Patent Ductus Arteriosus (PDA) Preterm Ductus

Anatomy & Physiology

The ductus may be small or as large as the descending aorta. The degree of shunting depends upon the relative resistance between the systemic and pulmonary circulations. If the pulmonary resistance is low then a large amount of blood flows into the pulmonary artery in both systole and diastole causing the continuous murmur. The increased pulmonary flow decreases lung compliance. The increased pulmonary flow returns to the left side of the heart which is therefore volume loaded and becomes hypertrophied.

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Presentation

Unless there is a large left to right shunt when failure to thrive, and recurrent chest infections occur the child may well be asymptomatic. The pulse volume may be increased, the precordium is often active and there is a continuous murmur in the left infraclavicular region.

Investigations

Electrocardiogram

If there is a significant shunt then there will be left ventricular hypertrophy evident.

Chest Xray

If there is a significant left to right shunt then the heart will be enlarged and pulmonary plethora present.

Echocardiogram

This easily allows the ductus to be seen and the size measured. An estimate of the shunt size can be made from the Doppler pattern and the size of the left atrium and left ventricle.

Natural History

Untreated even an asymptomatic ductus has a risk of endocarditis and if there is a significant shunt heart failure can occur.

Management
Closure is thus recommended once the chance of spontaneous closure has passed (a few months of age). The transcatheter method is preferred with either a stainless steel coil or a nitinol mesh plug depending upon the size. In either case the technique is usually undertaken under general anaesthetic with fluoroscopic guidance.
Coil Occlusion
The femoral artery is usually accessed for coil occlusions although the venous approach is also possible. The PDA is crossed with a catheter and the straightened out coil screwed to a stiff wire is pushed with the wire through the catheter and just advanced into the pulmonary artery. As it is pushed out of the catheter a coil forms. The catheter is then withdrawn releasing the loops of coils. When it is in a satisfactory position the coil is unscrewed form the wire and the wire and catheter removed.


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Amplatzer® Occlusion
The PDA plug (Amplatzer®) is always deployed from the venous side. A catheter is advanced from the femoral vein through the right heart to the ductus and out into the aorta. The device is attached to a wire by a screw thread, collapsed down and inserted into the catheter. It is advanced through the catheter by pushing the wire. As it reaches the end of the catheter the disc springs open. The catheter and device are then pulled back so the disc is pulled against the aortic wall. The catheter is then withdrawn enabling the plug to fit snuggly in the ductus. The wire is then unscrewed from the device and withdrawn along with the catheter.

Hover the mouse over the heart to see the animation

Prognosis

Once closed the prognosis is excellent with a normal lifespan.

Preterm Ductus

A premature baby may present with increasing need for respiratory support, acidosis. Correctable parameters such as anaemia, sepsis, hypoxia and volume overload should first be corrected if possible. Diuretic treatment and fluid restriction are also helpful. Antiprostaglandin drugs (indomethacin or ibuprofen) should be given if there are no contraindications (renal failure, NEC, low platelets, bleeding - intracranial, intrapulmonary or GI). Surgical ligation should be undertaken if treatment fails or is contraindicated.