|Ahead of print publication
Crossed Pulmonary Arteries: A Literature Review
Abhinav Agarwal1, Vimalarani Arulselvam1, Suad Rashid Al Amer2, Neale Nicola Kalis2
1 Mohammed bin Khalifa bin Salman Al-Khalifa Cardiac Center, Bahrain Defense Forces Hospital, Awali, Bahrain
2 Mohammed bin Khalifa bin Salman Al-Khalifa Cardiac Center, Bahrain Defense Forces Hospital, Awali; Department of Pediatrics, Royal College of Surgeons of Ireland – Medical University of Bahrain, Busaiteen, Bahrain
|Date of Submission||08-Mar-2021|
|Date of Acceptance||30-Apr-2021|
|Date of Web Publication||09-Jun-2021|
The Mohammed bin Khalifa bin Salman Al-Khalifa Cardiac Center, Bahrain Defense Force Hospital, PO Box 28743, Awali
Source of Support: None, Conflict of Interest: None
Crossed pulmonary artery (CPA) is a rare congenital malformation with only about 100 cases reported worldwide. It is often an incidental finding on cardiac imaging with symptoms rarely attributed to this anomaly. Sometimes, it can result in difficulties during catheterization and surgical procedures. Thus, it is necessary to diagnose CPA preoperatively to reduce misadventures. CPA is primarily diagnosed by computerized tomography angiography (CT angio) and missing it during echocardiography is common, even when an accurate diagnosis is possible by echocardiography alone. Echocardiography can also differentiate it from other causes of nonvisualization of pulmonary artery bifurcation. Recent studies suggest that CPA is not as rare as previously described. With increased utilization of CT angio, more cases of CPA are being picked up, which were not noted earlier on echocardiography. Missing CPA on echocardiography is attributed mainly to the lack of awareness regarding this condition among echocardiographers. Raising awareness can avoid missed diagnoses and aid in planning the interventional and surgical procedures.
Keywords: Criss-cross pulmonary arteries, crossed pulmonary artery, malposition of the origins of pulmonary arteries
|How to cite this URL:|
Agarwal A, Arulselvam V, Al Amer SR, Kalis NN. Crossed Pulmonary Arteries: A Literature Review. J Indian Acad Echocardiogr Cardiovasc Imaging [Epub ahead of print] [cited 2021 Jul 23]. Available from: https://www.jiaecho.org/preprintarticle.asp?id=318101
| Introduction|| |
Crossed pulmonary artery (CPA) is a rare cardiac anomaly with a hospital-based prevalence of 0.33% among patients with congenital heart disease (CHD). It was first described by Jue et al. in 1966 as malposition of the origins of two pulmonary arteries (PA) from pulmonary trunk that results in their crossing each other during their course to the respective lungs. Over the years, CPA has been described by several terms, i.e., criss-cross PA, malposition of PA, malposition of branch PA, and anomalous origin of PA from pulmonary trunk., To add to the confusion, some articles describe cases of malposition without crossing also under “CPA”. Hence, Recto et al. utilized the term “malposition of branch PA” instead of “CPA”. However, the term CPA is still widely recognized and used to describe both the types.
Chen and Feng in 2013 described only 39 cases to be reported since 1966. However, our literature search in 2020 revealed about 100 such cases.,,,,,,,,,,,,,,,,,,, Easy availability and increased utilization of cardiac computerized tomography angiography (CT Angio) have resulted in increased detection of CPA. Many case reports describe incidental detection of CPA on CT angio, during evaluation for other complex CHD., However, on active screening, various researchers identified 10–30 cases of CPA in a short span of 3 years, thus inferring that CPA might not be as a rare anomaly as perceived before.,,
| Classification|| |
Becker et al. classified this malformation based on the presence or absence of crossing. The typical/classical form of CPA which is more common has origin of left PA (LPA) superior and to the right of the origin of right PA (RPA) with PA crossing each other during their course to respective lungs. The atypical and lesser-known form of CPA has a supero-inferior orientation of both PA origins without the evidence of crossing (LPA being superior and RPA inferior). However, Recto et al. described these atypical forms as merely an illusion formed due to abnormal orientation of normally dividing main PA (MPA) with reference to echocardiography transducer position.
| Embryology|| |
Jue et al. suggested that this condition could result from a faulty differential growth within the pulmonary trunk during partitioning of truncus arteriosus with a counterclockwise rotation of normally formed main and branch PA., Counterclockwise rotation shifts the origin of LPA superior and to the right of RPA origin and concomitantly results in RPA origin becoming inferior and to the left of LPA origin. One case report described reversed crossing, i.e., RPA origin being superior and left and LPA origin being inferior and right, which the authors attributed to clockwise rotation of branch PA. Cuturilo et al. suspected that the abnormal rotation could lead to a spectrum of rotational anomalies, creating different positions of origins of branch PA. However, the theories regarding clockwise or counterclockwise rotation during the partitioning of the truncus arteriosus are yet to be proven in animal models.
| Clinical Features|| |
Isolated CPA is a benign condition with no hemodynamic consequences. Symptoms are mostly due to associated cardiac or arch anomalies. CPA with arch anomalies can present with noncardiac symptoms such as bronchial compression, and esophageal compression. El Batti et al. described the influence of associated CPA on vascular ring. CPA caused ligamentum arteriosum to connect at a higher than usual location to LPA, which reduced the effective area inside vascular ring and increased the severity of esophageal compression.
Recognition of this anomaly is important as it may also have other clinical and surgical implications. CPA is frequently associated with genetic syndromes and complex cardiac anomalies, so identifying this anomaly warrants further investigation. In the catheterization laboratory, it can create difficulty during cannulation of PA and may complicate the accurate interpretation of the location of catheters and the relationship of branch PA., CPA can be problematic during surgical procedures, especially during PA banding and may increase the likelihood of iatrogenic stenosis of RPA after PA band when associated with a short MPA.,, It can also increase the difficulty of surgical repair of adjacent structures., Surgeons might need to devise innovative methods to tackle CPA, and thus, knowledge of it beforehand can assist them in reducing procedure time and improve the patient prognosis.,
| Associated Anomalies|| |
As CPA is underdiagnosed and underreported, describing its association precisely with various CHDs could be misleading. CPA is known to be associated with conotruncal and arch anomalies, most commonly interrupted aortic arch, truncus arteriosus, coarctation of aorta, double outlet right ventricle, and Tetralogy of Fallot.,,,,,,,,,,, Recent case series reported cases of CPA in patients without any conotruncal or arch anomaly such as Ebstein's anomaly, cor triatriatum, ventricular septal defect, atrial septal defect, pulmonary stenosis, and branch PA stenosis.,,,,,, Some cases of isolated CPA have also been reported.,
Genetic syndromes frequently associated with CPA are 22q11 deletion, Trisomy 18, Noonan syndrome, Holt-Oram syndrome, and vertebral, anal, cardiac, tracheal, esophageal, renal, limb anomalies (VACTERL anomalies).,,,,
| Echocardiography|| |
PA anatomy is best visualized in parasternal short-axis and high left parasternal views. Probe manipulation in these planes can demonstrate the origin, spatial relationship, and course of branch PA. In CPA, PA have an unusual relation and origin is not side-by-side, thus it is not possible to visualize both PA together in a single plane from the left parasternal short axis. A superior to inferior sweep is required to visualize the separate origins and to delineate the course of PA. In typical CPA with crossing, PA lie perpendicular to each other at the point of crossing, and thus, if visualized together in one frame, one of them is seen in the long axis while the other one in the short axis [Figure 1]a. If by manipulating the probes, one manages to visualize both PA in long axis, it will not be possible to demonstrate the origins of both PA together in the same frame [Figure 1]b. In atypical CPA, origins will be seen at different levels, but the perpendicular image of branch PA will not be seen, as it is formed only because of crossing. In suprasternal views, normally, we find only RPA coursing below the arch of aorta but in CPA with crossing, we will see both PA coursing below the aortic arch. Sometimes, we can see patent ductus arteriosus also in the same view if it is present [Figure 1]c. CPA can also be diagnosed in the fetus in three-vessel tracheal view. Missing the diagnosis of CPA on echocardiography is a common phenomenon and Zhang et al. have listed common reasons for that. First, not many echocardiographers are aware of this anomaly. Second, they generally do not pay attention to the branch PA of otherwise normal children. Third, it can also get easily overlooked in the presence of other intracardiac malformations. Thus, Cuturilo et al. suggested that careful assessment of PA branches should be done in all patients with ventricular septal defect.
|Figure 1: (a) Two-dimensional and color flow echocardiographic image in parasternal short axis view showing perpendicular orientation of branch pulmonary arteries (left pulmonary artery is in long axis and right pulmonary artery is in short axis). (b) Two dimensional and color flow echocardiographic image in parasternal short axis view after probe manipulation showing the two branch pulmonary arteries in long axis. Please note that only the origin of right pulmonary artery from main pulmonary artery is clearly visualized and left pulmonary artery origin is not clear. (c) Two-dimensional and color flow echocardiographic image in suprasternal long axis view showing both pulmonary arteries imaged below arch of aorta (right pulmonary artery in short axis and left pulmonary artery in long axis). There is associated interrupted aortic arch with patent ductus arteriosus continuing as descending aorta. Color flow image assists in separating left pulmonary artery flow from patent ductus arteriosus|
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| Differential Diagnosis|| |
Other causes for nonvisualization of MPA bifurcation are PA sling and anomalous origin of one of the branch PA from aorta. In PA sling, LPA originates from RPA instead of originating from MPA and then courses between trachea and esophagus to reach the left lung. Origin of LPA from RPA can give an impression of CPA in echocardiography. CT angio and magnetic resonance imaging with three-dimensional reconstruction will be helpful in differentiating these cases [Figure 2].
|Figure 2: (a) Two-dimensional computerized tomographic image in transverse view showing left pulmonary artery origin from main pulmonary artery. Right pulmonary artery is visualized in cross-section at this level. (b) Two-dimensional computerized tomographic image in transverse view showing right pulmonary artery origin from main pulmonary artery. Left pulmonary artery is visualized in cross-section at this level. (c) Two-dimensional computerized tomographic image in sagittal view showing both the branch pulmonary arteries coursing below aortic arch. (d) Three-dimensional volume-rendered image (posterior view) showing interruption of aortic arch with patent ductus arteriosus continuing as descending aorta and criss-cross origin of pulmonary arteries. AAo: Ascending Aorta, DAo: Descending aorta, IAA: Interrupted aortic arch, LPA: Left pulmonary artery, PDA: Patent ductus arteriosus, RPA: Right pulmonary artery|
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| Conclusion|| |
Recent literature review suggests that CPA is not as rare as perceived before. Most of the reported cases have incidental detection of CPA on CT scans. Although CPA can be diagnosed confidently by echocardiography, it is still being missed. The echocardiographic analysis is mainly limited by the operator's technique and experience. Thus, it is necessary to familiarize echocardiographers with this “not so rare” anomaly to augment the detection rate of CPA and reduce surprises in the catheterization laboratory or operation theater. This will improve patient management and prognosis.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]