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L3. Transposition of Great Arteries (TGA):
It represent about 5% of CHD, but it is the most common cyanotic disease present in
the neonatal period.
In TGA the aorta arises from Rt ventricle and pulmonary artery arises from the Lt
ventricle. This will result in desaturated blood return to the Rt side of the heart and
pumped back to the body via the aorta, while the oxygenated blood from the lungs enter
the Lt side of the heart and pumped back to the lungs via the pulmonary artery.
Without mixing of the tow circulations, death occurs shortly after birth. This mixing may
occurs in atrial level (through a patent foramen ovale or ASD) or at ventricles (through a
VSD) or at great vessels (through PDA).
Clinical Features:
1. Cyanosis is always present and its severity depend on the amount of mixing
between systemic and arterial circulations.
2. Tachypnea.
3.
Single S2, and if there’s no VSD there’s no murmur.
4. Children with TGA and large VSD may present with signs of heart failure with
palpable Lt and Rt ventricular impulses, single S2 and load VSD murmur
(pansystolic murmur).
Diagnosis:
1. ECG: shows Rt axis deviation and RVH.
2. CXR: shows increase pulmonary vascularity and classical cardiac shadow which
called egg on a string caused by narrow superior mediastinum.
3. Echocardiography: shows the transposition of great artery, site and amount of the
shunt and any associated anomalies.
Treatment:
1. Prostaglandin E1 infusion immediately after birth to maintain the patency of ductus
arteriosus and allow mixing of the blood.
2. Balloon
atrial septostomy done if there’s no response to prostaglandin infusion.
3. Complete surgical repair by arterial switch operation, in which the aorta is
reconnected to the Lt ventricle and the pulmonary artery is reconnected to the Rt
ventricle. It is usually done within the first 2 weeks of life.
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Acquired Heart Diseases
Infective Endocarditis (IEC):
It include acute and subacute bacterial endocarditis in addition to non-bacterial
endocarditis caused by viruses, fungi and other microorganisms.
It is a significant cause of morbidity and mortality in children and adolescents.
IEC is often complicate CHD or rheumatic heart diseases and prosthetic heart valves,
but it can occur in children without any cardiac abnormalities (native heart).
Pathogenesis:
IEC is a consequence of jet streams of turbulent blood (from PDA, VSD, or systemic-
pulmonary shunt) which cause damage of vascular endothelium causing nonbacterial
thrombotic embolus which thought to be the initiating lesion for IEC.
Predisposing factors:
1. Prior congenital or rheumatic heart diseases.
2. Preceding dental, urinary tract or intestinal procedures.
3. Intravenous drug use.
4. Central venous catheter.
5. Prosthetic heart valve.
Causative MO (Etiology):
Streptococcus Viridans (alpha-hemolytic streptococci) and Staphylococcus
aureus are the most common causative agents for bacterial endocarditis.
Other MO e.g. St. pneumoniae, H. influenzae, coagulase-negative staphylococci and
fungi are less common.
In about 6% of cases, the blood culture is negative for any microorganism.
Clinical Features:
A. Symptoms:
1. Early manifestations are usually mild especially when St. Viridans is the infective
MO which include prolonged fever without other manifestations (except
occasionally weight loss) which might persist for several months.
2. Or the onset might be acute and sever with high intermittent fever and prostration
3. Other
“nonspecific” symptoms include fatigue, myalgia and arthralgia, headache,
chills, nausea and vomiting, chest and abdominal pain, dyspnea, night sweating
and CNS manifestations (stroke and seizures).
B. Clinical signs:
1. Elevated body temperature.
2. Tachycardia.
3. Petechiae.
4. New or changing heart murmur.
5. Splenomegaly.
6. Signs of heart failure and arrhythmias.
7. Clubbing.
8. Metastatic infections (Arthritis, meningitis, Mycotic arterial aneurysm, pericarditis,
abscesses, septic pulmonary emboli).
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9. Classical skin signs: it developed later in the course of the disease and they may
represent vasculitis caused by circulating Ag-AB complexes. These signs are:
a. Osler nodes (tender, pea-size intradermal nodules in the pads of the fingers
and toes)
b. Janeway lesions (painless small erythematous or hemorrhagic lesions on
the palms and soles).
c. Splinter
hemorrhages (linear lesions beneath the nails).
Diagnosis:
1. Blood culture: Is the main way for confirmation of diagnosis. 3-5 blood samples
should obtained for culture after perfect sterilization of skin to prevent contamination
because the bacteria which might contaminated skin might themselves the cause of
IEC.
In 90% of the cases, the causative agent is recovered from the first 2 blood cultures.
The timing of blood collection is not important because the bacteremia is relatively
constant.
The bacteremia is low grade in 80% of cases (<100 colony units\ ml of blood), so the
laboratory should be notified that IEC is suspected, so that, the blood cultured on
enriched media for longer than usual (>7 days) to detect fastidious bacteria or fungi.
2. Elevated ESR and C-reactive protein.
3. CBC shows anemia and leukocytosis.
4. Immune complexes detection.
5. Positive rheumatoid factor.
6. GUE shows hematuria.
7. Echocardiography shows evidence of valve vegetation, prosthetic valve dysfunction,
myocardial abscess, and new-onset valve insufficiency.
Complications:
1. Heart failure (most common) due to vegetation involving aortic or mitral valves.
2. Systemic emboli: CNS and pulmonary embolisms.
3. Mycotic aneurysm.
4. Valvular obstruction by large vegetation.
5. Acquired VSD.
6. Heart block due to involvement of conducting system.
7. Other complications: meningitis, osteomyelitis, arthritis, renal abscess and immune
complex-mediated GN.
Treatment:
1. Antibiotic therapy should be started immediately once the diagnosis is made.
Empirical antibiotic therapy (before obtaining blood culture results) include
Vancomycin (40mg\kg\24 hr in 2-3 divided doses) Plus Ceftriaxone (100mg\kg\24
hr once a day).
Antibiotic therapy should continue for 4-6 weeks and modified according to the blood
culture results.
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If the causative agent is St. Viridans the drug of choice is crystalline penicillin G
(200,000 IU\kg\day) or ceftriaxone
If the patient is sensitive to penicillin, is treated with ceftriaxone plus gentamycin or
Vancomycin.
If the causative agent is staphylococci, so it will treated by naficillin or oxacillin for
6 wk plus gentamycin for 3-5 days (optional).
If the patient is allergic to penicillin, the treatment is ceftazolin for 6 wk plus
gentamycin for 3-5 days (optional).
If the patient is infected by oxacillin-resistance strains then treated with Vancomycin
for 6 wks.
2. Treatment of heart failure by diuretics, after load reducing agents and digoxin.
Prevention:
Previously, antibiotics prophylactic therapy was recommended for any patient at risk for
development of IEC before doing any dental, genitourinary or lower GIT procedures.
But nowadays the prophylactic antibiotics indicated only before dental procedures in
patient with cardiac conditions which are associated with poor prognosis of IEC which
are include:
1. Prosthetic cardiac valve.
2. Previous IEC.
3. Congenital heart diseases:
a. Unrepaired cyanotic CHD including palliative shunts.
b. Completely repaired CHD with prosthetic materials during the first 6 mo after
the procedure.
c. Repaired CHD with residual defect at the site or adjacent to the prosthetic
device.
d. Cardiac transplant recipients.
4. Permanently damaged valve by rheumatic heart disease.
Prophylactic antibiotic regimens for dental procedures:
1. Oral amoxicillin 50 mg\kg.
2. If the patient is unable for oral intake, the prophylaxis by:
Ampicillin 50mg\kg IM or IV
Or Ceftriaxone 50mg\kg IM or IV
3. Patients allergic to penicillin and able for oral intake:
Cephalexin 50 mg\kg
Or clindamycin 20mg\kg.
Or Azithromycin or clarithromycin 15mg\kg.
4. Patients allergic to penicillin and unable for oral intake:
Ceftriaxone 50mg\kg IM or IV.
Or clindamycin 20mg\kg IM or IV.
Prognosis:
Mortality rate of IEC is 20-25% and serious morbidity occur in 50-60% despite of
antibiotic therapy.