Congenital heart defect

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 conditions Congenital heart defects are associated with an increased incidence of seven other specific medical conditions, 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 defect (ASD), and tetralogy of Fallot (ToF) are the most common congenital heart defects seen in the VACTERL association. ==Causes==

The cause of congenital heart disease may be genetic, environmental, or a combination of both. They are described in the table below. 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 (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. 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. 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. 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. Alcohol exposure in the father also appears to increase the risk of congenital heart defects. Being overweight or obese increases the risk of congenital heart disease. 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. Twins and Multiple Births Congenital heart defects happen more often in twins than in single babies. Monochorionic twins, who share a placenta, have a greater risk of these heart defects compared to dichorionic twins, who have their own placentas. A systematic review and meta-analysis of four studies conducted in 2007 showed a 9-fold increase in CHD risk in MC twins compared to singletons. ==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), 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. Spitzer (1923) treats them as returns to one of the phylogenesis stages. 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. 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).. Newborn screening and early detection Early detection of critical congenital heart disease (CCHD) in patients with CHD is important for reducing morbidity and mortality, as it allows for timely treatment and may help prevent future complications. Despite the use of standard screening tests such as prenatal ultrasound and physical examination, many cases of CCHD are missed during initial evaluation. Pulse oximetry is a non-invasive and reliable method that measures oxygen levels in the blood. The pulse oximeter is placed on the right hand and one foot to obtain oxygen saturation measurements. 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. Obstructive defects Obstructive 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 left side of the heart to the right, reducing the heart's efficiency. although approximately 30% of adults have a type of atrial septal defect called probe patent foramen ovale. An atrioventricular septal defect is more complex involving an atrial septal defect, a ventricular septal defect, and irregularities in the heart valves. 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. , (b) coarctation of the aorta, (c) patent ductus arteriosus, and (d) tetralogy of Fallot with ventricular septal defect. Defects • Aortic stenosis • Arrhythmogenic right ventricular cardiomyopathy • 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 • Early Repolarization Syndrome • Holmes heart • Hypoplastic left heart syndrome (HLHS) • Hypoplastic right heart syndrome (HRHS) • Mitral stenosis • Myocardial bridge • 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==

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. 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. 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. Mental health Supporting people with chronic diseases such as congenital heart disease with emotional problems and mental health is a treatment consideration. 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. 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. ==Epidemiology==

Heart defects are among the most common birth defect, occurring in 1% of live births (2–3% including bicuspid aortic valve). 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. == See also ==