Centers for Disease Control and Prevention

From Wikipedia, the free encyclopedia

Agency overview
Formed	July 1, 1946; 72 years ago
Preceding agencies	Office of National Defense Malaria Control Activities (1942) Office of Malaria Control in War Areas (1942–1946) Communicable Disease Center (1946–1967) National Communicable Disease Center (1967–1970) Center for Disease Control (1970–1980) Centers for Disease Control (1980–1992)
Jurisdiction	Federal government of the United States
Headquarters	Atlanta, Georgia, U.S.
Employees	15,000
Annual budget	US$11.1 billion (FY18)
Agency executive	Robert R. Redfield, Director
Parent agency	United States Department of Health and Human Services
Website	www.cdc.gov

The Centers for Disease Control and Prevention (CDC) is the leading national public health institute of the United States. The CDC is a United States federal agency under the Department of Health and Human Services and is headquartered in Atlanta, Georgia.

Its main goal is to protect public health and safety through the control and prevention of disease, injury, and disability in the US and internationally. The CDC focuses national attention on developing and applying disease control and prevention. It especially focuses its attention on infectious disease, food borne pathogens, environmental health, occupational safety and health, health promotion, injury prevention and educational activities designed to improve the health of United States citizens. In addition, the CDC researches and provides information on non-infectious diseases such as obesity and diabetes and is a founding member of the International Association of National Public Health Institutes.

History

CDC headquarters in Atlanta, Georgia, as seen from Emory University

 

CDC's Roybal campus in Atlanta, Georgia

 

Arlen Specter Headquarters and Emergency Operations Center

 

Tom Harkin Global Communications Center

 

CDC and MSF staff preparing to enter an Ebola treatment unit in Liberia, August 2014

The Communicable Disease Center was founded July 1, 1946, as the successor to the World War II Malaria Control in War Areas program of the Office of National Defense Malaria Control Activities.

Preceding its founding, organizations with global influence in malaria control were the Malaria Commission of the League of Nations and the Rockefeller Foundation. The Rockefeller Foundation greatly supported malaria control, sought to have the governments take over some of its efforts, and collaborated with the agency.

The new agency was a branch of the U.S. Public Health Service and Atlanta was chosen as the location because malaria was endemic in the Southern United States. The agency changed names (see infobox on top) before adopting the name Communicable Disease Center in 1946. Offices were located on the sixth floor of the Volunteer Building on Peachtree Street. 

With a budget at the time of about $1 million, 59 percent of its personnel were engaged in mosquito abatement and habitat control with the objective of control and eradication of malaria in the United States.

Among its 369 employees, the main jobs at CDC were originally entomology and engineering. In CDC's initial years, more than six and a half million homes were sprayed, mostly with DDT. In 1946, there were only seven medical officers on duty and an early organization chart was drawn, somewhat fancifully, in the shape of a mosquito. Under Joseph Walter Mountin, the CDC continued to advocate for public health issues and pushed to extend its responsibilities to many other communicable diseases.

In 1947, the CDC made a token payment of $10 to Emory University for 15 acres (61,000 m²) of land on Clifton Road in DeKalb County, still the home of CDC headquarters today. CDC employees collected the money to make the purchase. The benefactor behind the “gift” was Robert W. Woodruff, chairman of the board of The Coca-Cola Company. Woodruff had a long-time interest in malaria control, which had been a problem in areas where he went hunting. The same year, the PHS transferred its San Francisco based plague laboratory into the CDC as the Epidemiology Division, and a new Veterinary Diseases Division was established. An Epidemic Intelligence Service (EIS) was established in 1951, originally due to biological warfare concerns arising from the Korean War; it evolved into two-year postgraduate training program in epidemiology, and a prototype for Field Epidemiology Training Programs (FETP), now found in numerous countries, reflecting CDC's influence in promoting this model internationally.

The mission of CDC expanded beyond its original focus on malaria to include sexually transmitted diseases when the Venereal Disease Division of the U.S. Public Health Service (PHS) was transferred to the CDC in 1957. Shortly thereafter, Tuberculosis Control was transferred (in 1960) to the CDC from PHS, and then in 1963 the Immunization program was established.

It became the National Communicable Disease Center (NCDC) effective July 1, 1967. The organization was renamed the Center for Disease Control (CDC) on June 24, 1970, and Centers for Disease Control effective October 14, 1980. An act of the United States Congress appended the words "and Prevention" to the name effective October 27, 1992. However, Congress directed that the initialism CDC be retained because of its name recognition.

Currently the CDC focus has broadened to include chronic diseases, disabilities, injury control, workplace hazards, environmental health threats, and terrorism preparedness. CDC combats emerging diseases and other health risks, including birth defects, West Nile virus, obesity, avian, swine, and pandemic flu, E. coli, and bioterrorism, to name a few. The organization would also prove to be an important factor in preventing the abuse of penicillin. In May 1994 the CDC admitted having sent several biological warfare agents to the Iraqi government from 1984 through 1989, including Botulinum toxin, West Nile virus, Yersinia pestis and Dengue fever virus.

On April 21, 2005, then–CDC Director Julie Gerberding formally announced the reorganization of CDC to "confront the challenges of 21st-century health threats". The four Coordinating Centers—established under the G. W. Bush Administration and Gerberding—"diminished the influence of national centers under [their] umbrella", and were ordered cut under the Obama Administration in 2009.

Today, the CDC's Biosafety Level 4 laboratories are among the few that exist in the world, and serve as one of only two official repositories of smallpox in the world. The second smallpox store resides at the State Research Center of Virology and Biotechnology VECTOR in the Russian Federation. The CDC revealed in 2014 that it had discovered several misplaced smallpox samples and also that lab workers had potentially been infected with anthrax.

Organization

The CDC is organized into "Centers, Institutes, and Offices" (CIOs), with each organizational unit implementing the agency's activities in a particular area of expertise while also providing intra-agency support and resource-sharing for cross-cutting issues and specific health threats. Generally, CDC "Offices" are subdivided into Centers, which in turn are composed of Divisions and Branches. However, the Center for Global Health and the National Institute for Occupational Safety and Health are freestanding organizational units and do not belong to a parent Office. 

The current CIOs are:

• CDC Washington Office
• Center for Global Health
• National Institute for Occupational Safety and Health
• Office for State, Tribal, Local and Territorial Support
• Office of Equal Employment Opportunity
• Office of Infectious Diseases
  • National Center for Emerging and Zoonotic Infectious Diseases
  • National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
  • National Center for Immunization and Respiratory Diseases
• Office of Minority Health and Health Equity
• Office of Noncommunicable Diseases, Injury and Environmental Health
  • National Center for Chronic Disease Prevention and Health Promotion
  • National Center for Environmental Health/Agency for Toxic Substances and Disease Registry
  • National Center for Injury Prevention and Control
  • National Center on Birth Defects and Developmental Disabilities
• Office of Public Health Preparedness and Response
• Office of Public Health Scientific Services
  • Center for Surveillance, Epidemiology and Laboratory Services
  • National Center for Health Statistics
• Office of the Associate Director for Communication
• Office of the Associate Director for Laboratory Science and Safety
• Office of the Associate Director for Policy
• Office of the Associate Director for Science
• Office of the Chief of Staff
• Office of the Chief Operating Officer

The Office of Public Health Preparedness was created during the 2001 anthrax attacks shortly after the terrorist attacks of September 11, 2001. Its purpose was to coordinate among the government the response to a range of biological terrorism threats.

Budget and operations

In addition to its Atlanta headquarters, the CDC has other locations in the United States and Puerto Rico. Those locations include Anchorage; Cleveland; Cincinnati; Detroit; Fort Collins; Hyattsville; Morgantown; Pittsburgh; Research Triangle Park; San Juan, Puerto Rico; Spokane, Washington; and Washington, D.C.

The CDC offers grants that help many organizations each year advance health, safety and awareness at the community level throughout the United States. The CDC awards over 85 percent of its annual budget through these grants.

Workforce

As of 2008, CDC staff numbered approximately 15,000 (including 6,000 contractors and 840 Commissioned Corps officers) in 170 occupations. Eighty percent held bachelor's degrees or higher; almost half had advanced degrees (a master's degree or a doctorate such as a PhD, D.O., or M.D.).

Common CDC job titles include engineer, entomologist, epidemiologist, biologist, physician, veterinarian, behavioral scientist, nurse, medical technologist, economist, public health advisor, health communicator, toxicologist, chemist, computer scientist, and statistician.

The CDC also operates a number of notable training and fellowship programs, including those indicated below.

Epidemic Intelligence Service (EIS)

The Epidemic Intelligence Service (EIS) is composed of "boots-on-the-ground disease detectives" who investigate public health problems domestically and globally. When called upon by a governmental body, EIS officers may embark on short-term epidemiological assistance assignments, or "Epi-Aids", to provide technical expertise in containing and investigating disease outbreaks. The EIS program is a model for the international Field Epidemiology Training Program.

Public Health Associates Program

The CDC also operates the Public Health Associate Program (PHAP), a two-year paid fellowship for recent college graduates to work in public health agencies all over the United States. PHAP was founded in 2007 and currently has 159 associates in 34 states.

Leadership

David Sencer points to a depiction of Triatomine sp., which transmits Chagas disease.

 

The Director of CDC is a Senior Executive Service position that may be filled either by a career employee, or as a political appointment that does not require Senate confirmation, with the latter method typically being used. The director serves at the pleasure of the President and may be fired at any time. The CDC director concurrently serves as the Administrator of the Agency for Toxic Substances and Disease Registry.

Sixteen directors have served the CDC or its predecessor agencies.

• Louis L. Williams Jr., MD (1942–1943)
• Mark D. Hollis, ScD (1944–1946)
• Raymond A. Vonderlehr, MD (1947–1951)
• Justin M. Andrews, ScD (1952–1953)
• Theodore J. Bauer, MD (1953–1956)
• Robert J. Anderson, MD, MPH (1956–1960)
• Clarence A. Smith, MD, MPH (1960–1962)
• James L. Goddard, MD, MPH (1962–1966)
• David J. Sencer, MD, MPH (1966–1977)
• William H. Foege, MD, MPH (1977–1983)
• James O. Mason, MD, MPH, Ph.D (1983–1989)
• William L. Roper, MD, MPH (1990–1993)
• David Satcher, MD, PhD (1993–1998)
• Jeffrey P. Koplan, MD, MPH (1998–2002)
• Julie Gerberding, MD, MPH (2002–2008)
• Thomas R. Frieden, MD, MPH (2009–Jan 2017)
• Anne Schuchat, MD, RADM USPHS (Jan–July 2017, acting)
• Brenda Fitzgerald, MD (July 2017–Jan 2018)
• Anne Schuchat, MD (Jan–Mar 2018, acting)
• Robert R. Redfield, MD (March 2018–)

Datasets and survey systems

• CDC Scientific Data, Surveillance, Health Statistics, and Laboratory Information.
• Behavioral Risk Factor Surveillance System (BRFSS), the world’s largest, ongoing telephone health-survey system.
• Mortality Medical Data System.
• Abortion statistics in the United States

Areas of focus

Donald Henderson as part of the CDC's smallpox eradication team in 1966.

Communicable diseases

The CDC's programs address more than 400 diseases, health threats, and conditions that are major causes of death, disease, and disability. The CDC's website has information on various infectious (and noninfectious) diseases, including smallpox, measles, and others.

Influenza

The CDC has launched campaigns targeting the transmission of influenza, including the H1N1 swine flu, and launched websites to educate people in proper hygiene.

Division of Select Agents and Toxins

Within the division are two programs: the Federal Select Agent Program (FSAP) and the Import Permit Program. The FSAP is run jointly with an office within the U.S. Department of Agriculture, regulating agents that can cause disease in humans, animals, and plants. The Import Permit Program regulates the importation of "infectious biological materials."

The CDC runs a program that protects the public from rare and dangerous substances such as anthrax and the Ebola virus. The program, called the Federal Select Agent Program, calls for inspections of labs in the U.S. that work with dangerous pathogens.

During the 2014 Ebola outbreak in West Africa, the CDC helped coordinate the return of two infected American aid workers for treatment at Emory University Hospital, the home of a special unit to handle highly infectious diseases.

As a response to the 2014 Ebola outbreak, Congress passed a Continuing Appropriations Resolution allocating $30,000,000 towards CDC's efforts to fight the virus.

Non-communicable diseases

The CDC also works on non-communicable diseases, including chronic diseases caused by obesity, physical inactivity and tobacco-use.

Antibiotic resistance

The CDC implemented their National Action Plan for Combating Antibiotic Resistant Bacteria as a measure against the spread of antibiotic resistance in the United States. This initiative has a budget of $161 million and includes the development of the Antibiotic Resistance Lab Network.

Global health

The CDC works with other organizations around the world to address global health challenges and contain disease threats at their source. It works closely with many international organizations such as the World Health Organization (WHO) as well as ministries of health and other groups on the front lines of outbreaks. The agency maintains staff in more than 60 countries, including some from the U.S. but even more from the countries in which it operates. The agency's global divisions include the Division of Global HIV and TB (DGHT), the Division of Parasitic Diseases and Malaria (DPDM), the Division of Global Health Protection (DGHP), and the Global Immunization Division (GID).

The CDC is integral in working with the WHO to implement the International Health Regulations (IHR), a legally binding agreement between 196 countries to prevent, control, and report on the international spread of disease, through initiatives including the Global Disease Detection Program (GDD).

The CDC is also a lead implementer of key U.S. global health initiatives such as the President's Emergency Plan for AIDS Relief (PEPFAR) and the President's Malaria Initiative.

Travelers' health

The CDC collects and publishes health information for travelers in a comprehensive book, CDC Health Information for International Travel, which is commonly known as the "yellow book." The book is available online and in print as a new edition every other year and includes current travel health guidelines, vaccine recommendations, and information on specific travel destinations. The CDC also issues travel health notices on its website, consisting of three levels: 

"Watch": Level 1 (practice usual precautions) 

"Alert": Level 2 (practice enhanced precautions) 

"Warning": Level 3 (avoid nonessential travel)

Foundation

The CDC Foundation operates independently from CDC as a private, nonprofit 501(c)(3) organization incorporated in the State of Georgia. The creation of the Foundation was authorized by section 399F of the Public Health Service Act to support the mission of CDC in partnership with the private sector, including organizations, foundations, businesses, educational groups, and individuals.

Popular culture and controversies

Historically, the CDC has been relatively free of political manipulation.

Tuskegee Study of Untreated Syphilis in the Negro Male

For 15 years, the CDC had direct oversight over the Tuskegee syphilis experiment. In the study, which lasted from 1932 to 1972, a group of African American men (nearly 400 of whom had syphilis) were studied to learn more about the disease. Notably, the disease was left untreated in the research subjects and they never gave their informed consent to serve as research subjects. The Tuskegee Study was initiated in 1932 by the Public Health Service. The CDC took over the study in 1957.

The CDC's response to the AIDS crisis in the 1980s has been criticized for promoting some public health policies that harmed HIV+ people and for providing ineffective public education. The agency's response to the 2001 anthrax attacks was also criticized for ineffective communication with other public health agencies and with the public.

CDC zombie apocalypse outreach campaign

On May 16, 2011, the Centers for Disease Control and Prevention's blog published an article instructing the public on what to do to prepare for a zombie invasion. While the article did not claim that such a scenario was possible, it did use the popular culture appeal as a means of urging citizens to prepare for all potential hazards, such as earthquakes, tornadoes, and floods.

According to David Daigle, the Associate Director for Communications, Public Health Preparedness and Response, the idea arose when his team was discussing their upcoming hurricane-information campaign and Daigle mused that "we say pretty much the same things every year, in the same way, and I just wonder how many people are paying attention." A social-media employee mentioned that the subject of zombies had come up a lot on Twitter when she had been tweeting about the Fukushima Daiichi nuclear disaster and radiation. The team realized that a campaign like this would most likely reach a different audience from the one that normally pays attention to hurricane-preparedness warnings and went to work on the zombie campaign, launching it right before hurricane season began. "The whole idea was, if you're prepared for a zombie apocalypse, you're prepared for pretty much anything," said Daigle.

Once the blog article became popular, the CDC announced an open contest for YouTube submissions of the most creative and effective videos covering preparedness for a zombie apocalypse (or apocalypse of any kind), to be judged by the "CDC Zombie Task Force". Submissions were open until October 11, 2011. They also released a zombie-themed graphic novella available on their website. Zombie-themed educational materials for teachers are available on the site.

Gun violence

One area of current partisan dispute related to CDC funding is studying gun violence. The 1996 Dickey Amendment states "none of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control". Advocates for gun control oppose the amendment and have tried to overturn it.

In 1992, Mark L. Rosenberg and five CDC colleagues founded the CDC’s National Center for Injury Prevention and Control, with an annual budget of c. $260,000 that focused on "identifying the root causes of firearm deaths and the best methods to prevent them". Their first report which was published in the New England Journal of Medicine in 1993, entitled "Gun Ownership as a Risk Factor for Homicide in the Home" reported that the "mere presence of a gun in a home increased the risk of a firearm-related death by 2.7 percent, and suicide fivefold—a "huge" increase." In response, the NRA launched a "campaign to shut down the Injury Center." Doctors for Responsible Gun Ownership and Doctors for Integrity and Policy Research joined the pro-gun effort and by 1995, politicians also supported the pro-gun initiative. In 1996, Jay Dickey (R) Arkansas introduced the Dickey Amendment statement "which stated "none of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control" as a rider in the 1996 appropriations bill." In 1997, "Congress redirected all of the money previously earmarked for gun violence research to the study of traumatic brain injury." David Satcher, who was the CDC head from 1993 to 1998 advocated for gun violence research until he left in 1998. In 1999 Rosenberg was fired. Over a dozen "public health insiders, including current and former CDC senior leaders" told The Trace interviewers that CDC senior leaders took an overly cautious stance in their interpretation of the Dickey amendment. They could have done much more. Rosenberg told The Trace in 2016, "Right now, there is nothing stopping them from addressing this life-and-death national problem.”

The American Medical Association, the American Psychological Association and the American Academy of Pediatrics sent a letter to the leaders of the Senate Appropriations Committee in 2013 asking them "to support at least $10 million within the Centers for Disease Control and Prevention (CDC) in FY 2014 along with sufficient new funding at the National Institutes of Health to support research into the causes and prevention of gun violence. Furthermore, we urge Members to oppose any efforts to reduce, eliminate, or condition CDC funding related to gun violence prevention research." Congress maintained the ban in subsequent budgets.

Language guidelines

In December 2017, The Washington Post reported that the Trump administration had issued a list of seven words that were forbidden in official CDC documentation. Yuval Levin, after contacting HHS officials, wrote in National Review that the Post story was not accurate.

Publications

• CDC publications
• State of CDC report
• CDC Programs in Brief
• Morbidity and Mortality Weekly Report
• Emerging Infectious Diseases (monthly journal)
• Preventing Chronic Disease
• Vital statistics

Congenital heart defect

From Wikipedia, the free encyclopedia

Congenital heart defect
Synonyms	Congenital heart anomaly, congenital heart disease
The normal structure of the heart (left) in comparison to two common locations for a ventricular septal defect (right), the most common form of congenital heart defect.
Specialty	Cardiology
Symptoms	Rapid breathing, bluish skin, poor weight gain, feeling tired
Complications	Heart failure
Types	Cyanotic heart defects, non-cyanotic heart defects
Causes	Often unknown
Risk factors	Rubella infection during pregnancy, alcohol or tobacco, parents being closely related, poor nutritional status or obesity in the mother
Treatment	None, catheter based procedures, heart surgery, heart transplantation
Prognosis	Generally good (with treatment)
Frequency	48.9 million (2015)
Deaths	303,300 (2015)

A congenital heart defect (CHD), also known as a congenital heart anomaly or congenital heart disease, is a problem in the structure of the heart that is present at birth. Signs and symptoms depend on the specific type of problem. Symptoms can vary from none to life-threatening. When present they may include rapid breathing, bluish skin, poor weight gain, and feeling tired. It does not cause chest pain. Most congenital heart problems do not occur with other diseases. Complications that can result from heart defects include heart failure.

The cause of a congenital heart defect is often unknown. Certain cases may be due to infections during pregnancy such as rubella, use of certain medications or drugs such as alcohol or tobacco, parents being closely related, or poor nutritional status or obesity in the mother. Having a parent with a congenital heart defect is also a risk factor. A number of genetic conditions are associated with heart defects including Down syndrome, Turner syndrome, and Marfan syndrome. Congenital heart defects are divided into two main groups: cyanotic heart defects and non-cyanotic heart defects, depending on whether the child has the potential to turn bluish in color. The problems may involve the interior walls of the heart, the heart valves, or the large blood vessels that lead to and from the heart.

Congenital heart defects are partly preventable through rubella vaccination, the adding of iodine to salt, and the adding of folic acid to certain food products. Some defects do not need treatment. Others may be effectively treated with catheter based procedures or heart surgery. Occasionally a number of operations may be needed, or a heart transplant may be required. With appropriate treatment, outcomes are generally good, even with complex problems.

Heart defects are the most common birth defect. In 2015 they were present in 48.9 million people globally. They affect between 4 and 75 per 1,000 live births depending upon how they are diagnosed. About 6 to 19 per 1,000 cause a moderate to severe degree of problems. Congenital heart defects are the leading cause of birth defect-related deaths. In 2015 they resulted in 303,300 deaths down from 366,000 deaths in 1990.

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. Some children have no signs while others may exhibit shortness of breath, cyanosis, fainting, 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.

Associated symptoms

Congenital heart defects are associated with an increased incidence of some other symptoms, together being called the VACTERL association:

• V — Vertebral anomalies
• A — Anal atresia
• C — Cardiovascular anomalies
• T — Tracheoesophageal fistula
• E — Esophageal atresia
• R — Renal (Kidney) and/or radial anomalies
• L — Limb defects

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.

Causes

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

Genetic

Most of the known causes of congenital heart disease are sporadic genetic changes, either focal mutations or deletion or addition of segments of DNA. Large chromosomal abnormalities such as trisomies 21, 13, and 18 cause about 5–8% of cases of CHD, with trisomy 21 being the most common genetic cause. Small chromosomal abnormalities also frequently lead to congenital heart disease, and examples include microdeletion of the long arm of chromosome 22 (22q11, DiGeorge syndrome), the long arm of chromosome 1 (1q21), the short arm of chromosome 8 (8p23) and many other, less recurrent regions of the genome, as shown by high resolution genome-wide screening (Array comparative genomic hybridization).

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 (MYH6) are associated with atrial septal defects. Several proteins that interact with MYH6 are also associated with cardiac defects. The transcription factor GATA4 forms a complex with the TBX5 which interacts with MYH6. Another factor, the homeobox (developmental) gene, 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. 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.

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[19]				Upper limb abnormalities	Small or absent thymus Small or absent parathyroids Facial abnormalities

Molecular pathways

The notch signaling pathway, a regulatory mechanism for cell growth and differentiation, plays broad roles in several aspects of cardiac development. Notch elements are involved in determination of the right and left sides of the body plan, so the directional folding of the heart tube can be impacted. Notch signaling is involved early in the formation of the endocardial cushions and continues to be active as the develop into the septa and valves. It is also involved in the development of the ventricular wall and the connection of the outflow tract to the great vessels. Mutations in the gene for one of the notch ligands, Jagged1, are identified in the majority of examined cases of arteriohepatic dysplasia (Alagille syndrome), characterized by defects of the great vessels (pulmonary artery stenosis), heart (tetralogy of Fallot in 13% of cases), liver, eyes, face, and bones. Though less than 1% of all cases, where no defects are found in the Jagged1 gene, defects are found in Notch2 gene. In 10% of cases, no mutation is found in either gene. For another member of the gene family, mutations in 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.

Mutations of a cell regulatory mechanism, the Ras/MAPK pathway are responsible for a variety of syndromes, including Noonan syndrome, LEOPARD syndrome, Costello syndrome and cardiofaciocutaneous syndrome in which there is cardiac involvement. 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.

Environmental

Known environmental factors include certain infections during pregnancy such as Rubella, drugs (alcohol, hydantoin, lithium and thalidomide) and maternal illness (diabetes mellitus, phenylketonuria, and systemic lupus erythematosus).

Being overweight or obese increases the risk of congenital heart disease. Additionally, as maternal obesity increases, the risk of heart defects also increases. A distinct physiological mechanism has not been identified to explain the link between maternal obesity and CHD, but both prepregnancy folate deficiency and diabetes have been implicated in some studies.

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. 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. Around day 15 of development, the cells that will become the heart exist in two horseshoe shaped bands of the middle tissue layer (mesoderm), and some cells migrate from a portion of the outer layer (ectoderm), the neural crest, which is the source of a variety of cells found throughout the body. On day 19 of development, a pair of vascular elements, the "endocardial tubes", form. The tubes fuse when cells between then undergo programmed death and cells from the first heart field migrate to the tube, and form a ring of heart cells (myocytes) around it by day 21. On day 22, the heart begins to beat and by day 24, blood is circulating.

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.

On day 28, areas of tissue in the heart tube begin to expand inwards; after about two weeks, these expansions, the membranous "septum primum" and the muscular "endocardial cushions", fuse to form the four chambers of the heart. A failure to fuse properly will result in a defect that may allow blood to leak between chambers. After this happens, cells which have migrated from the neural crest begin to divide the bulbus cordis, the main outflow tract is divided in two by the growth a spiraling septum, becoming the great vessels—the ascending segment of the aorta and the pulmonary trunk. If the separation is incomplete, the result is a "persistent truncus arteriosis". The vessels may be reversed ("transposition of the great vessels"). The two halves of the split tract must migrate into the correct positions over the appropriate ventricles. A failure may result in some blood flowing into the wrong vessel (e.g.overriding aorta). The four-chambered heart and the great vessels have features required for 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.

Changes at birth

The ductus arteriosus stays open because of circulating factors including prostaglandins. The foramen ovale stays open because of the flow of blood from the right atrium to the left atrium. As the lungs expand, blood flows easily through the lungs and the membranous portion of the foramen ovale (the septum primum) flops over the muscular portion (the septum secundum). If the closure is incomplete, the result is a 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.

Theories

Rokitansky (1875) explained congenital heart defects as breaks in heart development at various ontogenesis stages. Spitzer (1923) treats them as returns to one of the phylogenesis stages. Krimsky (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. Hence these theories can explain feminine and neutral types of defects only.

Diagnosis

Many congenital heart defects can be diagnosed prenatally by fetal echocardiography. This is a test which can be done during the second trimester of pregnancy, when the woman is about 18–24 weeks pregnant. It can be an abdominal ultrasound or transvaginal ultrasound. 

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).

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.

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.

Hypoplasia

Hypoplasia can affect the heart, typically resulting in the underdevelopment of the right ventricle or the left ventricle. This causes only one side of the heart to be capable of pumping blood to the body and lungs effectively. Hypoplasia of the heart is rare but is the most serious form of CHD. It is called hypoplastic left heart syndrome when it affects the left side of the heart and hypoplastic right heart syndrome when it affects the right side of the heart. In both conditions, the presence of a patent ductus arteriosus (and, when hypoplasia affects the right side of the heart, a 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.

Obstruction defects

Obstruction defects occur when heart valves, arteries, or veins are abnormally narrow or blocked. Common defects include pulmonic stenosis, aortic stenosis, and 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.

Septal defects

The septum is a wall of tissue which separates the left heart from the right heart. Defects in the interatrial septum or the interventricular septum allow blood to flow from the right side of the heart to the left, reducing the heart's efficiency. Ventricular septal defects are collectively the most common type of CHD, although approximately 30% of adults have a type of atrial septal defect called probe patent foramen ovale.

Cyanotic defects

Cyanotic heart defects are called such because they result in cyanosis, a bluish-grey discoloration of the skin due to a lack of oxygen in the body. Such defects include persistent truncus arteriosus, total anomalous pulmonary venous connection, tetralogy of Fallot, transposition of the great vessels, and tricuspid atresia.

Defects

• Aortic stenosis
• Atrial septal defect (ASD)
• Atrioventricular septal defect (AVSD)
• Bicuspid aortic valve
• Cardiomyopathy
• Complete heart block (CHB)
• Dextrocardia
• Double inlet left ventricle (DILV)
• Double outlet right ventricle (DORV)
• Ebstein's anomaly
• Hypoplastic left heart syndrome (HLHS)
• Hypoplastic right heart syndrome (HRHS)
• Mitral stenosis
• Persistent truncus arteriosus
• Pulmonary atresia
• Pulmonary stenosis
• Rhabdomyomas (Tumors of the Heart)
• Transposition of the great vessels
  • dextro-Transposition of the great arteries (d-TGA)
  • levo-Transposition of the great arteries (l-TGA)
• Tricuspid atresia
• Ventricular septal defect (VSD)
• Wolff-Parkinson-White syndrome (WPW)

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.

• Coarctation of the aorta (CoA)
• Double aortic arch, aberrant subclavian artery, and other malformations of the great arteries
• Interrupted aortic arch (IAA)
• Patent ductus arteriosus (PDA)
• Scimitar syndrome (SS)
  • Partial anomalous pulmonary venous connection (PAPVC)
  • Total anomalous pulmonary venous connection (TAPVC)

Some constellations of multiple defects are commonly found together.

• Tetralogy of Fallot (ToF)
• Pentalogy of Cantrell
• Shone's syndrome/ Shone's complex / Shone's anomaly

Treatment

Most of the time CHD is serious and requires surgery and/or 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. 

Interventional cardiology now offers patients 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. 

Most patients 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.

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). In 2013, 34.3 million people had CHD. In 2010, they resulted in 223,000 deaths, down from 278,000 deaths in 1990.

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

Terminology

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