cvr 22 - great vessels foetal circulation changes at birth
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Great vessels, foetal circulation, changes at birthDr Jane HollandCVR 2214/03/11
Conus cordis / truncus arteriosus – septum formationTruncus cushions (swellings)
Right superiorLeft inferior
Right superiorGrows distally & to left
Left inferiorGrows distally & to right
⇒ Cushions twist around each other
Cushions fuseForm septum
Aortic channelPulmonary channel
Similar cushions develop in the conus cordis also
Unite distally with the truncus septum
⇒ conotruncal septumOutflow tract of right ventricleOutflow tract of left ventricle
Animation –http://www.med.uc.edu/embryology/chapter7/animations/contents.htm
Transposition of the great vessels
Conotruncal septum fails to spiralNot compatible with life unless another shunt is presentCyanosis, usually systolic murmur
Unequal division of conus cordis(Septum too anterior)
Pulmonary stenosisNarrow right ventricular outflow
Large VSD Ventricular septal defect
Overriding aortaFrom directly above septal defect
Hypertrophy of the right ventricleRaised right interventricular pressure
Tetralogy of Fallot
Right to left shuntCyanosis
Palpable thrillSystolic murmur
Pulmonary & left sternal border
Patients characteristically squat to improve symptoms
Persistent truncus arteriosus
Single outflow tract remains
Conotruncal ridges fail to fuseNo dividing septum
Cyanosis, systolic murmur
Always associated with a VSDMembranous portion of septum fails to develop superiorly
Aortic arches – initial development
Caudally, dorsal aortae fuseRemain paired in region of pharyngeal arches (cranially)
Each arch receives an arteryAortic archRun from aortic sac to dorsal aorta
Not all present simultaneouslyDevelop 1st ⇒ 6th
Many obliterate
1st arch – disappears*2nd arch – disappears*3rd arch
Common carotidProximal internal carotidExternal carotid branches off 3rd arch
4th archLeft – arch of aortaRight – subclavian artery
5th arch – disappears6th arch
Pulmonary trunkLeft - Ductus arteriosus
* Small remnants remain – NS module!!
Dorsal aortae
CraniallyInternal carotid arteries
Between 3rd & 4th arches Obliterates
More caudallyRight
Forms part of subclavianObliterates
LeftDescending aorta
Course of recurrent laryngeal nerve (supplies larynx)
6th arch
4th arch
Vitelline arteriesNumber of paired vessels from dorsal aortaSupply yolk sac (& then gut)Fuse – coeliac / SMA / IMA
Umbilical arteriesOriginally from dorsal aortaThen develop secondary connection to iliacsMedial umbilical ligaments
Venous system – initial development
Vitelline veinsForm plexus around duodenumRun through septum transversum to reach sinus venosusLiver cords disrupt these veins
Hepatic sinusoids formed
Right vitelline vein persistsForms hepatocardiac IVCDistally – Portal vein & SMV
Left vitelline veinMostly obliterates
Umbilical veinsInitially pass to either side of developing liver
Then develop connections to hepatic sinusoids
Proximal right & left umbilical veins obliterate
Remainder of right umbilical vein obliterates
Left vein now carries all blood from placenta to liver
Develops direct connection to right hepatocardiac channelDuctus venosusBypasses sinusoids of liver
PostnatalLeft umbilical vein Ligamentum TeresDuctus venosus Ligamentum venosum
Anterior cardinal veinsCephalic part of embryo
Posterior cardinal veinsRest of embryo
(Initially symmetrical)
Additional veins then formSupracardinal veins
Body wallSubcardinal veins
KidneysSacrocardinal veins
Lower extremities
Cardinal veins
Anterior cardinal veinsDrain cephalad embryoRight-left anastomosis
Brachiocepalic vein
Right forms SVC
Posterior cardinal veinsInitially drain rest of embryoMostly obliterate
Supracardinal veinsAzygos system of veins
Drain body wall
Subcardinal veinsAnastomosis formsLeft renal vein
Left subcardinal veinMostly disappearsDistal part persists as the left gonadal vein
Right subcardinal veinDevelops into part of IVC
Renal segment
Sacrocardinal veinsAnastomosis formsLeft common iliac vein
Right sacrocardinal veinDevelops into part of IVC
Foetal circulation
Postnatal circulation
Patent ductus arteriosusIn foetus, blood flows right to leftClosure postnatally:
Mediated by bradykininMuscular contraction
Neonate with PDA – blood flows left to rightPulmonary hypertension“machine-like” murmur
Systole & diastole
To close PDAIndomethacin
To keep DA patent PGE
Coarctation of aortaNarrowing of aorta below origin of left subclavian5-8% of all congenital heart defects
Diagnosis can be delayedPre- or Postductal
Pre-ductalINfantile – IN close to the heartDuctus arteriosus usually persists
PostductalLigamentum arteriosum
Collateral circulationIntercostal arteriesInternal thoracic artery
From subclavianSo proximal to narrowing
AcyanoticLeft to right shunt
ASDVSDPDA
Tetralogy of FallotTransposition of great vesselsTruncus arteriosusTricuspid atresiaTAPVR
CyanoticRight to left shuntReduced flow to pulmonary circulation5 T’s
Uncorrected ASD, VSD or PDAAll initially acyanotic – left to right shunts
Pulmonary hypertension developsAs pulmonary vascular resistance increases, the shunt reverses
Was Left to RightNow Right to Left
Late cyanosis develops
Eisenmenger’s syndrome