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Cardiovascular System Bio 11 Students, Drake University Tuesday 11-2

Introduction
8 out of every 1,000 children born has a heart flaw, these can be minor or life threatening. The heart has four chambers and should idealy pump blood, oxygenating it in the lungs, throughout the body. However, some children are born with a heart flaw and things do not go as smoothly.

A baby's heart beats 22 days after conception, at this stage it is just a simple tube, but within the next few days the small tube starts twisting and turning to form pathways and a heart shape. If some of the heart muscle fails to form or the heart does not twist in exactly the right way then heart flaws are possible. These can usually be detected and repaired before birth with a fetal EKG, or taking an ultrasound of the baby's heart. This is one of the causes of Blue Baby Syndrome, the tissue does not form correctly and leaves a hole in the heart. (3)

Background and History
Methemoglobinemia

The condition methemoglobinemia, also known as Blue Baby Syndrome, is caused by the ingestion of large quantities of nitrates in infants. Methemoglobinemia (Fe3+) is oxidized from the hemoglobin (Fe2+) in the red blood cells in infants (Knobeloch and others 2000). This makes the methemoglobinemia unable to carry oxygen, and the lack of oxygen in the skin leads the infants to have an unusual blue-gray skin color. If not recognized and treated promptly, this condition may result in coma or death of the infant(Knobeloch and others 2000). During the first six months of an infant’s life, it is most susceptible to acquiring methemoglobinemia because the enzyme used to convert methemoglobinemia back into hemoglobin is present in very low amounts in its body (Knobeloch and others 2000).

The largest cause of methemoglobinemia in infants is the use of contaminated well water for preparing an infant’s formula (Knobeloch and others 2000). Another environmental cause is the ingestion of foods that have high nitrate or nitrite concentrations. If treated promptly, noticeable improvement can be seen in the infant’s skin color and temperament within one week (Knobeloch and others 2000). One form of treatment would be to use only bottled water to prepare the infant’s formula.

While contaminated water is a common problem in rural communities, methemoglobinemia only led to six infant deaths between 1979 and 1996 (Knobeloch and others 2000). In less developed countries, methemoglobinemia is also a greater health concern compared to developed countries. For example, anywhere from 24 to 363 cases of methemoglobinemia were reported for every 100,000 live births in Romania in the Transylvania region from the years 1990 to 1994 (Knobeloch and others 2000). Of these cases, the average age of the infants at diagnosis was 39 days old (Knobeloch and others 2000). In Poland over a 14-year period, 239 cases were investigated by the Poison Information Center (Knobeloch and others 2000). Of those 239 cases, 90% were caused by contaminated water (Knobeloch and others 2000).

The United States is a far more developed country than the rural areas of Europe, but there are approximately 15 million families with unregulated wells in the United States that are used for drinking water (Knobeloch and others 2000). It is estimated that almost 2 million families are using water supplies which are above the federal standard for nitrate concentrations (Knobeloch and others 2000). Even though many people are drinking from contaminated water supplies, only two cases of methemoglobinemia have been reported in the United States since the 1960s (Knobeloch and others 2000).

Little information is known about the long-term effects of exposure to high nitrate concentrations. A few studies overseas have suggested that ingestion of nitrate-contaminated water over an extended period of time may increase the risk of gastric cancer, while a study conducted in the United Kingdom associated high rates of cancers of the central nervous system and brain to areas of high nitrate concentrations (Knobeloch and others 2000). There are studies that associate high levels of nitrate concentrations with other health effects such as insulin-dependent diabetes and thyroid disease, and then there are studies that show no correlation between high nitrate levels and these health problems (Knobeloch and others 2000). As one can see, more studies need to be conducted to test the long-term health effects of exposure to high nitrate concentrations.

Tetralogy of Fallot

Tetralogy of Fallot, also known as TOF, is a form of blue baby syndrome in which there are abnormalities in the heart of those afflicted. These abnormalities tend to represent 10% of all congenital cardiac malformations and is the most common congenital heart defect in infants (Doorn 2002, Tan and others 2005). TOF is usually characterized by a defect in the septum dividing the ventricular portions of the heart and any type of obstruction in the outflow of blood in the right ventricle(Doorn 2002). Ventricular septal defects usually come in the form of a hole or defect that allows blood to flow back and forth from the right ventricle to the left ventricle creating a type of shunt between the two ventricles (Doorn). This hole decreases the amount of pressure that the right ventricle can exert on the blood sent to the lungs for oxygenation, leading to the body being deprived of needed oxygen. Defects in the outflow tract or valve of the right ventricle will cause low pulmonary blood flow as well (Doorn 2002). Abnormalities of this nature tend to be quite extensive including hypoplasia and dyplasia of the pulmonary valve, and obstructions blocking blood flow before or after the right ventricular valve itself. (Doorn 2002) When these defects are combined there is a significant drop in pulmonary blood flow which leads to the characteristic blue skin color, known as cyanosis, of TOF.

TOF can be very deadly if no effort is made to surgically repair the specific cardiac abnormalities that are creating the problem. Statistics show that without surgery 35% of children will die in the first year of life, 50% will die with in the third year of life, and a handful will survive to adulthood (Doorn 2002). Even though the history of this disease shows the it has a very high mortality rate it is also one of the most surgically fixable cardiac problems. TOF was the first congenital heart disease to be palliated in 1944 and 10 years later became the first complex cardiac disease to undergo successful surgical repair (Doorn 2002). The advances in cardiology, surgery, and medicine in general have only improved the outlook of patients afflicted with TOF (Doorn 2002). Though improvements have been significant in the repair of TOF it is not a total cure especially in the long run. Follow ups of patients that have under gone surgery to repair TOF has often shown that reparative surgery is often necessary (Doorn 2002). Surgical repair may not be the complete cure but it is definitely a step in the right direction for those suffering from TOF.

Type I:
 * Bluish discoloration to the skin and mucous membranes (6)

Type II:
 * Mental retardation
 * Developmental delay
 * Failure to thrive
 * Seizeures
 * Other Nerologic promblems
 * Death in infancy (6)

Complications that can occur after surgical repair and long term recovery of Tetralogy of Fallot: Often times when these types of symptomatic problems occur the patient must under go operation again to repair the problem (Doorn 2002)
 * regurgitation of blood
 * reduction in exercise capacity
 * right ventricular dialation
 * ventricular arrithymias
 * possible sudden death
 * In cases where valve is replaced by synthetic versions detrioration can occur

Patients with methemoglobinemia from chemical exposure:
 * headache
 * fatigue
 * shortness of breath
 * lack of energy
 * potentially shock
 * seizures
 * death (6)