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). 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 main articles: hypoplastic left heart syndrome and hypoplastic right heart syndrome 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 main article: ventricular outflow tract obstruction 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. 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 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. 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.