4.5b Common Truncus (Q20.0)

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Common truncus or common arterial trunk is a structural heart defect characterized anatomically by having a single common arterial trunk, rather than a separate aorta and main pulmonary artery (see Fig. 4.15). This common trunk carries blood from the heart to the body, lungs and the heart itself – that is, the common trunk gives rise to the systemic, pulmonary and coronary circulation. A ventricular septal defect is present. Other terms for the condition are (persistent) truncus arteriosus.

The anatomy of common truncus varies, especially in the origin of the pulmonary arteries from the common truncus. Such variations are the basis of the two main classifications: the Edwards classification (types I–IV, of which types I–III are properly common truncus) and the van Praagh classification (A1–A4).

Fig. 4.15. Common truncus

Relevant ICD-10 codes

Q20.0 Common arterial trunk

Diagnosis

Prenatal. Common truncus can be diagnosed prenatally by fetal echocardiography, although in some cases it might be difficult to conclusively distinguish from other conditions (e.g. pulmonary atresia with ventricular septal defect or aortic atresia with ventricular septal defect). Common truncus can be missed prenatally if the outflow tract is not fully examined. Prenatal diagnoses should be confirmed postnatally, typically by echocardiography.

Postnatal. The clinical findings after birth depend on the volume of pulmonary blood flow and the status of the truncal valve (e.g. degree of valvar insufficiency). If the valve is severely insufficient, the infant might present early with heart failure, which might be characterized by fast breathing, fast heart rate, poor feeding and excessive sweating. Otherwise, the physiologically high pulmonary vascular resistance at birth will delay this presentation and lead to a degree of cyanosis, usually mild, at the outset.

Newborn screening for critical CHD via pulse oximetry can detect common truncus if sufficient degree of hypoxia is present at the time of screening.

Clinical and epidemiologic notes

As noted, the clinical presentation in the newborn period might include a combination of cyanosis and heart failure.

Common truncus is included among the conotruncal heart anomalies, together with tetralogy of Fallot, interrupted aortic arch type B, and d-transposition of the great arteries. Common truncus can occur in association with genetic conditions – especially deletion 22q11 – and can be familial.

Among modifiable risk factors, maternal pregestational diabetes is common and well established. The birth prevalence of common truncus is approximately is 0.5 to 1 in 10 000 births.

Inclusions

Q20.0 Common truncus

Exclusions

Pulmonary atresia with ventricular septal defect (common truncus type IV in the Edwards classification)

Checklist for high-quality reporting

Checklist for high-quality reporting
Common Truncus – Documentation Checklist
Describe in detail the clinical and echocardiographic findings: Anatomy – specify intracardiac anomalies, including the presence and type of ventricular septal defects, the origins of the pulmonary arteries, and the morphology of the truncal valve. Procedure – specify whether the cardiac findings are from a prenatal or postnatal echocardiogram, or from other investigations (e.g. catheterization, MRI), surgery or autopsy. Additional cardiac findings – specify any additional findings in addition to the basic anatomy of truncus (see above). Look for and document extracardiac birth defects: Common truncus can occur with genetic syndromes such as deletion 22q11, in which many external (e.g. cleft palate) as well as internal anomalies have been described. Report whether specialty consultation(s) have been done: In particular, report whether the diagnosis was done by a paediatric cardiologist, and whether the patient was seen by a geneticist. Report genetic testing (e.g. chromosomal studies, genomic microarray, genomic sequencing): Report whether this was done and if so, the results.

Suggested data quality indicators

Suggested data quality indicators
Category	Suggested Practices and Quality indicators
Description and documentation	Review sample of clinical descriptions for documentation of key elements: Anatomy: Presence of ventricular septal defect, origin of the pulmonary arteries, common valve, additional findings. How cardiac findings were detected (e.g. echocardiography). Who made the diagnosis (e.g. paediatrician, paediatric cardiologist). Specialists who evaluated the child, in particular, if a paediatric cardiologist and geneticist. Key evaluations done, especially genetic testing.
Coding	Coding is straightforward (Q20.0, common truncus/common arterial trunk). A ventricular septal defect is nearly always present so programmes need to have a rule about whether or not to codethe septal defect (many programmes do not code septal defects separately in this setting).
Clinical classification	Track proportion of congenital anomalies and syndromes occurring with common truncus: If < 10%, consider under-ascertainment of these co-occurring conditions, especially deletion 22q11.
Prevalence	Monitor prevalence: If low (< 0.3 per 10 000 births) suggests under-ascertainment. Compare prevalence among the smallest site/time units: Statistically significant dissimilar results suggest a possible methodological problem in one or more site/time units.