right or left ventricular dysfunction, as well as the level of pulmonary hypertension, are linked to an increased risk of pregnancy complications. fetal death is more likely in women who have moderate right ventricular hypertension or who have undergone a palliative shunt. in comparison to 0.8% of the general population, offspring of women with tetralogy have a 3–5% chance of developing congenital cardiac disease. if the 22q11 deletion is present, there is a 50% chance of transferring the damaged chromosome, with a high risk of a congenital cardiac abnormality. prognosis untreated, tetralogy of fallot rapidly results in progressive right ventricular hypertrophy due to the increased resistance caused by narrowing of the pulmonary trunk.: 199 this progresses to heart failure which begins in the right ventricle and often leads to left heart failure and dilated cardiomyopathy. mortality rate depends on the severity of the tetralogy of fallot. if left untreated, tof carries a 35% mortality rate in the first year of life, and a 50% mortality rate in the first three years of life. patients with untreated tof rarely progress to adulthood. patients who have undergone total surgical repair of tetralogy of fallot have improved hemodynamics and often have good to excellent cardiac function after the operation with some to no exercise intolerance (new york heart association class i-ii). long-term outcome is usually excellent for most patients, however residual post-surgical defects such as pulmonary regurgitation, pulmonary artery stenosis, residual vsd, right ventricular dysfunction, right ventricular outflow tract obstruction may affect life expectancy and increase the need for reoperation.: 205 cardiovascular and cerebrovascular complications in patients with repaired chd such as tof occur earlier in life compared to healthy subjects. chronic pulmonary regurgitation and right ventricular dilation and dysfunction is also common. within 30 years after correction, 50% of patients will require reoperation. the most common cause of reoperation is a leaky pulmonary valve (pulmonary valve insufficiency). this is usually corrected with a procedure called pulmonary valve replacement.: 136 one common prognostic factor with tof is the development of ischemia reperfusion injury. insufficient myocardial protection is considered one of the main causes of death in the correction of tof. comorbidities there are many comorbid conditions that can occur with tof that may exacerbate the condition. often, tof can present with low birth weight and prematurity. in both of these cases, mortality and morbidity were both seen to increase. differences in right atrial and ventricular mechanics and liver stiffness was also observed in adults with repaired tof, as well as pulmonary atresia and persistent pulmonary stenosis. in patients with pulmonary atresia, there is complete failure of forward flow from the right ventricle to the pulmonary arterial vasculature. as such, pulmonary blood flow is entirely dependent on shunting from the systemic circulation, typically through a patent ductus arteriosus. the pathophysiology of tof together with pulmonary arteriosus is uniquely attributable to defects of the pulmonary arteries. even after operative care, these patients remain at higher risk for pulmonary arterial stenoses and pulmonary hypertension. danon disease, which is a rare genetic disorder, was also observed to complicate tof. in particular, elongation of the qrs complex and a shortened pr interval. genetic abnormalities found in tof may lead to the earlier diagnosis of danon disease, helping to improve prognostic outcomes. epidemiology the prevalence of tetralogy of fallot is estimated to be 0.02–0.04%, which corresponds to approximately 200 to 400 cases per million live births. it accounts for 7–10% of all congenital heart abnormalities, making it the most common cyanotic heart defect.: 100–101 although males and females were initially believed to be affected equally, more recent studies have shown tof affects males more than females. about 1 in 100 newborns is diagnosed with a congential heart defect, of which 10% are diagnosed with tof. genetically, it is most commonly associated with down syndrome and digeorge syndrome. down syndrome and other chromosomal disorders are known to occur alongside congential heart defects such as tof. history tetralogy of fallot was initially described in 1671 by the danish researcher niels steensen. also referenced as nicolaus steno in latin, stensen was a pioneer in anatomy and geology. his work made significant contributions to the field of cardiac anatomy and pathology, which led to the condition initially being titled steno-fallot tetralogy. a further description was published in 1888 by the french physician étienne-louis arthur fallot, after whom it was ultimately named. in 1924, maude elizabeth seymour abbott, a pediatric cardiologist from montreal, canada, named it tetralogy of fallot. the short paper "dissection of a monstrous foetus in paris" in 1671 first described the conditions that would later together be known as tof. in particular, it highlighted the unusual formation of arteries, the stenosing of the pulmonary artery, the absence of the ductus arteriosus, an overriding aorta, and fetal cardiac circulation where blood was redirected to the aorta from the pulmonary artery. over a hundred years later in 1777, dutch physician eduard sandifort reported what he referred to as "the blue boy" patient. this patient, who was 16 months old, was initially thought to have asthma, though an autopsy postmortem revealed a cardiac malformation with no ductus arteriosus or ligamentum arteriosum, indicating that the child may have died from tof. another 13-year-old patient was reported by scottish physician william hunter in 1782. hunter described the patient, along with three others, as suffering from cyanosis after a posthumous examination in 1774. other cases, such as those presented by pulteney (1785), abernethy (1793), bell (1797), dorsey (1812), and farre (1814) also contributed to modern understandings of tof. the first reported case of tof was in america at the university of pennsylvania in 1816, with more cases being reported by peacock (1858 and 1869), widman (1881), and finally fallot (1888), after whom the condition is named. fallot was the first to elegantly describe the four key features that differentiate it from other cyanotic cardiac conditions, and was prominent in the disqualification of a patent foramen ovale as a fifth feature. fallot initially referred to it as "la maladie bleue", which is french for "the blue disease" or "cyanose cardiaque", translating to "cardiac cyanosis". the first surgical repair was carried out in 1944 at johns hopkins. the procedure was conducted by surgeon alfred blalock and cardiologist helen b. taussig, with vivien thomas also providing substantial contributions and listed as an assistant. this first surgery was depicted in the film something the lord made. it was actually helen taussig who convinced alfred blalock that the shunt was going to work. 15-month-old eileen saxon was the first person to receive a blalock–thomas–taussig shunt. furthermore, the blalock-thomas-taussig procedure, initially the only surgical treatment available for tetralogy of fallot, was palliative but not curative. the first total repair of tetralogy of fallot was done by a team led by c. walton lillehei at the university of minnesota in 1954 on an 11-year-old boy. total repair on infants has had success from 1981, with research indicating that it has a comparatively low mortality rate. today the adult tof population continues to grow and is one of the most common congenital heart defect seen in adult outpatient clinics.: 100–101 related disorders the following illnesses have symptoms that are comparable to tetralogy of fallot. for a differential diagnosis, comparisons between these disorders provides valuable knowledge. atrial septal defects atrial septal defects (asds) are a kind of congenital heart abnormality in which a tiny opening exists between the two atria of the heart. the burden on the right side of the heart is increased as a result of these abnormalities, as is the blood flow to the lungs. this leads to excessive blood flow to the lungs and an increased workload on the right side of the heart. another common finding associated with asds is right ventricular hypertrophy, also known as enlargement of the right ventricle. ventricular septal defects ventricular septal defects (vsds) are a kind of congenital heart abnormality in which one of the ventricles is missing. two atria and one big ventricle are common in infants with congenital abnormalities. symptoms of these diseases include an unusually high rate of breathing (tachypnea), a blue hue to the skin (cyanosis), wheezing, a rapid heartbeat (tachycardia), and/or an abnormally enlarged liver, which are similar to those of other congenital heart problems (hepatomegaly). vsds can also lead to a build-up of fluid around the heart, which can lead to congestive heart failure. atrioventricular septal defect atrioventricular septal defect (avsd) is an uncommon congenital heart condition characterized by faulty development of the heart's septa and valves. congestive heart failure is common in infants with the entire version of the condition. fluid builds up in other parts of the body, particularly the lungs. breathing difficulties may result from pulmonary congestion (dyspnea). mitral valve stenosis mitral valve stenosis is an uncommon cardiac abnormality that can occur at birth (congenital) or develop later in life (acquired). the aberrant narrowing of the mitral valve's opening characterizes this condition. there are two versions of this condition known as congenital and acquired characterized by different symptoms. congenital mitral valve stenosis symptoms include a wide array such as respiratory infections, breathing difficulties, heart palpitations and coughing. acquired mitral valve stenosis symptoms also include a wide array such as consciousness losses, angina, general weakness and abdominal discomfort. notable cases shaun white, american professional snowboarder and skateboarder beau casson, australian cricketer dennis mceldowney, new zealand author and publisher max page, volkswagen's "little darth vader" from the 2011 super bowl commercial billy kimmel, the son of talk show host jimmy kimmel; billy's diagnosis led kimmel to discuss access to health care on his show jimmy kimmel live!