Mavroudis - PA-VSD

PA-VSD Mav23

=extreme TOF

=complete pulm atreseia, no luminal continuity w RV

+/- complete atresia or absent branch PAs/MPA

-Qp is via extracardiac sources- PDA and Major Ao-Pulm Collateral Arts (MAPCAs), bronchial arteries, cor art to central PA fistula

-intracardiac is ~TOF: large perimembr mal-alignment VSD, w ant displacement of infundibulum (to the extreme); +Ao override theVSD, or ~DORV in some pts

-some have prev c/s this a variation of truncus (truncus arteriosus type IV aka pseudo truncus), but the VSD is diff than that of a contrucus (PM VSD vs a juxtarterial VSD)

-PA morphology is very variable

-MAPCAs are fr embryonic aortic arches

-midsize, muscular arteries, not the same as intrapulmonary arteries which are fr the forgut and are musculoelastic arteries

-Communicating MAPCAs = connect directly w central PA, so that the PA segments supplied by the MAPCAs can also be supplied by the central PAs

-Non-communicating MAPCAs = no connection w the central PAs, so MAPCAs are the sole supply of the segment of the lung for Qp

(all pts w/o central PAs have only noncommunicating MAPCAs)

-MAPCAs usually are fr the prox desc Ao; or can be fr subclavian arteries/branches, or abd Ao

MAPCA Patterns

-DA connects to central PA--> Nl periph PA distribution, no collaterals to that hemiTx

-PDA doesn't coexist w MAPCAs on the same side

-RU lobe and LL lobe segments are often supplied by a single, noncommunicating MAPCA, w RUL fr the subclavian artery and LLL fr the desc Ao

-MAPCAs can --> large Qp w high P to the pulm segment, --> CHF and then phtn in some pts

-MAPCAs can --> stenosis w intimal prolif at pts of bifurcation or pt of jct w the true elastic PAs --> less risk of phtn bc it doesn't transmit the high P of systemic circulation; protective, allows one to wait till p 1yo/early childhood to intervene

-MAPCAs may be of small diam, or have a long meandering course--> dec P exposure of the lung and be protective

-intimal prolif might --> complete obstruction--> lose circulation to the segment, so can be deleterious over time

-Bronchial Artery dilation/aneurysm may dvp, must ddx these fr MAPCAs.

-BA's follow the bronchial tree w arborization, and don't connect directly to the preacinar capillaries, so don't participate efficienty in resp fx. tend to be high resistance, so are not included in reconstruction...

Surgical Tx

1) Palliation

-Indications- relieve cyanosis or CHF

-if limited Qp--> establish a syst-PA shunt if not a candidate for complete repair

-best to place a shunt centrally --> less distortion to the small central PAs

-if no central PA, may need to relieve or bypass the stenotic parts of the MAPCAs w a patch angioplasty, PTFE graft, or unifocalization

-if CHF fr incr Qp--> if cannot do 1y repair, then try to reduce Qp w interruption of some communicating systemic collats, and unifocn of MAPCS to estab good Qp to the segment, via a surgical shunt or RV-ventral PA conduit/RVOT reconstruction without closing the VSD

-secondary lesions seen- Ao regurg fr Ao dilation, TR seen too; may require Tx too, usually seen in older pts later on

2) Reconstruction before Intracardiac Repair

-Goal- modify the pathologic anatomy to prepare for the final repair

-if hypoplastic central PA--> goal to induce growth/dilation of the PAs- systemic to PA shunt, or RVOT reconstruction w closure of the VSD

---> enlarge the PA over time; they prefer a shunt in neonate/small infant, via anast the small MPA to the Asc Ao- w direct anastomosis or via interposition of a short PTFE graft

-can be done w/o CPB, unless pt's circ entirely d/o the PDA

-dont place a BT shunt if pt has small PAs bc --> distortion/occlusion

-Older kids/adults- RVOT reconsutrction to estab continuity bn RV and the small PA confluence --> pronounced enlargement of teh central PAs

-? exposure of the hypoplastic pulm conf to full pulse P contour of the RV --> stimulate dilation of the PAs. Must make the RV-PA connection valveless, nonelastic conduit (so no pericardium or homograft bc that will --> aneurysm of the material, and absorb the P, so defeats the purpose...).

-Unifocalization-

-goal to eliminate extracardiac sources of Qp, by bringing together as many MAPCAs as possible to eventually be inforp'd into the RVOT

-done w a single stage complete repair or as a separate staged repair

-principles of unifocalization-

-avoid prosthetic material whenever possible for periph PA reconstruction

-when possible, join discontinuous PA segments supplied by noncommunicating collats, join w adequate mobilization of their feeding collat vessels, w a tissue to tissue anast.

-must bypass or repair stentoic parts of the MAPCAs

-may need to dissect into the lung along the lobar fissures to make distal anastomoses

-the syst-pulm shunt must be made so that both it and the unifoc'n graft can be accessed thru a median sternotomy normally used for complete repair

-if possible, the central PAs should be used for complete repair, even if small. If small, try to enlarge them before doing a complete repair

-unifoc'n procedures can improve/get rid of arborization abnormalities, but one must improve teh distribution of pulm art Q throughout the lung fields. Hyperperfusion to a PA segment w underperfusion of other segments might --> VQ mismatch--> phtn

-very hard to get normal Qp distribution/impossible at times

Complete Repair:

1) Interruption of extracardiac Qp Sources

-Interrupt the PDA, the prev surgical shunts, and the rest of the MAPCAs

-EXCEPT if there are residual noncommunicating collat arts that cannot be unifocalized to the PAs. If you interrupt these, you will lose Qp to those segments...

2) Close the ASD & VSD

-if pt requires VSD to remain open bc of inadequate Q to the PA tree, c/s it palliation not complete repair

3) Establish Unrestricted Comm'n bn RV and PA tree, incorporating as many pulm segments as possible

-Valved RV-PA conduit

-nonvalved conduit is poorly tolerated, bc PA tree imperfections can --> varying degrees of impedance to RV emptying.

-if possible, maintain the native PA bifurcation, avoiding use of a PA confluence prosthesis, bc obstruction to a prosthesis makes for a very tough problem later when u want to replace the RVPA conduit

4) Achieve Adequate RV Decompression (RVP:LVP low enough)

-? whats good

-RV:LV P <80% must be obtained at end of complete repair, if >80%--> reopen the VSD while still in OR

-may need to work on specific PA segments in OR or cath lab w stent/dilation

Strategies for Complete Repair of PA/VSD w MAPCAs

-Single stage vs multi-stage approaches

-Primary surgical repair of PA/VSD/MAPCAs - successful by some- ref 15, 16, 17

-median sternotomy, CPB needed, w unifoc all MAPCAs u can get to by exposing origin fr the prox desc Ao and connecting to the central PAs, w extensive patching of the hypoplastic vessels

-if successful unifoc'n, then the new pulm confluence is connected to RV w a valved homograft and VSD is closed.

-advantages- preserves all PA circulation infants/small kids, that if untreated the collats may be lost bc of intimal prolif--> underdp the lung segment ==> aggressive early approach (?) increase ability to salvage areas of lung that would otherwise be lost.

-disadvantages- possible lack of growth of the reconstructed PAs, complex anast needed for unifocn, risk of repair in small infants is higher than older pts w staged method (ref 19-22)

-if the VSD couldn't be closed bc of high RV P's post unifocn, then u are now exposing the lungs to high P--> Phtn, and are not protected by MAPCA stenosis anymore

-May be the best approach for pts w CHF Sx from excessive Qp and technically feasible

-Staged Repair

-first do initial stages to enlarge the small central PAs, do RVOT reconstruction, or alleviate arborization abNlies (unifocn first)

-perform final repair once the anatomic and HD condiction is improved so that you can close VSD w/o elevated RVP's....

-best for pts who present later in life, are stable, or need palliation

-to access the stenosis in periph MAPCAs, usually need a lateral thoracotomy

-final intracardiac repair is doen thru a median sternotomy w CPB

Results

-One stage results- ref 17,18- n=10 pts, 9/10 had complete repair, 1 needed VSD to remain open for high RVP's

-complications- bleeding in 1, 3 w phrenic n paralysis, 3 w severe bronchospasm

-Staged reconstruction results-

-Mayo clinic, n=496 fr 1977 to 1999 -

-173- 1 or more stages done, but not completed yet

-range 1mo to 35yo, mean 7yo. 20% not candidate for complete repair

-16.8% early mortality (n=29)

-76% had MAPCAs

-severe bronchospasm was a major cause of M&M

-24% late mortality (n=35)- - died fr neuro event, hemoptysis, pna

-325- complete repair in 1 or more stages

-age range 3 days to 55yrs at complete repair, mean 11yrs

-63% had 1 or more MAPCA

-at complete repair, 100 pts needed a central PA confluence prosthesis bc of absent/nonconfluent/unusable PAs

-valved conduit was used in most pts for RVOT reconstruction (57 w procine, 77 w homograft)

-postop RV:LV P ranged fr 0.3-0.9, mean 0.6

-3.7% (n=12) early deaths- 9 w low CO, 1 w neuro event, 2 sepsis

-12 pts had reopening of VSD for high RV P, one died early but remainder w/o late deaths

-f/u pd 1mo to 15 yrs, mean 6 yrs.

-15/311 survivors neede reop for conduit obstruction, 6 for recurrent/resid VSD, 2 Ao vlv replacement, 1 w TV annuloplasty

-10% underwent post repair PA dilation/stenting

-6 late deaths- 3 had RV htn, 1 w hemoptysis, 2 w sudden death