Congenital heart defect

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Congenital heart disease
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Congenital heart defect
Other namesCongenital heart anomaly, congenital heart disease
catheter based procedures, heart surgery, heart transplantation[6][3]
PrognosisGenerally good (with treatment)[7]
Frequency48.9 million (2015)[8]
Deaths303,300 (2015)[9]

A congenital heart defect (CHD), also known as a congenital heart anomaly, congenital cardiovascular malformation, and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth.[7] A congenital heart defect is classed as a cardiovascular disease.[10] Signs and symptoms depend on the specific type of defect.[3] Symptoms can vary from none to life-threatening.[7] When present, symptoms are variable and may include rapid breathing, bluish skin (cyanosis), poor weight gain, and feeling tired.[2] CHD does not cause chest pain.[2] Most congenital heart defects are not associated with other diseases.[3] A complication of CHD is heart failure.[2]

Congenital heart defects are the most common birth defect.[3][11] In 2015, they were present in 48.9 million people globally.[8] They affect between 4 and 75 per 1,000 live births, depending upon how they are diagnosed.[3][12] In about 6 to 19 per 1,000 they cause a moderate to severe degree of problems.[12] Congenital heart defects are the leading cause of birth defect-related deaths:[3] in 2015, they resulted in 303,300 deaths, down from 366,000 deaths in 1990.[9][13] The cause of a congenital heart defect is often unknown.

heart valves, or the large blood vessels that lead to and from the heart.[7]

Congenital heart defects are partly preventable through

catheter based procedures or heart surgery.[6] Occasionally a number of operations may be needed,[6] or a heart transplant may be required.[6] With appropriate treatment, outcomes are generally good, even with complex problems.[7]

Signs and symptoms

Digital clubbing with cyanotic nail beds in an adult with tetralogy of Fallot

Signs and symptoms are related to type and severity of the heart defect. Symptoms frequently present early in life, but it is possible for some CHDs to go undetected throughout life.[14] Some children have no signs while others may exhibit shortness of breath, cyanosis, fainting,[15] heart murmur, under-development of limbs and muscles, poor feeding or growth, or respiratory infections. Congenital heart defects cause abnormal heart structure resulting in production of certain sounds called heart murmur. These can sometimes be detected by auscultation; however, not all heart murmurs are caused by congenital heart defects.[citation needed]

Associated conditions

Congenital heart defects are associated with an increased incidence of seven other specific medical conditions, together being called the VACTERL association:[citation needed]

Ventricular septal defect (VSD), atrial septal defects, and tetralogy of Fallot are the most common congenital heart defects seen in the VACTERL association. Less common defects in the association are truncus arteriosus and transposition of the great arteries.[citation needed]

Causes

The cause of congenital heart disease may be genetic, environmental, or a combination of both.[16]

Genetic

Genetic mutations, often sporadic, represent the largest known cause of congenital heart defects.[17]
They are described in the table below.

Genetic lesions Attributable percent Examples Primary genetic testing method
Aneuploidies
5–8%[16] Survivable autosomal trisomies (chromosomes Karyotyping
Copy number variants 10–12%[18] 22q11.2 deletion/duplication (velocardiofacial/DiGeorge syndrome), 1q21.1 deletion/duplication, 8p23.1 deletion/duplication, 15q11.2 deletion (Burnside-Butler syndrome)
Array comparative genomic hybridization
(also known as chromosomal microarray analysis)
Inherited protein-coding
single nucleotide variant (SNV) or small insertion/deletion (indel)
3–5%[19] Holt–Oram syndrome, Noonan syndrome, Alagille syndrome Gene panel
De novo protein-coding SNV or indel ~10%[20][17] Mutations in genes highly expressed during heart development
Whole exome sequencing

Molecular pathways

The genes regulating the complex developmental sequence have only been partly elucidated. Some genes are associated with specific defects. A number of genes have been associated with cardiac manifestations. Mutations of a heart muscle protein, α-myosin heavy chain (

NKX2-5 also interacts with MYH6. Mutations of all these proteins are associated with both atrial and ventricular septal defects; In addition, NKX2-5 is associated with defects in the electrical conduction of the heart and TBX5 is related to the Holt–Oram syndrome which includes electrical conduction defects and abnormalities of the upper limb. The Wnt signaling co-factors BCL9, BCL9L and PYGO might be part of these molecular pathways, as when their genes are mutated, this causes phenotypes similar to the features present in Holt-Oram syndrome.[22] Another T-box gene, TBX1, is involved in velo-cardio-facial syndrome DiGeorge syndrome, the most common deletion which has extensive symptoms including defects of the cardiac outflow tract including tetralogy of Fallot.[23]

Examples of gene products and associated features
MYH6 GATA4 NKX2-5 TBX5 TBX1
Locus 14q11.2-q13 8p23.1-p22 5q34 12q24.1 22q11.2
Syndrome Holt–Oram DiGeorge
Atrial septal defects
Ventricular septal defects
Electrical conduction abnormalities
Outflow tract abnormalities
Non-cardiac manifestations[24] Upper limb abnormalities Small or absent thymus
Small or absent parathyroids
Facial abnormalities

The

Notch1 gene are associated with bicuspid aortic valve, a valve with two leaflets instead of three. Notch1 is also associated with calcification of the aortic valve, the third most common cause of heart disease in adults.[25][26]

Mutations of a cell regulatory mechanism, the

LEOPARD syndrome, Costello syndrome and cardiofaciocutaneous syndrome in which there is cardiac involvement.[27] While the conditions listed are known genetic causes, there are likely many other genes which are more subtle. It is known that the risk for congenital heart defects is higher when there is a close relative with one.[28]

Environmental

Known environmental factors include certain

diabetes mellitus, phenylketonuria, and systemic lupus erythematosus).[29] Alcohol exposure in the father also appears to increase the risk of congenital heart defects.[30]

Being

maternal obesity increases, the risk of heart defects also increases.[31] A distinct physiological mechanism has not been identified to explain the link between maternal obesity and CHD, but both pre-pregnancy folate deficiency and diabetes have been implicated in some studies.[32]

Mechanism

There is a complex sequence of events that result in a well formed heart at birth and disruption of any portion may result in a defect.[28] The orderly timing of cell growth, cell migration, and programmed cell death ("apoptosis") has been studied extensively and the genes that control the process are being elucidated.[23] Around day 15 of development, the cells that will become the heart exist in two horseshoe shaped bands of the middle tissue layer (

myocytes) around it by day 21. On day 22, the heart begins to beat and by day 24, blood is circulating.[33]

At day 22, the circulatory system is bilaterally symmetrical with paired vessels on each side and the heart consisting of a simple tube located in the midline of the body layout. The portions that will become the atria and will be located closest to the head are the most distant from the head. From days 23 through 28, the heart tube folds and twists, with the future ventricles moving left of center (the ultimate location of the heart) and the atria moving towards the head.[33]

On day 28, areas of tissue in the heart tube begin to expand inwards; after about two weeks, these expansions, the membranous "

fetal growth. The lungs are unexpanded and cannot accommodate the full circulatory volume. Two structures exist to shunt blood flow away from the lungs. Cells in part of the septum primum die creating a hole while muscle cells, the "septum secundum", grow along the right atrial side the septum primum, except for one region, leaving a gap through which blood can pass from the right artium to the left atrium, the foramen ovale. A small vessel, the ductus arteriosus allows blood from the pulmonary artery to pass to the aorta.[33]

Changes at birth

The ductus arteriosus stays open because of circulating factors including

patent foramen ovale. The two flaps may fuse, but many adults have a foramen ovale that stays closed only because of the pressure difference between the atria.[33]

Theories

Rokitansky (1875) explained congenital heart defects as breaks in heart development at various

ontogenesis stages.[34] Spitzer (1923) treats them as returns to one of the phylogenesis stages.[35] Krimski (1963), synthesizing two previous points of view, considered congenital heart diseases as a stop of development at the certain stage of ontogenesis, corresponding to this or that stage of the phylogenesis.[36] Hence these theories can explain feminine and neutral types of defects only.[citation needed
]

Diagnosis

Many congenital heart defects can be

]

If a baby is born with cyanotic heart disease, the diagnosis is usually made shortly after birth due to the blue colour of their skin (called cyanosis).[38]

If a baby is born with a septal defect or an obstruction defect, often their symptoms are only noticeable after several months or sometimes even after many years.[38]

Classification

A number of classification systems exist for congenital heart defects. In 2000 the International Congenital Heart Surgery Nomenclature was developed to provide a generic classification system.[39]

Hypoplasia

patent foramen ovale) is vital to the infant's ability to survive until emergency heart surgery can be performed, since without these pathways blood cannot circulate to the body (or lungs, depending on which side of the heart is defective). Hypoplasia of the heart is generally a cyanotic heart defect.[40]

Obstructive defects

Obstructive defects occur when heart valves, arteries, or veins are

coarctation of the aorta, with other types such as bicuspid aortic valve stenosis and subaortic stenosis being comparatively rare. Any narrowing or blockage can cause heart enlargement or hypertension.[41]

Septal defects

The septum is a wall of tissue which separates the

Cyanotic defects

Defects

Some conditions affect the great vessels or other vessels in close proximity to the heart, but not the heart itself, but are often classified as congenital heart defects.[citation needed]

Some constellations of multiple defects are commonly found together.[citation needed]

Treatment

CHD may require surgery and medications. Medications include diuretics, which aid the body in eliminating water, salts, and digoxin for strengthening the contraction of the heart. This slows the heartbeat and removes some fluid from tissues. Some defects require surgical procedures to restore circulation back to normal and in some cases, multiple surgeries are needed.[citation needed]

Interventional cardiology now offers minimally invasive alternatives to surgery for some patients. The Melody Transcatheter Pulmonary Valve (TPV), approved in Europe in 2006 and in the U.S. in 2010 under a Humanitarian Device Exemption (HDE), is designed to treat congenital heart disease patients with a dysfunctional conduit in their right ventricular outflow tract (RVOT). The RVOT is the connection between the heart and lungs; once blood reaches the lungs, it is enriched with oxygen before being pumped to the rest of the body. Transcatheter pulmonary valve technology provides a less-invasive means to extend the life of a failed RVOT conduit and is designed to allow physicians to deliver a replacement pulmonary valve via a catheter through the patient's blood vessels.[citation needed]

Many people require lifelong specialized cardiac care, first with a pediatric cardiologist and later with an adult congenital cardiologist. There are more than 1.8 million adults living with congenital heart defects.[44]

Mental health

Supporting people with chronic diseases such as congenital heart disease with emotional problems and mental health is a treatment consideration.[45] Since some people with congenital heart disease have a lower quality of life that is related to their condition, some people may struggle with finding a job, engaging in physical exercise, with their fertility, and clinical depression as examples. An estimated 31% of adults with congenital heart disease also have mood disorders.[45] Psychotherapy may be helpful for treating some people who have congenital heart disease and depression, however further research is needed to determine the best way to reduce depression including the length of treatments required for an improvement, type of psychotherapy treatments, and how the psychotherapy sessions are delivered.[45]

Epidemiology

Congenital heart anomalies deaths per million persons in 2012
  0-8
  9-12
  13-23
  24-31
  32-39
  40-47
  48-50
  51-56
  57-63
  64-124

Heart defects are among the most common birth defect, occurring in 1% of live births (2–3% including bicuspid aortic valve).[11] In 2013, 34.3 million people had CHD. In 2010, they resulted in 223,000 deaths, down from 278,000 deaths in 1990.[46]

For congenital heart defects that arise without a family history (de novo), the recurrence risk in offspring is 3–5%.[47][48] This risk is higher in left ventricular outflow tract obstructions, heterotaxy, and atrioventricular septal defects.[47][48]

Terminology

Congenital heart defects are known by a number of names including congenital heart anomaly, congenital heart disease, heart defects, and congenital cardiovascular malformations.[49]

See also

References

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External links