Transposition of the Great Arteries, Congenitally Corrected

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Prominent left parasternal impulse, soft S₁, loud single S₂ along the upper left sternal border

• Absence of left-sided aortic knob on chest x-ray

• Ventricular inversion (ie, ventriculoarterial and ventriculoatrial discordance) apparent on cardiac imaging

• Atria usually in normal position

GENERAL CONSIDERATIONS

• Rare condition with male predominance

• Usually associated with other abnormalities such as:

  • – Ventriculoseptal defects

  • – Pulmonic stenosis

  • – Tricuspid valve abnormalities

• When a ventricular septal defect is present, there is a risk of developing pulmonary vascular disease in the absence of pulmonary stenosis because of increased pulmonary blood flow

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• May be asymptomatic until the third or fourth decade of life

• Patients who develop systemic ventricular failure may experience fatigue, dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and edema

• Patients with heart block or tachyarrhythmias may have palpitations and/or syncopal episodes

PHYSICAL EXAM FINDINGS

• Prominent right ventricular impulse

• Loud single S₂ along the upper left sternal border

• Murmurs caused by associated defects (ventricular septal defect, pulmonic stenosis)

• Adults who develop systemic right ventricular failure may have a gallop and/or pulmonary rales

DIFFERENTIAL DIAGNOSIS

• Other causes of complete heart block

• Other causes of heart failure

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• No specific tests

ELECTROCARDIOGRAPHY

• Right atrial enlargement

• P-R prolongation

• Variable degrees of atrioventricular (AV) block

• Right ventricular hypertrophy

• Right-axis deviation

• Q waves in the right precordial leads

IMAGING STUDIES

• Chest x-ray findings:

  • – Absence of left-sided aortic knob

  • – Prominent right atrium and right ventricle

• Echocardiography:

  • – Atria are in the normal position with the morphologic left ventricle situated between the right atrium and pulmonary artery, and the morphologic right ventricle between the left atrium and aorta

  • – The systemic right ventricle is hypertrophied and may be dilated with reduced contractile function

  • – Associated abnormalities may be present, such as a ventriculoseptal defect, abnormalities of the tricuspid valve with variable degrees of tricuspid regurgitation, and/or pulmonary valve stenosis

DIAGNOSTIC PROCEDURES

• In the adult with associated ventricular septal defect, cardiac catheterization may be indicated to determine pulmonary vascular resistance or severity of pulmonic stenosis

TREATMENT

CARDIOLOGY REFERRAL

• All patients with transposition of the great arteries should be followed up regularly by a cardiologist who specializes in congenital heart disease

HOSPITALIZATION CRITERIA

• Atrial or ventricular tachyarrhythmias

• Symptomatic bradycardia

• High-grade AV block

• Heart failure

MEDICATIONS

• Endocarditis ...