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  • • A congenital heart lesion that decreases pulmonary arterial blood flow

    • Cyanosis and decreased oxygen delivery causes compensatory polycythemia (Hct > 70%) and spontaneous thrombosis

    • Exercise, acidosis, pain worsens cyanosis, can cause hypoxic spells

    • β-Blockers (decreases spasm), fluid intake, HCO3 administration, norepinephrine (increases systemic resistance) may help decrease hypoxia

    • Bronchial and mediastinal arteries enlarge

    • Ductus arteriosus maintains flow to lungs during fetal development

    • Early administration of alprostadil can allow time for optimization before definitive treatment

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Transposition of Great Arteries (TGA)

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  • • Normal ventricular arrangement (D-transposition)

    • Terminology often confusing:

    • -Dextrocardia: Right-sided heart, no relation to "looping" (levocardia is normal)

      -Levo- and dextro- (normal): Refers to ventricular looping; levo-: Right-sided morphologic LV, left-sided RV

      -D-, L-, A-: Indicates malposition of great vessels; letter designates relationship of aorta to pulmonary artery (PA) (D- to the right, normal; L-, to left; A-, anterior)

    Aorta connected to morphologic RV is most common (D-transposition)

    • -Normal looping, rightward aorta connected to RV, left-sided PA connected to LV, 2 independent circulations requiring mixing of blood for survival

      -Atrial septal defect (ASD), patent ductus arteriosus (PDA) common

      -Ventricular septal defect (VSD) in 25%; more common in unusual arrangements

      -LV outflow obstruction may occur

      -Coronary arteries still arise from aortic sinuses facing pulmonary valve, but origin and course may vary and make repair more difficult

      -Cyanosis proportional to mixing of blood

      -In VSD, more risk for pulmonary hypertension due to large left-to-right shunting

      -Normally, LV increases in size at 2-3 wks of life; in TGA, however, RV increases instead due to increased work load

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Corrected Transposition of Great Arteries (CTGA)

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  • • Referred to as L-transposition (true)

    • Right-sided morphologic LV connected to PA, left-sided morphologic RV connected to aorta

    • L- refers to aorta being to left of PA, does not refer to levo- loop

    • Blood flow in series through right and left side, so oxygenated blood reaches systemic

    • VSD in > 75%, subpulmonary obstruction in 50%

    • Coronary pattern reversed to correspond to ventricular arrangement

    • Conduction passes to right side of ventricular septum, superior to VSD

    • Mitral valve = right-sided, tricuspid valve = left-sided

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Symptoms and Signs

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TGA

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  • • Cyanosis at birth

    • -Deterioration with duct closure

      -Worsening hypoxia and acidosis

    • In VSD or large shunt, symptoms may be minimal in first few weeks of life

    • Progressive heart failure

    • Murmurs variable, nondiagnostic

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CTGA

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  • • Uncommon in infancy

    • Congestive failure eventually develops due to pulmonary stenosis, tricuspid insufficiency

    • Heart block (first, second, third) in infancy or later

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Laboratory Findings

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  • ECG: RV hypertrophy

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Imaging Findings

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  • Chest film: Enlarged heart, increased pulmonary circulation

    Echocardiography: Diagnostic

    Catheterization: Assess pressures and suitability of LV for switch

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  • • Evaluate for other cardiac ...

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