Tetralogy of Fallot finale

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Tetralogy of Fallot

Introduction:

Tetralogy of Fallot is a congenital heart defect. This type of heart defect changes the normal flow

of blood through the heart. It is the most common heart defect in children. The condition causes

mixing of oxygen-poor blood with the oxygen-rich blood being pumped out of the heart and into

the circulatory system of blood vessels.

It refers to a combination of abnormalities with four key features:

1)

P ulmonary stenosis: A narrowing of the right ventricular outflow tract and can occur

at the pulmonary valve (valvular stenosis) or just below the pulmonary valve(infundibular stenosis). Infundibular pulmonic stenosis is mostly caused by

overgrowth of the heart muscle wall (hypertrophy of the septoparietal trabeculae),

however the events leading to the formation of the overriding aorta are also believed

to be a cause. The pulmonic stenosis is the major cause of the malformations, with

the other associated malformations acting as compensatory mechanisms to the

pulmonic stenosis. The degree of stenosis varies between individuals with TOF, and

is the primary determinant of symptoms and severity. This malformation is

infrequently described as sub-pulmonary stenosis or subpulmonary obstruction .

2)

V entricular septal defect: A hole between the two bottom chambers (ventricles) of

the heart. The defect is centered on the most superior aspect of the ventricular septum

(the outlet septum), and in the majority of cases is single and large. In some cases

thickening of the septum (septal hypertrophy) can narrow the margins of the defect.

3)

³ Ov erriding´ aorta : An aortic valve with biventricular connection, that is, it is

situated above the ventricular septal defect and connected to both the right and the

left ventricle. The degree to which the aorta is attached to the right ventricle is

referred to as its degree of "override." The aortic root can be displaced toward the

front (anteriorly) or directly above the septal defect, but it is always abnormally

located to the right of the root of the pulmonary artery. The degree of override is

quite variable, with 5-95% of the valve being connected to the right ventricle.

4) Right v entricular hypertrophy : The right ventricle is more muscular than normal,

causing a characteristic boot-shaped (coeur-en-sabot) appearance as seen by chest X-

ray. Due to the misarrangement of the external ventricular septum, the rightventricular wall increases in size to deal with the increased obstruction to the right

outflow tract. This feature is now generally agreed to be a secondary anomaly, as the

level of hypertrophy generally increases with age



C ause:

U nknown

Risk Factors:

y

A viral illness in the mother, such as rubella (German measles), during pregnancy

y

M aternal alcoholism

y

P oor nutrition

y

A mother older than 40

y

A parent with tetralogy of Fallot

y

B abies who are also born with Down syndrome or DiGeorge syndrome

y

Diabetes

S igns and S ymptoms:

y

A bluish coloration of the skin caused by blood low in oxygen (cyanosis)

y

S hortness of breath and rapid breathing, especially during feeding

y

L oss of consciousness (fainting)

y

C lubbing of fingers and toes ² an abnormal, rounded shape of the nail bed

y

P oor weight gain

y

Tiring easily during play

y

Irritability

y

A heart murmur

A natomy and P hysiology:

Heart De v elopment

The heart begins in the embryo from day 18 and is complete by day 56. A primitive straight

cardiac tube composed of an outer myocardium and an inner endocardium loops to form a

primitive atrium and ventricle, followed rapidly by a large truncus arteriosus. The tube doubles

over on itself during the second month of gestation to form two parallel pumping system, each

having two chambers and a great artery ( the truncus arteriosus). As a consequence of this

doubling, the heart begins to situate in the left side of the chest. An endocardial cushion develops

within the common chamber and is the first of the structures to divide the chambers of heart.

From the endocardial cushion, the mitral and tricuspid orifices develop. The large truncus

divides into the aorta and pulmonary arteries. Rotation of the truncus coils the

aortopulmonaryseptum and creates the normal spiral relationship between the aorta and

pulmonary artery. The truncus arteriosus is connected to the dorsal aorta by different times

during the formation of the heart and vessels. Abnormalities of the regression of the arch system



in a number of sites can produce a wide variety of arch abnormalities. P artitioning of the heart is

accomplished by septa that form actively and passively. The major septa of the heart are formed

between the 27 th and 37 th days of development.

T he Normal Heart and How It Works

The normal heart is a strong, hard-working pump made of muscle tissue. It¶s about the size of a

person¶s fist.

The heart has four chambers. The upper two chambers are the atria, and the lower two are the

ventricles (Figure A). B lood is pumped through the chambers, aided by four heart valves. The

valves open and close to let the blood flow in only one direction.

The four heart valves are:

1.

the tricuspid valve, located between the right

atrium and the right ventricle;

2.

the pulmonary (pulmonic) valve, between the

right ventricle and the pulmonary artery;

3.

the mitral valve, between the left atrium and left

ventricle;

4. the aortic valve, between the left ventricle

and the aorta.

Each valve has a set of ³flaps´ (also called leaflets or cusps). The mitral valve normally has two

flaps; the others have three.

Dark bluish blood, low inoxygen, flows back to the heart

after circulating through the

body. It returns to the heart

through veins and enters the

right atrium. This chamber

empties blood through the

tricuspid valve ( B ) into the right

ventricle. The right ventricle

pumps the blood under low

pressure through the pulmonary

valve into the pulmonary artery.

From there the blood goes to the lungs where it gets fresh oxygen ( C ).



After the blood is refreshed with oxygen, it¶s bright red. Then it returns to the left heart through

the pulmonary veins to the left atrium. From there it passes through the mitral valve (D) and

enters the left ventricle.

The left ventricle pumps the red oxygen-rich blood out through the aortic valve into the aorta

(E). The aorta takes blood to the body¶s general circulation. The blood pressure in the left

ventricle is the same as the pressure measured in the arm.

Figure A shows the structure and blood flow in the interior of a normal heart. Figure B shows a

heart with the four defects of tetralogy of Fallot.

B abies and children who have tetralogy of Fallot have episodes of cyanosis . This is a bluish tint

to the skin, lips, and fingernails. C yanosis occurs because the oxygen level in the blood is below

normal.



Diagnostic P rocedures:

Echocardiography

Echocardiography (echo) is a painless test that uses sound waves to create a moving picture of the heart. During the test, the sound waves (called ultrasound) bounce off the structures of the

heart. A computer converts the sound waves into pictures on a screen.

Echo allows the doctor to clearly see any problem with the way the heart is formed or the way

it's working.

Echo is an important test for diagnosing tetralogy of Fallot because it shows the four heart

defects and how the heart is responding to them. This test helps the cardiologist decide when torepair these defects and what type of surgery is needed.

EKG (Electrocardiogram)

An EKG is a simple, painless test that records the heart¶s electrical activity. The test shows how

fast the heart is beating and its rhythm (steady or irregular). It also records the strength and

timing of electrical signals as they pass through each part of the heart.

An EKG also can help the doctor determine whether the right ventricle is enlarged (ventricular

hypertrophy).

C hest X Ray

A chest x ray is a painless test that creates pictures of the structures in the chest, such as the heart

and lungs. This test can show whether the heart is enlarged or whether the lungs have extra blood

flow or extra fluid, a sign of heart failure.

P ulse Ox imetry

For this test, a small sensor is attached to a finger or toe (like an adhesive bandage). The sensor

gives an estimate of how much oxygen is in the blood.

C ardiac C atheterization

During cardiac catheterization a thin, flexible tube called a catheter is put into a vein in the arm,groin (upper thigh), or neck and threaded to the heart.

S pecial dye is injected through the catheter into a blood vessel or a chamber of the heart. The dye

allows the doctor to see the flow of blood through the heart and blood vessels on an x-ray image.



The doctor also can use cardiac catheterization to measure the pressure and oxygen level inside

the heart chambers and blood vessels. This can help the doctor determine whether blood is

mixing between the two sides of the heart.

T reatment:

M edical:

y

administer oxygen(through face mask)

y

administer morphine sulfate(gen.beta bloacker), may be given orally to aid pulmonary

artery dilatation.

Morphine Sulfate (duramorph, astromorph, MS Contin)

D rug of choice for narcotic analgesia because of its reliable and predictable effects, safetyprofile, and easy of reversibility with naloxone

A dministered IV, may be dosed in number of ways and commonly titrated until desired effectobtained.

Metoprolol and Propranolol

Classification: Beta-Blockers

Used to treat tremors, angina, HPN, heart rhythm disorders, and other heart or circulatory conditions. It

also used to treat or prevent heart attack, and reduce the severity of migraine and headaches.

Phenylephrine

Classification- D econgestant

Brand names: A h-Chew D , Lusonal, Nasop, Neo-Syneprine

It works by constricting (shrinking ) blood vessels.

Constriction of blood vessels in the sinuse, nose, and chest allows drainage of these areas, which

decreass congestion. Constriction of blood vessels also affects blood pressure

S urgical:

y

B lalock- T aussig O peration

-T his is a palliative surgical repair. The physician will create a shunt between the

aorta and pulmonary artery.

-T emporary or P alliati v e S urgery

It was common in the past to do temporary surgery during infancy in babies who had tetralogy of

Fallot. This surgery improved blood flow to the lungs. A complete repair of the four defects was

done later in childhood.



N ow, most babies who have tetralogy of Fallot have their defects fully repaired in infancy.

However, some babies are too weak or too small to have the full repair. They must have

temporary surgery first. This surgery improves oxygen levels in the blood. It also gives the baby

time to grow and get strong enough for the full repair.

In the temporary surgery, the surgeon places a tube called a shunt between a large artery

branching off the aorta and the pulmonary artery. One end of the shunt is sewn to the artery

branching off the aorta. The other end is sewn to the pulmonary artery.

The shunt creates an additional pathway for blood to travel to the lungs to get oxygen. The shunt

is removed when the baby's heart defects are fixed during the full repair.

y

C omplete Intracardiac Repair

S urgery to repair tetralogy of Fallot is done to improve blood flow to the lungs and to make sure

that oxygen-rich and oxygen-poor blood flows to the right places. The surgeon will:

y

W iden the narrowed pulmonary blood vessels. The pulmonary valve is widened or

replaced, and the passage from the right ventricle to the pulmonary artery is enlarged.

These procedures improve blood flow to the lungs. This allows the blood to get enough

oxygen to meet the body's needs.y

C lose the ventricular septal defect (V S D). A patch is used to cover the hole in the septum.

This patch stops oxygen-rich and oxygen-poor blood from mixing between the ventricles.

Fixing these two defects resolves problems caused by the other two defects. W hen the right

ventricle no longer has to work so hard to pump blood to the lungs, it will return to a normal

thickness. Fixing the V S D means that only oxygen-rich blood will flow out of the left ventricle

into the aorta.

The incision (cut) that the surgeon makes to reach the heart usually heals in about 6 weeks. The

surgeon or a hospital staff member will explain when it's okay to give your baby a bath, pick him

or her up under the arms, and take your baby for his or her regular shots (immunizations).

C omplications:

1.

C ongestive heart failure- may occur in newborn but is uncommon beyond infancy.

2.

C erebral vascular accident (due to thrombosis or severe hypoxia)



P re v ention:

There is no known prevention for tetralogy of Fallot.

P re v alence Rate:

Tetralogy of Fallot is a rare, complex heart defect that occurs in about 5 out of every 10,000

babies. It affects boys and girls equally.

P rognosis:

S tudies of immediate and long-term follow-up in tetralogy of Fallot reveal excellent outcomes.

P atients born 30 years ago with tetralogy of Fallot have an 85% long-term rate of survival, and in

the absence of serious residue are able to lead normal lives as evidenced by the ability to carry

successful pregnancies for example [35-40]. C hronic issues that face the current population of

adults subsequent to their surgical repair include the hemodynamic manifestations of chronic

pulmonary regurgitation, recurrent or residual pulmonary stenosis, and ventricular arrhythmias.

The prognosis of patients born in the current era is expected to be substantially improved due to

advances in surgical and medical management that have occurred over the past couple of

decades. As for all patients with congenitally malformed hearts, the management of the patientwith Tetralogy of Fallot does not end at the time of complete repair. Follow-up by cardiologists

trained in congenital cardiac disease will remain a lifelong experience.

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Tetralogy of Fallot finale