D-Transposition of the Great Arteries (M/A)

TGA (MA51)

Epi:

-5-7% of all CHD

NHx: 30% die by 1 week old, 50% by 1mo, 70% by 6mo, 90% by 1yo without Tx

-Now, w Tx, >90% survive early/midterm

-Male>Female (60-70%)

-Extracardiac anomalies not common (<10%) (unlike Truncus 48%, VSD 34%, or TOF 31%)

Anatomy/Path:

Nomenclature

=Ao fr morphologic RV, PA fr morphologic LV

-Complete TGA = usual atrial arrangement, concordant AV, discordant VA alignment

-complete- redundant term but meant to indicate that the transposed GAs are physiologically incorrect

-as oppose to corrected TGA (systemic venous Q to PA and pulm vns Q thru Ao)

-both complete & corrected rep morphologically complete transpositions... (misplaced across the IVS)

-d-TGA = SDD =situs solitus of atria/viscera, D looped ventricles (right handed), D Aorta (ant & rightwrd)

- SDL =Ao at valve annulus level is to the L of the PA

-Rare type of TGA - Ao posterior (as expected) but still aligned with and connected to the ant morph RV

-"Simple TGA"- = excluding hearts w additional assoc'd xx like AV valve atresia, straddling/common AV orifice, single ventricle hearts w small outlet chambers

This chapter discusses: simple TGA w IVS, w VSD, w PDA, and w LVOTO (80% of all TGA)

&& Taussig-Bing Anomaly = DORV w subpulmonary VSD bc it can be similar to TGA w VSD

Morph & Etiology

-Likely in large part due to abNl dvp of the distal infundibulum (conus).

-It is Nly subpulmonary, Left sided, Ant, &--> prevent fibrous continuity bn pulmonary and tricuspid rings. In TGA, the conus is subAortic, Right sided, Ant, &--> prevent fibrous continuity bn Ao and Tricuspid rings.

-Nly, the pulm valve moves from post to ant on the LEFT side bn 30-34days of embryogenesis

-At same time, Ao vlv is stationary, ?bc it doesn't have a subAo infundibulum

-Thus, ?TGA is due to abNl dv of the subAo infundibulum without growth of the subpulm infundibulum. The Ao vlv protrudes sup'ly and ant'ly bc of the dvping subAo infundibulum, putting it Ant to RV

-The subpulm infundib doesn't dvp--> prevent Nl morph mvmt of pulm vlv from post to ant, and --> pulmonary to mitral vlv ring fibrous continuity...

Cardiac Segments

-Atria- usually Nl, w PFO (only 5% w true ASD)

-SA & AV nd are in Nl position; surgical damage @ crista terminalis/sup rim of FO can --> xx

-RV- may get RVH w time, e.g. in Mustard/Senning pts

-Nl inflow, Nl sinus portions, but the central fibrous body is shortened, and the AV and membranous IVS are smaller than Nl. Nl'ly the IVS has a sigmoidal shape, here it's very straight--> RVOT runs parallel to LVOT.

~always have subAo conus separating Ao vlv and TriVlv if IVS is intact.

-Outlet (infundibular) septum joins Nly w the IVS bn the limbs of the septal band

-In Nl heart, infundib goes sup/ant/left, but here it just goes superiorly to the Ao

-LV- pulmonary-mitral fibrous continuity usually (thus no conus below PA)

-LV post wall thickness, and cavity shape d/o pt age and other lesions, and are important for surgery

-Aorta- most often the Ao root is directly ant/right of PA trunk, w slight oblique relationship.

-Less common: Ao ant/left to PA; rarely Ao post/right to PA

-Coronary Arteries- very diverse anatomy, related to varied Ao/PA relationship & varied conus septum

-they tend to take the shortest route to the sinus of Ao root

-when Ao more posterior (= side-to-side GAs)- the circ or even entire LCA may arise fr posterior facing sinus, w RCA fr the Ao ant'ly.

-Septal (aka facing) sinuses are the 2 Ao sinuses that face the PA, and are adjacent to the AoPulm septum. They contain the coronaries in >99% cases.

-When GA's are directly Ant-Post, then the facing sinuses are leftward/rightward

-When the GA's are side-by-side, then the facing sinuses are ant/post

-WHen the Ao is ant/right of PA, then the facing sinuses are left/ant & right post

-Other classify sinuses by numbering them, or labeling them according to surgeon's perspective

-Major CA's are

-RCA- = CA passing in the R AV groove

-Circumflex- = CA passing in the left aV groove

-LAD- = CA paralleling the IVS on ant surface

-Note that the proximal part of any CA might have an intramural course, usually bn the GA"s, with the media of the Ao and coronary walls attached, without any adventitia in between

-In light of this, there are about 9 types of CA anatomies than account for >95% of pts

-May have >1 ostia at each sinus

-May have odd coronary course

-May have missing artery/branch

-Make sure to pay attn to course of sinus node artery bc damage to it can --> arrhythmias

-it's course is variable (Nly is the 1st branch of RCA), and courses thru ant/sup rim of FO

therefore easily damaged during a bAS or surgical septectomy

Coexisting Anomalies

-50% of pts have no other xx except PFO

-VSD- 40-45% - w 1/3 of these small, no HD xx

-VSD+LVOTO in 10%

-AV valve and valve tensor xx, and Ao obstructive lesions important for surgery

VSD-

-Membranous VSD- next to TriVlv annulus at ant-septal tricupsid vlv commissure, bn conal (outlet) septum above the muscular septum

-Might close/shrink w time

-Muscular VSD- usually midseptum, usually single defect

-Often close on their own

-Inlet Septum (Atrioventricular Canal) VSD- may be assoc w AV vlv or conduction xx

--> potential for TriVlv to straddle IVS

-+/- assoc w hypoplastic RV

-Outlet VSD aka Malalignment VSD-

-Ant/rightward malalignment defects assoc w diff degrees of PA override into RV

-The extreme degree of override--> DORV w a subpulm VSD ~ to Taussig-Bing hrt

-The anterior VSD can extend post'ly to TriVlv ("perimembranous extension")

-SubAo stenosis bc of the anterior malalignment of the infundib septum is assoc w Ao Arch hypoplasia, coarctation, or interrupted Ao ARch

-Post/Leftward malalignment defects assoc w diff degree of LVOTO-subpulm stenosis and annular hypoplasia, +/- pulmonary vlv atresia (!)

-Outlet septum defic VSD = Doubly COmmitted subarterial defect= absence of musclar outlet septum, so that the VSD's superior rim is the area of fibrous continuity bn Ao and Pulm vlv annuli

LVOTO-

-~25% of pts had LVOTO in 1 study

-Doppler gradients on echo/cath might overestimate amt of obstruction bc of incr Qp. esp of VSD

-Dynamic Obstruction- common, usually mild, may see leftward bulging of basal muscular IVS twd the lower pressure LV--> narrow LVOT at systole, then widely open at diastole

-This = reversal of P relationship, bc RV and LV...

-Rare if incr PVR or LVP, and rare if nonrestrictive PDA bc LV sees systemic systolic P

-Fixed Obstruction- see patch of endocardial thickening on septal bulge, then a sharp fibrous ridge or discrete membrane, like a membranous subAo stenosis, along the line of systolic mitral vlv contact. Less often, it is due to a tunnel-like subpulm fibromuscular ridge extending across the LVOT onto the base of the ant mitral leaflet.

-Pulm Valve stenosis/annular hypoplasia are rare, and are ~always assoc w a subvalvar obstruction too...

-TGA+VSD - 30% have LVOTO, usually more severe/complex than w intact VS

-usually subvalvar stenosis, +/- just a fibrous ring, or tunnel fibromuscular narrowing, or muscular obstruction bc of malposed outlet septum impinging into ant-med aspect of the LVOT/subpulm outflow tract

-Uncommon causes:

-malattachment of ant mitral vlv to muscular outlet septum by cords

-redundant tricuspid vlv tissue protruding thru VSD

-subpulmonic membrane

-aneurysm of the membranous septum

-muscle of Moulaert hypertrophy

Other Assoc Anomalies

-PDA

-Tricuspid Valve anomalies in 4% pts at surgery, but 1/3 pts at autopsy

-TGA+VSD - anomalous cord attachments to edges of the perimebranous or outlet septum malalignment defects--> now hard to close the VSD or form an intraventric tunnel during a Rastelli

-Subpulmonary Stenosis due to redundant septal valve tissue ("tricupsid pouch") thru VSD into LVOT- can have surgical importance, but treatable

-Inlet VSD may have overriding annulus, straddling cords, or both

-assoc w signif RV hypoplasia if extensive...

-Tricuspid Regurg- rare to have signif TR, but can occur after atrial level repair if there is severe RV dysfx w annular dilation of Tri vlv; and in TGA+VSD if VSD is repaired thru tri vlv

-In TGA, mitral vlv is bigger than tri vlv, (opposite true w Nl pts)

-Mitral Vlv xx (20% at autopsy)- espec in TGA+VSD, but only 4% fxly signif

-Cleft Ant mitral vlv leaflet

-Anomalous papillary muscles and cords

-redundant tissue tags

-MV and parts of the cords straddle VSD, or ant mitral vlv leaflet tethered to the septal attachments, causing LVOTO... These are the most surgically significant...

-CoAo, Arch Hypoplasia, Interrupted Arch - 5% of pts, much more common in ant malalignment VS

-especially common w these pts w DORV w subpulmonary VSD (=Taussig Bing anomaly)

-outlet septum may be displaced to the ant/right of the trabecular IVS, w additional anterior obstruction by the parietal band hypertrophy; both --> sub Ao narrowing

-Atrial appendages leftward juxtaposition- RAA passes just behind the transposed MPA - assoc w major cardiac xx - dextrocardia, VSD, bilat infundibulum, RV hypoplasia, tricuspid stenosis/atresia

Physiology:

-Major issues: decr DO2 to tissues, and incr RV and LV workload

-Systemic and Pulm circs are in parallel instead of in series...

-Only a small amt of blood is exchanged by the intercirculatory shunts

-SaO2 d/o these shunts- PFO/ASD, VSD, PDA, and bronchopulm collaterals

Intercirculatory Mixing

-Left-->Right Shunt = the effective Qs

-Right-->Left Shunt = the effective Qp

-effQp = effQs ; aka net anatomic R-->L = net anatomic L-->R ; this volume is the intercirculatory mixing, and survival depends on this flow

-the net shunts must be equal to each other or else in a short period of time, one of the blood volumes (systemic or pulm) would be depleted and the other overloaded....

-Amt of Intercirc Mixing d/o

-number, size, position of communications

-total amt of Q into the pulm circuit

-In pt w TGA+IVS, as the PDA closes, he will get severe cyanosis bc of inadequate mixing at PFO

-If the atrial/ventricular shunting site is of good size, then SaO2 d/o the Qp:Qs- incr Qp--> incr SaO2

-Subpulm or pulmonary stenosis or incr PVR --> Decr Qp --> decr SaO2 even if shunt size ok

-It seems, the shunting d/o local P gradients, which are influenced by the respiratory cycle phase, cardiac chamber compliance, HR, Qp volume, and SVR & PVR.

-In TGA+IVS, the interatrial shunt is fr RA to LA during ventric diastole bc the LV resistance is less than the RV resistance to filling.

-During ventric systole, the shunting is fr LA to RA bc teh LA is less distensible than the right, and net P of LA is > P RA

-Respiration: Inter-atrial R-->L (systemic to pulm) shunt increases w inspiration bc syst venous return increases and pulm venous return decreases.

-In TGA+VSD, less well established flow patterns.

-If large/unrestrictive, then pk Psys is equal in RV & LV.

-During ventric systole, some RV output goes preferentially to the lower resistance pulm circ, w concomitant increase in LA return.

-During ventric diastole, the increased pulm venous return --> more shunting of bld fr LA to RA/RV. Balance bn RA and LA/RV and LV compliances & with the PVR/SVR are important

-Also important is location of the VSD, degree of LVOTO, etc

-Large PDA w TGA+IVS, w bidirectional shunting initially, then systemic to pulmonary shunting as PVR drops.

Bronchopulmonary Collateral Circulation

- >30% of TGA pts <2yo have BP collaterals on angiography

- fx for intercirculator mixing

- also a source of incr PVR causing the increased pulm vasc dz seen in TGA pts

-may --> enough of a shunt postoperatively to require cath embolization...

-FICK principle to calculate Qp and Qs is NOT accurate

-VO2 isn't Nl in severely hypoxemic pt, so assumed values aren't reliable

-Because the systemic and pulm AV O2 differences are small, a minor error in O2 saturation measurement causes a big error in calculating flow

-Also the Qp fr the BP collaterals enters the pulm vasc bed after the pt measured by cath--> falsely high pulmonary artery O2 sat and Qp calculation...

-Qp amt

-LV compliance increases as PVR drops

-LV and RV outputs are determined by their PL, Compliance, AL, Contractility + autoregulation to ensure Qp=Qs

-BAS/surgical septectomy--> incr Qp as PVR drops, and the LV circulates more bld volume at a lower P.

-The incr Qp--> improve intercirc mixing and systemic SaO2

-If Qp decr bc of increased LVOTO/PS/incr PVR--> decr intercirc mixing and thus decr systemic

SaO2

-Though, not all pt w TGA+LVOTO have cyanosis due to decr Qp; it could be bc of progressive restriction of the atrial communication, limiting intercirc mixing, so you must check w a cath...

-Qp maldistribution in TGA - R>L Q

-abNl Rightward inclination of MPA- Q straight from LV to RPA via MPA...

-some LPA hypoplasia occurs

-usually not clinically significant

-In pt w TGA+IVS, the systemic arterial pO2 can be as low as 15-25mmHg initially, w severe metabolic acidemia over the next few days...

Arterial Blood Gases & Metabolic Responses

-TGA w/o good mixing, in a pt on RA: major diffs in bld gas from systemic artery and pulm vn:

-Pulm venous blood- due to 2y hypertentilation: O2 110mmHg on RA, CO2 low to 12-25mmHg

-Syst art blood- PO2 <35, pCO2 Nl/lightly elevated (~45) bc of limited L to R shunt

-Arterial blood gas on RA and 100%FiO2 help DDx cyanotic pt w TGA vs lung dz

-When systemic PaO2 <30 on RA, they will remain <35-40 w incr FiO2 if +poor mixing.

Fetal & Perinatal Physiology:

-Fetal Circulation:

-the main diff is that w TGA, RV ejects blood to Asc Ao, instead of Desc Ao via PDA

-w TGA, the SVC bld goes to RV and Asc Ao--> slightly less gluc and pO2 [ ] to coronary and cerebral

-Bld into pulm vasc bed and desc Ao us fr glucose/O2 rich placental return that's shunted across the PFO, w gluc/pO2 slightly higher than Nl fetus

-?effect: cardiac and cerebral structures are Nl in TGA (in 1 study), but incr # panc islet cells, and icnr weight of adrenal cortex in TGA pts, ~ to IDM babies

-Transitional Circulation:

-decr PVR postnatally as lungs expand--> incr LA P, like Nl neonate

-SVR increases bc placenta (low resistance circ) is removed

-Nly, RA P drops as R side of heart faces the rapidly decreasing PVR and as the interatrial P diff favors closing the FO. In TGA, the RA P is increased and RA P is similar to LA P, so FO stays open, --> bd shunt.

-TGA+IVS:

-widely patent DA, w bd shunting initially as PVR still high - systole: LV to PA to DA to Desc Ao; distole: RV to Ao to DA to PA to lungs. As PVR drops, the shunt is mainly RV-Ao to PA-lungs (Qp effective), & there is an equal amt of bld passing from the pulm circuit to systemic circuit at atrial level (Qp syst).

-If the decr PVR is delayed, --> persistent phtn, w little ductal shunting, and limited intercirc mixing

-Urgent BAS/surgical septectomy won't improve sev hypoxemia, so may need ECMO/early repair

-Or, if pt has intact atrial septum, even w a big PDA, the shunting can't be balanced by LA to RA shunt, so they'll get severely hypoxemic/acidodid soon after birth, +/- sev pulm edema/hemorrhage...

-As PDA closes, pt will become more hypoxemic..., at the same time, pt has incr VO2 bc incr metab, must maint temp, beta adrenergic stim..., thus decr mixed venous and therefore arterial O2 sats bc most of the circulating blood flow is recirc'd from systemic venous return.... Also high fetal Hgb limits O2 extraction bc it has higher O2 affinity .... can quickly cause major xx...

-Thus PDA is critical to maint and increase intercirc mixing in early postnatal pd...

Pulmonary Vascular Disease

-accelerated rate of dvpmt and increased freq of PVD, esp w TGA+VSD

-pulmonary/subpulm stenosis prevents early advanced PVD

-microthrombi seen in many pts's lungs at autopsy...

-large PDA, prolonged hypoxemia, polycythemia also implicated in PVD

-20% pts w TGA+large VSD have signif PVD by 2mo, 25% fr 3-12mo and 80% at 1yo

-In TGA+IVS, it's only 1% at 2mo, 17% at 3-12mo, and 34% at 12mo

Sx/Si:

-Sx d/o intercirc mixing, due to anatomy... Classification:

I TGA+IVS or TGA w small VSD & Increased Qp w small IC Shunt

-signif cyanosis an early Sx- first mild than rapidly progressive as PVR drops

-most within 1st HOL, but nearly all by end of 1st day of life

-rest of exam is pretty much useless, including CXR/ECG bc all can be Nl initially, thus get echo fast!

-Reverse Differential Cyanosis = upper body has higher SaO2 than lower body - rare, but means TGA w PDA and a PA to Ao shunt - seen sometimes in pt w TGA+IVS and large PDA

-can also mean Ao arch xx (interruption/coarc) or suprasystemic PVR

-PE: TWO types of sx set

-hyoxemia, Nl to loud S1, usually no systolic murmur, but can have a soft <2/6 SEM fr LVOTO at LUSB w incr Qp

- heart failure (if big VSD w large PDA)

-classic Sx of large PDA- murmur, bounding pulses, prominent middiat rumble, are only + in <1/2

-NEC risk is increased in TGA+PDA bc of retrograde diast Q in the desc Ao to steal.., decr DO2...

II TGA + Large VSD w incr Qp and Large Intercirculatory Shunt

-might not hve any Sx initially, though mild cyanosis can occur w crying

-Then CHF Sx at 2-6 weeks GA

-tachypnea/tachycardia, w only mild to no cyanosis

-minimal, then 3-4/6 pansystolic murmur w S3 and middiastolic rumble, gallop, and narrowly split S2 w loud pulmonary component

III TGA +VSD +LVOTO w Restricted Qp

-w sev PS or pulm atresia --> decr Qp

-only 5-8% of TGA pts

-Sx are like TOF w sev PS or Pulm Atresia, w extreme cyanosis since birth

IV TGA +VSD +Pulm Vasc Obst Dz w Restricted Qp

-The PVD isn't present at birth, but can rapidly progress

-...

CNS

-CNS xx rarely assoc w TGA

-Head Circ is slightly <Nl

-CVAs were rare but more common before recent timing/technique of repair

-likely due to microcytic anemia + desat as infant, then bc of polycythemia w incr viscosity later on

-Brain Abscesses- uncommon, but mainly in uncorrected kids >2yo

-slightly lower IQ if late repair of cyanotic heart disease

-REF 24 and 25 discuss benefits of early detection & correction respectively

ECG:

-RAD w RVH/BVH

-Usually Nl ECG initially, then at a few weeks old see RVH if TGA+IVS/small VSD - mainly see +T wave after 3-5 days when it should have inverted at R precordials

-If TGA+VSD, 1/3 of them have Nl QRS axis

-BVH in most of these pts

-Sometimes have newborn brady/jctl rhythm, or a-flutter after BAS

CXR:

-usually Nl as a neonate

-TGA+IVS--> egg shaped cardiac silhouette w narrow sup mediastinum, mild CM, incr pulm vasc markings

--TGA+IVS:

-Nl initially, w slightly larged heart in 2/3 pts, many/most w w Nl pulm vasc markings,

-1/3-1/2 pts DON'T have the egg shaped heart...

-superior mediastinal silhouette is narrow bc GA"s are in AP relationship and thymus is hypoplastic bc of cyanosis/stress

-R Ao Arch uncommon

-Then, after a few weeks, heart gets bigger and incr Pulm Markings seen...

--TGA+VSD

-much larger cardiac silhouette, more prominent pulm vasc markings w lower pulm vasc resistance; big hilar vessesl in older pt if much pulm dz; only diminished pulm vasc markings if there is severe LVOTO or atresia

Echo:

-Subcostal: see GA's well...

-AP4C: see that PA is the posterior vessel

-Suprasternal & High Parasternal- see Ao arises fr RV

Cath:

-increasingly not done routinely

-...

Angiography

-...

Balloon Atrial Septostomy:

-can do via umbilicus at first few days of life

-otherwise use femoral vein

-cross the PFO and place that into LA or a pulm vein, then inflate balloon and pull back quickly--> displaces balloon and atrial septum twd IVC & ruptures septum premum flap of FO, then repeat a few times...

-xx = damage to atrial wall, pulm vn, IVC, AV vlv

-must avoid bubbles in contrast...

-may be harder to get successful result in older pt bc of thicker PFO flap, thus may need surgical correction..

Treatment:

-Experience: 40 years of atrial level repair; 20 years of arterial level repair

-As of 1990, 80% of TGA get arterial switch (double that of 5 yrs earlier!)

Palliation

-BAS, atrial septostomy, partial venous correction, PA banding, sys to pulm shunts

BAS (Rashkind procedure)

-if sev hypoxia at birth --> 95% survival at 1mo instead of 20%!!

-Now, only do it if sev hypoxia instead of on everyone, bc pt's are going to OR earlier

Early Repair:

-Previously, we'd wait till 1yo to correct the TGA

--> M&M: CVA, pulm vasc dz, heart failure, thrombi

-5 of 106 kids died b4 Senning/Mustard done at 2/6 months; 0 of 76 died be for art swch @ 6 days

-BAS Success = ?criteria-

-bad physio/anatomy can --> bad outcome: FO too small, FO valve too thick (esp if older pt or +large VSD)

-Repeat BAS isn't effective usually, and blade BAS is rarely indicated

-see success well by echo

-Good BAS usually --> >5mm diameter ASD,

-though inadequate circ mixing w/o improved sats can occur in some pts

-this may be bc of delayed PVR drop so low Qp and thus low LA vol and LA P--> less mixing

Surgical ASD Creation (Blalock Hanlon Procedure & Atrial Septectomy)

-mainly historical bc we repair the TGA earlier now

-Make ASD by excising posterior part of the interatrial septum, w a "closed heart procedure"

-Atrial Septectomy (open heart)

-Both --> better atrial mixing, w mean SaO2 79% (slightly better than BAS)

-Mortality from these operations were <5% (initially 30% though)

Partial Venous Return Repair

-1950s: goal was to do a partial physiologic repair: connect IVC to LA w a graft/conduit and attach R pulm vns to RA--> obligate atrial shunting

-Some then had a Mustard to get complete physiologic correction

Pulmonary Artery Banding

-If large VSD w/o LVOTO:

--> heart failure & pulm vasc dz. PAB treats both of these well

-was more common before early repair

-5% operative mortality

-band them more loosely than Nly related GAs, bc pt needs higher Qp for best mixing

-Some may get SubAo stenosis afterwards hemodynamically (though the patient population that get the PAB in the first place are ones with a malalignment VSD, thus at risk for progressive AS anyway...)

Systemic To Pulmonary Anastomosis

-TGA/VSD w sev LVOTO have been successful w a sys to pulm shunt

-Gor Tex shunt, operative mortality 5%

-But take care to follow PVR closely bc of higher risk for pulm vasc obstructive dz...

PGE1 (w Early Arterial Switch +/- BAS)

-Benefit from increased SaO2 via PGE1 w/o BAS in pts to get early repair:

-some won't get better w PGE1--> c/s poor mixing bc of small FO

-PGE--> much incr Qp via PDA, but if FO too small, then you can get dangerously increased pulm congestion, so may need BAS at bedside STAT

-doing a BAS may eliminate need for PGE, so no xx (apnea, vasodilation, fever, rash)

-Routine BAS is still controversial...

Corrective Surgery

Surgery for TGA+IVS or TGA+VSD w/o outflow tract obstruction:

ATRIAL SWITCH - Physiologic Correction

-Senning Repair- atrial baffle w RA wall and interatrial septal tissue

-Mustard Operation- resect atrial spetum, then baffle from the pericardial tissue/synthetic tissue

--> Discordant AV connection, on top of the discordant VA connection ==> net Nl circulation, but still have a morphologic RV as systemic ventricle...

-Timing: if atrial septectomy/BAS done, then can delay corrective surgery by weeks/months, though 4% die by 1mo despite good BAS

-In past, Senning vs Mustard was controversial:

-Senning: easier, minimal/no prosthetic material/nonviable tissue, less decr in atrial volume and compliance, less postop systemic venous obstruction, less late dysrhythmias

-Mustard: lower early mortality, lower syst to pulm venous obstructions, less dysrhythmia

-neither proved better

-Results:

-CPB w hypothermia (+/- circ arrest) used w good early mortality

-10yr survival rate: 85-90%

-if TGA+VSD, mor complicated repair--> incr mortality

-1970s data- 23% early mortality, range 10-60%, long term survival only 60-70% @5yrs

-bc pt also has other anomalies, or phtn/vsc dz

-Postop abNlies seen:

-residual intra-atrial shunts

-caval and pulm venous obstructions

-RV dysfx

-Tricuspid Valve insufficiency

-arrhythmia

-Recent studies: less baffle leak and venous obstruction of late, but RV dysfx and dysrhythmias still a problem

-Residual Intra-Atrial baffle shunts- usualy at superior RA baffle suture line, can --> sys to pulm or pulm to sys venoush shunting, and seen on Doppler. Without another coexistent syst venous obstruction, there's no decr SaO2, bc it's net L to R shunting.

-Systemic & Pulmonary Venous pathway obstructions--> bad xx. R/F- neonate, bc limited space;

-causes: (?) improper baffle geometry & suture line placement, contraction of pericardial or synthetic material baffle, scar tissue/adhesions at baffle % atrial septal margins

-SVC obstruction- 5-10% pts w Mustard- UE plethora, chyloTx; if longstanding: hydrocephalus, but can be ASx even if severe bc azygous/hemiazygous can decompress the SVC.

-usually obstruct distal to SVC enterence @ site of the excision of the superior remnant of atrl sptm

-Tx w surgical correction, balloon dilation, stent, or innom vn to LAA

-IVC obstruction -serious but rare (1%) - likley infreq bc surgeons incise free atrial wall of the CS to enlarge the sinus opening into the systemic venous chaber, and widen area that serves as IVC enterence

-Pulmonary Venous Obstruction - seen immediately postop or within wks/months, less common but more deadly (2%). c/s if CXR has pulm vn congestion, unexplained desaturations postop, Dx w echo

-Cath: see signif diff bn posterior and anterior segments of the new pulm venous atrium

-Tx w reoperation PRN

-TR- usually no HD xx, rare (1-2%), likely due to manipulation of it, along w RBBB

-surgical repair +/- valve change has poor outcome long term

-Decr RV (systemic) fx- at 5-15yrs postop- signif decr resting/exercise response for RV ejection fraction, and abNly increased RV resting volume

-RV volume progressively increase, maybe bc of Q fr enlarged bronchial arteries (big from preop)--> volume overload the RV

-Improved exercise performance- lower HR and VO2

-10% of operative survivors have decr RV fx, w 90% in NYHA Class I, though sev, Sx RV failure is uncommon, assoc w increasing TR, seen more in pt's who had a VSD repair

-Why might RV fail under systemic P?

-RV myocardial fiber arrangements are suboptimal, w mismatch bn RV cor Q supply & demand, and diff myocardium w LV made mainly of stratum compactum (cor supplied), and RV of stratum spongiosum (w trabeculae carneae)

-RV can't pump as well bc the septum bulges post/left, and TriVlv has smaller paps so more TR

-RV fxly diminished bc it has an infundib, unlike LV, which is hypokinetic

-Myocardial fibrosis from pre-repair hypoxia damages fx

-On LV (pulm) side, there's abNl fx of the MV-LVOT subunit: abNl syst mvmt, course diastolic ant MV leaflet diastolic flutter, basal segment bulges in systole; and abNl Qp distrib (R>L)

-Post op dysrhythmias long term are a major problem- 30% have non-sinus rhythm by 1yr postop, 55% by 13 yrs post

-Mainly sinus brady, ectopic atrial rhythm, slow jctl rhythm, SVT- a-flutter

-Also AV conduction xx w surgical complete HB, PVCs

-may have tachy-brady syndromes/SSS...

-Late sudden unexplained death- 2-10%, w sudden sinus nd dysfx or rapid atrial rhythm

ARTERIAL SWITCH - Anatomic Correction

-Transect GA's in a way that allows reanastomosis of distal Ao segment to prox pulm art (--> neoaortic root), and transfer cor arts to this pulm segment, after excising them fr the Ao sinus w a cuff of adjacent aortic wall. The prox Ao segment (neopulmonary root) is then connected to distal PA w end-end anast using a Lecompte maneuver- pass the ant aorta posterior to the PA bifurcation; or the PA connections are established using a conduit fr RV to PA.

-The key physiologic issue is can the LV, which faced the low PVR, handle the sudden exposure to SVR? Must ensure enough LV muscle mass- usually only present in early infancy if pt has TGA+IVS, but can also be ok in an older pt w other xx that increases LV afterload- nonrestrictive PDA, LVOTO, delayed decr in PVR/pphn, or a large nonrestrictive VSD

-Better to completely correct it early on than doing a PAB and later arterial switch, bc older age at surgery increases mortality risk. PAB risk is of it being too loose--> allow for incr Qp w pulm vasc dz, and too close to pulm vlv--> distort it and damage the neoaortic valve--> neoAR

-Results:

-Mortality: <10% early mortality

-increased risk: intramural coronary art, retropulm LCA, multiple VSDs, AoArch xx, straddling AV vlv

-minimized if the surgeon is increased

-other R/F: Longer cross clamp (global myocardial ischemia), and longer circ arrest time

-Risk also decreases as # done/institution increases

-Early mortality: usually bc kink/obstructed cor art during transfer to neoaorta, or fr unprepared LV, or suture hemorrhage

-Late mortality: (1-2%)- bc myocard ischemia or pulm vasc obst dz, or at reoperation for supravalvar obstruction

-Complications:

-Supravalvar Pulm Stenosis =#1 short term xx - 5-30% need reintervention for supravalvar PS, but decr as MD's more experienced w the operation

-Diffuse hypoplasia of MPA--> ng mobilization of branch PAs--> tension at anastomosis, then as pt grows, the MPA might not grow enough--> flatten the RVOT in the AP direction

-Circumferential narrow at suture line--> discrete supravalvar narrowing

-Branch PA stenosis (L>R)- R/F = side by side GAs w Lecompte maneuver--> LPA may bowstring over the reconstructed neoAo--> LPA hypoplasia

-Pts may have obstruction at multiple levels

-Tx: reoperate, balloon angioplasty- if RVP =/>systemic P;

-surgery usually = patch angioplasty

-May need to extend patch accross neopulm annulus to infundib--> MUST know RCA course preop bc it's hard to see it intraop bc of adhesions, and if RCA goes anteriorly to get to the R AV groove, then a transannular patch will NOT work, and pt will need a conduit

-Balloon angioplasty isn't usually successful, but c/s w discrete lesion

-Supravalvar Ao Stenosis- much less common; pk sys ej grad at Ao anast of >20mmHg is very rare, in <5% pts, and reoperation done in <2% pts

-Post Lecompte, the ant side of Asc Ao is displaced post'ly somewhat bc the anteriorly placed PA trunk/bifurcation is stretched over it (see pic). But it only rarely causes a problem (only reported if pt had prior CoAo).

-Neoaortic root and valve over long term is concerning- the root is usually larger than the Asc Ao at correction (esp if TGA+VSD), so Ao must be tailored to it, but long term this usually isnt a problem and it grows well; becomes enlarged at neoaortic root/annulus over time.

-Dilation of Neoaortic Root over time is a problem, and is progressive (conflicting reports??), ?if due to removal of the isnuses of Valsalva and reimplantation of coronary buttons w a supravalvar suture line

-Neoaortic regurgitation frequent- but usually only trivial/mild AR

-Long Term Coronary growth/patency is crucial- pt may present w cardio shock or ASx...

-Immed postop may not beable to separate from CPB, so c/s reoperation to check and possibly use IMA as a bypass art for kinked coronary

-Ongoing risk fo acute circ collapse over weeks/months postop

-1-2% MI/death risk postop

-many patients will have some cor occlusion to some degree

-LV fx remains good at early/mid follow up studies

-Postop dysthrhythmias are very uncommon (unlike atrial repair)

Surgery for TGA with Low LV Pressure:

-When to delay repair?

-ill with NEC, renal failure, hemorrhage, premie/low BW

-TGA+VSD may await elective repair might get spont VSD closure--> not enough LV mass, so c/s primary atrial correction or a two stage arterial correction

-PAB to incr LV AL and stimulate hypertrophy--> can retrain the LV within days

-LV fx might be very impaired post PAB, so c/s placing a syst to PA shunt to ensure enough Qp. Pt often has LCOS--> acute fixed RV vol OD fr the shunt and acute transient LV dysfx fr PAB. Sx will improve as LV fx improves, so that you can do arterial repair within 7-10 days

LV Preparation

-The postnatal drop in PVR--> quick decr in LV AL after the DA closes--> LV muscle mass decreases w time to the pt that it's no good for sustain systemic P after the arterial switch

-A Prepared LV = can --> Nl/near Nl systolic P w Nl post wall thickness/muscle mass

-An Unprepared LV- hard to identify- LVP or LVP:RVP might not be predicitive of ability for the LV to be a systemic ventricle...

-Empiric Criteria: absolute LV Psys Nl for age, LV P at cath >70% systemic (RV) P, LV muscle mass Nl for BSA

Anatomic Correction without Coronary Translocation:

-Damus-Kay-Stansel Procedure in 1975: arterial level repair without cor translocation

-Used for TGA+coronaries that can't be moved, or for DORV w sev subAS (Taussig Bing type)

-Transect MPA and anastomose in end to side to Asc Ao--> perfuse coronaries retrograde

-Native Ao left intact

-Close VSD if present, so that Q is directed fr LV to the native pulm (neoaortic) vlv

-RV-PA conduit is placed

-DKS- limited long term f/u info-

-native AR is common (? bc no antegrode Q across it bc of the subAS and the retgrograde pressure load)--> wide PP, incr vol load on the systemic ventricle--> L to R shunt and pulm overcic. If they close the Ao vlv at surgery, then you cant decompress the suprasystemic RV in pts that get a conduit obstruction or in pts w high PVR. So the native Ao vlv is usually left open...

-TGA+large VSD in older pts- can reestablish VA concordance w a straight tunnel that doesnt obstruct pulm outflow trat, but must resect part of the outlet/infundib septum and enlarge the VSD by resecting the part of the IVS that is anterior to the VSD (they don't have AV conduction tissue).

-Aubert procedure- create an AP tunnel or baffle the LV outflow to the nontranslocated coronary ostia w a patch of native Ao or pericardium. The entire Ao root may be translocated to the LV w biventricular outflow tract reconstruction

Surgery for TGA with Associated LVOTO:

- LVOTO is usually due to relationship of IVS alignment w the infundibular septum

-older pts w mild/mod dynamic LVOTO after repair of TGA+IVS is common but unimportant

-transpulm/transmitarl resection for sev fixed abstruction due to a discrete fibromuscular subvalvar shelf in TGA+IVS has been done, but risk of conduction xx if you take out too much, and residual P grad common. If sev obst--> LV P syst is systemic/suprasystemic, and it can't be relieved by resection, so an atrial switch w an LV to PA valved conduit can be done successfully.

-Neonate/young infant w TGA+large VSD, + mod LVOTO can--> prevent heart failure and limit early/rapid progressive pulm vasc dz. You can delay surgical repair as long as there's enough mixing and peak systolic PA pressure is low

-Infant w TGA+large VSD and sev LVOTO--> very restricted Qp and sev hypoxemia--> may need syst to PA shunt (e.g BT shunt) initially and then do the correction later

-RASTELLI = intraventricular repair & place RV-PA conduit

-good for TGA+large VSD and extensive LVOTO bc it gets a complete bypass of the LVOTO and anatomic correction of the TGA

--> divide proximal MPA w pledgated mattress suture closure of the subvalvar obstruction or by oversewing a stenotic pulm valve orifice, then direct LV output to Ao with an intraventricular patch-tunnel, then connect RV to prox MPA with a valved extracardiac conduit.

-For Rastelli, the VSD must be big enough to permit unobstructed Q fr LV (to Ao, via baffel), so you might have to enlarge the VSD anteriorly

-now 95% survival of operation (previously 70-80%)

-REV = Reparation a l'atage ventriculaire (by Lecompte) - for TGA+LVOTO- better for younger pt, no conduit needed, no risk of intracardiac tunnel obstruction

--> high, ant RV incision, and radial excision of outlet septum--> unobstructed anterior RV; then establish a short/direct IV tunnel fr LV to Ao, and close PA orifice, and reimplant the transected PA into the RVOT cavity w/o a conduit.

-This allows for complete repair in early infancy, good for pt w an anatomic contrainidcation to Rastelli, and my reduce need for reoperation

-But, pts get PR postop (lifelong), so ? longterm xx

-Posterior Translocation of Aortic Root and Coronary Arteries- w enlargement of LVOT, a conduit placed fr RV to the PA anteriorly.

-Controversy over timing: some say do Rastelli early, others say do BT shunt first