Rush Center for Congenital
and Structural Heart Disease

Definition

 

   

 

Incidence

 

Patent ductus arteriosus is the 6th most common congenital heart defect. It is quite frequent in premature babies. In the past there were seasonal variation of the incidence of patent ductus arteriosus due to Rubella infection close to delivery. However, this is not common nowadays due to immunization. Patent ductus arteriosus risk is also increased at higher altitude due to sub-ambient oxygen concentration.  

 

 

Embryology

 

The sixth aortic arch arteries develop in the middle of the fifth week.  The proximal portions develop into the main and right pulmonary arteries, while the distal portion of the left aortic arch artery develop into the ductus arteriosus  

 

 

Pathology

 

The ductus arteriosus originates embryologicaly from the left aortic arch artery therefore it connects the left pulmonary artery to the aortic arch opposite to the left subclavian artery. Patent ductus arteriosus when it closes it usually does so beginning from the pulmonary artery end, leaving a diverticulum in the aortic site which eventually closes. The patent ductus arteriosus goes into the left pulmonary artery even in right aortic arch. Rarely does it originates from the right pulmonary artery. In tetralogy of Fallot the patent ductus arteriosus is usually absent or small. In pulmonary atresia the patent ductus arteriosus is small because in-utero the blood shunts left-to-right in small volumes to the lungs. In premature babies the patent ductus arteriosus closes later than it would in term babies. However, if the prematurity is taken into consideration it closes about the same time. Patent ductus arteriosus closes with high oxygen tension which explains why at high altitude the patent ductus arteriosus remain patent for a longer time. Oxygen concentration above atmospheric level does not assist in closing the patent ductus arteriosus faster then it would naturally. The etiology of higher incidence of patent ductus arteriosus in maternal rubella infection is not clear but it could be due to tissue changes in the ductus arteriosus similar to those observed in right pulmonary artery and left pulmonary artery branches. Indomethicin if given to the mother at pre-term will cause the patent ductus arteriosus to constrict. This is due to interference with the arachidonic derivative causing lack of Prostaglandin. Supplemental oxygen will cause the patent ductus arteriosus to close in full term but not in premature babies. On the other hand, prostaglandin is better at keeping the patent ductus arteriosus open in premature babies versus full term babies. Polycythemia in patent ductus arteriosus with pulmonary vascular obstructive disease and right-to-left shunting tends to be more so than other cyanotic congenital heart disease. This is thought to be because of increased cyanotic blood flow to the kidneys triggering the mechanism for polycythemia.  

 

 

Pathophysiology

 

The murmur in patent ductus arteriosus is characterized as being systolic and diastolic with a crescendo and decrescendo pattern, peaking at around the closure of the aortic valve (A2). Due to the left-to-right shunting at the patent ductus arteriosus the pulmonary venous return will be increased causing dilatation of the left atrium and stretching of the patent foramen ovale with more left-to-right shunting at the atrial level worsening congestive heart failure. The patent ductus arteriosus murmur is best heard over the second left intercostal space. Clicking noises during the murmur gives the characteristic machinery quality of the patent ductus arteriosus murmur.

Murmurs mimicking patent ductus arteriosus include AP window, venous hum, ruptured sinus of Valsalva (aorta to RA, RV or LA shunts), coronary artery to ventricular cavity fistula and tetralogy of Fallot with pulmonary atresia and large collaterals.

Patients present with congestive heart failure, this include easy fatigability (poor feeding in infants), shortness of breath, pallor sweating and cool extremities with exertion. Signs include bounding pulses, increase left ventricular apical impulse, thrill, continuous murmur and pulmonary sounds consistent with pulmonary edema such as rales and wheezing.

 
 

 

 

Clinical Manifestations

 

The symptoms are those of congestive heart failure secondary to increase pulmonary blood flow.
A continuous systolic and diastolic murmur is audible over the left subclavicular and left upper sternal border.
 

 

 

ECG

 

 
The ECG shows in large patent ductus arteriosus left ventricular hypertrophy and when the pulmonary artery pressure is elevated there will be biventricular hypertrophy pattern. Large patent ductus arteriosus could cause pulmonary vascular obstructive disease as early as ten months but is not usually encountered until after two years of age.

 

 

CXR

 

The chest x-ray shows an enlarged aorta and left atrium as well as left ventricle. There is also dilatation of the pulmonary arteries in severe cases.  

 

 

Echocardiography

 

The ductus arteriosus could be seen in the parasternal short axis and the suprasternal views. Color flow Doppler will show blood flow across the ductus. Pulmonary arterial pressure could be compared to systemic arterial pressure by assessing the pressure gradient across the ductus using Doppler flow velocity.  

 

 

Cardiac Catheterization

 

   

 

 

Treatment

 

The treatment of choice for patent ductus arteriosus is coil occlusion if possible. Indomethacin treatments used in premature babies with significant patent ductus arteriosus is usually given within the first 48 hours of age at a dose of 0.2 mg/kg as a first dose and repeated a second and third time q 12 hours if the patent ductus arteriosus is still open. In premature babies a smaller dose of 0.1 mg/kg is given because of poor renal maturity at that age. Complications of Indomethacin therapy include renal failure, abnormal platelet count and function. Eighty percent of patent ductus arteriosus in premature babies close with Indomethacin therapy.

Large ductus arteriosus may be difficult to close using coils will require surgical closure. In addition patent ductus arteriosus in premature infants who failed indomethacin therapy may not be amenable to coil occlusion because of their small size, these will also benefit from surgical closure.

 
 

 

 

Course and Prognosis

 

   

 

 

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