Congenitally Corrected Transposition Clinical Presentation

Symptoms usually reflect associated cardiac anomalies. The uncommon patient with isolated congenitally corrected transposition of the great vessels should be asymptomatic early in life. The diagnosis may be established via a chest radiograph or electrocardiogram performed for another reason; otherwise, this condition is usually diagnosed later in childhood or in early adult life when patients present with complete heart block or heart failure due to right ventricular decompensation or systemic tricuspid valve regurgitation. The most common presenting features are (1) bradycardia related to high-degree AV heart block; (2) a single loud second heart sound, which is often palpable to the left of the sternum, arising from the anteriorly positioned aortic valve; (3) heart murmur due to associated ventricular septal defect, pulmonic stenosis, or tricuspid regurgitation; (4) cyanosis; (5) heart failure; or (6) tachyarrhythmia. Associated cardiac structural findings include the following:

• Atrial situs: The atria are situs solitus in 85-90% of patients.
• Ventricular septal defect: This is the most common associated cardiac malformation, with an incidence of 60-70% in clinical series and nearly 80% in reviews of autopsied cases.

  • The defect is usually large and perimembranous in location but can occur in any position along the ventricular septum.
  • The perimembranous ventricular septal defect tends to be subpulmonary.
  • Subarterial ventricular septal defects, roofed by the semilunar valves, have been described in Asian patients but are uncommon in the Western world.
  • The resulting left-to-right shunt is usually large.
• Conduction system abnormalities

  • The sinus node is positioned normally but the anatomical situation precludes normal conduction because the AV conduction tissue is profoundly abnormal. The normal AV node cannot give rise to the penetrating AV bundle. An anomalous second AV node is the functional AV conduction system in many patients, generally located beneath the opening of the right atrial appendage at the lateral margin between the pulmonic valve and the mitral valve; thus, the node has an anterior position and gives rise to the AV bundle immediately underneath the right anterior pulmonic valve leaflet. This accessory node is not always present and may be hypoplastic or nonfunctional.
  • Complete heart block occurs in 30% of patients and may be present at birth or develop at a rate of 2% per year. Other conduction disturbances described include sick sinus syndrome, atrial flutter, re-entrant AV tachycardia due to an accessory pathway along the tricuspid valve annulus, and ventricular tachycardia.
• Coronary anatomy

  • The coronary arteries have a mirror image location.
  • Dabizzi et al found coronary artery-ventricular concordance in 11 of 13 patients who underwent angiography.^[6] Early entrapment of coronaries in fat or myocardium is also common in this cohort of patients.
• Left ventricular outflow tract obstruction

  • Left ventricular outflow tract obstruction (pulmonary outflow tract) occurs in 30-50% of patients and is typically associated with a ventricular septal defect. Freedom reported that, of patients with pulmonary outflow tract obstruction and a ventricular septal defect, approximately one third have tricuspid valve deformities.
  • Multiple obstructive lesions have been described, including wedging of the outflow tract by inverted mitral and tricuspid valves, fixed infundibular and valvar pulmonic stenosis, tissue bags derived from intact or perforated membranous septum, blood cysts attached to the pulmonary valve, or a subpulmonic tag originating from both sides of the ventricular septum.
• Abnormal tricuspid valve morphology: Incidence is 90% in autopsy series, but clinically relevant abnormalities are less common and include dysplasia (malformed or imperforate leaflets), apical displacement of the septal leaflet (Ebstein-like malformation), or straddling and overriding of an inlet ventricular septal defect.
• Straddling or overriding left AV valve (also abnormalities of cusp number or tension apparatus)
• Coarctation of the aorta
• Interruption of the aortic arch
• Aortic or subaortic stenosis
• Hypoplasia of one ventricle: Usually, the disturbed AV valve is ipsilateral to the hypoplastic chamber.
• Common arterial trunk (functional or anatomic aortic atresia)
• Abnormal conduction tissue

The physical findings depend on the associated anomalies.

• In patients with large left-to-right shunts, the precordium is hyperdynamic, with evidence of cardiac enlargement.
• Individuals with pulmonic stenosis tend to have a relatively quiet precordium, and cyanosis is prominent.
• A loud and often palpable single second heart sound is commonly present at the left sternal border and is related to the anterior and leftward position of the aorta.
• The murmur of left AV valve (tricuspid) regurgitation may be mistaken for the typical pansystolic murmur of ventricular septal defect since it is often maximal at the fourth intercostal space near the sternum rather than at the apex, reflecting the side by side orientation of the ventricles in congenitally corrected transposition with the ventricular septum in the sagittal plane.
• Although the murmur of pulmonary stenosis is often heard well at the pulmonary area, it may be loudest lower on the left side or at the aortic area, because of the inferior and posteriorly displaced pulmonary valve.

Causes and exposures associated with congenitally corrected transposition of the great arteries have not been identified clearly.

A substantial number of patients with congenital heart disease have a deletion of chromosome band 22q11. These deletions have been associated with abnormalities of the pulmonary arteries and aortic arch or its major branches regardless of the intracardiac anatomy.^[7] Rarely, these deletions are found in patients with transposition of the great vessels. In one series, none of 45 patients with transposition had the deletion.