• 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
Transposition of Great Arteries (TGA)
• 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
Corrected Transposition of Great Arteries (CTGA)
• 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
• Cyanosis at birth
• In VSD or large shunt, symptoms may be minimal in first few weeks of life
• Progressive heart failure
• Murmurs variable, nondiagnostic
• Uncommon in infancy
• Congestive failure eventually develops due to pulmonary stenosis, tricuspid insufficiency
• Heart block (first, second, third) in infancy or later
• Chest film: Enlarged heart, increased pulmonary circulation
• Echocardiography: Diagnostic
• Catheterization: Assess pressures and suitability of LV for switch
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