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Key Features

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Essentials of Diagnosis
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  • Hypoxemic spells during infancy

  • Right-sided aortic arch in 25% of patients

  • Systolic ejection murmur at the upper left sternal border

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General Considerations
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  • Most common cyanotic cardiac lesion

  • Accounts for 10%of all congenital heart disease

  • Atrial septal defect occurs in 15%

  • Obstruction to right ventricle (RV) outflow with a large ventricular septal defect (VSD) causes a right-to-left shunt at the ventricular level with arterial desaturation

  • The greater the obstruction and the lower the systemic vascular resistance, the greater the right-to-left shunt

  • Associated with deletions in the long arm of chromosome 22 (22q11, DiGeorge syndrome) in as many as 15% of affected children; this is especially common in children with an associated right aortic arch

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Clinical Findings

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Symptoms and Signs
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  • Few children are asymptomatic

  • Cyanosis

  • Easy fatigability

  • Dyspnea on exertion

  • Clubbing of fingers and toes

  • Growth and development are not typically delayed

  • Hypoxemic spells are one of the hallmarks of severe disease

    • Also called cyanotic or "Tet spells"

    • Can occur spontaneously and at any time

    • Episodes most commonly start at age 4–6 months

    • Characterized by

      • Sudden onset of cyanosis or deepening of cyanosis

      • Dyspnea

      • Alterations in consciousness, from irritability to syncope

      • Decrease or disappearance of the systolic murmur (as RV the outflow tract becomes completely obstructed)

    • On examination, an RV lift is palpable

    • S2 is predominantly aortic and single

    • A grade II–IV/VI, rough, systolic ejection murmur is present at the left sternal border in the third intercostal space and radiates well to the back

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Diagnosis

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Laboratory Findings
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  • Elevated hemoglobin, hematocrit, and red blood cell count due to chronic arterial desaturation

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Imaging
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  • Chest radiographs

    • Show a normal-size heart

    • RV is hypertrophied, often shown by an upturning of the apex(boot-shaped heart)

    • Main pulmonary artery segment is usually concave

    • If there is a right aortic arch, the aortic knob is to the right of the trachea

    • Pulmonary vascular markings are usually decreased

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Diagnostic Studies
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  • Electrocardiography

    • QRS axis is rightward, ranging from +90 to +180 degrees

    • P waves are usually normal

    • RV hypertrophy is always present

    • RV strain patterns are rare

  • Echocardiography

    • Reveals thickening of the RV wall, overriding of the aorta, and a large subaortic VSD

    • Obstruction at the level of the infundibulum and pulmonary valve can be identified

    • Size of the proximal pulmonary arteries can be measured

    • Anatomy of the coronary arteries should be visualized, since abnormal branches crossing the RV outflow tract are at risk for transection during surgical enlargement of the area

  • Cardiac catheterization

    • Establishes coronary artery and distal pulmonary artery anatomy when not clearly defined by echocardiography

    • Perform in patients with hypoplastic pulmonary arteries

    • Reveals a right-to-left shunt at the ventricular level in most cases

    • Arterial desaturation of varying degrees is present

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