Tetra logy of fallot is the most common congenital heart disease present in children. This condition is termed as cyanotic heart disorder as it results in inadequate flow of blood to lungs for oxygenation due to shunting as a result of hole in septum of heart.
Tetralogy of fallot is a congenital heart disease which is presented in the form of following four inborn abnormalities of heart
• Ventricular septal defect (VSD): Hole is present in the septum of heart separating ventricles.
• Right ventricular hypertrophy due to narrowing of pulmonary valve.
• Abnormal position of aorta.
• Stenosis of the pulmonary valve.
In tetralogy of fallot these four genetic abnormalities of heart occur. These congenital abnormalities of heart in combination of this disease and lead to cyanosis in child ultimately when left untreated lead to death of child.
There are other abnormalities which are usually associated with this disease are hypospadias, cleft lip or palate, skeletal and craniofacial abnormalities.
• Ventricular septal defect (VSD):
In this defect there occurs hole in the septum of heart which is separating the two ventricles of heart. The two ventricles of heart are left and right, the left ventricle contains pure blood (oxygen rich blood) and right ventricle contains impure blood (oxygen-poor blood). Due to hole present in the septum between the ventricles it leads to mixing of blood in both the ventricles and due to this the oxygenated blood in left ventricle is mixed with the deoxygenated blood and when this deoxygenated blood is pumped to rest of the body through left ventricle this lead to supply of blood which is less in oxygen compared to requirement of the body lead to cyanosis of the body.
• Right ventricular hypertrophy:
Right ventricular hypertrophy occurs when there appears extra pressure by blood on the walls of right ventricle due to narrowing of the passage of blood from right ventricle that is narrowing of pulmonary valve of heart. This narrowing leads to restriction of the blood outflow ultimately leading to increase in right ventricular work and pressure. This work overload leads to right ventricular hypertrophy.
• Abnormal positioning of aorta:
Aorta, the main artery of heart carrying the oxygenated blood from the heart to the circulatory system of the body. The normal outlet of aorta from heart is it rises from left ventricle but in this congenital abnormality of heart that is tetralogy of fallot the aorta exits the heart from the right and left ventricle.
• Stenosis of pulmonary valve (PS):
In tetralogy of fallot the severity of disease depends upon the degree of stenosis of pulmonary valve. As the VSD is already present the severity of disease depends upon the degree of stenosis of the pulmonary valve, if the stenosis is mild then minimal cyanosis occur, but if stenosis is from moderate to high then it leads to increase in cyanosis which is fatal.
Tetralogy of fallot is a congenital heart disorder occurring in infants.
It is estimated that around 3-6 infants out of every 10000 births are affected by this congenital heart disease.
Tetralogy of fallot occur more in males than in females.
There is not particular incidence reported in particular race.
The cause of tetralogy of fallot is unknown but some disease conditions of mother during gestation (pregnancy) period can lead to this disease and they are as follows
• Rubella infection during pregnancy can be a cause.
• Prenatal nutrition lacking.
• Use of alcohol during pregnancy.
• If the age of mother during gestation time is more than 40 years.
• Diabetes during pregnancy.
• Children who are born with Down syndrome are at higher risk of having this disease.
• The major cause of this con genital abnormality is genetic abnormality occurring in genes in chromosome 22. Deletion of segment of chromosome band 22q11 lead to formation of conotruncal malformation. In this malformation tetralogy of fallot is associated with number of lesions known as CATCH 22 include cardiac defects, abnormal faces, thymic hypoplasia, cleft palate, hypocalcemia.
In most of the cases the infants with tetralogy of fallot develop cyanosis in the first few months of life.
• In some cases where there is severe obstruction in right ventricular outflow, they turn blue at time of birth.
• The skin, lips and mucus membranes inside the mouth and nose take appearance of blue color.
• There are very few cases in which signs of cyanosis do not appear because in such cases there is mild pulmonary stenosis and ventricular septal defect is very small.
• In some cases the symptoms remain inert in the infant, symptoms become subtle and in such cases treatment is delayed due to lack of availability of symptoms.
Other symptoms associated with this condition are as follows
• In children suffering from tetralogy of fallot show slower growth and development if the stenosis of pulmonary valve is severe.
• The child gets tired easily with any exertion exercise.
• To resume his breath after physical activity child assumes squatting position to catch his or her breath.
In some cases there are chances of episodes of extreme blue coloring of the body that is extreme cyanosis also known as hypercyanosis or tet spells and this stage occur usually at the age of 2-3 years.
• Child becomes irritable due to repeated attacks of difficult breathing.
• Infants get spells during feeding crying or on straining.
• Spells take time from few minutes to hours.
Tetralogy of fallot is diagnosed by echocardiography.
Another test to help in finding the condition of tetralogy of fallot is X-ray chest. In this test the main finding that indicates tetralogy of falllot is absence of interstitial lung markings.
• Aortic stenosis
• Pediatric apnea.
• Pediatric foreign body digestion.
• Pediatric pneumonia.
• Pulmonary valvular stenosis.
• Sickle cell anaemia.
• Pediatric acute respiratory distress syndrome.
• Pediatric patent ductus arteriosis surgery.
If the case of tetralogy of fallot is unnoticed and left untreated then it can lead to heart failure.
Survival percentages of the patients who are left untreated suffering from this disease are as follows 75% after the first year of life, 60% by four years, 30% by ten years, and 5% by forty years.
Patients who undergo surgery have good prognosis and show good excellent cardiac function.
Treatment can be done with help of beta blockers such as propranolol.
Morphine is also helpful in emergency cases.
In emergency condition simple procedures are also helpful such as squatting and knee chest position.
Surgical procedures which are helpful are as follows
• The pott’s shunt surgery.
• Waterston-cooley shunt.
Other surgical procedures which are very helpful are as follows
Blalock – Thomas-Taussig procedure.
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