Pulmonary Vein Anomalies

1. Embryology of Pulmonary Veins:The primordial lung buds are surrounded by the vascular plexus of the foregut (splanchnic plexus), which initially lacks direct connections to the heart. During development, the common pulmonary vein (CPV) establishes a connection between the pulmonary venous plexus and the sinoatrial portion of the heart. Over time, connections between the pulmonary venous plexus and the splanchnic plexus regress, and the CPV incorporates into the left atrium (LA). This process allows individual pulmonary veins to connect separately and directly to the LA.
   

   Fig 2: Pulmonary veins - normal development
2. Congenital Anomalies:
   

   Fig 3: Pulmonary veins - normal anatomy
   

   Fig 4: Pulmonary veins anomalies

• Total Anomalous Pulmonary Venous Return (TAPVR):
  

  Fig 8: CARDIAC TOTAL ANOMALOUS PULMONARY VENOUS RETURN. (A-C) axial maximum intensity projections and (D) three-dimensional volume-rendered reconstruction of cardiac CTA images show four anomalous pulmonary veins bilaterally draining through a common pulmonary venous trunk that joint right atrium (RA). Observe the atrial septal (asterisk).
  Embryologic failure of the CPV to connect to the LA results in abnormal pulmonary venous drainage into the right atrium, coronary sinus, or systemic veins, causing a left-to-right shunt. CTA or MR angiography can delineate the drainage pathways and classify TAPVR into supracardiac, cardiac, infracardiac, or mixed types.
• Partial Anomalous Pulmonary Venous Return (PAPVR):
  

  Fig 10: SCIMITAR SYNDROME (INFRACARDIAC PARTIAL ANOMALOUS PULMONARY VENOUS RETURN). (A) chest X-ray, and (B) anterior and (C) posterior three-dimensional volume-rendering reconstructions of chest CTA images show the anomalous right pulmonary venous connection to inferior vena cava, next to the confluence of the hepatic veins, as a curved anomalous venous trunk resembling Turkish sword (increasing in its flow and caliber), located in right medial costophrenic sulcus near right heart border.
  A congenital anomaly where one or more pulmonary veins drain into systemic veins rather than the LA. PAPVR is associated with right heart volume overload and often presents with subtle or no symptoms. Imaging highlights the anomalous venous pathway and quantifies the hemodynamic impact. PAPVR can be classified based on the drainage site:
• Supracardiac PAPVR:Pulmonary veins drain into systemic veins above the heart, such as the superior vena cava or brachiocephalic vein. This is the most common form of PAPVR. Imaging demonstrates anomalous drainage into these veins, often associated with left-to-right shunting.
• Cardiac PAPVR:Pulmonary veins drain directly into the coronary sinus or right atrium. This type may present with subtle symptoms or be incidentally detected on imaging studies.
• Infracardiac PAPVR:Pulmonary veins drain into systemic veins below the heart, such as the inferior vena cava, hepatic veins, or portal veins. This type is less common and is more likely to result in significant clinical symptoms due to increased shunting.

Pulmonary Artery Anomalies

1. Embryology of Pulmonary Arteries:Pulmonary arteries originate from the ventral part of the sixth aortic arch during embryogenesis. Neural crest cells and endocardial cells develop in a spiraling configuration, forming the conotruncal septum, which separates the aortic and pulmonary outflow tracts. Disruptions in this process can result in various anomalies.
   

   Fig 12: Pulmonary arteries - normal development
   

   Fig 13: Pulmonary arteries - anatomy
2. Congenital Anomalies:

• Pulmonary Sling (Anomalous Origin of the Left Pulmonary Artery):
  

  Fig 18: PULMONARY SLING (TYPE IA). (A) chest X-ray, and (B) axial MIP, and (C) sagittal, (D-F) three-dimensional volume-rendered reconstruction of chest CT images show the anomalous origin of left pulmonary artery from the posterior aspect of the right pulmonary artery (black arrow), forming a "sling" around the distal trachea just above carina level (black arrowhead) as it courses toward left between trachea and esophagus (white arrowhead) at T4-T5 level, creating a mild indentation along the posterior tracheal margin with minimal tracheal stenosis (correlating with the lack of symptoms). Observe the vascular ring (asterisk) when associated with the aortic arch (white arrow).
  The left pulmonary artery arises anomalously from the right pulmonary artery, encircling the trachea and esophagus. Symptoms include stridor and respiratory distress. Imaging with CTA reveals the abnormal vascular course and its relationship to adjacent structures.
• Proximal Interruption of the Pulmonary Artery:This condition is marked by the absence of the proximal segment of one pulmonary artery. Collateral blood supply via systemic arteries may develop. CTA is critical in identifying the absent segment and mapping collateral circulation.
• Pulmonary Arteriovenous Malformations (PAVM):
  

  Fig 21: PULMONARY ARTERIOVENOUS MALFORMATION. (A) Technetium-99m albumin aggregated scintigraphy show pulmonary-systemic shunt. (B) Axial image of chest CT and (C) pulmonar angiography show a simple pulmonar arteriovenous malformation in the anterior segment of the right upper lobe (arrow). PULMONARY ARTERIOVENOUS MALFORMATION. (A-C) Three-dimensional volume-rendered reconstructions of chest CT show some simple pulmonar arteriovenous malformations in both lungs. PULMONARY ARTERIOVENOUS MALFORMATION. (A-C) Three-dimensional volume-rendered reconstructions of chest CT show some simple pulmonar arteriovenous malformations in both lungs.
  Abnormal direct connections between pulmonary arteries and veins result in shunting of blood and systemic hypoxemia. CTA and contrast-enhanced imaging techniques show the dilated feeding artery and draining vein, with 3D reconstructions aiding surgical planning.
• Truncus Arteriosus (Type 1):A rare congenital anomaly resulting from failure of the conotruncal septum to fully separate the aorta and pulmonary artery during development. This anomaly is characterized by a single arterial trunk exiting the heart and supplying systemic, pulmonary, and coronary circulations.
• Definition: The pulmonary arteries arise from a short common trunk just above the truncal valve.
• Clinical Manifestations: Symptoms include cyanosis, respiratory distress, and heart failure in neonates.
• Imaging Findings: Echocardiography is the primary modality for diagnosis. CTA or MRI provides detailed anatomy, including the common trunk, pulmonary arteries, and associated cardiac defects.
• Treatment: Surgical repair is required, involving separation of the pulmonary arteries from the truncal artery and reconstruction of the outflow tract.
• Pulmonary Artery Atresia:A severe congenital condition where the pulmonary artery is completely absent or non-patent, obstructing blood flow to the lungs.
• Embryology: Results from incomplete development of the pulmonary artery during the division of the truncus arteriosus.
• Clinical Manifestations: Presents with profound cyanosis and severe hypoxemia shortly after birth. Without intervention, it is life-threatening.
• Imaging Findings:
• Echocardiography: Detects atresia and associated right ventricular outflow tract abnormalities.
• CTA or MRI: Used to delineate pulmonary circulation, including collateral vessels supplying the lungs (e.g., bronchial arteries).
• Treatment: Management typically involves surgical procedures, such as systemic-to-pulmonary artery shunts or complete repair, depending on the associated cardiac defects and presence of collateral vessels.
• Anomalous Left Coronary Artery from the Pulmonary Artery (ALCAPA)
  

  Fig 22: Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA)
• Pathophysiology:
• ALCAPA is a rare congenital defect where the left coronary artery arises abnormally from the pulmonary artery instead of the aorta. This anomaly leads to myocardial ischemia and left-to-right shunting (coronary steal phenomenon) as pulmonary arterial pressure decreases postnatally.
• Clinical Presentation:
• Infantile Type: Myocardial infarction, congestive heart failure, and high mortality within the first year of life if untreated.
• Adult Type: Collateral circulation from the right coronary artery may develop, leading to chronic myocardial ischemia, dysrhythmias, or sudden death.
• Imaging Findings:
• CTA and MRI: Clearly depict the anomalous origin of the left coronary artery from the pulmonary artery and any collateral circulation.
• Echocardiography: Useful for initial detection, particularly in symptomatic infants.
• Treatment:
• Surgical restoration of a dual-coronary-artery system is the treatment of choice. This involves re-implanting the left coronary artery into the aorta or creating an alternative conduit to ensure adequate myocardial perfusion.