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Case 25 - Patent ductus arteriosus
- from Section 3 - Anatomic variants and congenital lesions
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- By Tessa S. Cook, University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 81-83
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Summary
Imaging description
A tubular connection between the proximal descending aorta and the main pulmonary artery which opacifies after intravenous contrast administration (Figure 25.1) most likely represents a patent ductus arteriosus (PDA). The luminal diameter of the PDA is typically larger at the aortic end than at the pulmonic end (Figure 25.2). Cine imaging can be used to confirm that there is flow through the vessel from the aorta to the pulmonary artery, rather than just a pseudoaneurysm of the aorta that abuts the main pulmonary artery. Sagittal oblique MR images through the aorta demonstrate the PDA and confirm its patency by capturing the flow jet (dark signal) caused by flow into the main pulmonary artery (Figure 25.3).
Importance
The significance of a patent ductus arteriosus detected on imaging depends on its effect on the patient. Evaluation of the functional significance of a PDA is ideally performed with a cardiac MRI that can quantify not only cardiac ejection fraction but also shunt fraction and direction. An incidentally discovered PDA may not need further imaging evaluation in an asymptomatic individual.
Typical clinical scenario
The ductus arteriosus (DA) is an embryological connection between the proximal descending aorta and the main pulmonary artery (MPA). It exists to shunt deoxygenated blood away from the pulmonic circulation (which is high resistance in utero) back into the aorta so that it can travel to the placenta for oxygenation. The incidence of patent ductus arteriosus is low in term infants (57 per 100,000 live births) but can be very high in preterm infants (1 in 3 live births).
Normally the DA closes within 24–48 hours of birth, although it can be kept open pharmacologically with the administration of prostaglandins, particularly in the case of congenital heart disease where a left-to-right shunt is necessary to survive until surgery (Figure 25.4). When it closes normally, the DA becomes the ligamentum arteriosum, a fibrous connection between the two great vessels without any lumen.
Case 56 - Aortic pseudodissection from penetrating atherosclerotic ulcer
- from Section 7 - Acute aorta and aortic aneurysms
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- By Tessa S. Cook, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 179-180
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Summary
Imaging description
Axial images of the aorta that are perpendicular to a penetrating atherosclerotic ulcer may demonstrate a displaced intimal flap (Figure 56.1), suggestive of a dissection. However, upon inspection of the coronal oblique multiplanar reformats, penetrating atherosclerotic ulcers (PAUs) are easily distinguished from dissection (Figure 56.2). Penetrating atherosclerotic ulcers will communicate with the aortic lumen via a single, narrow-necked intimal defect. Dissections communicate with the aorta through at least two separate intimal defects at the proximal entry point and the distal exit point with an intervening false lumen. The appearance of a pseudodissection from large PAUs occurs when the PAU is viewed in a plane perpendicular to its long axis. At the levels near the proximal and distal neck of the ulcer where the PAU projects along the long axis of the aorta, the wall of the ulcer compressed against the wall of the aorta can simulate a displaced intimal flap.
Importance
Distinguishing between a large PAU and an aortic dissection is important for the immediate management of the patient. A type B dissection is typically managed without surgical intervention. However, an enlarging PAU, such as in this patient, may lead more expediently to surgical repair, particularly if the patient is acutely symptomatic.
Typical clinical scenario
Penetrating atherosclerotic ulcers and aortic dissection lie on the spectrum of acute aortic syndrome. When symptomatic, PAUs can have a similar clinical presentation to acute aortic dissection, consisting of a sudden onset of chest pain and discomfort. There is debate as to whether penetrating atherosclerotic ulcers can progress to aortic dissection. PAUs are often discovered incidentally during CT angiography.
Differential diagnosis
Differential considerations for an apparent displaced intimal flap commonly include aortic dissection or traumatic aortic injury, as well as artifacts from beam hardening or cardiac motion. However, this case illustrates that in patients with severe atherosclerosis and hypertension, a large PAU resulting in a pseudodissection should also be considered. Multiplanar reformats are valuable in cases such as these to distinguish between true dissections and large PAUs imitating dissection.
Case 28 - Respiratory and cardiac gating artifacts in cardiac CT
- from Section 4 - Coronary arteries
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- By Tessa S. Cook, University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 90-92
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Summary
Imaging description
Respiratory motion and heart rate variability are two of the primary causes for image artifacts on a gated thoracic computed tomographic angiography (CTA). Respiratory motion artifacts affect both the heart and adjacent structures, such as the sternum anteriorly and the descending aorta posteriorly (Figures 28.1 and 28.2), and are best identified using sagittal multiplanar reformats (MPRs). On sagittal MPRs, respiratory motion will cause stair-step artifacts and discontinuity of the sternum, aorta, and cardiac chambers. Blurring of lung parenchyma will also be visible on axial images in lung windows. Coronary segments may appear blurred or absent altogether (Figure 28.3). Cardiac gating artifacts can be distinguished from respiratory motion as they only affect the heart (Figure 28.4); no sternal discontinuity will result on sagittal MPRs. The appearance of cardiac gating artifacts will vary depending on whether the study is being acquired with prospective triggering or retrospective gating. With prospective triggering, the stair-step or stepladder artifact may occur due to heart rate irregularity or arrhythmias resulting in capture of a different segment of the heart than is desired. With retrospective gating in combination with tube current modulation, gating artifacts may result in stair-step artifacts combined with a band of noisy data being reconstructed (Figure 28.5).
Importance
Obtaining a diagnostic coronary CTA depends on heart rate optimization and the patient's ability to breath-hold during the image acquisition. In the absence of one or both of these factors, the resulting artifacts may lead to suboptimal evaluation or even complete non-visualization of certain coronary segments. Effective protocoling of a coronary CTA should include assessment of the patient's heart rate and breathing, and implementation of necessary interventions, such as beta blockade, to decrease high heart rates or accommodate known arrhythmias. The ability to successfully acquire a diagnostic gated thoracic CTA examination can be affected by irregular heart rates or arrhythmias such as atrial fibrillation.
Case 22 - Congenital absence of the pericardium
- from Section 3 - Anatomic variants and congenital lesions
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- By Tessa S. Cook, University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
-
- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 72-73
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Summary
Imaging description
Congenital absence of the pericardium is most easily diagnosed on axial CT or MR images. The heart appears rotated into the left hemithorax (Figure 22.1). Lung can be seen interposed between the aorta and the pulmonary artery, where normally there is fat covered by a layer of pericardium (Figure 22.2). In some cases, pericardium will be clearly visible along the right heart but not along the left heart (Figure 22.3). If the pericardial defect is small, focal herniation of a portion of the heart or great vessels may occur, increasing the risk for strangulation.
Importance
Distinguishing between complete and partial absence of the pericardium can be difficult when the normal, thin pericardium is generally difficult to visualize. Identifying absence of the pericardium is particularly important when the defect is partial, as this can result in herniation and strangulation of a portion of the heart or adjacent great vessels, which necessitates surgical correction.
Typical clinical scenario
Congenital absence of the pericardium occurs in approximately 0.002–0.004% of individuals. Partial absence of the left pericardium only (the most common form) results from atrophy of the left common cardinal vein, which interferes with development of the pericardium on that side.
It is most commonly incidentally detected during thoracic imaging ordered for unrelated reasons. Additionally, most cases are asymptomatic, although positional dyspnea and non-exertional chest pain have been reported, as has right bundle branch block. In 30% of patients, it is associated with congenital heart disease, such as tetralogy of Fallot, atrial septal defect, bicuspid aortic valve or patent ductus arteriosus.
Differential diagnosis
The differential diagnosis falls within two major categories: causes of levoposition of the heart or focal outpouchings from the heart. Volume loss in the left hemithorax due to atelectasis, prior lobectomy or left-sided bronchial atresia can also lead to levoposition of the heart in the setting of an intact pericardium. Enlargement of the right heart due to valvular disease or other causes can displace the heart into the left hemithorax.
Case 89 - Persistent sciatic artery
- from Section 10 - Peripheral vascular
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- By Tessa S. Cook, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 275-277
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Summary
Imaging description
A persistent sciatic artery can easily be identified using CT angiography of the pelvis and lower extremities. Sequential enhanced axial images through the pelvis demonstrate a vascular structure in the left hemipelvis that courses along the left acetabulum (Figure 89.1) before diving inferolaterally along the anterior aspect of the gluteus maximus into the left thigh (Figure 89.2). The vessel is of greater caliber than the ipsilateral external iliac, superficial femoral, and profunda femoris arteries. Its course is better appreciated on three-dimensional volume renderings (Figure 89.3), where the associated enlargement of the ipsilateral internal iliac artery can also be well appreciated. While this persistent left sciatic artery is mildly tortuous proximally, it is relatively uniform in caliber throughout its visualized course and does not contain any thrombus.
Importance
The persistent sciatic artery is a very rare vascular variant that can become clinically significant if complicated by aneurysm or thrombosis. In such cases, patients often present with a pulsatile or enlarging gluteal mass or new onset of decreased pedal pulses, and surgical bypass (femoropopliteal or femorotibial) becomes necessary to restore blood flow to the leg.
Typical clinical scenario
The embryologic sciatic artery begins as a branch of the umbilical artery and perfuses the entire lower limb bud. By about the sixth week of gestation, the iliofemoral system begins to form and the sciatic artery begins to regress. Segments of the sciatic artery normally remain in the adult to form portions of the popliteal and peroneal arteries.
In cases where the sciatic artery persists, it arises from the internal iliac artery and follows the course of the inferior gluteal artery. After passing through the sciatic foramen into the thigh, it may run adjacent to the posterior cutaneous or sciatic nerves. This course can predispose patients to sciatic neuropathy if the vessel becomes enlarged due to aneurysm or thrombus. In cases where the superficial femoral artery is hypoplastic, patency of the sciatic artery becomes critical to preserve limb perfusion.
Case 87 - Suboptimal bolus timing in CT angiography of the extremities
- from Section 10 - Peripheral vascular
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- By Tessa S. Cook, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 269-271
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Summary
Imaging description
Images with inadequate arterial opacification from suboptimal bolus timing demonstrate gradually decreasing opacification in the lower extremity arteries as they course distally. Often, the distal calf vessels are most severely affected, sometimes demonstrating a complete lack of opacification, which can simulate occlusion due to atherosclerotic or thrombotic disease. (Figures 87.1 and 87.2). However, immediate delayed images through the lower extremities will show complete opacification of the distal vessels, allowing for accurate characterization of vascular disease in the calf (Figure 87.3).
Importance
The use of multidetector CT for the evaluation of the abdominal aorta and lower extremity vasculature has become a routine clinical examination in multiple patient populations. It is important to design protocols for these studies to avoid the common pitfall of suboptimal bolus timing. Disease in the aortoiliac or the femoropopliteal bed that results in sluggish downstream flow can be misinterpreted as occlusion in the calves if three-vessel runoff is not observed. Similarly, patients with very low cardiac output may require modifications to a standard protocol to account for the slow transit of contrast from the aorta to the feet. For this reason, it may be helpful to obtain immediate delayed images through the calves and feet, as the scanner may progress faster than the contrast bolus during the arterial phase of imaging. For dedicated lower extremity angiography, placement of the bolus tracker on the popliteal artery will also improve timing.
Typical clinical scenario
CT angiography of the abdominal aorta and lower extremities is performed for a variety of reasons. In the emergent setting, it is often required to assess for vascular injury in the setting of trauma or for acute vascular occlusion in a patient with a cold extremity. When ordered non-emergently, the goal is often to evaluate patients with peripheral vascular disease to determine if there is a need for surgical intervention. Regardless of the acuity, bolus timing is an important consideration. If there is stenosis proximally, distal vessels will demonstrate delayed opacification due to slower flow. However, if a study is obtained without proper timing, stenoses may erroneously be interpreted as occlusions.
Case 23 - Partial anomalous pulmonary venous return
- from Section 3 - Anatomic variants and congenital lesions
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- By Tessa S. Cook, University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 74-77
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Summary
Imaging description
Partial anomalous pulmonary venous return (PAPVR) is characterized by the inappropriate drainage of one or more pulmonary veins into the systemic venous circulation. Anomalous drainage of the left superior pulmonary vein to the left brachiocephalic vein or the right superior pulmonary vein to the superior vena cava (Figures 23.1 and 23.2) are the most common incidentally encountered forms of PAPVR in adults undergoing chest CT exams. Right upper lobe PAPVR is associated with a sinus venosus type atrial septal defect in 42% of patients (Figure 23.2). Scimitar syndrome is a specialized form of PAPVR that predominantly involves the right-sided pulmonary veins (Figure 23.3). In this scenario, the right inferior pulmonary vein drains below the diaphragm to join the IVC just distal to the hepatic vein confluence (Figure 23.1). Scimitar syndrome is often associated with right-sided thoracic anomalies, such as a hypoplastic right lung (Figure 23.2). PAPVR is a left-to-right shunt, and depending on the volume of shunting, right-sided cardiac chamber enlargement and pulmonary artery enlargement may be present (Figure 23.1).
Importance
PAPVR occurs in many forms, which together have a prevalence of less than 1%. Although rare, PAPVR can be detected incidentally in asymptomatic patients, which may prompt further evaluation to assess need for repair. In addition, in patients being evaluated for an occult shunt due to right-sided chamber enlargement, PAPVR is an important subtype of shunt that may be missed by echocardiography. Cross-sectional imaging becomes important for characterization of the anatomy, particularly in patients who are symptomatic and are undergoing preoperative evaluation. Surgical therapy is generally considered if the Qp:Qs is at least 1.5:1, because of the risk of pulmonary hypertension and right ventricular failure.
Typical clinical scenario
The timing of diagnosis of PAPVR is closely related to the degree of symptoms and number of associated anomalies. Patients who are incidentally found to have PAPVR as adults are rarely symptomatic and have few associated anomalies, while those who are diagnosed earlier in life typically have more severe symptoms and a higher number of associated congenital malformations.
Case 40 - Vein graft aneurysms after CABG
- from Section 4 - Coronary arteries
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- By Tessa S. Cook, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 127-128
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Summary
Imaging description
When incidentally detected on radiography, saphenous vein graft aneurysms most commonly present as mediastinal masses (Figure 40.1). This leads to follow-up cross-sectional imaging to narrow the broad differential diagnosis, which will more clearly characterize the “mass” as a large aneurysm (Figure 40.2). Vein graft aneurysms can easily grow to 6 cm or more in greatest diameter, and may be filled with a large amount of thrombus. It is important to identify whether the native coronary artery distal to the aneurysm is patent (Figure 40.3), because this will dictate treatment options (e.g., closure or embolization vs. endovascular stenting).
Importance
Saphenous vein graft aneurysms are an uncommon complication of coronary artery bypass grafting (CABG), thought to occur in less than 1% of patients. However, because of the increased risk of rupture, they are associated with significant morbidity and mortality. If the thrombus within the aneurysm sac is unstable, there is also an increased risk of myocardial infarction in the territory distal to the graft. In addition, as the aneurysm grows, it can exert a mass effect on adjacent structures, such as cardiac chambers or the pulmonary veins, resulting in heart failure.
If the graft and native vessel remain patent, percutaneous repair with a covered stent is the preferred therapy to preserve perfusion. However, if the graft is thrombosed, the aneurysm can be occluded using coil embolization or a closure device. In some cases, such as when the luminal diameter of the coronary arteries is too small to permit passage of the percutaneous repair apparatus, patients may undergo surgical repair involving resection of the aneurysm and replacement of the vein graft.
Typical clinical scenario
Saphenous vein grafts are often used for CABG. In rare cases, aneurysms of the vein grafts can form (as much as a decade or longer after the procedure) due to aggressive atherosclerosis. Such aneurysms are often incidentally detected during follow- up imaging or chest radiography for unrelated reasons.