6 Pulmonary Artery and Vein



Hiro Kiyosue and Miyuki Maruno

6 Pulmonary Artery and Vein



Pulmonary Artery


The pulmonary trunk (the main pulmonary artery) originates at the base of the right ventricle, and the origin is located anterior to the aortic sinus. It moves posteriorly on the left side of the ascending aorta in the pericardial sac, and divides into the right and left pulmonary arteries in front of the left main bronchus at the level of T5 to T6 vertebra (Fig. 6‑1). The diameters of the pulmonary trunk, the right pulmonary artery, and the left pulmonary artery are approximately 24, 16, and 18 mm, respectively. Their upper limits are about 30, 20, and 22 mm, respectively. 1 The left pulmonary artery is slightly larger than the right pulmonary artery. The mean pressure of the pulmonary artery is 9 to 18 mm Hg in normal conditions, and it is elevated greater than 25 mm Hg in pulmonary hypertension. The wedge pressure, representing left atrial pressure, is 6 to 12 mm Hg, which is elevated in several pathological conditions such as left heart failure and mitral valve stenosis. The right pulmonary artery runs transversely behind the ascending aorta and superior vena cava to reach the root of the right lung (Fig. 6‑1 , Fig. 6‑2 , Fig. 6‑3). The right pulmonary artery divides into a superior and an inferior trunk (interlobar artery) behind the superior vena cava in the mediastinum (Fig. 6‑2 , Fig. 6‑3). The superior trunk generally gives off segmental arteries supplying the upper lobe. The inferior trunk (interlobar artery) runs laterally and inferiorly between the superior pulmonary vein and the right main bronchus, which gives off segmental arteries to the middle lobe and the inferior lobe. The segmental pulmonary arterial branches run along the accompanying branches of the bronchial tree. The left pulmonary artery ascends posteriorly, and arches over the left main bronchus laterally to the root of the left lung (Fig. 6‑1 , Fig. 6‑2). It gives off several superior lobar arteries (the number varies from two to seven branches) to supply the superior lobe, then it becomes interlobar artery which branches off into the segmental arteries to feed the left lower lung lobe. In both lungs, segmental and subsegmental branches are usually located in the vicinity of corresponding bronchi, however, branching patterns of the segmental/ subsegmental arteries are variable especially in upper lobes (Fig. 6‑2). The segmental and subsegmental arteries of both the pulmonary arteries are summarized in Table 6‑1.

Fig. 6.1 Normal CT Anatomy of the pulmonary artery and vein. Anterior (a), right lateral (b), posterior (c), and left lateral (d) views of 3D CT angiography (3DCTA). AV, anterior vein; CBV, common basal vein; CV, central vein; IPV, inferior pulmonary vein; IT, inferior trunk; LPA, left pulmonary artery; PT, pulmonary trunk; RPA, right pulmonary artery; SPV, superior pulmonary vein; ST, superior trunk.
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Fig. 6.2 Coronal multiplanar reconstruction (MPR) images showing pulmonary arterial and venous branches. AA, ascending aorta; AV, anterior vein; CV, central vein; IT, inferior trunk; LA, left atrium; LAA, left atrial auricle; LIPV, left inferior pulmonary vein; LPA, left pulmonary artery; LSPV, left superior pulmonary vein; LV, left ventricle; RA, right atrium; RV, right ventricle; RPA, right pulmonary artery; SVC, superior vena cava.
(i-p)
(q-t)
Fig. 6.3 Axial multiplanar reconstruction (MPR) CT images showing arterial and venous branches. AA, ascending aorta; CBV, common basal vein; CV, central vein; DA, descending aorta; IT, Inferior trunk; LAA, left atrial auricle; LIPV, left inferior pulmonary vein; LPA, left pulmonary artery; LSPV, left superior pulmonary vein; PT, pulmonary trunk; RPA, right pulmonary artery; RSPV, right superior pulmonary vein; ST, superior trunk; SVC, superior vena cava.














































































































































Table 6.1 Segmental and subsegmental arteries of the pulmonary artery

Right pulmonary artery


Left pulmonary artery


Segmental artery


Subsegmental artery


Segmental artery


Subsegmental artery


Upper lobe

 

Upper lobe

 

A1, apical


A1a, apical


A1+2, apicoposterior


A1+2a, apical

 

A1b, anterior

 

A1+2b, posterior


A2, posterior


A2a, posterior

 

A1+2c, lateral

 

A2b, lateral


A3, anterior


A3a, lateral


A3, anterior


A3a, lateral

 

A3b, anterior

 

A3b, anterior

 

A3c, superior


Middle lobe

   

A4a, lateral


A4, lateral


A4a, superior


A4, superior lingula


A4b, medial

 

A4b, lateral


A5, inferior lingula


A5a, superior


A5, medial


A5a, superior

 

A5b, inferior

 

A5b, inferior


Lower lobe

 

Lower lobe

   

A6a, superior


A6, apical


A6a, superior


A6, apical


A6b, lateral

 

A6b, lateral

 

A6c, medial

 

A6c, medial


A7, medial

 

A7, medial


A7a, posterior


A8, anterior


A8a, lateral

 

A7b, anterior

 

A8b, basal


A8, anterior


A8a, lateral


A9, lateral


A9a, lateral

 

A8b, basal

 

A9b, basal


A9, lateral


A9a, lateral


A10, posterior


A10a, posterior

 

A9b, basal

 

A10b, lateral


A10, posterior


A10a, posterior

 

A10c, basal

 

A10b, lateral

   
 

A10c, basal

   

For the right upper lobe, the apical (A1: A1a, apical; and A1b, anterior) segmental/subsegmental artery arises from the superior trunk. The anterior subsegmental artery (A3b) of the anterior segmental artery (A3) usually arises from the superior trunk. The posterior (A2: A2a, posterior; and A2b, lateral) segmental/subsegmental arteries and lateral subsegmental artery (A3a) of A3 can originate from either the superior trunk or the interlobar artery (so-called ascending pulmonary artery). 2 ,​ 3 The segmental arteries of the right middle lobe (A4, lateral; A5, medial) arise from the anterior aspect of the interlobar artery independently or from a common trunk. These segmental arteries further divide into subsegmental arteries (A4a, lateral; A4b, medial; A5a, superior; and A5b, inferior). The middle lobe segmental arteries occasionally originate from the artery to the basal segments (Fig. 6‑2). 4 ,​ 5 The middle lobe arteries rarely give off a branch to the lower lobe. The lower lobe apical segmental artery (A6) originates from the posterolateral aspect of the interlobar artery opposite to the middle lobe artery. It runs posteriorly, accompanying the corresponding bronchus (B6), and divides into three subsegmental arteries (A6a, superior; A6b, lateral; and A6c, medial). One of these subsegmental arteries can rarely originate independently from the interlobar artery. After branching the A6, the left pulmonary artery divides into basal segmental arteries (A7, medial; A8, anterior; A9, lateral; and A10, posterior). They originate from the inferior pulmonary trunk either independently or via an anterior (A7 and A8) or a posterior trunk (A9 and A10). Each basal segmental artery subdivides into the following subsegmental arteries: A7a, dorsal; A7b, ventral; A8a, lateral; A8b, basal; A9a, lateral; A9b, basal; A10a, posterior; A10b, lateral; and A10c, basal. The basal segmental arteries are occasionally duplicated or even triplicated surrounding a corresponding bronchus. 6


For the left upper lobe, the anterior segmental artery (A3) arises from the anterosuperior aspect of the left pulmonary artery at the arch, and then the apicoposterior segmental (A1+2) or the subsegmental arteries (A1+2a, apical; A1+2b, posterior; and A1+2c, lateral) arise independently or with a common trunk from the posterosuperior aspect of the left pulmonary artery. The anterior segmental artery (A3) further subdivides into three subsegmental arteries (A3a, lateral; A3b medial; and A3c, superior). The left pulmonary artery enters the major fissure, becoming interlobar artery, and runs on the side of the lower lobe bronchus. The lingular segmental arteries (A4, superior; and A5, inferior) arise from the anterior aspect of the interlobar artery independently or as a single trunk. The lingular arteries rarely originate from the other upper lobe arteries or the basal segmental arteries. Branching pattern and course of the segmental arteries to the left lower lobe are similar to the right pulmonary artery. The apical segmental artery of the left lower lobe (A6) usually originates at slightly higher portion of the interlobar artery compared to its fellow on the right side. Medial basal segmental artery (A7) is often subtle or unidentified on the left side.


Intrapulmonary arteries divide and subdivide along the bronchi and bronchioles which lie in the central portion of the secondary and then the primary pulmonary lobules. There, they become arterioles proceeding along the respiratory bronchioles and alveolar ducts to form capillary networks in the alveolar walls for gas exchange. 7 These capillary networks continue to the pulmonary venules which join the pulmonary veins which are located in the interlobular septa.



Pulmonary Vein


The pulmonary vein in the interlobular septa join together to form segmental pulmonary veins. Unlike the segmental pulmonary arteries, the segmental pulmonary veins are not close to the bronchi, instead they run within the intersegmental septa. The segmental pulmonary veins join to form two common trunks of the superior pulmonary vein and the inferior pulmonary vein which connect to the left atrium on each side. The orifices of the inferior pulmonary veins are more dorsal than those of the superior pulmonary veins (Fig. 6‑2). 8 The orifices of the left pulmonary veins are located more superiorly than those of the right pulmonary veins (Fig. 6‑1). 9 ,​ 10 There are some variations of the pulmonary veins. The left superior and inferior pulmonary veins occasionally form a single common trunk before entering the left atrium (Fig. 6‑4). Other variations are accessory pulmonary veins, including one or more accessory middle pulmonary veins and the upper pulmonary vein which directly connect to the left atrium (Fig. 6‑5 , Fig. 6‑6). Recognition of these variations of the pulmonary veins is important for thoracic surgery and catheter ablation treatment of arrhythmic cardiac diseases.


Subsegmental pulmonary veins and their relationship to the pulmonary (sub)segments are summarized on Table 6‑2.






























































































































































Table 6.2 Subsegmental pulmonary veins and relevant subsegments

Right pulmonary veins


Left pulmonary veins


Subsegmental vein


Bounded (sub)segments


Subsegmental vein


Bounded (sub)segments


Upper lobe

 

Upper lobe

 

V1a


S1a/b


V1a


S1+2a subsubsegments


V1b


S1b/S3b


V1b


S1+2a/S3c


V1l


S1/S2,3


V2a


S1+2a/b


V2a


S1a/S2a


V2b


S1+2b/c


V2b


S2a/b


V2c


S1+2c/S3a


V2c


S2a/S3a


V3a


S3a/S4a


V2t


S2 /S6


V3b


S3b/S4b


V3a


S3a/b


V3c


S3b/c


V3b


S3b/S4


V4a


S4a/S5


V3c


S3b subsubsegments


V4b


S4b/S5


Middle lobe

 

V5a


S5a/b


V4a


S4a/b


V5b


S5b


V4b


S4b/S5

   

V5a


S5a/b

   

V5b


S5b

   

Lower lobe

 

Lower lobe

 

V6a


S6a/b, c


V6a


S6a/b, c


V6b


S6b/c


V6b


S6b/c


V6c


S6c/S10a


V6c


S6c/S10a


V7


S7/S8,10


V7


S7/S8,10


V8a


S8a/b


V8a


S8a/b


V8b


S8b/S9b


V8b


S8b/S9b


V9a


S9a/b


V9a


S9a/b


V9b


S9b/S10b


V9b


S9b/S10b


V10a


S10a/b, c


V10a


S10a/b, c


V10b


S10b/c


V10b


S10b/c


V10c


S10c/S7


V10c


S10c/S7


The right superior pulmonary vein usually receives the segmental or lobar veins from the right upper lobe and the middle lobe, which are located anterior and inferior to the right pulmonary artery. The subsegmental veins of posterior segment (V2a, apical; V2b, posterolateral; and V2c, horizontal) join to form the central vein which is located at the central portion of the upper lobe and descend between the B2 (posterior) and B3 (anterior) segmental bronchi (central vein type), and then join to the superior pulmonary vein superiorly (Fig. 6‑2 , Fig. 6‑6). At the right lung apex, the apical (V1a) and the anterior (V1b) subsegmental veins of the apical segment join to form apical segmental vein (V1) which runs downward. These V1 subsegmental veins totally or partially join to form the central vein or descend anteromedial to the central vein (anterior vein) joining the superior pulmonary vein anterosuperiorly. Subsegmental veins of anterior segment (V3) can join the central vein, the anterior vein, or independently to the superior pulmonary vein. V3d (lateral) subsegmental vein generally joins the central vein. In some cases, the common trunk of V1 and V2 subsegmental veins runs anteriorly far above the bifurcation of the B2 and B3, which descend anteromedially to the upper bronchi (semicentral vein type) (Fig. 6‑7). This type of upper lobe venous drainage is more frequently seen in the left lobe. One or two subsegmental veins of the V2 (especially V2t, terminal) occasionally descend on the posterior surface of the bronchus intermedius, which drain either into the superior pulmonary vein or the inferior pulmonary vein. 11 In the right middle lobe, two segmental veins of V4 (lateral) and V5 (medial) are generally formed by the subsegmental veins. The V4a (posterior) and V4b (anterior) join to form the V4, and the V5a (superior) and V5b (inferior) form the V5, respectively. The segmental veins join together to form the middle lobe vein which usually joins the superior pulmonary vein. In some cases, the segmental veins or subsegmental veins independently join to the superior pulmonary vein. The middle lobe vein or the segmental vein occasionally drains directly into the left atrium or the inferior pulmonary vein (Fig. 6‑5 , Fig. 6‑6 , Fig. 6‑8). 12 Exceptionally, the lateral segmental vein (V4) or its subsegmental vein empties into the anterior segmental vein (V3) of the upper lobe. 13

Fig. 6.4 3D-MR angiographic images of the pulmonary artery (a) anterior view, (b) left lateral view, (c) posterior view, and (d) right lateral view. BT, basal trunk; ILA, inferior lobar artery; IT, inferior trunk; LPA, left pulmonary artery; PT, pulmonary trunk; RA, right atrium; RPA, right pulmonary artery; RV, right ventricle; ST, superior trunk; SVC, superior vena cava.
Fig. 6.5 Left common pulmonary vein. Coronal maximum intensity projection (MIP image) (a) and posterior view of the volume rendering (VR) image (b) of 3DCTA show left pulmonary vein joints to form a single pulmonary vein (left common pulmonary vein [LCPV]) draining to the left atrium. An accessory pulmonary vein (black arrow) from the right middle lobe draining directly into the left atrium (LA) between the right superior pulmonary vein (RSPV) and the right inferior pulmonary vein (RIPV). (c) Right accessory pulmonary vein. VR image of 3DCTA shows an accessory pulmonary vein (white arrow) from the right middle lobe draining directly into the left atrium between the RSPV and the right inferior pulmonary vein (RIPV). LIPV, left inferior pulmonary vein; LPA, left pulmonary artery; LSPV, left superior pulmonary vein; RPA, right pulmonary artery.
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(m-r)
(s-w)
Fig. 6.6 Axial CT anatomy of the pulmonary segmental vessels of the upper and middle lobes CT images show “central venous drainage type” of the upper veins in both lungs. The central vein (CV) is formed by V2 (and V1) subsegmental veins, runs inferiorly through the angle formed by the bifurcation of the right upper lobe bronchus into B2 and B3. Note a variation of an accessory pulmonary vein (Acc PV) from the right middle lobe joining directly to the left atrium. AV, anterior vein; IPV, inferior pulmonary vein; IT, inferior trunk; LA, left atrium; LAA, left atrial auricle; SPV, superior pulmonary vein; ST, superior trunk.
(g-l)
Fig. 6.7 “Semicentral vein” type upper lobe venous drainage. Axial CT images show V2 subsegmental veins and V1 running anteroinferiorly around the B1 and join to form a venous trunk at the anteromedial aspect of the B2-B3 bifurcation in the right upper lobe. SPV, superior pulmonary vein; ST, superior trunk.
Fig. 6.8 Uncommon variation of the segmental pulmonary veins of V2 and V4. Right lateral (a) and posterior (b) 3DVR images and sequential axial images (c) of the CTA show uncommon variations of the subsegmental veins of the right lung. V2b runs inferomedially and joins with V2t to form V2b+ (white arrowheads) which runs inferiorly along the posterior surface of the bronchus intermedius. It then runs inferomedially in the mediastinum and terminates at the superior aspect of the junction between the right superior pulmonary vein and the left atrium. The other V2 subsegmental veins (V2a and V2c) run anteroinferiorly and join the superior pulmonary vein. Another uncommon variation is also noted in the right middle lobe veins. V4 (arrow) extends posteriorly and joins the right inferior pulmonary vein. IPV, inferior pulmonary vein; LA, left atrium; LAA, left atrial auricle; LLB, lower lobe bronchus; MLB, middle lobe bronchus; SPV, superior pulmonary vein.
(c7-c13)

The right inferior pulmonary vein is formed by all five segmental veins of the right lower lobe. It occasionally receives segmental or subsegmental veins from the middle lobe or the upper lobe (V2). Three basal segmental veins of the V8 (anterior), the V9 (lateral), and the V10 (posterior) ascend medially by crossing behind their respective bronchi to form the common basal vein. The V7 (medial) basal segmental vein is a small intersegmental vein which ascends posteriorly to join the common basal vein at the anteroinferior aspect. The V6 (lower lobe apical segmental vein) descends from the apex of the lower lobe, crosses behind the basal bronchus to join the common basal vein to form the inferior pulmonary vein. The V6 segmental vein rarely receives a V2 subsegmental vein and ends directly into the left atrium.


Branching pattern of the left pulmonary veins is similar to that of the right pulmonary veins. As mentioned before, semicentral type of venous drainage of the upper lobe vein is more frequent in the left lung. One or both lingular veins may, like the middle lobe veins, empty into the inferior pulmonary vein or directly into the left atrium. However, the direct drainage of lingular vein into the left atrium is much less frequently on the left side.

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Mar 16, 2021 | Posted by in CARDIOVASCULAR IMAGING | Comments Off on 6 Pulmonary Artery and Vein
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