="pmid12881932">{{cite journal |vauthors=Green A, Pye S, Yetman AT | title = The physiologic basis for and nursing considerations in the use of subatmospheric concentrations of oxygen in HLHS | journal = [[Advances in Neonatal Care]] | volume = 2 | issue = 4 | pages = 177–86 |date=August 2002 | pmid = 12881932 | doi = 10.1053/adnc.2002.33542 }}</ref> [[Nitric oxide]] is a potent pulmonary vasodilator, and thus reduces PVR and improves venous return. Any factor that increases PVR will impede right sided flow.<ref>{{cite journal |author1=Khambadkone S. |author2=Li J. |author3=De Leval M. R. |author4=Cullen S. |author5=Deanfield J. E. |author6=Redington A. N. | year = 2003 | title = Basal pulmonary vascular resistance and nitric oxide responsiveness late after Fontan-type operation | url = | journal = Circulation | volume = 107 | issue = 25| pages = 3204–3208 | doi=10.1161/01.cir.0000074210.49434.40 | pmid=12821557| doi-access=free }}</ref><ref>{{cite journal | author = Norwood W. I. | year = 1991 | title = Hypoplastic left heart syndrome. The | url = | journal = Annals of Thoracic Surgery | volume = 52 | issue = 3| pages = 688–695 | doi=10.1016/0003-4975(91)90978-y| pmid = 1898174 }}</ref>
===Stage 2: Glenn Procedure===
Performed at 4-6 months of age, this procedure connects the superior vena cava to the pulmonary arteries, reducing the workload on the right ventricle.


===Surgical===
===Stage 3: Fontan Procedure===
Surgical operations to assist with hypoplastic left heart are complex and need to be individualized for each patient. A cardiologist must assess all medical and surgical options on a case-by-case basis.
This final surgery, performed at 18 months to 3 years of age, connects the inferior vena cava to the pulmonary arteries, completing the separation of oxygenated and deoxygenated blood.
 
Currently, infants undergo either the staged reconstructive surgery ([[Norwood procedure|Norwood]] or [[Sano shunt|Sano procedure]] within a few days of birth, [[Glenn procedure|Glenn]] or ''Hemi-Fontan procedure'' at 3 to 6 months of age, and the [[Fontan procedure]] at 1 1/2 to 5 years of age) or cardiac transplantation.<ref>[http://www.chop.edu/service/cardiac-center/heart-conditions/hypoplastic-left-heart-syndrome-hlhs.html Hypoplastic Left Heart Syndrome (HLHS) | The Children's Hospital of Philadelphia<!-- Bot generated title -->]</ref> Current expectations are that 70% of those with HLHS may reach adulthood.<ref name="HLHS Review 2012 Feinstein" /> Many studies show that the higher the volume (number of surgeries performed) at a hospital, the lower the mortality (death) rate.<ref name="pmid20136852">{{cite journal|last=McHugh|first=KE|author2=Hillman, DG |author3=Gurka, MJ |author4= Gutgesell, HP |title=Three-stage palliation of hypoplastic left heart syndrome in the University HealthSystem Consortium|journal=Congenital Heart Disease|date=Jan–Feb 2010|volume=5|issue=1|pages=8–15|pmid=20136852|doi=10.1111/j.1747-0803.2009.00367.x}}</ref><ref name="pmid18080151">{{cite journal|last=Hirsch|first=JC|author2=Gurney, JG |author3=Donohue, JE |author4=Gebremariam, A |author5=Bove, EL |author6= Ohye, RG |title=Hospital mortality for Norwood and arterial switch operations as a function of institutional volume|journal=Pediatric Cardiology|date=July 2008|volume=29|issue=4|pages=713–7|pmid=18080151|doi=10.1007/s00246-007-9171-2}}</ref> Factors that increase an infant's risk include lower birth weight, additional congenital anomalies, a genetic syndrome or those with a highly restrictive atrial septum.<ref name=":3">{{Cite journal|last=Vojtovič|first=P.|last2=Tláskal|first2=T.|last3=Gebauer|first3=R.|last4=Reich|first4=O.|last5=Chaloupecký|first5=V.|last6=Tomek|first6=V.|last7=Krupičková|first7=S.|last8=Matějka|first8=T.|last9=Hecht|first9=P.|date=December 2014|title=Long-term results of children operated for hypoplastic left heart syndrome in Children's Heart Centre|journal=Cor et Vasa|volume=56|issue=6|pages=e449–e455|doi=10.1016/j.crvasa.2014.07.006|issn=0010-8650|doi-access=free}}</ref>) For patients without these additional risk factors, 5 year survival now approaches 80%.<ref name=":3" />  Studies show that about 75% of those children who survive surgery show developmental delays in one or more areas, such as motor, cognitive, or language impairments, with about a third of single-ventricle children without a genetic syndrome having significant impairments.<ref>{{Cite journal|last=Mussatto|first=Kathleen A.|last2=Hoffmann|first2=Raymond G.|last3=Hoffman|first3=George M.|last4=Tweddell|first4=James S.|last5=Bear|first5=Laurel|last6=Cao|first6=Yumei|last7=Brosig|first7=Cheryl|date=2014|title=Risk and prevalence of developmental delay in young children with congenital heart disease|journal=Pediatrics|volume=133|issue=3|pages=e570–577|doi=10.1542/peds.2013-2309|issn=1098-4275|pmc=3934337|pmid=24488746}}</ref> Current research focuses on charting the connections between neurodevelopment injuries, surgical and intensive care procedures, and genetic susceptibility with the goal of modifying interventions that impair neurodevelopmental and psychosocial outcomes.<ref>{{Cite journal|last=Wernovsky|first=Gil|last2=Licht|first2=Daniel J.|date=2016|title=Neurodevelopmental Outcomes in Children with Congenital Heart Disease – What can we impact?|journal=Pediatric Critical Care Medicine|volume=17|issue=8 Suppl 1|pages=S232–S242|doi=10.1097/PCC.0000000000000800|issn=1529-7535|pmc=4975480|pmid=27490605}}</ref>  An alternative to the traditional Norwood is the Hybrid procedure.<ref>{{Cite journal|last=Yabrodi|first=Mouhammad|last2=Mastropietro|first2=Christopher W.|date=2016-10-04|title=Hypoplastic left heart syndrome: from comfort care to long-term survival|journal=Pediatric Research|language=En|volume=81|issue=1–2|pages=142–149|doi=10.1038/pr.2016.194|issn=0031-3998|pmc=5313512|pmid=27701379}}</ref>
 
Some physicians offer "compassionate care", instead of the surgeries, which results in the child's death, usually within 2 weeks of birth.  Compassionate care is overseen by a physician, and may be carried out either in the hospital or at home.  However, due to the vast improvement of surgical intervention, with many hospitals achieving over 90% survival, there is debate on whether or not "compassionate care" should still be offered to families.<ref name="pmid18762602">{{cite journal|last=Wernovsky|first=Gil|title=The Paradigm Shift Toward Surgical Intervention for Neonates With Hypoplastic Left Heart Syndrome|journal=Archives of Pediatrics & Adolescent Medicine|date=1 September 2008|volume=162|issue=9|pages=849–54|doi=10.1001/archpedi.162.9.849|pmid=18762602}}</ref> A study in 2003 concluded that a selection of physicians who are experts in the care of children with HLHS were evenly split when asked what they would do if their own children were born with HLHS, with 1/3 stating that they would choose surgery, 1/3 stating that they would choose palliative (compassionate) treatment without surgery, and 1/3 stating that they are uncertain which choice they would make.<ref name="pmid12804748">{{cite journal|last=Kon|first=Alexander A.|author2=Ackerson, Lynn |author3=Lo, Bernard |title=Choices physicians would make if they were the parents of a child with hypoplastic left heart syndrome|journal=The American Journal of Cardiology|date=31 May 2003|volume=91|issue=12|pages=1506–1509|doi=10.1016/S0002-9149(03)00412-0|pmid=12804748}}</ref>
 
The three-stage procedure is a [[Palliative care|palliative]] procedure (not a cure), as the child's circulation is made to work with only two of the heart's four chambers.
 
==== Norwood procedure ====
The first step is the [[Norwood procedure]].<ref name=":0">{{Cite journal|title = Hypoplastic Left Heart Syndrome|journal = Journal of the American College of Cardiology|pages = S1–S42|volume = 59|issue = 1|doi = 10.1016/j.jacc.2011.09.022|first = Jeffrey A.|last = Feinstein|first2 = D. Woodrow|last2 = Benson|first3 = Anne M.|last3 = Dubin|first4 = Meryl S.|last4 = Cohen|first5 = Dawn M.|last5 = Maxey|first6 = William T.|last6 = Mahle|first7 = Elfriede|last7 = Pahl|first8 = Juan|last8 = Villafañe|first9 = Ami B.|last9 = Bhatt|pmid=22192720|date=Jan 2012|pmc = 6110391}}</ref> In this procedure, the right ventricle is used to pump blood into the systemic circulation. Since the right ventricle is no longer directly pumping blood to the lungs, a shunt is required in order to pass deoxygenated blood through the lungs. Either the subclavian artery can be connected to the pulmonary circulation ([[Blalock-Taussig shunt]]), or a shunt is made directly from the right ventricle to the pulmonary circulation ([[Sano shunt]]). The narrow aorta is enlarged using a patch to improve blood flow to the body.<ref>{{cite web|url=http://hlhs-awareness-uk.com/images/new%20norwood.gif|title=new norwood.gif|archiveurl=https://web.archive.org/web/20101124170629/http://hlhs-awareness-uk.com/images/new%20norwood.gif|archivedate=November 24, 2010|url-status=dead}}</ref>
 
During this time the baby may be medically fragile and have feeding problems because the heart is working very hard. There is a considerable degree of venous mixing in the right ventricle, leading to lower oxygenation saturation. In addition, both the Blalock-Taussig and the Sano shunts expose the lungs to systemic arterial pressures, leading to long-term pulmonary hypertension and eventually heart failure.<ref name=":0" />
 
====Hybrid procedure====
The Hybrid procedure may be used in place of the Norwood.<ref name=":0" /><ref>{{Cite journal|title = Hybrid Procedure for Neonates With Hypoplastic Left Heart Syndrome at High-Risk for Norwood: Midterm Outcomes|journal = The Annals of Thoracic Surgery|doi = 10.1016/j.athoracsur.2015.06.098|pmid = 26433522|first = Michael O.|last = Murphy|first2 = Hannah|last2 = Bellsham-Revell|first3 = Gareth J.|last3 = Morgan|first4 = Thomas|last4 = Krasemann|first5 = Eric|last5 = Rosenthal|first6 = Shakeel A.|last6 = Qureshi|first7 = Caner|last7 = Salih|first8 = Conal B.|last8 = Austin|first9 = David R.|last9 = Anderson|volume=100|issue = 6|pages=2286–2292|year = 2015}}</ref><ref>{{Cite journal|title = Hypoplastic Left Heart Syndrome in the Emergency Department: An Update|journal = The Journal of Emergency Medicine|pages = e51–e54|volume = 46|issue = 2|doi = 10.1016/j.jemermed.2013.08.061|pmid = 24188609|first = Monika|last = Chauhan|first2 = Christopher W.|last2 = Mastropietro|year = 2014}}</ref>  The Hybrid procedure does not necessitate the use of heart-lung bypass or performing a [[Median sternotomy|sternotomy]].  Instead of a six-hour surgery, the Hybrid typically takes one to two hours.  In this procedure, a stent is placed in the [[ductus arteriosus]] to maintain its patency, and bands are placed over both the left and right pulmonary artery branches to limit pressure and over-circulation to the lungs.<ref>[http://www.childrenshospital.org/views/august05/cardiacsurgery.html Children's Hospital Boston | Pediatric Views<!-- Bot generated title -->]</ref>  Outcomes with the Hybrid approach are comparable to those with the Norwood.<ref>{{cite journal  |vauthors=Galantowicz M, Cheatham JP, Phillips A, etal |title=Hybrid approach for hypoplastic left heart syndrome: intermediate results after the learning curve |journal=Ann. Thorac. Surg. |volume=85 |issue=6 |pages=2063–70; discussion 2070–1 |date=June 2008 |pmid=18498821 |doi=10.1016/j.athoracsur.2008.02.009 }}</ref>
 
====Glenn procedure====
The second stage&mdash;the [[bidirectional Glenn procedure|bidirectional Glenn]] or ''Hemi-Fontan'' (see also [[Kawashima procedure]])&mdash;relieves some of the problems introduced by Stage I palliation.<ref name=":0" /> In this operation, the [[superior vena cava]] is ligated from the heart and connected to the pulmonary circulation. At this time, the Blalock-Taussig or Sano shunt is taken down. The lungs are no longer exposed to systemic arterial pressures, but much lower venous pressures. Although venous blood from the upper half of the body is no longer mixing with oxygenated blood in the right ventricle, there is still venous mixing from the lower half of the body, leading to some degree of oxygen desaturation.<ref name=":0" />
 
====Fontan procedure====
[[File:Fontan procedure.svg|thumb|upright=1.5]]
The final procedure, the [[Fontan procedure]], completes the repair of the hypoplastic left heart.<ref name=":0" /> Although there are several variations, the functional effect is to redirect venous blood from the lower body (through the inferior vena cava) away from the right atrium to the pulmonary artery. This should eliminate any mixing of oxygenated and deoxygenated blood in the right ventricle. The right ventricle performs the traditional job of the left, supplying the body with oxygenated blood, while the passive systemic venous pressure performs the traditional job of the right, passing deoxygenated blood to the lungs.<ref name=":0" />
 
===== Fetal surgery =====
Interventions performed during fetal development are under investigation. In fetuses with hypoplastic left ventricles and an intact interatrial septum, percutaneous [[atrial septostomy]] has been attempted.<ref name=":2" />


==Prognosis==
==Prognosis==
95% of untreated infants with HLHS die in the first weeks of life.<ref name=":12" />
The prognosis for children with HLHS has improved significantly with advances in surgical techniques. However, these children require lifelong follow-up with a cardiologist and may face complications such as arrhythmias, heart failure, and the need for additional surgeries.
 
Early survival has improved since the introduction of the Norwood procedure.<ref name="HLHS Review 2012 Feinstein" /> Since there are no long-term studies of HLHS adults, statistics are usually derived from post-Fontan patients; it is estimated that 70% of HLHS patients may reach adulthood.<ref name="HLHS Review 2012 Feinstein" />
 
Prognosis is dependent upon the health of the child, as there is an increased demand on respiratory and heart rate in infants during common childhood illnesses. This fragile population has little cardiac reserve to accommodate these demands and provide hemodynamic stability during illnesses. <ref>{{Cite journal|last=Nieves|first=Jo Ann|last2=Uzark|first2=Karen|last3=Rudd|first3=Nancy A.|last4=Strawn|first4=Jennifer|last5=Schmelzer|first5=Anne|last6=Dobrolet|first6=Nancy|date=2017-04-01|title=Interstage Home Monitoring After Newborn First-Stage Palliation for Hypoplastic Left Heart Syndrome: Family Education Strategies|url=https://aacnjournals.org/ccnonline/article/37/2/72/20689/Interstage-Home-Monitoring-After-Newborn-First|journal=Critical Care Nurse|language=en|volume=37|issue=2|pages=72–88|doi=10.4037/ccn2017763|issn=0279-5442}}</ref>
 
Children with HLHS and other comparable single-ventricle conditions, as a group, have poorer [[Developmental disability|neurodevelopmental]] outcomes than their healthy peers. Deficits in language, [[Executive functions|executive functioning]], and higher rates of [[Anxiety disorder|anxiety]] and [[Depression in childhood and adolescence|depression]] disorders have been demonstrated.<ref>{{Cite journal|last=White|first=Brian R.|last2=Rogers|first2=Lindsay S.|last3=Kirschen|first3=Matthew P.|date=2019|title=Recent advances in our understanding of neurodevelopmental outcomes in congenital heart disease|journal=Current Opinion in Pediatrics|language=en|volume=31|issue=6|pages=783–788|doi=10.1097/MOP.0000000000000829|pmid=31693588|pmc=6852883|issn=1040-8703}}</ref> Some of these outcomes may be a consequence of genetic factors associated with HLHS, and others may be modifiable through changes to procedures and to the healthcare environment. There is an emerging clinical consensus around the importance of continuous neurodevelopmental surveillance from the earliest years into adulthood.<ref>{{Cite journal|last=Marino|first=Bradley S.|last2=Lipkin|first2=Paul H.|last3=Newburger|first3=Jane W.|last4=Peacock|first4=Georgina|last5=Gerdes|first5=Marsha|last6=Gaynor|first6=J. William|last7=Mussatto|first7=Kathleen A.|last8=Uzark|first8=Karen|last9=Goldberg|first9=Caren S.|date=2012-08-28|title=Neurodevelopmental Outcomes in Children With Congenital Heart Disease: Evaluation and Management: A Scientific Statement From the American Heart Association|journal=Circulation|language=en|volume=126|issue=9|pages=1143–1172|doi=10.1161/CIR.0b013e318265ee8a|pmid=22851541|issn=0009-7322|doi-access=free}}</ref><ref>{{Cite journal|last=Gurvitz|first=Michelle|last2=Burns|first2=Kristin M.|last3=Brindis|first3=Ralph|last4=Broberg|first4=Craig S.|last5=Daniels|first5=Curt J.|last6=Fuller|first6=Stephanie M.P.N.|last7=Honein|first7=Margaret A.|last8=Khairy|first8=Paul|last9=Kuehl|first9=Karen S.|date=2016-04-26|title=Emerging Research Directions in Adult Congenital Heart Disease: A Report from a National Heart, Lung, and Blood Institute/Adult Congenital Heart Association Working Group|journal=Journal of the American College of Cardiology|volume=67|issue=16|pages=1956–1964|doi=10.1016/j.jacc.2016.01.062|issn=0735-1097|pmc=4846980|pmid=27102511}}</ref>
 
As is true for patients with other types of heart defects involving malformed valves,<ref>{{cite web |url=http://www.mayoclinic.com/health/endocarditis/DS00409/DSECTION=4 |title=Endocarditis: Risk factors |publisher=MayoClinic.com |accessdate=2007-10-23 |format= |website=}}</ref>  HLHS patients run a high risk of [[endocarditis]], and must be monitored by a cardiologist for the rest of their lives to check on their heart function.
 
Heart transplantation may be indicated, typically after Fontan completion.<ref name="HLHS Review 2012 Feinstein" /> One multi-center study (of patients undergoing the Fontan from 1993-2001) reported a 76% 1-year survival rate in patients who survived to transplant.<ref>{{cite journal |author=Taylor, D. O., Stehlik, J., Edwards, L. B., Aurora, P., Christie, J. D., Dobbels, F., ... & Hertz, M. I. |year=2009 |title=Registry of the International Society for Heart and Lung Transplantation: twenty-sixth official adult heart transplant report—2009 |journal=The Journal of Heart and Lung Transplantation |volume=28 |issue=10 |pages=1007–1022 |pmid=19782283 |doi=10.1016/j.healun.2009.08.014}}</ref>
 
==Epidemiology==
HLHS occurs in an estimated 1 out of 4,300 live births in the United States, or an estimated total of 960 live births per year in that country.<ref>{{Cite news|url=https://www.cdc.gov/ncbddd/heartdefects/hlhs.html|title=Hypoplastic Left Heart Syndrome Facts {{!}} Congenital Heart Defects|date=2017-10-26|work=Centers for Disease Control and Prevention|access-date=2017-11-30|language=en-us}}</ref><ref>{{cite journal |author=Parker SE, Mai CT, Canfield MA, Rickard R, Wang Y, Meyer RE, Anderson P, Mason CA, Collins JS, Kirby RS, Correa A; National Birth Defects Prevention Network. |title=Updated National Birth Prevalence estimates for selected birth defects in the United States, 2004-2006 |journal=Birth Defects Res a Clin Mol Teratol. |volume=88 |issue=12 |pages=1008–16 |year=2010 |pmid=20878909 |doi=10.1002/bdra.20735 }}</ref> Overall, it is estimated to make up 2-3% of all cases of congenital heart disease, and is the most common single-ventricle defect. It is thought to be more common in male infants, 1.5 times as common as in female infants.<ref name=":1">{{Cite web|url=https://www.uptodate.com/contents/hypoplastic-left-heart-syndrome|title=Hypoplastic left heart syndrome|last=Fulton|first=David R.|date=October 26, 2017|website=Up To Date|access-date=2017-11-30}}</ref>
 
==References==
{{Reflist}}
 
== External links ==
{{Medical resources
| DiseasesDB      = 31507
| ICD10          = {{ICD10|Q|23|4|q|20}}
| ICD9            = {{ICD9|746.7}}
| OMIM            = 241550
| MedlinePlus    = 001106
| ICDO            =
| eMedicineSubj  = ped
| eMedicineTopic  = 1131
| meshName        = Hypoplastic+Left+Heart+Syndrome
| meshNumber      = C14.240.400.625
| Orphanet        = 2248
}}
{{Commons category|Hypoplastic left heart syndrome}}
*[http://www.gosh.nhs.uk/medical-conditions/search-for-medical-conditions/hypoplastic-left-heart-syndrome/ Hypoplastic left heart syndrome] information for parents.


{{Congenital malformations and deformations of circulatory system}}
==Related pages==
{{Channelopathy}}
* [[Congenital heart defect]]
* [[Echocardiography]]
* [[Heart transplant]]


[[Category:Congenital heart defects]]
[[Category:Congenital heart defects]]
[[Category:Syndromes affecting the heart]]
[[Category:Cardiology]]
[[Category:Rare diseases]]
{{stub}}

Revision as of 19:25, 22 March 2025

Congenital heart defect



Hypoplastic left heart syndrome (HLHS) is a rare congenital heart defect in which the left side of the heart is underdeveloped. This condition affects normal blood flow through the heart, as the left side of the heart is unable to effectively pump blood to the body.

Anatomy and Pathophysiology

In HLHS, several structures on the left side of the heart are affected, including the left ventricle, mitral valve, aortic valve, and aorta. The left ventricle is typically small and non-functional, the mitral and aortic valves may be stenotic or atretic, and the ascending aorta is often underdeveloped.

The underdevelopment of these structures leads to a reliance on the right ventricle to pump blood to both the lungs and the rest of the body. Blood flow to the body is dependent on a patent ductus arteriosus, a fetal blood vessel that connects the pulmonary artery to the aorta, which normally closes shortly after birth.

Clinical Presentation

Newborns with HLHS may appear normal at birth but can rapidly develop symptoms as the ductus arteriosus begins to close. Symptoms include:

  • Cyanosis (bluish skin color)
  • Rapid breathing
  • Poor feeding
  • Lethargy
  • Cold extremities

Without intervention, HLHS is usually fatal within the first few days or weeks of life.

Diagnosis

HLHS can be diagnosed prenatally using fetal echocardiography. Postnatal diagnosis is typically confirmed with an echocardiogram, which can visualize the underdeveloped structures of the heart. Additional tests may include chest X-ray and electrocardiogram (ECG).

Treatment

Treatment for HLHS involves a series of surgeries or, in some cases, a heart transplant. The surgical approach, known as the Norwood procedure, is typically performed in three stages:

Stage 1: Norwood Procedure

This surgery is performed shortly after birth. It involves reconstructing the aorta and connecting it to the right ventricle, allowing the right ventricle to pump blood to the body.

Stage 2: Glenn Procedure

Performed at 4-6 months of age, this procedure connects the superior vena cava to the pulmonary arteries, reducing the workload on the right ventricle.

Stage 3: Fontan Procedure

This final surgery, performed at 18 months to 3 years of age, connects the inferior vena cava to the pulmonary arteries, completing the separation of oxygenated and deoxygenated blood.

Prognosis

The prognosis for children with HLHS has improved significantly with advances in surgical techniques. However, these children require lifelong follow-up with a cardiologist and may face complications such as arrhythmias, heart failure, and the need for additional surgeries.

Related pages

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