Mavroudis - PA-IVS

PA-IVS Mavroudis21

Epi/Definition

-Uncommon- 4.5/100,000 live births

-<1% of CHD

-assoc w R heart and cor art xx

--> need individual mgt based on spectrum of R heart & cor art morphology

-?cause

-if it occurs later in dvp, less likely to have an under-dvp'd R heart and cor fistula dvp

-MPA is usually well dvp'd, and a PDA is present--> so there is likely at least some time in utero w antegrade RV outflow Q

Morphology

-nearly always normal situs, and AV/VA concordance, with confluent branch PAs

-usually a single PDA

-usually Nl PDA/branch PA confluence, w Nl MPA size, but it tapers as it goes twd prox MPA

-Pulm Valve- varies from a tiny dimple w a long segment of muscular atresia, to a fused trileaflet vlv w well dvpd commissures/sinuses

-R Hrt- often markedly abNl

-enlarged hrt fr RA dilation

-Sev TR would --> massive enlargement, like a severe Ebstein's, w large dilated TV annulus and redundant sail-like anterior leaflet, and downward displacement of septal/post leaflets

-90% pts- RV hypertrophy & hypoplastic, w small cavity (severe in 1/2 pts)

-RV size correlates closely with TV annulus size (ref 13)

-some (ref 15) categorizes PA/IVS bu RV unipartite (inlet), biartite (in/outlet) or tripartitie (in/out/trabec parts)- but questionable bc even very small RV's can have all 3 parts, and massive hypertrophy obliterating the trabec/outlet parts

-even very hypoplastic tripartite ventricles can grow and dvp Nl fx after decompression

-so tripartite RV is important in considering viability

-remainder of pts have thin and very dilated RV

-Cor Arts

- >1/2 pts have a cor art abNly

-#1 is cor art fistulas w the RV - communicate via endothelium lined channels - sinusoids

-if a fistula enters a sinusoid, the combo is called a coronary-cameral fistula

-can have coronary artery stenosis from local myointimal hyperplasia; rarely --> complete interruption

-likely bc of injury to intima secondary to turbulent competitive Q fr high P RV thru the fistulas...

-rarely, there's no connection bn cor art and the Ao, and all Q is fr the RV

-important bc Qcor may depend on desaturated venous blood fr the RV

-presence of and xx from the cor fistula are correlated w degree of TV annular hypoplasia, RV hypoplasia, and RV P

-See sev RVH, myocardial fiber disarray, ischemic changes/diffuse fibrosis, sev EFE in some, sinusoids w/o cor fistula too in 1/2 of pts,

-5-10% see TV incompetence w dilation of and marked thinning of the RV, but without cor fistula/sinusoids.

NHx

-2 week mortality- 50%, 6 month 85% - survival beyond neonatal pd requires an alternate Qp

-rarely pts live to 20s bc of PDA or AP collaterals

Pathophys

-PGE dependent at birth for PDA

-cyanotic

-obligate R to L shunting at atrial septum

-usually unrestrictive, otherwise see low CO/hypotension

-Qp:Qs ranges fr 2-4 d/o PVR:SVR, w SaO2 70-90%; if >90% c/s pulm overcirc

-wide PP bc of diastolic runnoff to pulm arts via PDA

-RV has systemic/suprasystemic P if not sev TR

-diminished myocardial perfusion, myocardial O2 consumption is near maximal

-elevated wall tension in RV--> incr O2 demand, limit Q bc decr cor perfusion pressure; low Ao diast P bc of PDA runnoff...

-thus Qcor might not mainly occur during diastole like Nl, --> reduction in RVP may decr Qcor...

Presentation/Dx

-......

-recs cath in all cases - only means to conclusively define the cor art anatomy and fistulas

-also, may intervene w BAS...

Mgt

-Initial Tx

-Dx alone = Indication for surgery

-Options: 1) decompress RV via valvotomy or transannular patch, 2) Systemic-pulm shunt alone, 3) Systemic-pulm shunt + RVOT procedure

-final options: 1) biventric repair, 2) 1.5 repair, 3) Fontan/univentric repair, 4) OHT

-initially must balance minimizing mortality, and optimize chance for biventric repair

-however while a shunt has initial lowes mortality, it might prevent the chance for a biventricular repair later on- bc pts w a severely hypoplastic RV can be Tx'd w medium-term mortality the same as those w less severe RV morph...

-limited data/single center data w various approaches/algorithms (ref 19, 27-31)

-one method- decompress RV w pulm valvotomy, and make a shunt in all pts w an RV infundibulum

-if no infundib, or if +RV dependent fistulas, do a shunt alone

--> mixed results

-ability to to 1, 1.5, or 2 ventric repair d/o subsequent RV dvp

-but this is problematic bc there is much morph variability w pts w an RV infundibulum, which may cause many pts to get a shunt unnecessarily

-no consensus on Tx intervention best (ref 19, 25-27, 30, 33-44)

-limited data on predicting when RV's (even severely small ones) will dvp to Nl Fx after establishing RV-PA continuity (ref 16, 17, 45-49)

-for those with intermediate RV's, if you don't establish RV-PA continuity as a neonate, it won't grow enough to get to biventric repair (ref 16, 17, 41), so you should treat them in a way that doesnt preclude laterbiventric repair, as long as the mortality risk of the initial procedure isn't greater than that of a procedure that would preclude a future biventric repair...

-CHSS study (ref 13) is the only one of size enough to rely on (1987-1991, 171 neonates)

-3 procedures: RVOT obst relief, RVOT relief + shunt, or shunt alone

-Survival Overall: 1month 81%, 4yrs 64%

-TV Z score correlated very closely to RV cavity volume

-Smaller TV Z score, +RV dependent cor arts, and choice of initial procedure were r/f for death

-TV Z score was only a factor for death when the initial procedure included RV decompression

-if you also had a shunt, TV size did not affect survival

-of pts who underwent valvotomy as the initial procedure--> 55% needed transannular patch within 3 yrs

-51% of pts who did not get a shunt initially, needed one within 1 month

-early risk of a combined RVOT and shunt procedure, vs a shunt alone was similar of Z score was -4 or larger --> if Z score -1 to -4, rec a combined RVOT procedure + shunt; but more recent analysis, of larger # pts (n=247, longer f/u time) --> if Z score is smaller than -3 Z scores, they have higher initial mortality for a combined procedure than for a shunt alone

-No pt in this group (Z smaller than -3) underwent biventric repair

==> New Recs based on CHSS:

-Mild RV Hypoplasia - TV annular Z 0 to -2:

-Goal: RV growth, minimize intervention

-Initial Tx: decompress RV w RV-PA continuity, cath/surg

-no good data on cath vs surg...

-Most will need valvotomy or TAP - valvotomy alone doesn't need CP bypass

-TAP will improve longterm risk of recurrence of PS, but will be more likely to have PR which may be worse for long term RV fx; no data to prove which is best

-ASD should be left early to allow for R to L decompression, to allow RV time to gain fx for entire CO

-in up to 1/2 pts, severe postop hypoxemia may --> need a shunt

-Mod RV Hypoplasia - TV annular Z -2 to -3:

-+potential to get to biventric repair in future, chance d/o size of RV

-bc the RVOT procedure + shunt has same mortality risk as shunt alone, rec doing both

--> keeps the chance you can do a biventric repair in the future if RV grows

-Initial Tx: valvotomy or TAP, as above

-Sev RV Hypoplasia - TV annular Z smaller than -3

-no pt in CHSS undwerent successful bv repair if Z was < -3

-early mortality for a combined procedure in pts w sev RV hypoplasia was WORSE than w shunt alone--> just do the shunt, & many of these pts have extensive fistula/RV dependent Qcor

-Initial Tx: shunt alone

RV-Dependent Coronary Circulation

-if + RV dependence, then def do NOT decompress RV, and move twd univentric repair, w a shunt alone initially

-some rec OHT w/u initially

-?what is significant RV dependency

-most pts w fistulae can undergo safe RV decompression

-risk is higher if only a single coronary w RV dependence, and higher still if 2 cor art affected

-"bc most pts w RV cor dependency has sev RV hypoplasia, can base mgt based on TV Z score alone"

Severe TR

-Ebstein's anomaly or unguarded TV orifice - usually enlarged TV annulus, dilated RV w poor fx

-clinically are like Ebstein's, w sev cyanosis

-high mortality

-RVOT procedure + TV plasty has poor Px

-most survivors need univentric repair

-most centers just do a shunt initially, some go for OHT, others create tri-atresia + shunt

Other Procedures

-TV disruption, TV closure, RV thromboexclusion, ligation of cor fistula, TV repair for TR --> no evidence that they help

Subsequent Surgical Mgt

-Nearly all need at least 1 secondary surgery

-if shunt initially, then --> cath at 3-6mo for pre-Glenn/BTS takedown

-do Glenn by 1 yo, then Fontan bn 2-4yo

-The Fontan must be modified if pt has RV dependent Qcor

-ensure RV P maintained

-direct oxygenated Q to RV

-allow cor sinus to drain to low pressure atrium

--> lateral tunnel or extracardiac Fontan w construction of Ao to RV conduit to maint Qcor

-no proof that this is better than a standard Fontan

-but even short RV decompression w CP Bypass can be lethal fr ischemia, so c/s an alter strategy during Fontan creation

-If RVOT surg initially and mild RV hypoplasia, without shunt,

-cath at 3-6mo to check RV fx/RVOT obstruction during temporary ASD occlusion, to check whether RVOT is capable of full CO

-if it is only valvar PS and RV fx is good, then can do balloon valvuloplasty and close the ASD

-More often, residual RVOTO not amenable to ballooning, and surg is needed- infundib rsxn w repeat valvotomy or TAP, and close the ASD (unless RV dysfx or borderline RVOTO)

-if borderline R heart dvp, then c/s a Glenn w RVOT enlargement (1.5 repair)

-can close ASD if pt tolerates, but if CO decreases fr decr LV filling, then leave it open

-no long term evidence of outcome (ref 58)

-If initial combined shunt + RVOT surg, w mild-mod RV hyoplasia

-cath at 3-6 months to assess RV growth, TV;

-catg at 6mo if good growth & --> test occlude the BT shunt, if SaO2 is maintained then you can coil occlude the BT shunt, then test occlude the ASD too and c/s closing it if RV can handle to full CO.. mgt options are the same as pts w mild RV hypoplasia as above (2 vs 1.5 repair)

-if mild-mod RV hypoplasia, without good growth to allow for bv repair,

-c/s univentric repair- takedown BTS and do a Glenn, w plan to Fontan vs 1.5 repair

-c/s 1.5 repair w RVOT enlargement and Glenn and closing teh ASD (or keep popoff if needed)

-c/s (Mee approach) TV valvotomy +/- repair, infundib muscle rsxn w repeat pulm valvotomy or TAP, and enlargement of trabecular part of RV by dividing the hypertrophied muscle bundles. Keep the shunt open, and restrict the ASD to promote RV growth

-if the RV does subsequently improve, then occlude the BT shunt and close the ASD, and if the RV does not dvp well enough, then do a 1.5 for Fontan palliation

-few centers that use it have good results (ref 19, 30)

Surgical Technique

RVOT Obstruction Relief

-median sternotomy

-valvotomy- can be done off bypass

-clamp distal PA just prox to branches, so Qp is via PDA...

-longitudinal pulm arteriotomy, check out atretic P vlv,

-perforate the valve and insert a hemostate to dilte the annulus; side biting vasc clamp to arteriotomy and then release the distal PA clamp and suture close the arteriotomy

-Transannular Patch

-RA cannula for drainage, start CP bypass

-maint normothermia bc no Ao crossclamping needed

-clamp distal PA to improve exposure

-open PA longitudinally

-incise pulm vlv plate in the AP direction, and PA incision extended proximally across the annulus, to the RV fee wall

-place a dilator in RVOT (of appropriate diameter of desired size...), and suture the RV incision, w oval patch..., then wean fr bypass...

-ligate PDA if systemic sats are good

Systemic-PA Shunt

-if only doing a shunt, then do mBTS via R thoracotomy

-allows for spont closure of PDA

-distal innom artery dissection

-prox R SCA exposured

-open pericardium parallel and post to the phrenic N, and ant to the RPA

-encircle the upper lobe branch and continuation of the RPA w a silk suture

-4-5mm PTGE chosen, beveled on 1 end,

-give heparin to pt

-suture beveled end of conduit to an arteriotomy in prox RSCA, then cut to appropriate length w/o a bevel, and clamp prox RPA w tension placed on the silk suture to control distal branches of teh PA, then suture distal end of shunt to the side of the upper lobe branch of the RPA.....

-stop PGE

-if also doing RVOT surg, then do it via median sternotomy

-and can do on bypass if being used bc it is easier

-and ligate the PDA after weaning fr CPB

-if also doing RVOT surg but w/o CPB, then they prefer to construct the shunt initially, to allow them to occlude the PDA during RVOT surg (w single lung perfusion just to R lung), to improve visualization of RVOT