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Patent ductus arteriosus (PDA)
Is a persistent opening between the two major blood vessels leading from the heart. The heart problem is present from birth. That means it is a congenital heart defect.
An opening called the ductus arteriosus is part of a baby's blood flow system in the womb. It usually closes shortly after birth. If it remains open, it's called a patent ductus arteriosus.
- Before a baby is born, the fetus's blood does not need to go to the lungs to get oxygenated.
- The ductus arteriosus is a hole that allows the blood to skip the circulation to the lungs.
- However, when the baby is born, the blood must receive oxygen in the lungs and this hole is supposed to close.
- If the ductus arteriosus is still open (or patent) the blood may skip this necessary step of circulation.
- The open hole is called the patent ductus arteriosus.
- Normally the heart's left side only pumps blood to the body, and the right side only pumps blood to the lungs.
- In a child with PDA, extra blood gets pumped from the body artery (aorta) into the lung (pulmonary) arteries.
- If the PDA is large, the extra blood being pumped into the lung arteries makes the heart and lungs work harder and the lungs can become congested.
CLINICAL FEATURES
- The history of the mother’s pregnancy and of perinatal events may provide clues associated with a high incidence of PDA, such as exposure to rubella in the first trimester in a non-immunized mother.
- PDA is also more common in premature infants, especially those with birth asphyxia or respiratory distress.
- Symptoms depends on the degree of left-to- right shunting; and it is determined by the size of the PDA, ductal resistance, cardiac output, as well as the systemic and pulmonary vascular resistances.
- Patients with small PDA are asymptomatic.
- With larger PDAs, symptoms may develop.
- The most common symptom is exercise intolerance followed by dyspnea, peripheral edema, and palpitations.
SIGNS
- Tachycardia and tachypnea may be present in infants with CHF.
- Bounding peripheral pulses.
- Wide pulse pressure.
- Hyperactive precordium: With a large shunt.
- Systolic thrill: may be present at the upper left sternal border.
- The P2 is usually normal, but its intensity may be accentuated if pulmonary hypertension is present.
INVESTIGATION
- With small shunt the ECG is normal.
- Left ventricular hypertrophy of the volume overload type, with deep Q waves and increased R- wave voltage in the left precordial leads, is noted with increasing shunt size with left ventricular volume overload.
- Right ventricular hypertrophy is seen with pulmonary hypertension.
- Chest radiographs may be normal with a small-shunt PDA.
- Cardiomegaly of varying degrees occurs in moderate- to large-shunt PDA with enlargement of the LA, LV, and ascending aorta.
- Pulmonary vascular markings are increased.
- With pulmonary vascular obstructive disease, the heart size becomes normal, with a marked prominence of the PA segment and hilar vessels.
- TTE has a 42% sensitivity and 100% specificity for the diagnosis of PDA.
- On 2-D echo, the left-sided chambers (LA and LV) are dilated due to increased venous return from the pulmonary circulation.
- This constitutes left ventricular volume overload.
- Due to dilatation of left atrium, the ratio between size of the left atrium and proximal aorta (LA : Ao ratio) exceeds 1.3.
- Continuous wave Doppler echocardiogram positioned through the PDA, showing retrograde flow throughout the cardiac cycle Pulsed-Doppler echocardiogram shows increased diastolic flow in the branch pulmonary artery
- Catheter may easily pass from PA to Ao through the PDA.
- It gives a specific appearance “Hair pin” appearance.
- Steps up of O2 saturation in PA in comparison to RA.
- Pressure study: RV & PA pressure is normal, but elevated in large PDA.
- PVR is normal in infant & children but elevated in adult.
- LV graphy: to see associated VSD
- Aortography: to see PDA & associated CoA
- Magnetic resonance imaging (MRI) and computed tomography may be useful in defining the anatomy in patients with unusual PDA geometry and in patients with associated abnormalities of the aortic arch.
| ECG | |
| CXR | |
| Echocardiogram | |
| Cardiac Catheterization Catheter trajectory |
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| Oxymetry | |
| MRI & CT |
MANAGEMENT
If the PDA isn't causing problems, a catheter treatment to close the opening may be done when the baby is older. Open-heart surgery to close the PDA . This treatment is called surgical closure. Heart surgery may be needed if medicine doesn't work or the PDA is large or causing complications.
