Jonas - TOF

TOF (Jonas16)

Embryology

Classic Theory of TOF

-conotruncus is subdivided by spiral septation into ea GA

-unequal septation--> hypoplastic PA relative to Ao

-may have stenosis along PA branches etc

Van Praagh Theroy of TOF

-single xx- subpulmonary conus underdevelopment--> Ao vlv overlies IVS so it lies more ant and rightward, --> less Q to pulm vlv, so the pulm vlv and MPA become hypoplastic

Anatomy

2 major items that are important for surgeon:

VSD

-almost always large & unrestrictive

-anterior malalignment type of VSD

= VSD bn conal septum & IVS (thus aka conoventricular VSD)

-often see some membranous septum remnant, useful in surgery

-if there is sev RVOTO, then can see suprastyemic RVP (but this is uncommon bc VSD usually unrestrictive)--> sev RVH--> worse Px if not Tx early

RVOTO

-often see bicuspid pulm vlv w commissural fusion of cusps and annular hypoplasia

-sometimes see tethered free edges of the cusps to teh PA wall--> hourglass narrowing at STJ

-see crowding at infundibulum bc conus septum projects into RV

-if not corrected, the hypertrophy of RV at moderator and other bands can cause them to combine and further exacerbate the amt of RVOTO--> viscous cycle. RVP would still be systemic and not suprasystemic bc of the unrestrictive VSD, it will cause worsening of cyanosis.

Other, less surgically relevant features:

-RVH- failure for the postnatal RVH to decrease

-Ao Dextroposition- less dvpd pulm art infundib--> moves more post and inf as it dvps, relative to Ao position. --> Ao lies more anterior, with the end of that spectrum being DORV w a conus starting to form under Ao vlv, causing the Ao vlv to be lifted even more ant and sup relative to pulm vlv, and then goes twd end of spectrum w TGA- w fibrous continuity bn pulm vlv and mitral vlv, and Ao vlv is separate fr the other 3 vlvs, w its own subAo conus/infundib.

Other Assoc Anomalies

-Coronary Arteries- as Ao moves more fwd relative to PA, the distance the LMCA must cross to pass behind the PA befor dividing into ant desc and circ coronary arteries increases--> 5% of pts thus have anomalous distrib where the ant desc cor art arises fr RCA and passes leftward, across the infundibulum of the RV, before turning inf'ly in the ant IV groove. The circ cor art conginues to arise fr the usual spot and passes behind the MPA before entering the L AV grove. Rarely, the RCA arises fr LCA and goes rightward across the RV infundibulum

-Multiple VSDs- espec w midmuscular and ant and apical muscular septum

-Discontinuous PAs

-clinically important PA branch hypoplasia is very rare, though MPA is often underdvpd

-common for ductal tissue to extend into LPA--> stenosis

-rarely, at the severe end, they can be discontinuous, usually bn MPA and LPA, w LPA Q fr PDA

-PFO - almost always there

-R Ao Arch- in 1/4 pts

Workup

-...

-ensure PA patency

-r/o AP collaterals

-assess for additional VSDs

-assess for coronary anomalies- anom ant desc fr RCA across the RV infundib

-this isn't totally necessary, bc its an untouched chest so easy for surgeon to see cor anatomy in OR

-coronary anatomy will be very important in planning the ventriculotomy

-define interatrial septum anatomy- PFO/small ASD can allow for a pop-off in postop pd, but a large 2nd ASD must be made smaller. If no PFO/ASD, then the surgeon should make a small ASD.

-Jonas: not important to define the PA branch sizes (unlike w pulm atresia): preop measurements give little indication of postop size, since the distending P will be very diff once you resolve the RVOTO

-PA compliance in pt who hasn't had prior surgery is likely great, so the PAs will enlarge much p op

-also if pt has sats in 70-80s then he likely has a full Qp cardiac output (unless +MAPCAs), so PAs preop can carry the full CO, so no reason to think they can't do the same postop, regardless of their size

-check MV dimensions and z score, check LV length relative to apex. As long as LV is at least 80% the distance fr AV vlv to apex,and as long as the MV is not >2-2.5z score below Nl, then the LV will likely be able to manage a full CO postop

-no need for cath, can ppt a TOF spell.. need for emergent surgery

Rx Tx

-it is disadvantageous to use vasoconstrictors (e.g. for tet spell) just before starting CP bypass, espec if you're about to use hypothermic circ arrest. Instead, best to tolerate the lower sats and get on CPB fast.

-some are doing balloon dilation of RVOT/PA pre-op to hope to mitigate need for a transannular patch (but no evidence of efficacy yet), and disadvantage of balloon dilation is that it can --> pulm overcirc if RVOTO is mainly valvar, bc u'd get massive L to R shunt through the big VSD. Also, one can perf the infundibulum, requiring emergent surgery/ECMO

Surgical Indications & Timing

-Initially, bc of major CPB xx early on, they did a 2 stage approach w an initial aplliative shunt- Potts and Waterston shunts were very damaging bc--> sev distortion of L or R PAs, and classic Blalock shunt--> thrombosed often. Not until modified BT shunt w PTFE by Leval in early 1980s did BTS become more successful (ref 29), but even this --> scarring/distortion at at distal anastomosis.

-Early Primary Repair Advantages:

-TOF--> AbNly low P exposure of pulmonary vessels; may --> less capillary:alveoli ratio

-delaying surgery may decr lung dvp over first few yrs of life

-RV is exposed to systemic P's bc of unrestrictive VSD--> RVH, then fibrosis and decr compliance

-the decr RV compliance can be permanent

-LV fx might not be as good if delay TOF repair

-arrhythmias more common w delayed repair beyond infancy

-ch cyanosis on brain dvp has xx

-psychosocial xx of family agitation while pt still cyanotic etc.

-Indications:

-Sx:

-PGE dependence

-if Qp so low bc of sev RVOTO that pt needs PGE

-here you must must r/o MAPCAs as pt is similar to pulm atresia pt...

-Worsening Cyanosis

-RVOTO almos always worsens in first weeks/months bc of incr muscular outflow tract obst or (less often) bc worsening vlvr stenosis. This can --> decr SaO2

-Cyanotic Spells

-usually seen in an agitated child, then very low SaO2 to 20-30s, w pt then gray, pale, coma, bc low CO, these can --> brain injury/death --> indication for immed hospitalization and OR soon

-Elective Repair:

-Jonas performs elective repair as an early infant, and feels no incr risk of transannular patch use (ref 18) which some are concerned about. He feels the pts in earlier studies had Sx at surgery thus more sev dz and that is why they had incr risk of transannular patch use

-Contraindications to Early Primary Repair:

-Jonas says no current true c/i xx to early repair, but prior concerns were:

-Anomalous coronary artery- anom ant desc CA fr RCA and passing across RV infundib. c/i xx bc you might need to place an RV-PA conduit. Jonas: usually you can do a transannular patch and place patches either above or below (or both) the CA to avoid using a conduit

-rarely, when they did need to place a small conduit, every attempt should be made to enlarge RVOT, reason being that by creating a ~DORV you might be able to hold off another surgery for yrs. (and considering that the other option would have been to do a BTS, you're really not doing more surgeries...)

-Multiple musclar VSDs- you can now place sutures to fix these; only if there's a Swiss cheese septum would you c/s deferring surgery

-Discontinuous PA's- must establish continuity as soon as possible to promote Nl PA dvp. The anast site might need balloon angioplasty in future, it's of low risk

Surgical Mgt

History:

-1945 - Blalock & Taussig--> subclavian artery to PA anast.

-1946 - Potts--> Desc Ao to LPA anast

-1948 - Sellors & Brock expand scope of palliative operations by adding closed pulmonary valvotomy and infundibulotomy

-1954- Lillehei et al--> cross circulation in a 10mo--> first intracardiac TOF repair w VSD closure and RVOTO relief. He did it on total of 11 pts w 6pts <2yo.

-1955- Kirklin et al--> 1st successful repair w a heart-lung machine

-1955 - Davidson--> first central Ao-Pulm shunt by direct suture

-1956 - Lillehei realizes we need to enlarge RV infundib w a patch and extend the patch across the stenotic pulm valve.

-1962 - Waterston--> first Asc Ao to RPA anast

-1962 - Klinner--> 1st prosthetic conduit bn SCA and PA;

-1960s (published) Klinner was first to use a nonvalved prosthetic conduit fr RV to PA for TOF w Pulm Atresia

-1966 - Ross & Somerville --> report 1st interposition of valved Ao homograft for TOF w pulm atresia w initial success but then high mortality

-1969- Barrat-Boyes & Neutze--> reinitated primary repair of infants w Sx w TOF w PS applying the technique of hypothermic circulatory arrest

-1972- Castenada introduces early repair of Sx infants w TOF, even at <3mo, in Boston.

-1980s- Leval et al--> refine Klinner's shunt bn SCA and PA

-Then, Laks & Castaneda--> modified BT shunt using SCA ipsilateral to the Ao Arch

Technique:

CPB Method:

-Elective repair at bn 1-3mo, usually pt weights 4-6kg--> okay to use double caval cannulation

-Asc Ao cannulation w standard way

-Venous cannulation w straight or R angle caval cannulas

-Mod to deep hypothermia for myocardial protection, alleviate need for multiple cardioplegia doses

-If pt >5-6kg or >3mo, then mod hypothermia at 25C or above w multiple doses of cardioplegia

-If pt <3.5-4kg, Jonas prefers using a single venous cannula in RA and to rely on the TV competency to prevent air being entrained into the cannula. You might need to stop bypass for 10minutes d/o where VSD is located in ref to TV and its cords. Use deep hypothermia if using a single venous cannula so that you can do circ arrest quickly

-If pt <2.5-2kg, Jonas prefers elective hypothermic circ arrest, w much of the intial phase of surgery on continuous CPB w single venous cannula, including the ventriculotomy, division of infundib muscle, and placing initial sutures.

-Best to complete VSD closure and start RVOT patch under hypothermic circ arrest

-Usually need max 30-40min circ arrest

Ventricular Approach to Repair TOF w PS

-Prefers a ventricular approach for most pts.

-Advantages:

-infundibulum can be enlarged w/o aggressive rsxn of muscle (xx of that is endocardial scarring)

-allows VSD exposure w/o traction on TV annulus, so avoids TV/conduction bundle injury

-Must ensure certain items before doing Ventric Approach:

-Transannular Patch- As you are cooling the pt, dissect free the MPA, PA bifurcation and LPA origin, and ligate PDA if present. Measure MPA size and pulm annulus diameter, and compare w preop echo. If the annulus and MPA are >2-3 SDs below Nl --> then pt will need transannular patch

-Ventriculotomy Location- Study the coronary artery anatomy during cooling, and plan the incision to avoid dividing the large RV cor art extending twd apex. Usually, you must divide the branches of this artery bc they run transverse at the narrowest area of muscular obstruction in infundib. Often see dimpling in the infundib at this level. This cor art branch supplies the hypertrophied muscle that's causing the obstruction (presumably), so cutting it shouldn't affect fx.

-Must ensure you preseve the major branch of the RCA that extends twd apex- often need to use slightl oblique incision in infundib. If you extend it across the annulus, then curve superiorly along the full length of the MPA beyond the RPA takeoff (see pic).

-If >mild stenosis at LPA origin, then extend the incision across this origin stenosis by 3-4mm

-Ventriculotomy Length

-Must limit length to that of the infundibulum. Ln d/o conal septum length which varies much in TOF. If hypoplastic conal septum, then you can limit the incision to 5-6mm. The goal is to finish it a few mm cephalad to the moderator band connection to the RV free wall, (also is the origin of the TV ant pap muscle)

Infundibular Muscle Bundles Division

-Van Praagh: the ant malalignment VSD is a defect lying bn the parietal & septal extensions of the septal band. They usually fuse w conal septum, and fix it in its anterior location.

-Dividing both the parietal (to free wall) and septal connections of the conal septum--> able to bring the conal septum more posterior by the VSD patch.

-So, you must incise the L and R ends of conal septum. Must do this far enough away fr the pt where the VSD sutures will be placed, bc they won't hold well if placed in cut muscle.

Preserve Moderator Band

-Must preserve moderator band bc it is the central pillar of teh RV, tethering the ant free wall to the post septal wall.

-In older pts, it might be very hypertrophied and can --> more RVOTO. If so, then partly divide it. Also can divide some of the additional muscle bundles on ant RV wall that are assoc w the septal band.

-In neonates/younger children, you should be able to do a simple division of the muscle bundle at the infundib and not the moderator...

Transventriculotomy VSD closure

-Jonas prefers interrupted plegetted horizontal mattress sutures, and not continuous like others

-Start at 3 o'clock w the middle of the conal septum representing 12 o'clock and the post and inf corner of the VSD rep 6 o'clock. The sutures are placed deeply initially to allow better traction which allows better exposure, then when you pass the pap muscle bundle of the conus, (going clockwise) you can suture so they emerge 2mm below the inf edge of the VSD.

-Conduction bundle is close to the post-inf margin of the VSD. It is less exposed as w pt w a membranous or inlet VSD, but ensure to avoid it at this aspect of the VSD.

-If + fibrous continuity bn TV and AoV (common), then c/s opening the TV and place sutures thru it fr the RA size of the septal leaflets w pledgets in the RA. MUST avoid entangling the TV cords, and avoid large bites of folded TV leaflet tissue --> TR.

-After passing the TV (while closing the VSD clockwise), then must ascend the Ao vlv annulus. Must avoid placing the patch in such a way that it straddles one of the ridges & valleys that run at level of the Ao annulus, or you can cause a residual intramyocaridal VSD (bc of Q thru the "valleys")

-Ao patch should lay right up to the level of the Ao annulus, w sutures exiting fr the fibrous Ao annulus to anchor them, so the sutures don't cut through the muscle tissue (which is very soft this age).

-After reaching the conal septum, the muscle gets smoother (no ridge/valley), and sutures can pass thru the full thickness of the conal septum. Here, use small 2mm pledgets made of pericardium, and not the Teflon ones which are relatively large and could cause RVOTO.

-Use a Dacron patch to thread onto the sutures. - -> fibrous reaction to seal the irregularities at the VSD margin Jonas: residual VSDs more common w pericardium.

RVOT Patch

-soak autologous pericardial patch in gluaraldehyde for 30min & cut to shape. ensure patch ends are blunt and not diamond shaped to permit augmentation of LPA or MPA diameter w the toe pf the patch, and augment the inf end of the ventriculotomy w the heel of the patch

-patch should be big enough that when blood distorts the shape of the artery, it is still of Nl diam.

Lines & Pacing Wires

-place LA line & 2 pacing wires to Tx possible JET

-place PAP line- allows for testing for residual VSD, and pullback to RA checks for residual RVOTO postop

Foramen Ovale Management

-Jonas: leave it patent, bc limited RV output in early postop pd bc of acute vol OD on by pulm regurg bc of the transannular patch, and bc RV was adapted for P load fr PS and unrestrictive VSD, so no good for sudden incr in volume work and so RAP may increase. High RA P (>10) isn't tolerated well by neonate/young infant, can --> 'leaky capillary syndrome', so allowing popoff is helpful

-Fraser: need for a pop-off = RV failure (!) thus better to wait for pt to be older--> no need for popoff

CPB Wean

-Dopamine 5mcg/kg/min useful

-if difficult wean, then c/s residual anatomical problem

-Residual RVOTO

-check simultaneous monitoring of teh PA line and the RV - RVP would have to be systemic or more to cause difficulty weaning

-check w TEE for dynamic obstruction

-Residual VSD

-see elevated LAP and systemic hypotension

-RAP would be < LAP (usually it is >LAP)

-confirm by checking sats and seeing a step up bn RA and RV/PA

-check w TEE to locate/size the VSD

-c/s undetected muscular VSDs

-VSDs are poorly tolerated postop bc:

-periph PAs are thin walled and distensible, and PVR isn't high, so large L-->R

-PR w vol OD to RV exacerbates the already present postop RV overload

-Older pts may have more restrictive RV physiology bc of more RVH

-Coronary obstruction

-RVOT patch sutures pass very close to LAD, and tension on the epicardium can cause partial obst, which would --> ST changes and discolored myocardium w TEE showing hypokinesis

Surgical Results

Early Mortality

-1988-1996 at Boston, in pts <3mo (median 27 days)

-91% had Sx bc of cyanosis (+/- tet spells)

-3% early mortality (!!)

-other reports of 3.6% mortality, and other similar numbers

-Karl review of 366 pts (median 15mo) w 2 deaths in hospital = 0.5% mortality

-Kirklin study in 1980s bn Alabama and Boston of 1 vs 2 stage repair: 100 consec pts--> "authors concluded that there was a possible disadvantage for the 2 stage approach employing preliminary shunting and later repair" (!??)

Long Term Results after an Early Primary Repair

-Bacha 2001 boston results bn 1972-1977 57 pts <24mo at surgery, w f/u for 45 of the 49 long term survivors, median f/u 23yrs

-8 early deaths

-1 late death in the subsequent 24 years

-most pts were ASx, w no influence on outcome if they had a transannular patch, but it did predict higher need for reintervention. Most of these reinterventions were for recurrent RVOTO (8 pts)

-other studies showing residual/recurrent RVOTO a serious long term xx

Transannular Patch No Longer Risk Factor

-was demonstrated as a r/f for early mortality initially in Tx of TOF, today most studies don't show this.

-the above Kirklin study didn't show it as a r/f.

Primary vs Two-Stage Repair

-Fraser & Mee support initial placement of mod BTS and then repair at 6-12mo

-Jonas: most centers feel primary early repair can be down w great low mortality and low rate of reintervention, especially when you c/s that 2 stage repair guarantees a 2nd surgery..., and there's signif risk to a mod BTS

-Toronto 1997 report: HSC in Toronto--> 90% survival w 2 stage vs 97% w primary repair

(this does NOT reflect TCH outcomes)

Transatrial vs Transventricular Repair

-Studies have shown great outcome w transatrial approach- Karl & Hirsch reports w use of a limited ventriculotomy, w less late RV dysfx

-Jonas: centers that mainly use a ventriculotomy approach to repair TOF focus on other factors assessing late RV fx

-RVOT width, preservation of moderator band, avoid excessive RV muscle devision, preserve TV fx by avoiding sutures snaring TV cords/leaflets, minimize cor art branch damage, avoid distal PA obst.

Late Pulmonary Valve Replacement

-rarely need to replace pulm vlv, even decades later in most centers, but in some they show need for late valve replacement often

-indication for valve replacement was progressive CM and evidence of RV dilation/dysfx

Role of the Monocsup Valve

-some ppl like them, but follow up studies show they don't fx after a time (most by 24mo postop)

-one study--> no diff in early postop PR or mortality, number of reoperations, or hospital stay

TETRALOGY OF FALLOW WITH ABSENT PULMONARY VALVE SYNDROME

-...

-if you think resp Sx are related to dilated PAs then check CT/MRI for relationships to the airway, check for compression/dilation...

-bronchoscopy for baseline check of airway compression

Rx Tx

-if needed, positive P ventilation, c/s paralysis, and putting child in prone to relieve airway obst

Surgical Tx

-indications- no alternative to surgery.

-is signif resp distress as neonate, then do it emergently

-if wheeze/freq URI do it soon

-if ASx, do it electively in first few months of life

-Repair:

-For Neonates w signif Sx...

-replace central PA and insert Homograft pulm vlv at MPAç

-isolate PAs

-cross clamp Ao

-transect MPA at annulus and transect RPA and LPA, leaving a cuff oftissue proximal to the hilar pranches to allow suturing w/o stenosis at hilar branches. Must pick the right homograft w good annulus and branch PAs

-VSD closure, Infundibular Muscle Bundle Division

-VSD closure and infundibular muscle bundle revision

-incision at pulm annulus and infundib muscle, close VSD w Dacron patch

-Pulm Homograft Insertion

-Jonas: leave PFO open for pop-off

-hard to wean CPB because of ventilation issues/tracheobrachomalacia and distal sm airway obstruction.

-Elective repair for pts w moderate PA dilation

-if few Sx, then don't need to replace PAs w homograft, instead plasty them

-Reduction Pulm Arterioplasty:

-TOF repair

-reduce MPA and branch PA size w plasty w sutures running along post wall of PAs, ensuring not to make them too narrow.

Surgical Outcome

-very rare, w wide spectrum of xx, so hard to assess surgical risks and outcomes

-...