7/23/2019 The cause http://slidepdf.com/reader/full/the-cause 1/2 The cause(s) of most congenital heart diseases (CHDs) are unknown, although genetic studies suggest a multifactorial etiology. A study from Portugal reported that methylene tetrahydrofolate reductase (TH!") gene polymorphism can #e considered a suscepti#ility gene for tetralogy of !allot. $%, &' A more recent study has reported that VEGF genetic polymorphisms, &*+CA and -%C/, may #e associated with an increased risk for tetralogy of !allot, whereas the risk is potentially reduced with 0-CT polymorphism. $-' Prenatal factors associated with a higher incidence of tetralogy of !allot (T1!) include maternal ru#ella (or other 2iral illnesses) during pregnancy, poor prenatal nutrition, maternal alcohol use, maternal age older than %3 years, maternal phenylketonuria (P45) #irth defects, and dia#etes. Children with Down syndrome also ha2e a higher incidence of tetralogy of !allot, as do infants with fetal hydantoin syndrome or fetal car#ama6epine syndrome. As one of the conotruncal malformations, tetralogy of !allot can #e associated with a spectrum of lesions known as CATCH (cardiac defects, a#normal facies, thymic hypoplasia, cleft palate, hypocalcemia). Cytogenetic analysis may demonstrate deletions of a segment of chromosome #and 788 (Di/eorge critical region). A#lation of cells of the neural crest has #een shown to reproduce conotruncal malformations. These a#normalities are associated with the Di/eorge syndrome and #ranchial arch a#normalities. The hemodynamics of tetralogy of !allot depend on the degree of right 2entricular ("9) outflow tract o#struction ("91T1). The 2entricular septal defect (9:D) is usually nonrestricti2e, and the "9 and left 2entricular (;9) pressures are e7uali6ed. <f the o#struction is se2ere, the intracardiac shunt is from right to left, and pulmonary #lood flow may #e markedly diminished. <n this instance, #lood flow may depend on the patent ductus arteriosus (PDA) or #ronchial collaterals. Diagnosis Hemoglo#in and hematocrit 2alues are usually ele2ated in proportion to the degree of cyanosis. Patients with significant cyanosis ha2e the following, in association with a tendency to #leed= • Decreased clotting factors • ;ow platelet count • Diminished coagulation factors • Diminished total fi#rinogen • Prolonged prothrom#in and coagulation times Arterial #lood gas (A>/) results are as follows= • 1?ygen saturation 2aries • pH and partial pressure of car#on dio?ide (pC1) are normal unless the patient is in e?tremis <maging studies include the following= • @chocardiography • Chest radiographs • agnetic resonance imaging ("<) @chocardiography has the following attri#utes= • Colorflow Doppler echocardiography accurately diagnoses ductus arteriosus, muscular 9:D, or atrial septal defect • The coronary anatomy can #e re2ealed with some degree of accuracy • 9al2ar alterations can #e detected with ease • <n many institutions, echocardiography is the only diagnostic study used #efore surgery Chest radiographs ha2e the following attri#utes= • 1ften normal initially • Diminished 2ascularity in the lungs and diminished prominence of the pulmonary arteries gradually #ecome apparent • The classic #ootshaped heart ( coeur en sabot ) is the hallmark of the disorder "< has the following attri#utes=

The cause

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7/23/2019 The cause

http://slidepdf.com/reader/full/the-cause 1/2

The cause(s) of most congenital heart diseases (CHDs) are unknown, although genetic studies suggest a

multifactorial etiology. A study from Portugal reported that methylene tetrahydrofolate reductase (TH!") gene

polymorphism can #e considered a suscepti#ility gene for tetralogy of !allot. $%, &' A more recent study has

reported that VEGF genetic polymorphisms, &*+CA and -%C/, may #e associated with an increased

risk for tetralogy of !allot, whereas the risk is potentially reduced with 0-CT polymorphism. $-'

Prenatal factors associated with a higher incidence of tetralogy of !allot (T1!) include maternal ru#ella (or

other 2iral illnesses) during pregnancy, poor prenatal nutrition, maternal alcohol use, maternal age older than

%3 years, maternal phenylketonuria (P45) #irth defects, and dia#etes. Children with Down syndrome also ha2e

a higher incidence of tetralogy of !allot, as do infants with fetal hydantoin syndrome or fetal car#ama6epine

syndrome.

As one of the conotruncal malformations, tetralogy of !allot can #e associated with a spectrum of lesions

known as CATCH (cardiac defects, a#normal facies, thymic hypoplasia, cleft palate, hypocalcemia).

Cytogenetic analysis may demonstrate deletions of a segment of chromosome #and 788 (Di/eorge critical

region). A#lation of cells of the neural crest has #een shown to reproduce conotruncal malformations.

These a#normalities are associated with the Di/eorge syndrome and #ranchial arch a#normalities.

The hemodynamics of tetralogy of !allot depend on the degree of right 2entricular ("9) outflow tract o#struction

("91T1). The 2entricular septal defect (9:D) is usually nonrestricti2e, and the "9 and left 2entricular (;9)

pressures are e7uali6ed. <f the o#struction is se2ere, the intracardiac shunt is from right to left, and pulmonary

#lood flow may #e markedly diminished. <n this instance, #lood flow may depend on the patent ductus

arteriosus (PDA) or #ronchial collaterals.

Diagnosis

Hemoglo#in and hematocrit 2alues are usually ele2ated in proportion to the degree of cyanosis. Patients withsignificant cyanosis ha2e the following, in association with a tendency to #leed=

• Decreased clotting factors

• ;ow platelet count

• Diminished coagulation factors

• Diminished total fi#rinogen

• Prolonged prothrom#in and coagulation times

Arterial #lood gas (A>/) results are as follows=

• 1?ygen saturation 2aries

• pH and partial pressure of car#on dio?ide (pC1) are normal unless the patient is in e?tremis

<maging studies include the following=

• @chocardiography

•

Chest radiographs• agnetic resonance imaging ("<)