Epi
-<3% of CHD
=single arterial trunk fr the base of both entricules, with a semilunar valve, outflow VSD, with PA's coming off the truncus.
Type I = single MPA comes off the truncal art, then bifurcates into 2 PAs
Type II = PAs arise from a common origin directly off the truncal art (no MPA)
Type III = RPA and LPA originate from separate orifices at the lateral aspects of the truncus
"Type IV" = lungs supplied by systemic arteries (really this is pulm atresia/VSD with MAPCAs)
-rarely, one of the PA's arises from the PDA
-LPA may make a vascular sling, bc it arises fr the RPA and compresses the tracheobronchial tree
-30% of pts have R Ao Arch
-10% of pts have interrupted Arch (usually Type B)
Truncal Valve
-50% are tricuspid, 30% are bicuspid, 15-20% quadracuspid; very rarely unicuspid
-often has some degree of truncal valve dysplasia--> regurg or stenosis, or both
Cor Arts
-various patterns of origin. Usually 2, but might have a single cor art.
-LCA may originate high fr the posterior wall of the truncus
VSD
-usually subarterial
-80% pts- posterior margin is muscular, completely separated fr the ant leaflet of TV, made fr the post limb of the trabecula septomarginalis fused w the ventriculoinfundibular fold (= infundibular subarterial defect)
-20% have a perimembranous infundibular defect- post margin extends back to the ant leaflet of TV
-may have effacement of the ventriculo-infunib fold--> continuity bn truncal vlv and TV
-there's always continuity bn MV and truncal vlv (like w MV and Ao...)
-1/2 of pts have overriding truncal vlv over the VSD, relates equally to both ventricles, in some it is mainly fr RV usually, sometimes is mainly fr LV
DiGeorge Syndrome
-common w truncus arteriosus
-see thymic/parathyroid aplasia/hypoplasia, T cell immune defic (reduced T helper cell subset), hypoCa, predilection to infection
-see facial dysmoprhism
-fatal graft vs host rxn seen w blood transfusion, so must irradiate the bld
-Ca supp may be needed...
Sx
-Pulmonary overcirc--> CHF by early infancy, w systemic steal- low diastolic P fr runoff; decr Qcor w decr ventric function.
-Sx worse w valvar regurgitation
NHx
-median age of death varied fr a few weeks to 6 months
-if pt survives >1yr, they get progressive phtn fr pulm vasc dz bc of pressure exposure...
Echo
-check for IAA
-check for ductal origin of a PA
-check for multiple VSDs
Indications for Surgery
-should go to OR early- before 2-3mo even if ASx. May want to wait till WOL 2-3 for PVR to drop, unless there is CHF Sx despite Rx Tx
-we no longer band the PA first
-Older pts- may need cath to check for phtn (??really)
-there is much streaming within the truncal art, so BP and O2 in PAs might be diff than that of truncus, so at cath must check sats and P at each PA
-if PVR >10Wu, Px is better if NO surgery (!)
Surgery
1) midline incision
2) harvest pericardium for a prox extension of the homograft conduit to the RV if needed
3) purse suture at RAA to retract fr truncal art, and use for cannulation
4) dissect the PAs to hilum & mobilize the Ao
5) snare the PAs so that as soon as CBP is initiated you can snare them to prevent runoff to PAs and flooding of the lungs
6) place Ao cannula as distally as possible, cannulate bicaval, start CPB & hypothermia
7) if signif truncal regurg, must cross clamp the Ao as CPB is initiated
8) Detach the PAs
-Type I - incision on at/sup aspect of MPA, then go infly to detach it completely
-close the hole in the Ao by direct suture, or w a patch to prevent valve distortion
-Type II & III- transect the Ao and detach PAs w buttons, then do end/end anastomosis of Ao
9) VSD Closure
-RV incision fr midpoint of the anterior RV wall to base near the L side of truncal annulus
-divide heavy RV trabeculations to see the VSD, prevent later subvlvr PS
-close w pericardium patch, avoiding sutures in post margin if it is a PM defect
-must acct for the amt of truncal override into RV to prevent narrowing of LVOT
10) Some don't close PFO to allow for popoff
11) Establish RV PA continuity
-most use a valved conduit- Ao or pulm cryopreserved homografts, porcine valved Dacron conduits, bovine jugular vein grafts, pericardial composite valve conduits
-close RA & rewarm
-unclamp Ao
-mobilize the PAs, then bring them to the R of the Ao
-place the valve as distally as possible to prevent sternal compression later
-bring the conduit behind the Ao and to the left
-+/- place a hood to connect the conduit to the RV
-Ao homograft is their conduit of choice
Special Considerations
-Repair of Truncus Arteriosus w TV Regurgitation
-Truncal Regurg is still challenging
-Mild-Mod- Tx conservatively
-Severe regurg- must repair it, or maybe replace it (rare)
-Regurg often is fr prolapse of a quadricuspid valve
--> suture the prolpasing leaflet to make a bicuspid vlv
-Annular valvoplasty- excise the small prolapsing leaflet w annular remodeling can be done
-Severe Truncal regurg fr gross dysplasia--> need to replace the vlv
-Repair of Truncus Arteriosus with Interrupted Aortic Arch
-Type B is #1
-cannulate descending Ao and RA
-PAs are snared as soon as CPB is begun
-hypothermia and circ arrest
-head and neck vessels are snared
-excise the PAs fr the truncus, and the DA fr the PA end (so it is attached to desc Ao)
-mobilizing the desc Ao and bring it superiorly to be anastomosed to the posterolateral Asc Ao thru a longitudinal incision.
-currently, they do complete or partial transection of the truncus, and arch augmentation and small asc Ao w a patch of pulm homograft. Allows for better size match w the prox Ao--> tension free anast. Recommend the Lecompte maneuver w anterior translocation of the PA bifurcation to prevent compression of the RPA and facilitate placement of the RV-PA conduit
-Repair of Truncus Arteriosus with Discontinuous PA's
-Most commonly the LPA arises fr the PDA and th RPA fr the truncus
-Both are detached fr the Ao connections
-the 2 PAs should be anastomosed together directly
-if you can't, then the larger artery is sewn end to end to the homograft, and the other sewn end to side; or you can sew the pulm homograft with its bifurcation can be used w end to end anast to both PAs
-Repair of Truncus Arteriosus w Prior PA Banding
-PAs are detached fr the truncus, then close the Ao defect
-enlarge the PA orifice by incising laterally on the RPA and LPA well beyond the fibrotic band
-if PA wall is good quality, the homograft conduit can be trimmed in a fishmouth manner so that there there isa flap like extension that can be sutured to a patch to enlarge the proximal banded area of the PAs...
-sometimes the PAs beyond the band are thin and fragile and direct anasatomosis would tear the vessels, so then use a patch of pericardium/pulmonar homograft fr hilum to hilum, across the banded area to both PAs, w a large patch onto which a homograft will be anchored...
Postoperative Mgt
-Phtn crisis is a major cause of M&M, but much less freq bc we Tx as neonate by before 3mo.
Results
-much decrease in operative mortality over the 1990s
-2005 study- 3-17% operative mortality d/o the diff studies
-1998 multicenter study- mortality 27-44%
-Long term
-may need reop for RVOT