- Chest radiography
- If significant left-to-right shunt through the PDA is present, the pulmonary arteries, pulmonary veins, left atrium, and left ventricle are enlarged. Also, the ascending aorta may be prominent.
- Usually, chest radiographic findings are normal until the magnitude of the ratio of pulmonary to systemic circulation (QP/QS) exceeds 2:1. With marked pulmonary overcirculation, pulmonary edema may occur. In elderly individuals, the PDA may calcify and be visible on a standard radiograph.
- Doppler echocardiography
- The echocardiographic findings are typically diagnostic. Relying on alternative imaging techniques to make the diagnosis of PDA is unusual. By 2-dimensional echocardiography, the PDA can be seen most easily in the parasternal short axis view and from the suprasternal notch. The classic PDA connects the junction of the main pulmonary artery and the left pulmonary artery with the aorta just below and opposite the left subclavian artery.
- If no other abnormalities are present, Doppler echocardiography reveals continuous flow from the aorta into the main pulmonary artery. If the magnitude of the left-to-right shunt is large, continued flow around the aortic arch into the ductus arteriosus in diastole and flow reversal in the descending aorta are evident. Also, variable levels of continuous flow in the branch pulmonary arteries related to the magnitude of shunt are observed. As the shunt magnitude increases, increased flow in the pulmonary veins is evident and the left atrium enlarges. With a small or moderate-sized PDA, the left ventricular size is often normal, but as shunt magnitude increases, the left ventricular diastolic size also increases.
OTHER TESTS
- Electrocardiogram
- With a small PDA, the ECG findings are typically normal. Left ventricular hypertrophy may be present with a larger PDA. This is typically seen as tall R waves in the lateral precordial leads (V6).
- In the neonate, especially the premature neonate with a large PDA, T-wave inversion and ST segment depression may be present, suggesting ischemia or a supply-demand mismatch. This is thought to be related to increased myocardial work due to the left-to-right shunt and pulmonary overcirculation in the face of low aortic and coronary diastolic blood pressure due to the runoff of blood from the aorta into the pulmonary arteries.
