Patent ductus arteriosus (PDA) is a medical condition in which the ductus arteriosus fails to close after birth: this allows a portion of oxygenated blood from the left heart to flow back to the lungs from the aorta, which has a higher blood pressure, to the pulmonary artery, which has a lower blood pressure. Symptoms are uncommon at birth and shortly thereafter, but later in the first year of life there is often the onset of an increased work of breathing and failure to gain weight at a normal rate. With time, an uncorrected PDA usually leads to pulmonary hypertension followed by right-sided heart failure. The ductus arteriosus is a fetal blood vessel that normally closes soon after birth. This closure is caused by vessel constriction immediately after birth as circulation changes occur, followed by the occlusion of the vessel's lumen in the following days. In a PDA, the vessel does not close, but remains patent (open), resulting in an abnormal transmission of blood from the aorta to the pulmonary artery. PDA is common in newborns with persistent respiratory problems such as hypoxia, and has a high occurrence in premature newborns. Premature newborns are more likely to be hypoxic and have PDA due to underdevelopment of the heart and lungs. If the congenital defect transposition of the great vessels is present in addition to a PDA, the PDA is not surgically closed since it is the only way that oxygenated blood can mix with deoxygenated blood. In these cases, prostaglandins are used to keep the PDA open, and NSAIDs are not administered until surgical correction of the two defects is completed. In full-term newborns, PDA occurs in 1 in 2,000 births, and accounts for 5–10% of congenital heart disease cases. PDA occurs in 20–60% of all premature newborns, where its incidence is inversely linked with gestational age and weight.
Signs and symptoms Common symptoms include:
dyspnea (shortness of breath) Signs include:
tachycardia (a heart rate exceeding the normal resting rate) continuous "machine-like" (also described as "rolling-thunder" and "to-and-fro") heart murmur (usually from aorta to pulmonary artery, with higher flow during systole and lower flow during diastole) cardiomegaly (enlarged heart, reflecting ventricular dilation and volume overload) left subclavicular thrill bounding pulse widened pulse pressure increased cardiac output increased systolic pressure poor growth differential cyanosis, i.e. cyanosis of the lower extremities but not of the upper body. People with patent ductus arteriosus typically present in good health, with normal respirations and heart rate. If the PDA is moderate or large, widened pulse pressure and bounding peripheral pulses are frequently present, reflecting increased left ventricular stroke volume and diastolic run-off of blood into the (initially lower-resistance) pulmonary vascular bed. Eisenmenger physiology is pulmonary hypertension due to a left-to-right shunt. Prominent suprasternal and carotid pulsations may be noted secondary to increased left ventricular stroke volume.
Risk factors Known risk factors include:
Preterm birth Congenital rubella syndrome Chromosomal abnormalities (e.g., Down syndrome) Genetic conditions such as Loeys–Dietz syndrome (would also present with other heart defects), Wiedemann–Steiner syndrome, and CHARGE syndrome. Fetal alcohol spectrum disorder
Diagnosis
PDA is usually diagnosed using noninvasive 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 no specific rhythms or ECG patterns can be used to detect PDA. A chest X-ray may be taken, which reveals overall heart size (as a reflection of the combined mass of the cardiac chambers) and the appearance of blood flow to the lungs. A small PDA most often accompanies a normal-sized heart and normal blood flow to the lungs. A large PDA generally accompanies an enlarged cardiac silhouette and increased blood flow to the lungs.
Prevention Some evidence suggests that intravenous NSAIDs, such as indomethacin, administrated on the first day of life to all preterm infants reduces the risk of developing a PDA and the complications associated with PDA. Intravenous indomethacin treatment in premature infants also may reduce the need for surgical intervention. Administering ibuprofen probably helps to prevent PDA and reduce the need for surgery but it also likely increases the risk of kidney complications.
Treatment Symptomatic PDA can be treated with both surgical and non-surgical methods.
Conservative Neonates without adverse symptoms may simply be monitored as outpatients.
Surgery Surgically, the DA may be closed by ligation (though support in premature infants is mixed). This can either be performed manually and be tied shut, or with intravascular coils or plugs that leads to formation of a thrombus in the DA. Devices developed by Franz Freudenthal block the blood vessel with woven structures of nitinol wire. Newer procedures performed effectively in older, bigger children include catheter PDA occlusion and video-assisted thoracoscopic PDA clipping.
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