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Cardiac Malpositions and Abnormalities of Atrial & Visceral Situs (MA55)
Cardiac Malpositions and Abnormalities of Atrial & Visceral Situs (MA55)
Definitions:
-Malposition = dextro, meso, levocardia; pericardial defects, ectopia cordis
-d/o the base-apex axis
-Dextrocardia - classic def = heart is located in R hemithorax w apex pointing to the right
-may occur w atrial situs solitus, inversus, or ambiguus.
-Isolated Dextrocardia = dextro w atrial situs solitus
-occurs bc of congen dvp'l malposition
-a secondary dextrocardia (e.g. bc of CDH, would cause heart to be in R chest, but facing L)
-Mesocardia - base-apex axis is directed twd midline of Tx, ow if ventricular apices are equally directed bn both R and L sides. (often these get lumped in w true dextrocardia dx)
-usually w situs solitus of atria
-Levocardia - is a malposition only if it occurs w situs inversus or ambiguus of atria, bc despite abNl atria and AV connection, the heart ends up in L chest w apex pointing leftward.
-Situs Solitus = Nl site/position of atria/viscera
-Situs Inversus = reversed site/position of atria/viscera
-Situs Ambiguus = ? site/position of atria/viscera...
-Heterotaxia = anomalous position of viscera
Segmental Diagnosis:
-Consider 6 Cardiac Segments:
-Systemic/Pulm Veins
-Atrial Situs
-AV Connection
-Ventricles & Infundibulum
-VA connection
-GAs and DA
Visceral & Atrial Situs Abnormalities:
-Check visceral/atrial situs, including syst/pulm veins
-often pulm vns to LA and IVC to RA
-atrial & visceral situs are usually concordant
-visceral situs d/o side of liver and stomach
-panc & spleen usually on the same side of vertebrae as stomach
-Abd situs ambiguus w R isomerism--> midline liver w mirror image R liver lobes; & +malrotatated bowel, w IVC & Ao together on same side of vertebral column
-situs ambiguus w asplenia = R isomerism
-asplenia syndromes are usually assoc w pulm stenosis/atresia
-situs ambiguus w polysplenia = L isomerism
-polysplenia syndromes are assoc w azygous to IVC & bilat venous return (R L to RA, L lung to LA)
-Atria don't always correspond to visceral situs, so still must use atrial morphology:
-RA:
-defined by fossa Ovalis limbus- seen in OR/echo, or if no atrial septum check the RA free wall
-RA = large, pyramidal appendage, crista terminalis, pectinate muscles
-by angio/echo, use RAA to ID RA - see large, wide-based, triangular RAA
-LA:
-LA appendage narrow, tubular, hooked shape, but more variable than RAA
-some advocate use of suprahepatic IVC to atrial connection to define the RA, bc it should be right even if there is atrial-visceral discordance, or the coronary sinus
-Pulmonary Situs
-d/o sidedness of R and L lungs
-d/o relation of PA to the bronchi (NOT # of lobes in ea lung)
-R Lung = PA travels ant to Upper lobe & intermed bronchi
-L Lung = PA travels over to the Main bronchus & post to Uppler lobe bronchus
-can infer this on CXR bc distance fr carina to origin of upper lobe bronchus is 1.5-2x greater for L lung than R lung. (Applies even w R AoArch). With Pulm isomerism, they are = in length...
-if you see bilat trilobed lungs, c/s situs ambiguus w asplenia (2 R sides)
-if you see bilat biloped lungs, c/s situs ambiguus w polysplenia (2 L sides)
-also must describe the atrial side (spatially; e.g. R sided left atrium)
-Ventricular spatial arrangement d/o IV septum orientation:
-levocardia- RV ant, LV post
-dextrocardia- RV post, LV ant
-mesocardia- verticle midline septum w side-by-side ventricles
-rarely see horizontal IVS w "over-under/upstairs-downstairs/sup-inf" ventricles
-Aorta position
-describe relative to PA trunk
-Nl = R & post Ao
-Make sure to ID insertion of SVC, IVC, hepatic vns, CS, pulm veins
AV Connections & AV Valve Morphology:
= which atria is connected to which ventricle
-AV discordance = L-looping of ventricles
-usually the tube bends ant/right (d-looping)
-if it bends post/left (L-looping)-->discord bn atria and ventricles
-Types of AV connections (all of which can be concordant or discordant:
-absent, atretic, overriding, criss-cross
-Univentricular AV connection = both atria connect to 1 ventricle (DOESN'T describe concordance/disordance of atria & ventricle relationship, just describes the CONNECTIONS)
-Single-, Double-, Common-inlet ventricles all can have AV concordance or discordance
-Criss-Cross AV Connection-
=rotational/situs abnormality of the ventricles--> cross the AV connection
-often have a sup-inf ventricle relationship, usually bc of R or L-ward rotation of the ventricle, that crosses the AV connection
-often large VSD--> allows for overriding AV connections (=abNl AV vlv connection/alignment)
-often +straddling AV valve chordae (=tensor apparatus cross the IVS w abNl insertions...)
-Types:
-A- abNl chordae attach to opposite side w/in 1cm of the IVS crest
-B- abNl chordae attach to opposite side below the upper 1cm of the IVS crest
-C- abNl chordae attach to opposite ventricular wall or free standing pap muscle within the other ventricle (not attaching to IVS at all)
Ventricular Situs & Morphology:
-Levocardia, dextrocardia, mesocardia (see above)
-also must describe the ventricular location, relationships, morph...
Great Artery Relations:
-describe both the connections and the relations
-8 relations possible bn PA and Ao, d/o relative position of the semilunar valves:
-Ao R & post (Nl)
-Ao Lat (side-by-side)
-Ao R ant (d-malposed)
-Ao directly anterior
-Ao L ant (l-malposed)
-Ao Lat (L side-by-side)
-Ao L post (inverted Nl)
-Ao directly posterior
Dextrocardia:
Dextrocardia w Situs Solitus
-Isolated Dextrocardia w AV Concordance & Nly Related GAs
-apex points right, heart in R chest
-Sx d/o assoc xx- VSD, CoAo, AVSD
-usually Nl bronchi branching, and visceral situs solitus w L sided stomach, R liver
-ECG = Dextrocardia = P wave frontal plane 70-80degr axis, QRS axis shows RAD
-R wave progression shows a translocation (shift) of the usually horixontal R wave progression, twd R chest--> Nl L precordials, then gradual reduction in R wave voltage as you go R ward (????)
-must get V3R and V6R to see the more typical QRS pattern and R wave progression that's usually seen in the L chest...
-Isolated Dextrocardia w AV and VA Discordance & L anterior Ao-Corrected TGA
-most common type seen
-assoc xx common- VSD, pulm stenosis, also DORV, DILV,
Dextrocardia w Situs Inversus
-Dextrocardia w Situs Inversus & Inverted Nly Related GAs (Ao is L and post)
-heart & all cardiac structures are inverted, so Nl AV & VA concordance& connection
-uncommon
-assoc xx- TOF, Pulm atresia, complete AVSD, 2nd ASD
-see visceral situs inversus & dextrocardia together...
-ECG- P wave axis is R and inf bc of atrial inversion
-Dextrocardia w Situs Inversus, AV Concordance, & VA Discordance w Ao L & Ant
-it's an inverted TGA (so morph LV is on R but Ao on L/ant)
-a common form of dextrocardia w situs inversus
-Dextrocardia w Situs Inversus, AV and VA Discordance, w Ao R & Ant
-it's an inverted c-TGA
-rare
-usually w severe assoc xx--> bad hemodynamic impairment
-Dextrocardia w Situs Inversus, AV Discordance, VA Concordance w Inverted Nly Related GA (Ao L & post)
-=isolated ventricular noninversion = inverted form of isolated ventricular inversion, so hemodynamics are like d-TGA
-very rare
Situs Ambiguus
-could have RA or LA isomerism (w asplenia/polysplenia respectively)
Asplenia
-...
Polysplenia
-...
Levocardia:
-Heart in Nl position
-Isolated Levocardia = levocardia in setting of either situs inversus or situs ambiguus
Mesocardia:
-midline heart
Echo Features of Cardiac Malposition:
-Visceral SItus
-Check: liver, hepatic veins, IVC, stomach, spleen, abd Ao
-spleen should be post-lat to the stomach; interrogate it from a post-lat appraoch
-see tissue more dense than liver, w comma-shaped curvilinear splenic vein, if missing check the other side...
-if no spleen seen, & +Howell Jolly bodies on CBC--> 100% confidence it is asplenia
-if asplenia, often see midline liver, often w 2 lobes of = size, that look like R lobes
-check to see if hepatic veins drain directly into atrium, instead of IVC
-IVC & Ao are often on same side w asplenia, (on RIGHT side, in parallel AP orientation)
-If polysplenia, see multiple separate spleens post to stomach
-often see interrupted IVC w azygous continuation & a midline abd Ao
-w IVC interruption, see hepatic veins drain directly into atrium on either side
-liver & stomach location vary, but usually inverted
-Venous Connections
-Check: systemic & pulm venous anatomy/connections
-c/s bilat SVC to each atria, interrupted IVC w azygous/hemiazygous continuation to SVC, anom pulm vn return
-Atrial Situs
-Check atrial situs after checking visceral and venous structures
-Must Check all major venous connections to the heart- SVC, IVC, hep vns, pulm vn x4, cor sinus (marker of the RA), if CS is dilated c/s LSVC, and look for unroofed CS
-Check relation bn septum primum and septum secundum (one of the most reliable determinant of atrial sidedness...),
-inf rim of sept 2nd (seen as superior limbus of fossa ovalis) --> assoc w morph RA
-remnant of sept primum (seen as valve of the FO on echo)--> assoc w morph LA
-Check RAA & LAA morphology for sidedness
-RAA = broad, triangle shape
-LAA = fingerlike, narrow
-AV Connection
-check best in R and L PSSA, and AP4C and sub4C views
-check valve commitment and valve abNlies..., (stradddling/overriding valves)
-Cardiac Base-Apex Axis
-determine dextrocardia/levocardia/mesocardia
-Ventricles, VA connection, GAs
-PSLA and PSSA very good for checking concordance, double outlet connection, etc
Treatment:
-...d/o specific anatomy...
Congenital Pericardial Defects:
-range fr a partial defect to absent pericardium
-uncommon, hard to dx clinically
-due to defective formation of the pleuropericardial membrane or defective formation of the septum transversum (if diaphragmatic)
-1/3 have assoc pulm lesion- bronchigenic cyst, sequestration, & congen hrt dz (TOF)
-Sx- only Sx if assoc dz- CDH, CHD; or only nonSp Sx like vague L chest discomfort, recurrent pulm infctn, palpn, dizzy, syncope; if partial could have herniation thru the defect w ventricular strangulation --> death,
-Dx- few Si on PE, may have cresc-descresc murmur at LSB bc turbulant Q in a very mobile heart, hyperactive apical impulse if displaced heart
-CXR- displaced cardiac silhouette to the L, or prominent L heart border w bulging at Ao knob, PAs, LV
-may have L PTx w a pneumopericardium
-CT & MRI make Dx easier...
-Tx- no Tx if completely absent; if partial then needs surgery - enlargement to avoid strangulation or closure w a flap of mediastinal pleura (preferred); if diaphragmatic, then must reduce abdominal contents into abdomen and repair the diaphragm defect...
Ectopic Cordis:
-a form of pericardial defect, but also has partial/complete displacement of heart outside of thorax
-5 types: cervical, thoracocervical, thoracic, thoracoabdominal, abdominal (really only use thoracic and thoracoabdominal)
-Assoc w TOF if thoracoabdominal
-Cervical- usually intact sternum, rare (may just = retention of heart in embryonic neck position)
-Thoracic- the classic type, w sternal cleft so heart protrudes outside of chest, completely absent parietal pericardium, cephalic orientation of apex, epigastric omphalocele or diastasis recti, small thoracic cavity
-thoracic size has important Px implications for surgical correction...
-assoc w intra and extracardiac xx- forebrain prolapse, meningocele, cleft lip/palate
-Thoracoabdominal- partial absence/cleft of lower sternum, crescentic midline ant diaphragmatic defect, defect of the diaphragmatic parietal pericardium--> free pericardioperitoneal communication, omphalocelelike ventral abd defect or diastasis recti w partial displcement of the ventrcular portion of heart thru the diaph defect into the epigastrium; & intracardiac CHD
-assoc w TOF, DORV, VSD, ASD, TriAtresia, Ebstein, common atrium, CAVCD, APVR, CoAO, TGA...
-Tx-
-usually poor surgical outcome
-prosthetic reconstruction of chest wall and covering heart w skin
-some do a staged approach w enlagement of post pericardial space by dividing post pericardial attachments to the rib margins
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