*Department of Obstetrics and Gynaecology, University of Messina, Italy
Tennessee Women"s Care, Nashville, TN

Synonyms:   None

Definition:  The association between an underdeveloped pulmonary artery with valve atresia and a large ventricular septal defect, with or without major aortic-pulmonary collateral arteries ^(4). It is considered the most severe form of tetralogy of Fallot ^(2).

Case report: A patient presented at 19 weeks of gestation.

The views of the heart at 19 weeks are shown, and they demonstrate

• the overriding aorta;
• the hyperechogenic focus;
• the septal ventricular defect;
• the absence of pulmonary flow with the aorta visible in the three vessel view;
• a moderate atrial septal defect.

The fetus was noted to have a single umbilical artery and echogenic cardiac foci. The aorta was seen overriding the interventricular septum with a large ventricular septal defect. The triple screen suggested a risk of 1/500 for trisomy 21 and 1/5000 for trisomy 18.   No amniocentesis was done.  The woman underwent another ultrasound screening during the 38th week.

These are views at 37 weeks, including a 85 MB 4D volume. (Watch out that this is large file and it is probably impractical over modem). If you do not have 4DView or the special 4DFetusView, you can get those from Tools > Computer Pearls > 4DFetusView or simply by clicking: 4DFetusView . The review of the 4D volume is done under Case 149.

The ventricular septal defect and overriding aorta were again noted. The cardiac axis was left deviated and the aorta was descending on the right of the spine. The pulmonary artery could not be detected either in black and white or with Doppler. We suspected that the baby had either a Tetralogy of Fallot or Truncus Arteriosus.

The baby was born at 40 weeks gestation by vaginal delivery with no complications (2,657 g and 54 cm long).He cried at delivery, but remained centrally cyanotic with a slight reduced tone. The Apgars were 7 at one minute and 7 at five minutes.
An echocardiogram and X-rays were performed immediately. The investigations showed:

• pulmonary atresia with ventricular septal defect;
• moderate atrial septal defect;
• right aortic arch;
• multiple aorticopulmonary collateral arteries (MAPCAS);
• single umbilical artery;
• growth restriction;
• hemivertebra in the thoracic spine,
• fused ribs opposite the hemivertebra,
• one butterfly vertebra;
• a sacral dimple (but no evidence of tethered cord or other spinal problems);
• mild hydronephrosis on right kidney (VCUG was normal testing for reflux)
• and VATER syndrome.

The newborn screen suggested a possible thyroid problem (TSH was 183 and T3 was .33) but a FISH test for DiGeorge (22q11deletion) was negative. 
The newborn was put on prostaglandin to maintain the ductus arteriosus. Catheterization demonstrated confluent pulmonary arteries (3mm to 3.5mm) fed from two collaterals arising off the aorta.  The pulmonary arteries are supplying the upper and lower right lobes of the lungs and the upper left lobe.  The lower left lobe is supplied by a collateral originating from the aorta. 
      
History:  According Kutsche and Van Mierop, who studied the morphology of the heart, pulmonary atresia with ventricular septal defect reflects an arrest of the heart maturation earlier than that of pulmonary atresia with and intact ventricular septum. The etiology of this condition may be related to an abnormality of mesenchymal and/or neural crest migration.

Embryology: The main pulmonary trunk originates from truncal septation. The right and left pulmonary artery derives from proximal sixth arch derivative and the ductus arteriosus from distal sixth arch derivatives.
In pulmonary atresia and ventricular septal defect, the heart may have a normal truncal septation connected with aorta through a ductus arteriosus but the right and left branch of pulmonary arteries may originate from the aorta^(1).
The majority of these defects originate in a left-sided heart with concordant atrioventricular connections ^(1). The aorta may override the ventricular septal defect and originate above the right ventricle.

Prevalence: From the New England Regional Infant Cardiac Program the frequency is 0.42:10,000 livebirths.

Sonographic findings:

Findings in 4- and 5-chamber view are similar to those in the tetralogy of Fallot.  In a 3-vessel-view we can find no patent pulmonary valve, the pulmonary artery is very thin or not present and the ductus arteriosus is tortuous.
With color Doppler we can demonstrate the retrograde perfusion of the ductus arteriosus into the pulmonary artery, the aortic flow, the retrograde perfusion of the pulmonary artery, and the anterograde perfusion of main pulmonary artery branches. The retrograde perfusion of the ductus is, sometimes, easier to see during the visualization of the longitudinal aortic arch. It is commonly tortuous.

Implications for targeted examinations:  The echocardiography is very important before the treatment because it has to analyze:
• if there is a complication in the cardiac anatomy,
• if the pulmonary arteries are confluent and how large are they,
• what is their source of blood supply,
• what side is the aortic arch on,
• if the branching of the brachiocephalic vessels are normal and normal size
• and if there are any associated anomalies.
The most important thing is to define the connection of the pulmonary veins.

Differential diagnosis: Truncus arteriosus communis, tetralogy of Fallot and double outlet right ventricle

Associated anomalies: These are 
Extracardiac anomalies:

• Aneuploidies: 20 % deletion 22q11.2

Cardiac anomalies:

• Isomerism
• Right-sided or double aortic arch
• Major Aortic-Pulmonary Collateral Arteries (MAPCA)

Prognosis: The natural history of patients with this disorder is variable and depends on the nature of the pulmonary blood supply.

For those babies with small pulmonary arteries requiring ductal patency, the anatomical and functional closure of the ductus will usually result in an inadequate pulmonary flow, hypoxemia, and death in the newborn period.

The babies with a good aortopulmonary collateral flow will not be hypoxic, but quite pink from congestive heart failure. These babies may not die in the neonatal period, but instead develop an ischemic myocardium and succumb in early infancy, as do babies with truncus arteriosus.

Occasionally we can find some balanced babies that survive until the third or fourth decade of life but, the majority of untreated infants with pulmonary atresia and ventricular septal defect will die in the first decade of life. Survival after complete surgical repair (which is usually carried out in the third month of life) is more than 90% and about 80% of survivors have normal exercise tolerance.

Recurrence risk: Unknown

Management: The most important therapy for the infant is to begin intravenous prostaglandin. If there is no improvement in arterial oxygenation, it's important to see if the ductus arteriosus is present and if it is closed. The baby with the heart failure will benefit of an anti congestive therapy until it is possible to establish the nature of the pulmonary circulation.
The postpartum surgical corrections have to achieve a biventricular heart with a closed ventricular septal defect, continuity between the right ventricle and pulmonary artery, with a low flow pressure.

The operative management of absent pulmonary valve remains controversial regarding the need for pulmonary valve implantation and remodeling of pulmonary arteries. Some authors suggest that surgical treatment of absent pulmonary valve should also include pulmonary arterioplasty to reduce bronchial obstruction, with no need for pulmonary valve insertion. This procedure is feasible and is recommended especially in markedly symptomatic infants ⁽³⁾. The options are:

1) A central aortopulmonary artery shunt (avoiding the smallest branch of pulmonary arteries that could stenose)
2) Reconstruction of the right ventricular outflow tract directly (when the pulmonary atresia is very short) or
3) The creation of an aortopulmonary window with an anastomosis.

Using such techniques, a good correction is possible in many cases ⁽⁴⁾

References

1) Freedom RM, Smallhorn JF, Burrows PE: “Pulmonary atresia and ventricular septal defect” Chap 16: page 230-252 -Neonatal heart disease; Ed. Springer-Verlag 1992

2) Allan L, Sharland G. and Cook A. :“Tetralogy of Fallot” -Ch11: page 101 -Color Atlas of Fetal Cardiology; Ed. Mosby-Wolfe1994

3) Godart F et al:”Absent pulmonary valve syndrome: surgical treatment and considerations”, Ann Thorac Surg. 1996 Jul; 62(1):136-42.

4) Parry A J and Hanley F L: “ Infants with congenital heart disease in the first year of life” Ch37: page 475-476 -Fetal Cardiology, Edited by Yagel S, Silverman N and Gembruch U; Martin Dunitz 2003