Page 3 - Carotid and peripheral vascular interventions textbook
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                                         Right internal                        Left internal
                                           jugular vein                        jugular vein

                                   subclavian vein                                subclavian vein
                                         brachiocephalic vein
                                                                           brachiocephalic vein


                 Figure 14-1. Central venous anatomy. Note the anatomical difference in the path of right and left central veins. The route from the right
                 internal jugular vein into the brachiocephalic and superior vena cava (SVC) is almost vertically down. The vein on the left has to take a longer,
                 tortuous course to reach the SVC.

                 and brachiocephalic vein. The left internal jugular vein   one of these pathways will cause blood-f ow to f nd new
                 merges with the left subclavian vein, and then takes a lon-  collateral pathways to return the heart (15,16). There are a
                 ger tortuous path to connect with the cavo-atrial junction.   lot of anastomotic collateral pathways that may potentially
                 The left internal jugular vein has smaller cross-sectional   bypass the subclavian vein, brachiocephalic vein, and
                 area compared with the right internal jugular vein. These   SVC (Fig. 14-2).
                 anatomic factors can result in greater contact from an        With subclavian vein occlusion, superf cial and
                 implanted foreign body to the wall of the vessel wall when   muscular veins around the shoulder, neck and thorax
                 it is located from the left-handed side. Left-sided internal   are recruited as collateral pathways, which empty into
                 jugular catheters additionally have more movement than   the azygous veins, jugular veins, or brachiocephalic
                 right-sided catheters with rotation of the neck and head,   veins. Shoulder collaterals involve the intercostal veins,
                 resulting in more endothelial injury and stenosis.  suprascapular vein, subscapular vein, and lateral thoracic
                     The azygos vein is a vein which drain the intercostal   vein. Vessels involved in the neck collaterals include the
                 venous system into the lower SVC. The azygos system   inferior thyroid vein, jugular venous arch, external jugular
                 can potentially connect to the whole venous body supply.   vein, internal jugular vein, and vertebral vein.
                 Occlusions in one portion of the thorax contribute to divert      With brachiocephalic vein blockage, the principal
                 minimally some of the f ow into the azygos system where   collateral pathway is up the ipsilateral jugular vein to the   429
                 it is consequently redirected to bypass the occlusion. Any   brachiocephalic or contralateral jugular veins through
                 occlusion above the azygos vein can be redirected into   multiple head and neck collaterals. With SVC occlusion,
                 the SVC via the azygos system. However, if the SVC is   collaterals forms as a consequence of the occlusion’s
                 occluded at the location of the azygos, blood can only   position relative to the azygos vein. The azygos vein
                 access the heart via the inferior vena cava (IVC).   supplies venous return to the inferior SVC and is the
                                                                 single major vein to supply into the SVC apart from the
                 COLLATERAL CIRCULATION                          left and right brachiocephalic veins. As the azygos system

                                                                 functionally connects in some way to the whole venous
                     For a healthy patient, blood returns to the heart   system, that collateral is an important bypass channel
                 through conventional venous pathways. Blockage of any   when SVC develops obstruction.
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