Case Presention

Persistent Truncus Arteriosus : An Antenatal Diagnosis

Mrs .G , 25 yrs old primi. Non consangunious marriage, no risk factors.
Early pregnancy dating scan & NT normal.

Scan at 26-27 weeks revealed:
Cephalic presentation. Placenta appeared posterior. Liquor –Normal.
Cardiac activity and Fetal movements normal. Umbilical cord showed 3 vessels.
Fetal outflow tracts difficult to visualize, though 4 CH view appeared normal.

Detailed fetal echocardiography revealed :
Isolated dextrocardia noted.Abdominal organs show normal arrangement. The right sided ventricle is the morphological right ventricle(and the tricuspid valve).The IVC and SVC are seen to confluence with the right atrium. Outflow tract imaging reveals a single large great artery arising from both ventricles. The root of this artery is seen to straddle an outflow segment ventricular septal defect.

The Pulmonary arteries are seen to arise from the left aspect of this arterial trunk just after its origin. The trachea is to the right of the arch formed by this common trunk. The neck arteries are seen to arise from this arch. Foetal heart rate of 154/min noted. Colour Doppler study shows flow of blood fromn both ventricles into the common trunk.

IMPRESSION: Dextrocardia with persistent truncus arteriosus.

Scan pictures:



Owing to the poor prognosis, termination was suggested.
Post mortem of the fetus confirmed the diagnosis.

Discussion: Persistent Truncus arteriosus.

Synonyms: Single outlet of the heart.

Definition: A congenital anomaly in which a single common artery arises from the heart and supplies the coronary, pulmonary, and systemic circulations.

Prevalence: 0.3:10,000 live births, may be slightly less common in males than females (M :]F - 0.72 : F1).

Etiology: Multifactorial inheritance.

Pathogenesis: Failure of the aorticopulmonary septum to develop and separate the truncus arteriosus into the aorta and the pulmonary artery.

Associated anomalies: Truncus arteriosus is frequently associated with other cardiac Anomalies. Extracardiac anomalies also occur in 20% to 50% of cases.

Anomalies associated with truncus arteriosus

Fetal hydrops and cardiac arrhythmias have been described in those cases of truncus arteriosus diagnosed prenatally.

The incidence of chromosomal abnormalities in association with truncus arteriosus has been reported to be approximately 5% (1 in 22). Chromosomal abnormalities reported include partial trisomy 4q, abnormal banding pattern in chromosome 8, and a C﷓G translocation . Trisomy 13 translocation has been detected in a case of truncus arteriosus diagnosed prenatally .

Differential diagnosis: Tetralogy of Fallot, atresia of pulmonary artery.

Prognosis: Persistent truncus arteriosus is associated with a high mortality rate. Approximately 65% of untreated patients do not survive more than 6 months, and up to 90% die before one year of age.

Infants with truncus arteriosus usually develop progressive congestive heart failure. This is due to a large left﷓to﷓right shunt that develops postnatally secondary to the decrease in pulmonary vascular resistance. This shunt may eventually result in pulmonary hypertension. Truncal valve incompetence, when present, usually worsens the progressive congestive heart failure and is associated with a poorer prognosis. Aortic diastolic pressures are frequently low and lead to an increase in pulse pressure and a decrease in coronary blood flow. The decrease in coronary perfusion along with increased myocardial oxygen demand that occurs with congestive heart failure is thought to make these patients more prone to subendocardial ischemia .

Management: Includes careful evaluation for associated anomalies, karyotype analysis, and serial ultrasound examinations to detect signs of congestive heart failure.

When prenatal diagnosis of truncus arteriosus is made before viability, termination of pregnancy can be offered. A meticulous search for associated anomalies should be performed. Chromosomal analysis is advised, especially in the presence of associated anomalies. Serial ultrasonic evaluation is recommended to follow fetal growth, amniotic fluid volume, and to detect signs of fetal hydrops. Truncal valve competence can be assessed with pulsed Doppler or with color flow imaging. If incompetence of the truncal valve is detected, the fetus may be at increased risk of developing hydrops.

If there are no other complicating factors, standard obstetrical management for labor and delivery is recommended. However, it is essential for delivery to occur in a tertiary care center where a pediatric cardiologist is available to assist in the neonatal management of these patients.

Treatment: Surgery is needed to treat this condition. Two procedures are available:one is banding of the pulmonary arteries coming off the truncus; the other is complete repair. Complete repair appears to be the preferred option but as the child grows, repeat surgical procedures may be necessary.