The portal for rare diseases and orphan drugs

Prevalence is unknown. Annual incidence has been reported to be around 1/33,000 live births, accounting for approximately 0.05% of congenital heart malformations.

Associated malformations typically include ventricular septal defects, obstructions of the outlet from the morphologically left ventricle, and morphological anomalies of the tricuspid valve, although any anatomically feasible lesion can co-exist. The clinical picture and age of onset depend on the associated malformations, with bradycardia, a single loud second heart sound, and heart murmurs being the most common manifestations. Cyanosis is observed in patients with pulmonary stenosis and a ventricular septal defect, while cardiac failure develops earlier in life if there is a hemodynamically significant ventricular septal defect, evidenced in children by easy fatigability, poor weight gain, and feeding intolerance. In the rare cases where there are no associated malformations, congenitally corrected transposition can lead to progressive atrioventricular valvar regurgitation and failure of the systemic ventricle.

The etiology of congenitally corrected transposition is currently unknown.

Diagnosis can be made by fetal echocardiography, but is more commonly made postnatally based on clinical signs and echocardiography. The anatomical delineation can be further assessed by magnetic resonance imaging (MRI) and catheterization. Diagnosis can also be made late in life when the patient presents with complete heart block or cardiac failure.

The differential diagnosis is centered on assessing whether the patient presents isolated malformations, or a spectrum of malformations, and includes double inlet left ventricle (see this term) with left-sided incomplete right ventricle, isomerism of atrial appendages with left-handed ventricular topology.

Prenatal diagnosis of congenitally corrected transposition can readily be made during fetal life by an experienced sonographer.

CCT is sporadic. There is, however, a higher incidence in families with previous cases of the condition, with a recurrence risk in siblings of between 2.6% to 5.2%.

Medical management involves treatment of the failing systemic morphologically right ventricle, with timing depending on the severity of the associated malformations. It involves treatment with diuretics, angiotensin-converting enzyme (ACE) inhibitors, and digoxin. If there are conduction abnormalities, the patient may require implantation of a pacemaker, for example in the setting of advanced 2nd or 3rd degree atrioventricular block, or in the presence of symptoms of ventricular dysfunction. Surgical management consists of repair of the associated malformations, or redirection of the systemic and pulmonary venous return associated with an arterial switch, the so-called double switch approach. Regular follow-up by a pediatric cardiologist or by an adult cardiologist who has had special training and experience caring for patients with congenital heart disease is recommended.

Prognosis depends on the associated malformations, and on the type and timing of surgical interventions. Life expectancy depends on the associated malformations and the severity of the individual lesions.