Echocardiography in Pediatric and Adult Congenital Heart Disease, 2nd Ed.

19. Patent Ductus Arteriosus and Aortopulmonary Window

PATENT DUCTUS ARTERIOSUS

The ductus arteriosus is a normal fetal cardiac structure that connects the pulmonary artery to the descending aorta. Normally, the ductus arteriosus develops embryologically from the distal left sixth arch. It functionally closes within the first day of life. However, it may remain patent either in isolation or in association with other congenital cardiac malformations. In premature infants, continued patency of the ductus arteriosus is common after birth and closure is dependent on maturation. The clinical significance of a patent ductus arteriosus (PDA) is determined by the magnitude and direction of shunting across it. Echocardiography is useful in defining the morphologic features of the PDA, the shunt flow dynamics across it, and its hemodynamic effects on the heart.

Two-Dimensional Echocardiography

As an isolated lesion, a PDA is seen as a tubular structure connecting the superior junction of the main pulmonary artery and left pulmonary artery to the ventral aspect of the proximal descending aorta just beyond the origin of left subclavian artery. A PDA can be best visualized from the parasternal short-axis, high-left parasternal short-axis, and suprasternal long-axis views.

In the parasternal short-axis view, the PDA is seen arising from the main pulmonary artery and connecting to the descending aorta. Angulating the transducer superiorly and leftward toward the pulmonary artery bifurcation provides images of the PDA (Fig. 19.1, Video 19.1). A dropout between the main pulmonary artery and the descending aorta may occur in standard parasternal short-axis views. For optimal imaging of the PDA, avoiding any foreshortening or dropout, a high-parasternal view, also called the “ductal view,” is used. To obtain this view, the transducer is positioned between the suprasternal notch and the standard parasternal region in the left infraclavicular region. The plane of transducer is directed similar to the suprasternal long-axis views through the left pulmonary artery. In this view, the PDA can be seen between the origin of left pulmonary artery and the descending aorta (Fig. 19.2, Video 19.2). With slight rotation of the transducer to obtain the long-axis view of the aorta, the entire length of the PDA can be visualized. However, a small PDA may not be apparent in this view as it is positioned vertically within the scan plane and therefore imaged with the lateral resolution of the transducer. If the ductus is right-sided, similar views can be obtained by scanning from a right parasternal approach.

In the suprasternal long-axis views, a PDA is seen connecting the main pulmonary artery and the descending aorta, beyond the origin of the left subclavian artery. In this view, better imaging of the PDA can be obtained by tilting the imaging plane anteriorly toward the left pulmonary artery. The PDA is seen in this view, between the origin of the left pulmonary artery and the descending aorta (Video 19.3).

Direct visualization of a PDA in the parasternal long-axis view is difficult. The transducer is angled leftward and superiorly toward the right ventricular outflow tract and main pulmonary artery, and the color flow from the PDA toward the transducer can be seen from a left-to-right shunt across the PDA.

Figure 19.1. Parasternal short-axis view of the patent ductus arteriosus (PDA) (arrow) connection between the main pulmonary artery (MPA) and descending aorta (DAo). Ao, aorta; LA, left atrium; RV, right ventricle.

Figure 19.2. A high-left parasternal short-axis view (ductal view) of a large patent ductus arteriosus (PDA) between the origin of left pulmonary artery (LPA) and descending aorta (DAo), in a patient with hypoplastic left heart syndrome. In this view, the right pulmonary artery (RPA), left pulmonary artery, and PDA (arrows) are demonstrated from right to left of the image. Notice the small aorta (Ao).

Morphologic Variations in Patent Ductus Arteriosus

A PDA with a left aortic arch connects the aortic isthmus with the proximal left pulmonary artery. A PDA with a right aortic arch can be either right-sided (between the descending aorta and the right pulmonary artery), left-sided (between the innominate artery or left subclavian artery and the left pulmonary artery), or bilateral. To image the PDA arising from the base of innominate artery, the transducer is rotated from the suprasternal or high-parasternal view into a frontal plane such that the aorta is seen in its short axis and the right pulmonary artery is seen in its long axis. From this position, the innominate artery can be visualized by angulating the transducer toward the right or left depending on the side of the aortic arch. The bifurcation of the innominate artery into the subclavian and carotid arteries along with the origin of the PDA at its base can be seen in this view. In the rare instance when there are bilateral PDAs, one ductus is seen in the usual position and the other may arise from the base of either the subclavian artery or the innominate artery on the contralateral side (Video 19.4). The PDA in a normal heart runs in an oblique course, forming an obtuse angle with the descending aorta. This normal course of a PDA is altered in congenital heart diseases associated with right ventricular outflow tract obstruction, such as tetralogy of Fallot and pulmonary atresia. In these cases, the PDA has a nearly vertical orientation between distal aortic arch and the pulmonary artery and therefore is at an acute angle to the descending aorta and is often referred to as a reverse-oriented ductus. Such PDAs are often long and tortuous (Fig. 19.3, Video 19.5) and may be difficult to visualize in a single imaging plane. In hypoplastic left heart syndrome as well as with an interrupted aortic arch, the PDA is almost always large when imaged soon after birth and is at an obtuse angle to the descending aorta (Video 19.6). In the presence of an interrupted aortic arch, one should remember that the true aortic arch is superior to the continuum formed by the pulmonary artery, the PDA, and the descending aorta.

Hemodynamic Consequences of a Patent Ductus Arteriosus

The hemodynamic consequence of a large left-to-right shunt across a PDA is volume overload of the left heart and hence dilatation of the left atrium and left ventricle. Historically, the left atrium–to–aortic root (LA/Ao) ratio on M-mode examination has been used for indirect quantification of PDA size. This ratio was popular before the introduction of two-dimensional and Doppler echocardiography. The LA/Ao ratio has been reported to be greater than 1.15 (mean, 1.38 ± 0.19) in neonates with a large left-to-right shunt across a PDA, requiring surgical ligation. This M-mode assessment is obtained from the parasternal short-axis view measuring the anterior-posterior dimensions of the left atrium. Using this single dimension, measurement of the left atrium may result in inaccurate estimation of the left atrial size. If the LA/Ao ratio is used in isolation, it has a low specificity for diagnosing a significant-sized PDA. Thus, the usefulness of this ratio has decreased with the advent of two-dimensional and Doppler echocardiography, where one not only can assess the size and flow across the PDA but also can determine left heart enlargement through direct visualization. In addition to the finding of a dilated left atrium and left ventricle, the atrial septum can be seen bulging toward the right atrium. The left ventricular systolic function is often hyperdynamic. In the subcostal views, increased pulsatility of the descending aorta can be seen as a result of large diastolic runoff to the pulmonary arteries resulting in a widened pulse pressure.

Figure 19.3. Suprasternal long-axis view of the aortic arch of a tortuous patent ductus arteriosus (PDA) in a patient with pulmonary atresia. AAo, ascending aorta.

Doppler Examination

Color Doppler echocardiography provides information regarding the direction and amount of shunt flow across a PDA. Color Doppler has markedly improved the ability of echocardiography to identify a PDA, especially if it is small. Color Doppler also guides optimal alignment of the spectral Doppler beam. In addition, spectral Doppler interrogation of the PDA provides useful information regarding the shunt direction and pressure gradients throughout the cardiac cycle.

With an isolated large PDA with normal pulmonary artery pressure and a large left-to-right shunt, continuous red flow from the aorta into the pulmonary arteries will be seen with color Doppler (Fig. 19.4, Videos 19.1 and 19.7). A small isolated PDA with normal pulmonary artery pressure will have a high-velocity turbulent jet across it extending to the lateral wall of the pulmonary artery with a color mosaic caused by aliasing (Fig. 19.5). A pulsed Doppler signal of the main pulmonary artery close to the pulmonary valve shows that the systolic part of the left-to-right ductal shunt is directed away from the sample volume by the dominant forward flow across the pulmonary valve. However, during diastole as the pulmonary valve is closed, the left-to-right signal from ductal shunt is seen above the baseline. A pulsed Doppler signal of the mid-portion of main pulmonary artery may show antegrade diastolic flow below the baseline as the jet of a PDA strikes the closed pulmonary valve and deflects back along the medial wall of pulmonary artery (Fig 19.6). When the ductus is very large, the left-to-right shunt across it may completely fill the pulmonary artery, resulting in loss of secondary flow patterns in the pulmonary artery as described above. A variety of other conditions can produce diastolic flow in the pulmonary arteries that can be confused with a PDA. These include pulmonary insufficiency, a coronary fistula, anomalous origin of coronary artery from pulmonary artery, an aortopulmonary window, and surgically created systemic–to–pulmonary artery shunts.

Figure 19.4. Parasternal short-axis view with color Doppler showing continuous flow (red) from the patent ductus arteriosus (PDA) into the main pulmonary artery (MPA). Ao, aorta; RV, right ventricle.

Figure 19.5. Color Doppler imaging in the parasternal short-axis view showing a high-velocity, turbulent jet across a small patent ductus arteriosus (PDA) into the main pulmonary artery (MPA) in a patient with normal pulmonary artery pressure. This high-velocity Doppler flow is indicative of a large pressure gradient between the aorta and the pulmonary artery. Ao, aorta.

Spectral Doppler interrogation of a restrictive PDA with left-to-right flow and normal pulmonary artery pressure will demonstrate continuous flow above the Doppler baseline with a peak in late systole (Fig. 19.7). Spectral Doppler of a large PDA with an unrestricted left-to-right shunt will have a pulsatile flow pattern with the highest velocity at end-systole and a very low peak velocity at end-diastole. This is because the relative pulmonary and aortic pressures are equal at end-diastole in large PDAs (Fig 19.8).

Using the modified Bernoulli equation, one can calculate the peak gradient across the PDA using the late systolic peak velocity. This measurement has been shown to closely correlate with the peak instantaneous gradient between the aorta and pulmonary artery at catheterization. If the systemic arterial systolic blood pressure is obtained simultaneous to Doppler interrogation across the PDA, one can derive the pulmonary artery systolic pressure by subtracting the peak gradient across the PDA from the systolic blood pressure. In assessing peak Doppler velocities across a PDA to obtain pressure gradients, it is important to remember that for a left-to-right shunt the sample volume should be positioned at the pulmonary end of the PDA. Conversely, for a right-to-left shunt, the sample volume should be positioned at the aortic end of the PDA. Doppler estimation of pulmonary artery pressure using the PDA velocity may not always be accurate and can be limited by the position of the sample volume, interference from signals from adjacent structures such as the left pulmonary artery, and the unusual shape, tortuosity, and size of the PDA.

Figure 19.6. Continuous-wave Doppler of the main pulmonary artery. A continuous antegrade flow during diastole is seen as the jet of the patent ductus arteriosus deflects back from the closed pulmonary valve into the main pulmonary artery.

In the presence of severe pulmonary hypertension or in congenital cardiac malformations in which the systemic circulation is dependent on the PDA (i.e., critical aortic stenosis, critical coarctation, hypoplastic left heart syndrome, and interrupted aortic arch), there is a right-to-left shunt across the PDA. Color Doppler will demonstrate blue color flow in the PDA representing blood flow from the pulmonary artery into the descending aorta (Video 19.8). A spectral Doppler interrogation of such a PDA shows continuous flow below the Doppler baseline with a peak Doppler velocity in early systole.

In normal neonates, a bidirectional shunt across the PDA is present for the first few hours of life but rapidly changes to a continuous left-to-right shunt before functional closure. In pulmonary hypertension, a bidirectional shunt is present across the PDA. Color Doppler demonstrates a right-to-left shunt in systole (blue color flow) and a left-to-right shunt in diastole (red color flow) (Video 19.9). On spectral Doppler, a negative deflection arising from the right-to-left shunt signifies flow from the pulmonary artery to aorta in mid-to-late systole, whereas a positive deflection arising from left-to-right shunt represents flow from the aorta to pulmonary artery in late systole with extension into late diastole (Fig. 19.9). One should be cautious to differentiate the negative deflection from a right-to-left ductal shunt from a negative deflection caused by flow within the left pulmonary artery. Spectral Doppler from the left pulmonary artery begins at the onset of systole and peaks early, while the right-to-left shunt across a PDA begins later in systole and peaks in mid to late systole.

Figure 19.7. Continuous-wave Doppler tracing obtained from the parasternal short-axis view in a patient with a small patent ductus arteriosus (PDA) and normal pulmonary artery pressure. There is continuous left-to-right shunting across the PDA in systole and diastole, with a peak Doppler velocity obtained in late systole. The high-velocity of the jet (4 m/s) across the PDA indicates normal pulmonary artery pressure.

Figure 19.8. Doppler of a large PDA with an unrestricted left-to-right shunt. The highest velocity is noted at end-systole with a very low peak velocity at end-diastole due to nearly equal pulmonary and aortic pressures at end-diastole in large PDAs.

Pulsed-wave Doppler allows assessment of flow disturbances on either side of the PDA. In a PDA with large left-to-right shunt, there is increased diastolic forward flow in the left pulmonary artery and retrograde diastolic flow in the postductal descending aorta. These retrograde diastolic flow signals are M-shaped, with peaks in early diastole and with atrial systole (Fig. 19.10). These findings are useful markers of a hemodynamically significant shunt across the PDA. In the presence of a large left-to-right ductal shunt, reversed diastolic flow may also be present in other systemic arteries, including the brachial, femoral, carotid, and cerebral arteries. It is important to remember that the finding of retrograde flow in the descending aorta is not specific for a PDA but can be seen in any condition with significant diastolic runoff from the aorta, including significant aortic insufficiency, systemic–to–pulmonary artery shunts, anomalous origin of a pulmonary artery from the ascending aorta, an aortopulmonary window, a ruptured sinus of Valsalva aneurysm, or cerebral arterio-venous malformations.

Figure 19.9. Continuous-wave Doppler tracing from a neonate with pulmonary artery hypertension. There is a bidirectional shunt across the patent ductus arteriosus (PDA) with a positive deflection from left-to-right shunting from the aorta to the pulmonary artery beginning in late systole and extending into late diastole. A negative deflection resulting from a right-to-left shunt is demonstrated from the pulmonary artery to aorta in mid-to-late systole. With continuous-wave Doppler, a negative deflection caused by flow within the left pulmonary artery (LPA) may interfere with that from a right-to-left shunt across a PDA. These signals can be differentiated in that Doppler flow from the LPA begins at the onset of systole and peaks early, while the right-to-left shunt across the PDA begins later in systole and peaks in mid to late systole.

Figure 19.10. Pulsed-wave Doppler within the descending aorta from suprasternal imaging in a patient with a large left-to-right ductal shunt with the sample positioned at the origin of the patent ductus arteriosus (PDA). The positive deflection in diastole (M-shaped signal) reflects retrograde flow from the descending aorta into the PDA that peaks in early diastole and after atrial systole. The negative deflection results from forward flow in the descending aorta during systole.

The magnitude of shunt flow across a PDA can be calculated as the difference between the pulmonary and systemic blood flow. Because the shunting occurs distal to the pulmonary valve, calculation of flow across the pulmonary valve provides a measure of systemic flow, and not the pulmonary flow, which is the sum of systemic and ductal shunt flow. Therefore, the flow across the aortic valve represents the actual pulmonary flow. In children with a PDA, close correlation has been found between cardiac catheterization and the Doppler-estimated pulmonary–to–systemic flow ratio. However, in neonates, this Doppler estimation is less reliable, because of possible errors in the measurement of the small vessels.

Transesophageal Echocardiography

In adolescent or adult patients, it may be difficult to image the PDA using a transthoracic probe because of poor echocardiographic windows. In such cases, transesophageal echocardiography (TEE) provides improved imaging of the PDA and its shunt flow because of a closer spatial relationship between the PDA and the transducer within the esophagus.

Ductal Aneurysm

Ductal aneurysms have been reported mostly in the fetus, neonates, and infants but can also occur in older children and adults. These aneurysms may spontaneously regress or may result in complications including compression of adjacent structures, thromboembolism, infection, and rupture. In the parasternal short-axis view, a ductal aneurysm is seen as a saccular dilation adjacent to the left of the main pulmonary artery that extends into the superior mediastinum and may rarely become gigantic (Fig. 19.11). The maximal diameter of the aneurysm is at the aortic end. With color Doppler interrogation, swirling of blood may be seen within the aneurysm. The aneurysm is typically closed at the pulmonary end, but in some cases the ductus may still be patent and can be easily recognized with color Doppler. Thrombus formation within the ductal aneurysm with extension into the branch pulmonary arteries can occasionally be seen on parasternal short-axis views. Normally, the PDA constricts at the pulmonary end first, and a small conical bulge along the posteroinferior aspect of the aortic arch is seen which is the ductus diverticulum and should not be mistaken for a ductal aneurysm.

Echocardiographic Limitations in Imaging the Patent Ductus Arteriosus

When the lumen of the PDA is smaller than the lateral resolution of the transducer, then the PDA cannot be visualized directly. Doppler interrogation can overcome this limitation. Patient size, on either extreme, may be a problem. In very small preterm neonates, especially with pulmonary disease or those on ventilators, it may be difficult to obtain optimal images. Similarly, in older children and adults, the ductal view may be more difficult to obtain. A dropout artifact may resemble a PDA, but this error can be avoided by interrogating the PDA along its entire length, rather than just at the aortic or pulmonary end.

Figure 19.11. Parasternal short-axis view demonstrating a giant ductal aneurysm in an asymptomatic 4-year-old girl. The aneurysm is in communication with the descending aorta. A compressed proximal right pulmonary artery (RPA) is seen. Ao, aorta.

Echocardiographic Evaluation After Device Closure or Surgical Ligation of Patent Ductus Arteriosus

In recent decades, significant advances have been made in the transcatheter approach to ductal closure. Various devices including the Portsmann plug, Rashkind device, Gianturco embolization coils, and, more recently, the Amplatzer ductal occluder device have been used for percutaneous closure of a PDA (Fig. 19.12, Video 19.10). Residual shunting across the PDA may be present after percutaneous closure or surgical ligation. Color Doppler is a sensitive technique for detecting residual ductal shunting. When the ductal occlusion procedure has used a Rashkind device, residual shunting is characteristically seen at the superior margin of the device, whereas with an Amplatzer ductal occluder, residual shunting is most often central through the device. Color and spectral Doppler interrogation of the left pulmonary artery and descending aorta should be performed after both percutaneous PDA closure or surgical ligation because there is a risk for partial occlusion of these structures with either approach. In a multicenter USA Amplatzer PDA occlusion device trial, 89% of the 433 patients demonstrated complete closure on the day after the procedure and 99.7% at 1-year follow-up. In this report, two patients developed partial obstruction of the left pulmonary artery with a peak gradient greater than 20 mm Hg. Inadvertent surgical ligation of the left pulmonary artery instead of the PDA may occur in small infants or premature neonates.

AORTOPULMONARY WINDOW

An aortopulmonary window is a communication between the ascending aorta and the pulmonary artery above the semilunar valves. Mori et al. proposed three types of aortopulmonary connections:

■Type I, proximal defect—This is the most common and is present midway between the semilunar valves and pulmonary bifurcation.

■Type II, distal defect—This is a communication between the left posterior wall of the ascending aorta and the junction of the right pulmonary artery and the main pulmonary artery. This type is commonly associated with aortic origin of the right pulmonary artery.

■Type III, total defect—This is a very large defect and involves the entire length of pulmonary trunk from immediately above the semilunar valves to the level of the pulmonary bifurcation and proximal portion of the right pulmonary artery.

About half of the patients with an aortopulmonary window have other associated anomalies. These include type A interruption of the aortic arch, aortic origin of the right pulmonary artery (especially in those with distal or total defect), anomalous origin of one or both coronary arteries from the pulmonary artery, tetralogy of Fallot, right aortic arch, ventricular septal defect, and transposition of the great arteries.

Two-Dimensional Echocardiography

An aortopulmonary window can best be seen as a defect between the ascending aorta and the pulmonary artery from the parasternal short-axis, subcostal, and suprasternal views With slight anterosuperior angulation in the parasternal short-axis view, one can recognize this defect and delineate its extent up to the bifurcation of the pulmonary arteries, including the origin of the right pulmonary artery from the aorta (Fig. 19.13, Video 19.11). This defect cannot typically be seen in parasternal long-axis views. In the subcostal long-axis view, the transducer should be rotated counterclockwise into a position where the ascending aorta is seen in its long axis with the pulmonary trunk crossing it (Fig. 19.14 and Video 19.12). In this view, the wall separating the great arteries is aligned along the lateral resolution of the transducer. Therefore, a dropout seen in the region where the aorta and right pulmonary artery intersect can be mistaken for an aortopulmonary window. A “T”-artifact at the edge of the defect can help distinguish an actual defect from an artifactual dropout. The subcostal view is especially useful for determining the proximity of the defect to the origin of the left coronary artery. In the suprasternal long-axis view, as the lower border of the ascending aorta is followed superiorly, instead of the usual circular pattern of the main pulmonary artery, an aortopulmonary window is seen as a semicircle.

Figure 19.12. PDA occluder device. A: AGA medical Amplatzer ductal occluder device. B: Parasternal short-axis scan demonstrating Amplatzer device in PDA (arrow).

Figure 19.13. Aortopulmonary window. A: A high-parasternal short-axis scan demonstrating characteristic defect (asterisk) between aorta (Ao) and main pulmonary artery (PA) B: Color Doppler demonstrating defect (asterisk) and origin of branch pulmonary arteries.

Secondary effects of an aortopulmonary window result from the large left-to-right shunt across it. The left atrium and left ventricle are dilated, and so are the pulmonary arteries. The right ventricle may occasionally be hypertrophied.

Doppler Echocardiography

In a large aortopulmonary window, the jet of blood flow from the aorta enters the pulmonary artery perpendicular to its long axis and then rapidly expands (Video 19.13). In a small restrictive aortopulmonary window, color Doppler interrogation shows a continuous high-velocity turbulent jet from the aorta to the pulmonary artery. In larger defects with normal pulmonary vascular resistance, a continuous antegrade flow is seen in the pulmonary arteries distal to the aortopulmonary window as a result of a large left-to-right shunt from aorta to pulmonary artery (Fig. 19.15, Video 19.14). Abnormal retrograde diastolic flow is seen in the descending aorta during diastole caused by runoff from the aorta into the pulmonary arteries. The antegrade flow in distal MPA and branch pulmonary arteries distinguishes an aortopulmonary window from a PDA. In the presence of pulmonary hypertension, a low-velocity bidirectional flow will be present across the aortopulmonary window. Even though this is an extremely rare cardiac defect, appropriate diagnosis is possible with echocardiography.

Figure 19.14. Subcostal coronal view. A large aortopulmonary window (asterisk) is seen between the aorta (Ao) and the main pulmonary artery (PA).

Figure 19.15. Pulsed-wave Doppler of the branch pulmonary arteries in aortopulmonary window. A continuous antegrade flow is seen in the pulmonary arteries distal to the aortopulmonary window as a result of a left-to-right shunt during systole and diastole from the aorta into the pulmonary arteries.

Transesophageal Echocardiography

An aortopulmonary window can be well visualized by transesophageal echocardiography in the mid-esophageal short-axis view with the probe slightly pulled up to see the ascending aorta in short-axis and the main and right pulmonary artery (Fig. 19.16, Video 19.15). It can also be viewed in the mid-esophageal long-axis view of the aorta by rotating the probe toward the right, where you can visualize the pulmonary artery crossing the aorta. These views are also helpful in postoperative assessment for any residual defects.

Echocardiographic Evaluation After Closure of an Aortopulmonary Window

A large aortopulmonary window is closed surgically using a patch. A small aortopulmonary window or a residual surgical defect may be closed using transcatheter devices. Closure of the aortopulmonary window with either technique can be complicated by stenosis within the ascending aorta or pulmonary artery or a residual defect. These can be best assessed using the two-dimensional and Doppler echocardiographic approach described earlier to locate the aortopulmonary window.

Figure 19.16. Transesophageal imaging demonstrating large aortopulmonary window. Ao, aorta; MPA, main pulmonary artery; RPA, right pulmonary artery.

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Questions

1.From where can optimal imaging of the entire length of a patent ductus arteriosus can be obtained?

A.Parasternal short-axis view

B.Parasternal long-axis view

C.High left parasternal short-axis view

D.Subcostal coronal view

E.Apical four-chamber view

2.Where will peak velocity be demonstrated in a spectral Doppler of a small patent ductus arteriosus with left-to-right shunt and normal pulmonary artery pressures?

A.Early systole

B.Late systole

C.Early diastole

D.Late diastole

E.Mid-diastole

3.Which of the following cardiac lesions is highly suggested by the imaging of the patent ductus arteriosus in the newborn shown in the video?

[Insert Video Question 3 Chapter 19]

A.Tetralogy of Fallot with absent pulmonary valve

B.Hypoplastic left heart syndrome

C.Pulmonary atresia with ventricular septal defect

D.Truncus arteriosus

E.Coarctation of aorta

4.Based on a fetal echocardiogram, a newborn has a large aortopulmonary window and a suspected arch anomaly. Which arch anatomy are you most likely to find on the transthoracic echocardiogram?

A.Interrupted aortic arch Type A

B.Interrupted aortic arch Type B

C.Interrupted aortic arch Type C

D.Coarctation of aorta

E.Double aortic arch

5.In which of the following conditions can the Doppler signal in the descending aorta shown here not be seen?

A.Patent ductus arteriosus

B.Aortic insufficiency

C.Aortopulmonary window

D.Coarctation of aorta

E.Aortopulmonary collaterals

6.What is the continuous antegrade flow noted in both the branch pulmonary arteries in this video likely due to?

[Insert Video Question 6 Chapter 19]

A.A small patent ductus arteriosus

B.A large aortopulmonary window

C.Severe pulmonary insufficiency

D.Anomalous origin of right pulmonary artery from the ascending aorta

E.Distal branch pulmonary artery stenosis

7.A four-week-old full-term newborn has a large unrestricted shunt across a patent ductus arteriosus and severe left atrial and ventricular enlargement. The spectral Doppler of this PDA will show:

A.continuous left-to-right shunt with very little variation in systolic and diastolic velocities.

B.continuous left-to-right shunt with low peak systolic velocity and high end-diastolic velocity.

C.right-to-left shunt in systole and left-to-right shunt in diastole.

D.continuous right-to-left shunt.

E.left-to-right shunt with highest velocity in end-systole and very low end-diastolic velocity.

8.Based on the parasternal short-axis view shown in this video obtained from a six-week-old infant with tachypnea and poor weight gain, what is the diagnosis?

[Insert Video Question 8 Chapter 19]

A.Large patent ductus arteriosus

B.Large aortopulmonary window

C.Anomalous origin of right pulmonary artery from the aorta

D.Pulmonary sling

E.Truncus arteriosus

9.What does the suprasternal image shown here from a newborn with a murmur demonstrate?

[Insert Video Question 9 Chapter 19]

A.Origin of right-sided ductus from the base of the innominate artery

B.Origin of right-sided ductus from the descending aorta

C.Origin of left-sided ductus from the base of left subclavian artery

D.Origin of left-sided ductus from the descending aorta

E.Origin of left-sided ductus from the base of left carotid artery

10.A 15-year-old child has a patent ductus arteriosus with a Doppler pattern shown here. His systemic blood pressure is 118/65 mmHg. What are the pulmonary artery pressures based on this information?

A.Suprasystemic

B.Normal

C.Half-systemic

D.Two-third systemic

E.Unable to determine

Answers

1.Answer: C. In the standard parasternal short-axis view there is foreshortening and drop-out in the region of the patent ductus arteriosus (PDA). This can be avoided by using the high left parasternal short-axis view, which is also called the “ductal view.” In the parasternal long-axis view and the subcostal coronal view, the PDA is difficult to visualize on 2-D imaging, but with color Doppler imaging of the right ventricular outflow tract, a left-to-right shunt across the PDA can be seen into the main pulmonary artery. A PDA cannot be visualized in the typical apical four-chamber view as the great arteries are not seen in this view.

2.Answer: B. In a small patent ductus arteriosus with a left-to-right shunt and normal pulmonary artery pressures, the pressure difference between the aorta and pulmonary artery is the highest during late systole. Therefore, the peak velocity is noted during this phase of cardiac cycle.

3.Answer: C. The video shows a long tortuous ductus arteriosus that has an acute angulation with the descending aorta. This morphology of ductus arteriosus is seen in association with right ventricular outflow tract obstruction such as in pulmonary atresia with ventricular septal defect. In Tetralogy of Fallot with absent pulmonary valve, the ductus arteriosus is usually absent. In hypoplastic left-heart syndrome, the ductus arteriosus is at an obtuse angle to the descending aorta. In truncus arteriosus, the ductus arteriosus is usually absent unless it is associated with interrupted aortic arch. The descending aorta appears widely patent and there is no evidence of coarctation of aorta.

4.Answer: A. Even though interrupted aortic arch Type B is the most common type of arch interruption, Type A is the one most commonly associated with an aortopulmonary window, followed by Types B and C. Even though an association with coarctation of aorta and double aortic arch has been reported, it is extremely rare.

5.Answer: D. This Doppler signal shows diastolic flow reversal in the descending aorta. This pattern can be seen in any condition resulting in run-off from the descending aorta during the diastolic phase of the cardiac cycle. With a patent ductus arteriosus, aortopulmonary window, and aortopulmonary collaterals, the run-off during diastole is due to the left-to-right shunt from the aorta into the pulmonary artery. With aortic insufficiency, the blood leaks back from the aorta into the left ventricle during diastole resulting in a diastolic run-off pattern. In coarctation of aorta there is continuous forward flow during diastole and no flow reversal.

6.Answer: B. The continuous antegrade flow noted in both the pulmonary arteries here is due to a large aortopulmonary window since there is continuous left-to-right shunting across this defect from the aorta to the pulmonary arteries during systole and diastole. A small patent ductus arteriosus results in a turbulent jet of left-to-right shunt along the lateral wall of the main pulmonary artery but does not cause antegrade flow in both pulmonary arteries. With severe pulmonary insufficiency, retrograde flow reversal is noted during diastole. In anomalous origin of right pulmonary artery from ascending aorta, continuous forward flow is noted in the right pulmonary artery and not the left pulmonary artery. Moreover, this image shows a normal bifurcation of the main pulmonary artery into the right and left pulmonary arteries. With distal branch pulmonary artery stenosis, this sort of flow disturbance can be seen at the site of stenosis or distal to it, but not proximally.

7.Answer: E. This infant has a large unrestricted patent ductus arteriosus (PDA). The severe left-heart dilation is due to a large left-to-right shunt. Doppler of such a PDA shows the highest velocity in end-systole and very low and occasionally even zero velocity at end-diastole due to equalization of aortic and pulmonary pressures during end-diastole. The more unrestricted the PDA, the larger the variation between the systolic and diastolic velocities (pulsatile flow pattern). A right-to-left shunt in systole and a left-to-right shunt in diastole (bidirectional shunt) or a continuous right-to-left shunt is seen in pulmonary hypertension.

8.Answer: B. This parasternal short-axis image shows a large defect between the ascending aorta and the main pulmonary artery—i.e., an aortopulmonary window. Both the branch pulmonary arteries are seen arising normally from the main pulmonary artery, therefore this is neither a pulmonary sling nor anomalous origin of right pulmonary artery from the aorta. This is not truncus arteriosus, as the ascending aorta and pulmonary artery are separate from each other. While a large patent ductus arteriosus can certainly cause these symptoms, it is not seen on this image.

9.Answer: A. This is a suprasternal view scanning towards the right side, showing a right-sided ductus arteriosus originating from the base of the innominate artery. This newborn had discontinuous branch pulmonary arteries and the right pulmonary artery can be seen coming off the ductus arteriosus in this image.

10.Answer: B. The peak velocity across the patent ductus arteriosus is approximately 5 m/sec, thereby predicting a peak gradient of 100 mmHg. Given this information, the estimated pulmonary artery systolic pressure would be 18 mmHg (118-100 mmHg), which is normal.