Patent ductus arteriosus overview

# Overview
Patent Ductus Arteriosus (PDA) is a remnant of the distal sixth aortic arch and connects the pulmonary artery at the junction of the main pulmonary artery and the origin of the left pulmonary artery to the proximal descending aorta just after the origin of the left subclavian artery. Normally, the ductus closes within a few hours or days of birth; when it does not, the result is patent ductus arteriosus. This defect is common in premature infants but rare in full-term infants. Symptoms include shortness of breath and cardiac arrhythmia, and may progress to congestive heart failure if left uncorrected.

# Anatomy
Patent ductus arteriosus is a heart condition that is normal but reverses soon after birth. In a persistent PDA, there is an irregular transmission of blood between two of the most important arteries (aorta and pulmonary artery) in close proximity to the heart. Although the ductus arteriosus normally seals off within a few days, in PDA, the newborn's ductus arteriosus does not close but remains patent.

# Historical Perspective
PDA is a congenital heart defect when a child's ductus arteriosus fails to close after birth, producing a heart murmur described in 1898 by Gibson as the classic machinery murmur.

# Pathophysiology
The pathophysiological consequences depend on the size of the defect and the pulmonary vascular resistance.

# Causes
Causes of patent ductus arteriosus is not known. However, increased incidence have been associated with mother's rubella and genetic causes

# Epidemiology and Demographics
The PDA is commonly found in infants and constitutes only 2% of all congenital defects found in adults. The incidence is greater is in children who are born prematurely with history of perinatal asphyxia and infants with congenital rubella.

# Risk Factors
Like many congenital heart disease, the cause of patent ductus arteriosus is not clear. Clinical studies suggest that the genetic and environmental factors both play an important role during the pregnancy.

# Natural History, Complications and Prognosis
The natural history of unoperated patients of patent ductus arteriosus depends on the amount of left to right shunting. The left to right shunting, in turn, depends on the size of the ductus and the difference in resistance between the left and right side of heart. PDA can cause complications such as heart failure, infective endocarditis, rhythm disturbance, pulmonary hypertension and Eisenmenger syndrome.

# Diagnosis

## Laboratory Findings
Polycythemia may be present if the child has any other congenital heart disease. Hypoxemia or hypercarbia may be present.

## Chest X Ray
The findings on chest x ray depends on the degree of shunting between left and right system.

## MRI
Magnetic resonance imaging can be helpful as a diagnostic tool in conditions where the echocardiographic findings are inconclusive.

## CT
Computed tomography can be helpful as a diagnostic tool in conditions where the echocardiographic findings are inconclusive.

## Echocardiography
Echocardiogram is the non-invasive method and can diagnose patent ductus arteriosus. Echo along with doppler can be used to visualize the shunt from the aorta to the left pulmonary artery.

## Other Imaging Findings

### Cardiac Catheterization
Cardiac catheterization serves to establish the presence of a PDA by assessment of the increase of oxygen in the pulmonary artery. It also serves to identify the anatomy of the PDA, the severity of a left-to-right shunt, and the presence of pulmonary hypertension.

# Treatment

## Medical Therapy

### Preterm Infants
Prostaglandin E2 plays a key role in maintaining the patency of ductus arteriosus before birth. Thus, prostaglandin E2 inhibitors are used as a therapeutic options to close the patent ductus arteriosus.

### Term and Older Children
In term infants and older patients, the prostaglandin E2 inhibitors (indomethacin and ibuprofen) have not shown to be effective. This is so because the ductus in premature baby is different histological from in older patients. As a result, pharmacologic therapy is only used routinely in preterm infants.

## Surgery
Infants without overt symptoms may simply be monitored as outpatients, while symptomatic PDA can be treated with both surgical and non-surgical methods. Surgically, the ductus arteriosus may be closed by ligation, wherein the DA is manually tied shut, or with intravascular coils or plugs that lead to the formation of a thrombus in the duct. Surgical ligation of the PDA can be accomplished with excellent results in uncomplicated patients. Recent experience with transcatheter closure has also been favorable, being today the procedure of choice for most patients.In certain cases it may be beneficial to the newborn to prevent the closure of the ductus arteriosus. For example, in transposition of the great vessels, a PDA may prolong the child's life until surgical correction is possible. The ductus arteriosus can be induced to remain open by administering prostaglandin analogs.

## Primary Prevention
The development of a fetal heart starts during the first trimester of pregnancy. Thus, many times the fetal heart has already developed, by the time the female becomes aware of being pregnant. There are some risk factors that if avoided before and during pregnancy can decrease the occurrence of congenital heart diseases.