PATENT DUCTUS ARTERIOSUS

'Patent ductus arteriosus' ('PDA') is a congenital heart defect wherein a child's ductus arteriosus fails to close after birth. Symptoms include shortness of breath and cardiac arrhythmia, and may progress to congestive heart failure if left uncorrected.

Contents

Overview

Normal ductus arteriosus closure

Patent ductus arteriosus

Signs and symptoms

Diagnosis

Treatment

References

External links

Overview

Normal ductus arteriosus closure

In the developing fetus, the ductus arteriosus (DA) is a shunt connecting the pulmonary artery to the aortic arch that allows much of the blood from the right ventricle to bypass the fetus' fluid-filled lungs. During fetal development, this shunt protects the right ventricle from pumping against the high resistance in the lungs, which can lead to right ventricular failure if the DA closes in-utero.
When the newborn takes its first breath, the lungs open and pulmonary pressure decreases below that of the left heart. At the same time, the lungs release bradykinin to constrict the smooth muscle wall of the DA and reduce bloodflow. Additionally, because of reduced pulmonary resistance, more blood flows from the pulmonary arteries to the lungs and thus the lungs deliver more oxygenated blood to the left heart. This further increases aortic pressure so that blood no longer flows from the pulmonary artery to the aorta via the DA.
In normal newborns, the DA is closed within 15 hours after birth, and is completely sealed after three weeks. The fall in circulating maternal prostaglandins contributes to this. A nonfunctional vestige of the DA, called the ligamentum arteriosum, remains in the normal adult heart.

Patent ductus arteriosus

Patent ductus arteriosus, or PDA, is a heart crisis that happens almost immediately following birth in some babies. In PDA, there is an irregular transmission of blood amid 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 infants 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.In some babies, on the other hand, the ductus arteriosus remains open. This opening permits blood to surge unswervingly starting from the aorta into the pulmonary artery.
A patent ductus arteriosus allows oxygenated blood to flow down its pressure gradient from the aorta to the pulmonary arteries. Thus, some of the infant's oxygenated blood does not reach the body, and the infant becomes short of breath. The heart rate hastens, thereby increasing the speed with which blood is oxygenated and delivered to the body. Left untreated, the infant will likely suffer from congestive heart failure, as his heart is unable to meet the metabolic demands of his body.
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.

Signs and symptoms

While some cases of PDA are asymptomatic, common symptoms include:

★ tachycardia or other arrhythmia

★ respiratory problems

★ shortness of breath

★ continuous machine-like murmur murmur

★ enlarged heart

Diagnosis

PDA is usually diagnosed using non-invasive techniques. Electrocardiography (ECG), in which electrodes are used to record the electrical activity of the heart, can be used to detect cardiac arrhythmias associated with PDA.
A chest X-ray may be taken, which reveals the structure of the infant's heart and the size and configuration of its chambers. In some instances, the X-ray itself may reveal a patent ductus arteriosus.
Echocardiography, in which sound waves are used to capture the motion of the heart, is also useful in detecting PDA.

Treatment

Infants without adverse symptoms may simply be monitored as outpatients, while symptomatic PDA can be treated with both surgical and non-surgical methods.^[1] Surgically, the DA may be closed by ligation, wherein the DA is manually tied shut, or with intravascular coils or plugs that leads to formation of a thrombus in the DA. Fluid restriction and prostaglandin inhibitors such as indomethacin have also been used in successful non-surgical closure of the DA. This is an especially viable alternative for premature infants.
In certain cases it may be beneficial to the newborn to prevent 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.

References

1. 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.

External links

★ Patent Ductus Arteriosus information from Seattle Children's Hospital Heart Center

★ High-Risk Newborn - Patent Ductus Arteriosus (PDA)

★ Patent Ductus Arteriosus from Merck

★ Fetal Circulation at berkeley.edu

★ Information about PDA - The Hospital for Sick Children