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1、23SuperiorVenaCavaSyndromeFrancescoPumaandJacopoVannucciUniversityofPerugiaMedicalSchool,ThoracicSurgeryUnit,Italy1.Introduction1.1AnatomyThesuperiorvenacava(SVC)originatesinthechest,behindthefirstrightsternocostalarticulation,fromtheconfluenceoftwomaincollectorvessels:theri
2、ghtandleftbrachiocephalicveinswhichreceivetheipsilateralinternaljugularandsubclavianveins.Itislocatedintheanteriormediastinum,ontherightside.Theinternaljugularveincollectsthebloodfromheadanddeepsectionsoftheneckwhilethesubclavianvein,fromthesuperiorlimbs,superiorchestandsupe
3、rficialheadandneck.Severalotherveinsfromthecervicalregion,chestwallandmediastinumaredirectlyreceivedbythebrachiocephalicveins.Afterthebrachiocephalicconvergence,theSVCfollowstherightlateralmarginofthesternuminaninferoposteriordirection.Itdisplaysamildinternalconcavityduetoth
4、eadjacentascendingaorta.Finally,itentersthepericardiumsuperiorlyandflowsintotherightatrium;novalvedividestheSVCfromrightatrium.TheSVC’slengthrangesfrom6to8cm.Itsdiameterisusually20-22mm.ThetotaldiametersofbothbrachiocephalicveinsarewiderthantheSVC’scaliber.Thebloodpressurera
5、ngesfrom-5to5mmHgandtheflowisdiscontinuousdependingontheheartpulsecycle.TheSVCcanbeclassifiedanatomicallyintwosections:extrapericardialandintrapericardial.Theextrapericardialsegmentiscontiguoustothesternum,ribs,rightlobeofthethymus,connectivetissue,rightmediastinalpleura,tra
6、chea,rightbronchus,lymphnodesandascendingaorta.Intheintrapericardialsegment,theSVCenterstherightatriumontheupperrightfaceoftheheart;infrontitisclosetotherightmainpulmonaryartery.Ontherightside,thelungisinitsproximity,separatedonlybymediastinalpleura.Therightphrenicnerverunsn
7、exttotheSVCforitsentirecourse[1](Figure1).TheSVCreceivesasingleaffluentvein:theazygosvein.TheazygosveinjoinstheSVCfromtherightside,atitsmidlength,abovetherightbronchus.TheAzygosveinconstantlyreceivesthesuperiorintercostalvein,alargevesselwhichdrainsbloodfromtheuppertwoorthre
8、erightintercostalspaces.InthecaseofSVCobstruction,theazygosveinisresponsibl
