Mavroudis ASD Ch 16

-First closed in 1952, by John Lewis (Minnesota) w hypothermia & inflow occlusion

-First to use CP bypass (5/6/53), by John Gibbon

-First to use purcutaneous cath closure

-Now most closed by cath

Anatomy & Pathology

-Septum Secundum - thick, superior part, made fr infolded atrial roof

-Septum Primum - lower part, made of a thin flap of tissue, w the lower edge fusing to the endocardial cushion. Goes upwards and to the left of the limbus of the septum secundum (to bec ome the flap valve that closes the foramen ovale)

-At IVC os, there is the CS os & the eustachian valve

-Crista Terminalis = thick part of the infolding of the lateral RA wall running fr the sup to inf aspect.

ASD Types:

-Ostium Secundum (80%)

-Ostium Primum (10%)

-Sinus Venosus (10%)

-also - common atrium, coronary sinus ASD, and PFO

Secundum ASD

=@ fossa ovalis (part of the septum primum)

Sinus Venosus ASD

=@ jct of SVC and RA, more posterior & cranial to the superior limbic band

-near always assoc w PAPVR of the R sup PVn to RA. Tends to enter LA at jct of SVC and RA along the R'ward margin of the ASD (see pick). Sometimes it goes directly into SVC (near azygous entrance)

-Rarely, the SVn defect is near the IVC orifice, and it is assoc w a R inf PVn anomalous entry

Ostium Primum Defect

-Crescent shaped defect at inf part of the septum, just adjacent to the AV vlvs

-it is part of a CAVC defect, so aka partial AVSD/AVCD. assoc w cleft ant leaflet of the left AV vlv

Common Atrium

-failure of entire atrial septum to dvp; assoc w heterotaxy syndrome

Patent Foramen Ovale

-no defic in septum primum, and limbus is normal, but the flap never closed

-in true PFO (as oppose to ASD), it only opens when P o nR is > P on L, e.g. w cough/valsalva

Unroofed Coronary Sinus

-allows for LA to RA shunt, though septum itself is in tact

-often have LSVC to CS or sometimes direct to LA

Pathophys

-L to R shunting usually bc RV more compliant than LV --> Qp:Qs >1

-Large ASD can --> Qp:Qs >4:1

-rarely assoc w cyanosis fr L-->R bc the pt had a big eustachian vlv that directs Q thru ASD to L side (like prenatally)...

-rarely have cyanosis fr an unroofed CS

-if pt has common atrium, then --> mixing enough to cause cyanosis

NHx

-may get a-flutter & a-fib long term

-may get RV dysfx, pulm htn, paradoxical emboli, and then eventual CHF

-mean age at death w/o surgery is 36 years in pts w signif ASD (Ref 6)

-Unlikely to close on own if >8mm (Ref 7)

-Likely to close on own if <4mm (Ref 7)

-Unlikely to close after 4yo (Ref 8)

-Unlikely to get bacterial endocarditis, so no need for SBE ppx (Ref 9)

-Usually ASx, just hear a murmur fr relative PS, & hear fixed split S2 bc R side needs mroe time for Qp...

-+diastolic rumble in some fr relative TS

-RV vol OD and pulm vasc bed OD is well tolerated for years, so it is rare for infants to have CHF fr an ASD alone, and less likely to get pulm vasc dz than VSD or AVSD pts

-10-25% of adults w untreated ASD had phtn (phtn = PAP >30mmHg)

-5-15% had high PVR (ref 10)

-but it was mainly with Sinus Venosus defects than 2nd ASD (16% vs 4% of total group)

-If pt did get phtn to the pt of R-->L shunting, then closure is c/i xx

-Late mortality in untreated ASD pts is CHF & arrhythmias

-Mayo clinic study found 55% chance of late a-fib if closed >44yo vs 4% if closed by 11yo (ref12)

==> Rec closing ASDs

Indication to close:

-ASx ASD w cath/echo evidence of Qp:Qs 1.5:1 or more

-usually, if pt has murmur/fixed split S2 or other Si/Sx then it is >1.5:1 shunt

-pref to close before kindergarden for convenience

-long term Px worsens if you delay it till Sx or adulthood.

Cath Closure for 2nd ASD only

-Amplatzer

-CardioSEAL

-Helex septal occluder

-but must have the right rims for it, #1 reason for surgical ref is poor inf rim)

-xx of cath closure- device malposition & dislocation

Surgical Closure

1)-Median Sternotomy - many can do it w/o opening the entire sternum

-Right Thoracotomy - alt approach, but incr risk of air embolus and R phrenic n injury (not used by Mavroudis group)

2) Divide thymus at midline; no need to resect it

3) Autologous Pericardial Patch harvest

-At start of case, harvest it, and use stay sutures to retract the corners and place in a saline solut'n

4) CP Bypass- Ao cannula and 2 venous cannulas

-for 2nd ASD, cannulate the RAA first, and then later advance it to SVC

-Cannulate IVC at jct w RA, low enough so that if there's no inf rim of the ASD, you can get good exposure in that area

-if Sinus Vn Defect, must cannulate SVC directly w a RA cath at jct of innom vn

5) Cool pt to 32C

6) For an AVSD, vent at the R sup PVn..., otherwise they don't vent...

7) Caval Tapes at SVC & IVC placed

8) Cardioplegia given & caval tapes are snared

9) 2nd ASD: RA incision fr RAA to IVC. Don't cross the crista terminalis (to maintain SA nd to AV nd conduction fibers)

SnVn ASD: RA incision fr RAA tip twd SVC-RA jct, and if needed extend across the jct of SVC to RA, along the R lateral margin of the SVC

10) 2nd ASD: use sucker for Q through ASD fr LA. If much Q, c/s a PDA or high pump flow

-don't suck the LA empty bc a full LA ensures no air entering it fr RA...

-Suture the patch starting at inf aspect of ASD, near IVC, and ensure you don't bite into estuach. vlv (if you suture eustachian vlv to septum secundum, you might get an obligatory IVC to LA shunt!)

-then suture superiorly first near crista terminalis, then near CS. By the CS, don't take deep bites or you might injure the AV nd. Complete the sutures at highest pt of the L and RA jct

-before knotting the suture, make an opening at the jct of patch and ASD and make pt Valsalva to push blood and air fr LA/PVns thru ASD; note some bubbling as L side is de-aired. As pt is valsalva'd (once the bubbles resolve), then pull the suture tight and tie the knot. Then repeat the valsalva to assess for leaks at teh patch

-then decompress the L side of the heart by venting thru the cardioplesia needle site

-don't vent too strongly or you will pull air into the L side

-close the RA incision, and de-air before releasing the cross clamp

-rewarm pt as you close the RA incision

-Wean from bypass, remove venous cannulas, and use modified ulatrafiltration for 10 min to decr need for pRBC, then reverse the heparin w protamine, and remove the Ao cannula

-Extubate in OR or next day

-Alt 2nd ASD Techniques:

-directly suture the edges of the defect, or use PTFE patch, or use Dacron (polyester)

-Direct suture w 2 layers of running suture..., though use of a patch can reduce recurrence

Sinus Venousus ASD:

-nearly always need a patch bn SVC and RA, and direct suture can --> SVC or R Sup PVn stenosis

-TEE should be used for all Sn Vn ASD, check at end for residual defect

-Beware proximity of SA nd

-Beware the R phrenic n, on the other side of the pericardium next to the R lateral part of the SVC

-20-40% can be closed w a simple pericardial patch

-start suture line bn the R Sup PVn orifice and the SVC orifice, then continue it around the rest of the ASD. May need to enlarge the ASD so that the RUPV isn't stenosed- do this w incision twd FO and rsxn of part of the limbus.

-ensure sutures are superficial at post part of SVC, to avoid SA nd injury

-If the PVn enters the SVC, then the patch might need to extend into teh SVC itself to partition it into R and L side. Use a two patch technique to prevent billowing of the patch, which would cause SVC stenosis. In doing this, when you incise at the SVC-RA jct, make it as lateral as possible to avoid SA nd injury.

-Don't confuse the azygos vn w the anom R sup PVn (azygous usually has dark bld!, and PVn nearly bloodless bc pt is on CPB)

-Alt Sn Vn ASD approach: - flaps of RAA or direct anastomosis of SVC to RAA for complex defects to avoid SA nd injury (Ref 30)- transect SVC and oversew above R PVn insertion, then anastomose the SVC to the RAA and close the ASD w a patch..., others use RAA to make an atriocavoplasty

Ostium Primum ASD:

-vent thru R Sup PVn

-cardioplegia then open RA

-then remove vent fr MV orifice and LV, and place in post LA

-irrigate L AV vlv w cold saline to assess for MR

-close cleft in L AV vlv w interrupted sutures, then replace the vent into the LV

-some don't close the cleft if no regurg

-start suturing pericardial patch at pt where the leaflets bridge the IVS crest, then suture clockwise twd CS (taking superficial bites there to avoid AV nd). Then bring a 2nd suture line counterclockwise

Technical Pitfalls

-may be hard to see inf part of ASD, espec if IVC cannula is too high

-if you mistake a large eustachian valve for the lower edge of teh ASD, then you might cause an IVC to LA shunt

-if LSVC to CS, c/s a L Glenn when you close the CS roof defect...

Surgical Outcome

-no death & no recurrence at their institution w 1/2 suture and 1/2 pericardial patch closure

-no change in long term survival fr Nl ppl....

-in their results w Sinus Venosus defect- R PVn stenosis in <10%, 7% w SA nd dysfx

-Ostium Primum ASD results- some get MR, AV block w pacer, LVOTO; ones tudy 98% survival at 10 yrs, but 9% needed reoperation for subAo obstruction, L AV vl regurg

Cath Closure Outcome

-about 98% success

Surgical Outcome in Older Pts

-higher risk, so controversial whether to Tx, but on th ewhole it seems to improve survival and NYHA class...