Truncus Arteriosus

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Thirty percent of patients have DiGeorge’s syndrome and chromosome 22q11 deletion

• Clinical presentation is congestive heart failure or cyanosis, depending on pulmonary blood flow and associated lesions

• Imaging studies show a single great vessel arising from the heart and a single semilunar valve that gives rise to the aorta, the pulmonary arteries, and the coronary arteries

GENERAL CONSIDERATIONS

• Truncus arteriosus is an uncommon congenital anomaly, characterized by a single arterial trunk with a single semilunar valve (truncal valve) arising from normally formed ventricles

• The defect arises from a failure of the single truncus in the embryo to divide into pulmonary and aortic vessels

• The pulmonary artery, aorta, and coronary arteries arise from a single main trunk

• In one-third of patients, the truncal valve is bicuspid or quadricuspid

• Truncal valve regurgitation occurs in 50% of patients

• Associated anomalies include:

  • – Coronary artery anomalies

  • – Interrupted aortic arch

  • – Persistent left superior vena cava

  • – Aberrant subclavian artery

  • – Atrial septal defect

  • – Atrioventricular septal defect

• Combined ventricular output is directed into the common arterial trunk, and the magnitude of pulmonary blood flow is determined by the ratio of resistances to flow in the pulmonary and systemic vascular beds

• Because of mixing of the systemic and pulmonary venous blood, decreased systemic arterial oxygen saturation is common

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Young infants may present with pseudo-sepsis and shock from high-output failure as a result of significant pulmonary overcirculation

• Poor feeding

• Diaphoresis

• Congestive heart failure symptoms

PHYSICAL EXAM FINDINGS

• Cyanosis

• Tachypnea

• Elevated jugular venous pulsation

• Pulmonary rales

• Single S₂ systolic flow murmur

• Diastolic murmur along the left sternal border from truncal valve regurgitation

• An S₃ gallop may be present

• Crescendo/decrescendo murmurs in the lung fields may be due to branch pulmonary stenosis

DIFFERENTIAL DIAGNOSIS

• Tetralogy of Fallot with pulmonary atresia

• Double outlet right ventricle

• Origin of the right pulmonary artery from the aorta

• Other causes of cyanosis or heart failure

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Arterial blood gases: reveal arterial oxygen desaturation of varying degrees

ELECTROCARDIOGRAPHY

• Normal QRS axis or minimal right-axis deviation

• Biventricular hypertrophy

• Left atrial enlargement and increased left ventricular forces in patients with substantial pulmonary overcirculation

IMAGING STUDIES

• Chest x-ray:

  • – Cardiomegaly and increased pulmonary vascular marking

  • – A plethoric single truncal root may be detected

  • – A right aortic arch in some patients

• Echocardiography is sufficient to confirm diagnosis; characteristic findings—a single arterial trunk arising from the ventricles with variable override of the ventricular septum

  • – Two-dimensional imaging can determine the number, thickness, ...