Atrioventricular Septal Defects (M/A)

Nomenclature:

= septal defect of both atrial and ventricular septum and/or AV valve abNly

-aka AV Canal Defects aka Endocardial Cushion Defects

-Partial = primum ASD & 2 distinct mitral and tricuspid valve annuli

-mitral valve will always have a cleft

-Transitional =Partial AVSD w small inlet VSD thats partially occluded by dense cord attchmts to IVS

-Complete = primum ASD that's contiguous w an inlet VSD -->ing common AV valve with single annulus

-Intermediate =Complete AVSD w distinct R and L AV valve orifices, though still 1 common annulus

-The orifices are R and L AV valve orifices (NOT called TV/MV orifices)

Px:

-overall very good surgical outcome w <2% surgical mortality and >95% 20yr survival

-but 1/4 of pts need reoperation, most commonly bc incr L AV vlv regurg or bc of LVOTO

Epi:

-5% of CHD

-40-50% of Downs kids have CHD, & of these 40% have AVSD (usually CAVSD)

-common in heterotaxy pts, espec if asplenia

Embryology:

-most due to ng EC dvp

-partial AVSD = incomplete fusion of the sup & inf ECs--> cleft at midpart of the ant mitral leaflet;-->MR

-complete AVSD = no fusion at all bn sup and inf ECs--> separate ant and post bridging leaflets form, along the subjacent ventric septum

-The primum defect is usually large--> displace the ant mitral leaflet down, to level os septal TV leaflet

-so w AVSD, septal leaflets have same level of insertion, unlike Nl heart (where MV is higher)

--> shorter distance fr cardiac crux to LV apex

&--> apex to Ao vlv distance is Increased (thus incr risk of LVOTO) (--> crx-Apx < Apx-Ao)

-->unlike Nl hrt where the crux-Apex & Apex-Ao distances are equal

-->this disproportion--> displace LVOT ant'ly, longer/narrower LVOT--> gooseneck deformity

--> subAo stenosis can incr post valve repair...

-Assoc w conotruncal xx (TOF, DORV) bc the dextrodorsal conus cushion (see pic), contributes to dvp of the R AV vlv and the outflow tract

-The AV valve orifice may shift, so that the valve is assoc w only one ventricle, mainly...--> unbalanced

CXR:

-cardiomegaly, prominent vasc markings

-RA enlargement bc of MR jet directed into RA (!), instead of LA

ECG:

-AVSD position--> determines AV conduction tissue location

--> displace AV Nd post'ly to near the CS os, and His bundle inf'ly along inf rim of AVSD

-prolong PR bc incr intra-atrial conduction time fr high RA to low septal RA

-P wave- RA, LA, or biatrial enlargement in about 1/2 pts

-RV vol OD--> RVH w rsR' or RSR' in right precordials in most pts; 10% have qR pattern

-LVH if signif MR

Cath:

-not usually needed

-may see higher RA sats fr L-->R

Tx:

-Goal: Close the ASD, restor/preserve L AV vlv competence

-approximate edges of valve cleft w interrupted nonabsorbable sutures

-may need to add eccentric annuloplasty sutures to correct persistent central leaks

-must avoid injuring conduction tissue

--> 2 leaflet left sided AV vlv

-might instead fix L AV vlv as a 2 leaflet vlv if there is a mitral cleft (use cleft as a leaflet), do an annuloplasty so that you get coaptation of the 3 leaflets

-3% surgical mortality (in hospital death)

-R/F- CHF, cyanosis, FTT, age <4yo at operation, mod-sev L AV regurg

-some ppl get bradyarrhythmias postop- SA nd dysfx, heart block

Special Forms of Partial AVSD:

-Malaligned Atrial Septum (aka Double Outlet RA)

-if AS is deviated to the L of the AV jct (rare)--> both R and L AV vlv can be seen fr RA, which connects to both via the large primum ASD

-if very extreme deviation--> pulm vn obst like cor triatriatum

-Common Atrium

-~no atrial septum (thus always an AVSD if there's 2 ventricles)

-Sx-present as early infant fr incr Qp, tired, tachypnea, FTT; but if incr pulm vasc dz, then decr L-->R so the child will begin to gain weight... (thus KIDS W CAVC AND NOT FTT ARE WORRYING!!!)

-hyperactive precordium, prominent RV impulse

-S2 widely split, fixed

-S2 loud, proportionate to amt of pulm htn

-cresc-decresc SEM at LUSB, w rad to axillae/back

-distinct holosyst murmur of MR at apex

-middiastolic murmur at LLSB fr incr RA to RV Q (relative TS)

-often see asplenia and cardiac/abd situs xx

-Echo

-SC4C view best for dx (if u see a muscle bundle/band going thru atria, that's the septum)

-Cath

-complete mixing, Qp>Qs unless really bad phtn

-incr RVP more than w a partial ASD or secundum ASD

-Tx

-first Tx w heart failure meds- digox + diuretics

-repair early to prevent phtn

COMPLETE AVSD

Path:

-large septal defect w ASD and VSD --> common AV valve spanning across the defects

-the septal defect extends through inlet to the level of the membranous septum which is often absent

-Common AV valve - has 5 leaflets

-posterior bridging leaflet drapes over the inlet VSD = fusion of the septal tricuspid leaflet and inf half of the ant mitral leaflet

-the 2 lateral leaflets = post tricuspid leaflet and post mitral leaflets

-the R sided ant leaflet = the Nl ant tricuspid leaflet

-the ant bridging leaflet = sup 1/2 of the ant mitral leaflet

-the extent that the ant bridging leaflet straddles the IVS into the RV varies much, and --> classification (Rastelli A, B, C...)

-Intermediate Complete AVSD- If the common AV vlv is divided into R and L orifices (even though there's only 1 annulus) by a tongue of tissue that connects the 2 bridging leaflets

-there are 5 papillary muscles, 1 for each leaflet

-the 2 left sided paps are closer together than in Nl heart--> smaller lat leaflet than a Nl post mitral leaflet. They are rotated counterclockwise, so that the post muscle is further fr the septum than Nl, and ant muscle closer to the septum

-the pap arrangement, along w prominent ant-lat muscle bundle, can --> LVOTO

-and the leaflets are prone to dvp progressive regurg-->thicken leaflets, and changes like MVP

-there is intraventricular communication along the septal surface bn the 2 briding leaflets and at the interchordal spaces beneath the leaflets

-post briding leaflet usually overhanges the IVS and has many septal chordal attachmants.

-Sometimes, cords can fuse--> obliterate the interchordal spaces bn the leaflet

-Rastelli Classification- d/o relationship of ant bridging leaflet to the ventricular septum:

-Type A = ant bridging leaflet inserts entirely along the ant-sup rim of the IVS (most common)

--> forms a true commissure w R sided ant leaflet

-beneath the commissure is a distinct medial pap or a direct cord insert to IVS

-IVS communication beneath the ant bridging leaflet may be minimal/absent if cord fusion

-Type B = ant bridging leaflet is larger, and R sided ant leaflet smaller than type A--> the bridging leaflet straddles IVS, using a ap muscle atchmt along septal or moderator band in RV

-free interventricular comm'n bc no cordal anchors bn the ant bridgng leaflt and the IVS

-Type C = ant bridging leaflet even larger than Type B

-its medial pap muscle atchmts fuse to R sided ant pap muscle, so that the latter leaflet is very small. The ant bridging leaflet isn't attached to the IVS, so there's free IV communication ("free floating leaflet")

-Type A is usually isolated, seen w Down's a lot

-Type C seen w other complex xx- TOF, DORV, TGA, heterotaxies

-can often see TOF+Type C w Down's

-can often see DORV+Type C w asplenia

Si/Sx:

-incr RR, FTT as early infant bc of incr Qp

-nearly all present by 1yo

-if Sx don't dvp early on, c/s premature pulm vasc obstructive dz (AND WORRY!!!)

-AV regurg makes Sx worse

-Postop, L AV regurg is the #1 reason to reoperate

-1/5 pts get sev L AV vlv regurg postop in one study; preop AV regurg was a R/F

-If bad phtn, then maybe no desaturation...

-PE: hyperactive precordium, accentuated S1, variable S2

-elevated PAP--> loud P2

-loud holosys murmur at LLSBand apex if L AV regurg

-separate cresc-decresc SEM at LUSB bc incr Qp

-middiastolic murmur at LLSB, and often at apex bc incr Q thru common AV vlv

Echo:

-check crux at AP4C/SC4C

-check for additional ASDs

-see VSD - posterior inlet type

-see displaced R and L AV vlvs twd apex

-check for APVR (rare assoc'n)

-must assess valve morphology well, w number of orifices, whether a tongue of tissue conects the sup and inf bridging leaflets to --> 2 orifices (intermediate type)

-check at subcostal en face view of AV vlvs

-sup and inf angulation of the probe to check all 5 vlvs

-can also assess by TEE in the OR

-check for double orifice L AV vlv (rare)

-this--> less total L AV vlv orifice area than just a single L AV orifice --> incr risk of postop stenos.

-check at subcostal/PSSA

-check for single LV pap uscle

--> reduces effective valve area, and makes repair harder bc of more leaflet hyoplasia

-check on subcoastal/PSSA when you look for a double orifice L AV vlv

-check sizes of each ventricle (!), as one may be more hypoplastic

-if LV hypoplasia, then check for Ao arch hypoplasia & CoAo

-if LV dominance, often see atrial and ventricular septal malalignment

-subcostal en face view shows relative AV vlv sizes

-Echo can show severity of valve imbalance/malalignment but this doesn't always correlate to the degree of ventric hyoplasia. Also, vol OD to RV can --> septum bows twd LV--> makes LV lookhypoplastic even if it's not. Also, large ASD can --> preferential Q thru ASD --> underfill LV--> LV looks more hypoplastic than it is.

CXR

-big heart - RA big w increased convexity of RH border, and LA big--> flattened LH border

-prominent PAs and incr pulm vasc markings

ECG

-incr PR

-prolonged AV nd conduction w 1st degr AVB

-most have RA enlargement by voltages

-2/3 pts have rsR, RSR', or Rr' at V1, and remainder of pts have a qR or R in V1 = RVH

-+/-LVH

Cath

-usually not needed

-might c/s checking for incr PVR if older pt

-cath--> incr SaO2 at RA and RV,

-PAP is ~systemic in CAVC (vs partial--> <60% systemic P)

-L-->R shunt--> incr QP, related to PVR/SVR...

-bad AV regurg--> shunt bn all 4 chambers

-angio- can see LVOT gooseneck +/- LVOTO indication...

Clinical Course:

-these kids get pulm vasc dz, so must intervene surgically early on, usually by 1yo (4-8mo usually)

Down's Syndrome & AVSD

-more likely to have complete AVS

-more likely to have TOF w it

-less likely to have situs or splenic xx; less likely to have LVOTO, LV hypoplasia, CoAo, or other VSDs

-? if phtn is really worse

-when checking hemodynamics, must c/s that tri21 pt may have ch nasopharyngeal obstruction, hypoventilation, sleep apnea--> CO2 retention, relative hypoxia, --> incr PVR

-Downs pts--> higher PVR:SVR but improves w 100% FiO2 so it is the apparent hypoxia and hypoventilation that can be corrected during the cath. Though, fixed incr PVR is seen in 11% Downs pts <1yo.

-Surgical outcome for Downs pt is same as general population

Unabalanced AVSD

= one ventricle and it's AV vlv is hypoplastic, while the other gets much of the AV vlv...

-usually RV dominant AVSD w hypoplstic LV; the L AV vlv can become stenotic post correction

-usually dilated RA and PA w bulging RVOT anteriorly, often w much RVH and thick free wall (2xLV)

-LA dilated and LVOT long/narrow

-small post L AV vlv leaflet bc of lateraly displaced PM papillary

-in past most pts w severely unbal AVSD get Fontan, recently had success if AV vlv index was >0.5, here they fenestrate the atrial septum. underfilling of morph LV bc of large shunt at atrium and bowing IVS into LV--> LV looks like it's too small to work out, but it still might be able to work

-Thinks that portend a better outcome w 2 ventric repair in this setting:

-restrictive interventricular communication, antergrade Q thru Asc Ao fr LV, closed DA or only L-->R shunting, similar upper and lower extrem SaO2.

Intermediate AVSD

-rare subtype of CAVSD

=ant and post bridging leaflets are fused atop the IVS, and the common AV valve is thus divided into distinct R and L AV orifices (though still only 1 annulus). = large primum ASD and large inlet VSD usually

-Sx/Si like other complete AVSD

Tx:

-must do sooner than partial AVSD

-must do it before pulm vasc obst dz occurs

-ideally do electively by 6mo, do sooner if +FTT

-If Sx--> c/s palliative PA band or just do a complete repair

-complete repair preferred, though some say do PAB if younger bc worse outcome of repair @ <6mo

-one person rec PAB if pt <5kg that's unresponsive to Rx Tx

-today most do complete repair if +FTT, so few actually get a PAB

-Surgical Goal: close the ASD & VSD, make 2 separate and competent AV vlvs fr what tissue is there

-single or double patch to separate close the ASD/VSD

-reconstruct L A vlv as a bileaflet valve

-some c/s the L AV vlv cleft to be a true commissure and so c/s it a trileaflet valve, so some prefer a 2 patch technique that keeps the L AV vlv as trileaflet, now the method of choice

-R/F at repair- age, severity of AV regurg, preop fxl class

-xx- sinus and AV nd xx w complete HB (rare)

Special Problems at Surgery:

-Parachute MV

-if you close the mitral cleft, it might --> obstruct the mitral orifice, so if there's signif AV regurg, may need to replace the valve altogether

-Double Orifice MV

-don't just cut the leaflet bn the 2 orifices; usually the 2 orifices are together big enough to suffice

-RV or LV hyoplasia

-may preclude septation, so go toward Fontan w a PA band first

-TOF

-ant dsiplaced infundib septum so that the usual inlet VSD seen w AVSD extends anterirly and superiorly twd the perimembranous area. In TOF, there's obst to RVOT

-M/A: prefers to treat cyanotic pts initially w a syst to pulm shunt and then complete repair at 2-4yo

-SubAo Stenosis

-usually a fibromuscular membrane, should be resected at OR

-if it appears late after repair of AVSD (usually the case)- ?related to uncorrected inlet VSD, w formation of endocardial fibrous tags and fibromuscular ridges. Tx w local resection, but some pts need a Konno procedure

REOPERATION AFTER REPAIR OF AVSD

Partial AVSD:

-for AV regurg or AV stenosis of L AV valve, subAo Stenosis residual recurrent ASD

-10-15% need reop for L sided AV valv regurg

-R/F = residual intraop regurg, sev dysplastic L AV vlv, failure to close the anterior (septal) leaflet

-repair possible if it's bc of unrepaired cleft, and not bc of sev dysplastic leaflets

-must--> eccentric commissural annuloplastic sutures to correct the central regurg

-may need to replace the vlv if sev dysplastic valve leaflets

-L AV stenosis:

-may need reoperation for very hypoplastic orifice, eg bc parachute deformity, or need prosthetic vlv replacement, though u must replace it w a larger valve there's no reliable technique to enlarge the mitral annulus. Rarely, some sew the new, larger prosthetic valve in LA above the original mitral annulus (!)

-Late LVOTO bc subAo stenosis is more freq in partial AVSD than complete

-likely bc during repairthe defic part of the inlet VSD isn't reconstructed so that the ant (septal) leaflet of the L AV vlv hinges on the line of fibrous fusion to the crest of the IVS--> standard repair doesn't modify the elongated and potentially narrowed LVOT. W complete AVSD, the inlet VSD is reconstructed w a subvalvar patch that widens the LVOT..

-repair via:

-transaortic rsection of the fibrous/fibromuscular membrane

-or patch enlargement of LVOT w tranAo and RV approach (modified Konno)

Complete AVSD:

-17% need late reoperation within the next 20yrs

-L and R AV regurg, L AV stenosis, residual ASD/VSD

Postop Echo Assessment

-must check valve morph well!

-check Doppler or AV regurg & stenosis