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Patent Ductus Arteriosus (PDA) on Cardiac CT

Patent ductus arteriosus (PDA) is a congenital heart defect wherein a neonate's ductus arteriosus fails to close after birth. Symptoms are uncommon but in the first year of life include increased work of breathing and poor weight gain. With age, the PDA may lead to congestive heart failure if left uncorrected.

Patent ductus arteriosus:
Patent ductus arteriosus, or PDA, 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 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. PDA is common in neonates with persistent respiratory problems such as hypoxia, and has a high occurrence in premature children. In hypoxic newborns, too little oxygen reaches the lungs to produce sufficient levels of bradykinin and subsequent closing of the DA. Premature children are more likely to be hypoxic and thus have PDA because of their underdeveloped heart and lungs.

A patent ductus arteriosus allows that portion of the oxygenated blood from the left heart to flow back to the lungs (following the pressure gradient from the higher pressure aorta to the pulmonary arteries). If this shunt amount is substantial, the neonate becomes short of breath because there is not only the normal amount of unoxygenated blood that has returned from the body to go to the lungs but in addition there is the amount shunted through the PDA. The neonate's work of breathing is increased, using up more calories and often interfering with feeding in infancy. This condition as a constellation of findings is called congestive heart failure.

In some cases, such as in transposition of the great vessels (the pulmonary artery and the aorta), a PDA may need to remain open. In this cardiovascular condition, the PDA is the only way that oxygenated blood can mix with deoxygenated blood. In these cases, prostaglandins are used to keep the patent ductus arteriosus open.

Diagnosis:
PDA is usually diagnosed using non-invasive techniques. Echocardiography, in which sound waves are used to capture the motion of the heart, and associated Doppler studies are the primary methods of detecting PDA. Electrocardiography (ECG), in which electrodes are used to record the electrical activity of the heart, is not particularly helpful as there are no specific rhythms or ECG patterns which can be used to detect PDA.

A chest X-ray may be taken, which reveals the overall size of neonate's heart (as a reflection of the combined mass of the cardiac chambers) and the appearance of the blood flow to the lungs. A small PDA most often shows a normal sized heart and normal blood flow to the lungs. A large PDA generally shows an enlarged cardiac silhouette and increased blood flow to the lungs.

References
1. http://emedicine.medscape.com/article/162796-overview "Patients typically present in good health, with normal respirations and heart rate. If the ductus is moderate or large, widened pulse pressure and bounding peripheral pulses are frequently present, reflecting increased left ventricular stroke volume and diastolic runoff of blood into the initially lower-resistance pulmonary vascular bed. Prominent suprasternal and carotid pulsations may be noted secondary to increased left ventricular stroke volume."

2. Zahaka, KG and Patel, CR. "Congenital defects.'" Fanaroff, AA and Martin, RJ (eds.). Neonatal-perinatal medicine: Diseases of the fetus and infant. 7th ed. (2002):1120-1139. St. Louis: Mosby.

3. Wikipedia, Patent Ductus Arteriosis (PDA)

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