Abnormal Systemic Venous Connections (M/A)

Abnormal Systemic Venous Connections (MA38)

-portal vn is the only one that doesn't send blood to the heart

-mainly a problem in heterotaxy pts

Embryology:

-3 venous systems of embryo

-cardinal vns & their tributaries --> form SVC and IVC

-umbilical, vitelline, omphalomesenteric vns--> carry Q fr placenta, yolk sac, intestin

-pulm vns--> return Q fr lungs

Cardinal & Umbilicovitelline Venous System Development

-Sinus Venosus = cavity that all vns will drain to eventually

-dvps fr enlargement of the confluence of the umbilical vns

-joins the atrial part of the heart, thru a slitlike opening- the sinoatrial foramen

-middle part = transverse sinus, L and R parts are L and R horns of sinus venosus

-the 3 pairs of venous systems (cardinal, umbilical, vitelline) drain into ea ipsilateral horn of s.v.

-R & L umbilical vns dvp 1st

-at same time, vitelline plexus of liver is formed, and becomes more prominent on R side

-it connects to sinus venosus thru the R hepatocardiac channel, which drains to R horn of s.v.

-it also connects to yolk sac via L omphalomesenteric vn

-Ant cardinal vns then dvp

-drain Q fr the fused neural folds that will form CNS

-then, the post cardinal vns appear lateral to the sp cord, and they join the ant cardinals to form the R and L common cardinals and drain together w the umbilical and vitelline vns to the R and L horns of the sinus venosus

-each horn of s.v. drains for a short time into their respective side of the common atrium

-Then, L horn of s.v. invaginates to separate fr the LA. The transverse part of the s.v. shifts R next, which completes the isolation of the LA fr the 3 pairs of vns that enter the sinus venosus (cardinals, umbilicals, vitellines). They now drain to the RA thru the sinoatrial foramen.

R SVC and Coronary Sinus Development

-RSVC extends fr the confluence of R and L innom vns to the RA

-made of the prox part of the R ant cardinal vn and R common cardinal vn

-After L innom vn forms, then L SVC involutes (to become Ligament of Marshall)

-when the transverse part of the s.v. shifts rightward, it pulls teh L horn of the s.v. along the AV groove. The L horn of the s.v. and the adjacent part of the common cardinal vn get Q fr the cardiac vns to --> the CoronarySinus.

-Thus you see:

-orifice of CS is always in the anatomic RA

-persistent LSVC always continues w the CS since the L common cardinal vn is part of the CS and of the LSVC

-Fx'l connection of a persistent LSVC w the LA (or any other vn), only occcurs if CS is unroofed.

IVC Development

-posterior cardinal vn forms, then ant cardinal vns, both running in the dorsolateral part of the urogenital fold, assoc w the mesonephri (wolffian bodies).

-subcardinal vns divert venous drainage of mesonephri, form at ventromedial side of mesonephri and ventral to the posterior cardinals. They connect the mesonephri to the post cardinals, eventually growing twd midline, bringing the subcardinals closer together, and then communicate w each other w the intersubcardinal anastomoses that becomes a large medial venous space called the subcardinal sinus. w establishment of the subcardinal sinus, the small vssls connecting the subcardinals w the post cardinals drain medially into the subcardinal sinus instead of lateral twd the posterior cardinals --> posterior cardinals disappear at level of the subcardinal sinus.

-bld fr posterior part of body collects into the distal part of the post cardinals, but then returns to heart via the subcardinal sinus. The increased growth of embryo--> incr Q thru the sinus--> a new unpaired venous channel forms (the hepatic segment of the IVC), it lies in a notch along the dorsal side of the liver, made of a confluence of small vssls that appear in a fold of the dorsal body wall, just to R of dorsal mesentery. It connects w liver plexus cephalically and the mesonephri caudally via the subcardinal sinus to allow Q fr mesonephri to liver plexus. The unpaired liver channel then connects the subcardinal sinus w the confluence of hepatic vns and the ductus venosus--> large vssl forming suprahepatic part of IVC to enter RA

-then dorsal to subcardinal sinus, the supracardinal vns appear, which connect subcardinal sinus w the cephalic remnant of the post cardinals, via the azygous and hemiazygous vns. They also connect the subcardinal sinus w ileac vns via caudal premant of posterior cardinal vns.

-then infrarenal part of the L supracardinal vn involutes, and the infrarenal part of R supracardinal vn becomes the infrarenal part of the IVC.

-by 7th week GA, the vns channels connect the L side w the R side of the paired vns via the:

-L innominate vn

-hemiazygous vn

-L renal vn

-L common iliac vn

--> all venous Q except pulm vn Q goes thru SVC and IVC

Ductus Venosus Development

-paired umbilical vns connect placenta w R and L horns of s.v.

-as liver grows, it fuses w the lateral body wall, and at this site multiple vssls dvp and connect the umbilical vns w liver plexus. the umbilical stream passes thru these vessels into the liver, and the early direct connection of umbilical vns to s.v.v involute.

-distal to their entrance into the embryo, the umbilical vns fuse--> only 1 umbilical vn in the umbilical cord.

-inside embryo, the R umbilical vn involutes except for a small part that drains the body wall.

-as embryo grows, there's incr Q thru the umbilical vn--> a new large channel is made thru the liver, the ductus venosus, to connect L umbilical vn w the R hepatic vns

-by 7th week GA, placental Q gets to RA via L umbilical vn, DV, suprahepatic segment of IVC

-as it goes thru the liver, the DV gets Q fr R and L heptic vns and delivers it into RA

-after birth DV becomes ligamentum venosum and the L umbilical vn becomes ligamentum teres

Azygos & Hemiazygos Vns

-Azygos connects suprarenal IVC w the R SVC

-formed by suprarenal segment of the R supracardinal vn and the cephalic remnant of the R post cardinal vn.

-starts at R renal vn/R lumbar vn or IVC and passes thru Ao opening of diaph, to enter thorax, running up medial to thoracic verebrae, to the R of the Ao and thoracic duct, and gets Q fr the lower 10 segments of R intercostal vns. At level of T4, it arches anteriorly to connect to post side of SVC

-Hemiazygos-

-first part is teh L lower, smaller azygous that starts at lumbar region of a lumbar vn or fr the L renal vn, passes thru L crus of diaphragm, and goes up on L side of spine to level of T9, then turns to R, behind Ao and thoracic duct, and ends by connecting into azygos vn

-left upper hemiazygos varies inversely w size of L superior intercostal vn

-gets Q fr L intercostal vns that didnt drain into L sup intercostal vn and Q fr lower hemiazygos and then ends in the R azygos or lower hemiazygos.

Portal Vn Development

-Venous return fr primitive gut circulation goes thru vitelline vns of yolk sac --> confluence w the R and L omphalomesenteric vns, --> enter s.v posteriorly. As the omphalomesenteric vns approach the hrt, they lie next to the liver. The proximal part of the omph. vns break up into a maze of small channels that go thru the liver. The distal part brings Q fr yolk sac and intestine to the liver. When yolk sac disappears, and GI grows, the omphalic (yolk sac) part disappears too. The mesenteric part continues and grows along w the intestine, forming the mesenteric vns, which anastomose to each other. The L mesenteric vn then involutes above the anastomosis. The R mesenteric vn involutes below the anastomosis. --> unpaired hepatic portal vn connecting vns of intestine and spleen to liver.

SVC ANOMALIES

Bilateral SVC w Nl Drainage to RA

Anatomy

-Persistent LSVC - bc the L ant and L comm cardina vns didn't involute

-usually drain to RA via CS, rest drain to LA through unroofed CS

-0.3% incidence; incr w CHD...

-LSVC size varies

->1/2 pts have a L innominate vn, though size varies

-LSVC starts at jct of L jugular and L subclav vns, then penetrates pericardium and goes along post wall of LA to join CS at post AV groove

-see big CS and posterior displacement of os into RA floor

-rarely have the thebesian valve present

Sx -ASx usually

Dx -CXR- see shadow at L upper border of mediast

-c/s LSVC if u see dilated CS

-see LSVC fr suprasternal notch, SCSA, high PS,

-usually LSVC size is inverse to L innom size

-DDx pulm vns...

-if see reversal of Q at LSVC, c/s stenosis at CS jct

Tx- none

Bilateral SVC w Unroofed CS

Anatomy

-partial/completely missing wall bn LA and CS = unroofed CS

--> LSVC to LA = ~intraatrial communication

-must DDx persistence of an embryonic connection bn LA and a systemic vn (a levoatrialcardinal vn) or bn L pulm vn and systemic vns

Sx

-most pts w this also have a large coronary sinus ostium that fx as an interatrial communication

--> L-->R shunt

-systemic desat bc mix LSVC Q w pulm vn bld in the LA

-amt of desat d/o amt of Q in LSVC, usualy sats 85-95%

-at risk for R-->L shunt xx - emboli, brain abscess, stroke, death

-if os to CS is atretic, then no signif interatrial commn and only sx are cyanosis

Dx

-echo- see drainage to LA fr subcostal view and fr precordial/suprastenrals

-check post AV groove to see defic septum at CS

Tx

-can ligate LSVC if it's small and L innom looks big enough, then close the intratrial com'n so that CS drains into LA

-if innom is too small, then reroof the CS--> =baffle LSVC at post wall of LA, into the RA, avoiding pulm vn orifice...,

Absent RSVC in Visceroatrial Situs Solitus

Anatomy

-rare.

-pts have LSVC draining to RA via CS and y L sided azygous vn to LSVC

-about 1/2 w other CHD

Sx- ASx unless other xx

Dx- important to know about in order to avoid xx w transvenous pacer implantation, venous canulation for CPB/ECMO, and RV or PA lines thru subclavian/jugular vns.

Tx- none needed

LA or BiAtrial RSVC Drainage

Anatomy

-rare

--> unexplained cyanosis and clubbing in pts w/o other Sx of heart xx

-?bc of a defect in wall bn SVC and LA...

Sx- cyanosis, polycythemia, SOB, DOE, systemic emboli, brain abscess, etc

Tx- divert Q to RA

Retroaortic Innominate Vn

Anatomy

-rare

-the confluence of L subclav and L comm jugular vn forms L innom, it then goes inf to run a couse similar to LSVC, after passing ant to LPA and before getting to LA it turns R and goes horizontally behind the Asc Ao to reach the SVC below insertion of azygos. In RAIV the insertion into SVC is just above the RA jct

Sx

-usually ASx

Dx- echo, angio, mri - track L innom vn fr origin to SVC; ddx fr LSVC

Tx- none

CS ANOMALIES

CS Defect & Unroofed CS

Anatomy

-~always assoc w LSVC

-when it occurs w/o LSVC, it's rare, and Sx are like ASD (except via CS os)

-might have atretic CS os, so the unroofed part is the only egress for CS flow

Sx- as above if w LSVC, if no LSVC then see Sx like 2nd ASD

Dx- echo of CS in L AV groove, check doppler...

CS Orifice Atresia

Anatomy- rare, often w thin membrane related to thebesian valve

-varied types of CS outlet (e.g. to IVC etc)

Sx- no myocardial ischemia if there's an alt egress for Q....

Dx- see retrograde Q in CS, twd innom vn

CS Aneurysm or DIverticulum

-may be assoc w arrhythmias- WPW

Dx- echo

Tx- surgery...

IVC ANOMALIES

Interrupted IVC

-no hepatic part of the IVC. Azygos continues into R or L SVC

Sx- usually ASx by itself, but is assoc w heterotaxy...

Dx- echo- see azygos vn fr subxiphoid window; subcostal SA see renal to hepatic segment of IV in Nl pt just ant and R of Ao. Azygos is much smaller vessel, seen next to vertebre in Nl pt.

-w heterotaxy, IVC might next to abd Ao to L or R of spine, if interrupted you wont see it comopletely run fr renal to RA in the sagital view..., see big azygos w connections to L and R SVC- see drainage of azygos vn to SVC fr parasternal and suprasternal views

-no specific Tx...

Bilateral IVC

-common w heterotaxy + asplenia

-...

IVC Drainage to LA

-fetally, the eustachian valve directs Q to LA. If it persist in same size as fetally then IVC Q can drain to both atria, via PFO

-...

--> cyanosis, w assoc xx

Tx- redirect it to RA

DUCTUS VENOSUS ANOMALIES

Anomalous Termination of the Umbilical Vns & Absent Ductus Venosus

-sometimes L umbilical vn went to CS, R to RA

Sx- some ASx, some w intestinal obstruction, gender ambiguous, ...

...

Postnatal Persistence of the Ductus Venosus

- DV shunts Q away fr portal vn septum proximally to the distal hepatic vns or IVC distally

--> intrahepatic portal systemic shunts bc of abNl persistence of the omphalomesenteric syst.

Sx- 3 fo 10 pts had portal-systemic encephalopathy

Dx- US or CT--> large tortuous vessel starting fr portal vn that connects to the hepatic vn or IVC

Tx- ? no successful Tx. might not need Tx is no encephalopathy

Persistent Valves of Sinus Venosus

-eustachian and thebesian vlavs, and crista terminalis

-might see Chiari networks- fine filamentous structures fr persistence of R or L valve (?)

-usually extend fr crista terminalis to esutachian or thebesian vlvs

-no hemodynamic xx for live pts, but have recently found pts on autopsy w R vlv of s.v. ...

-Embryology

-s.v. is external to primitive RA initially. R horn of s.v. gets hepatic vn Q (precursor to IVC), and the ant cardinal vn (precursor to SVC). L horn of s.v. is the precursor to CS

-R and L s.v. valves of s.v. separate s.v. fr primitive RA. The s.v. septum joins the R and L valves of s.v., then the septum primum appears an starts to septate the atrium. at this pt, the s.v. opening into the common atrium is well gaurded by the R and L valves of the s.v.

-then the sv is absorbed into the common atrium. the R and L valves of sv join cranially to form the septum spurium, which maint the valves in a state of tension. this septum starts to divide the common atrium fr post-sup to ant-inf, then the L vlv of sv retrogresses and is absd into the limbus region of sept secundum. R vlv of sv then starts to enlarge.

-by 3mo GA, the R vlv of sv almost completely divides the RA into the sinus portuion (sinus venosus) which gets SVC, IVC, CS and FO, and the muscular portion of RA which communicates w TV and RAA

-The R vlv of sv near completely segregates all syst vn Q fr SVC, IVC and CS fr the TV, shunting it into the LA.

-the R vlv of sv then near completely regresses by birth w the remnant persisting as the crista terminalis (at pt where it separated the RA into the 2 parts). This separates the ant, muscular part of RA fr the posterior sv part of RA in the fully dvpd heart. The superior part of R vlv of sv plus a part of the sv septum persist as the eustachian vlv gaurding IVC os. the Inf part of the R vlv of sv plus part of the sv septum persist as the thebesian vlv