Mavroudis - AS

Aortic Stenosis Mav29

Epi

-Congenital LVOTO = 10% of CHD

-usually at Ao vlv (60-75% of cases), but can be sub (15-20%) or supra (5-10%)

-may be part of Shone's or HLHS

VALVAR AORTIC STENOSIS

-many have assoc VSD, PDA, small LV, CoAo

-<10% will have critical AS

-Critical AS = PDA dependent for Qs

-may be assoc w multiple L side obst lesions, sev L heart hypoplasia.... HLHS spectrum

-ref 6- largest multictr crit AS trial, n=320 neonates Dx @ <30 DOL --> Norwood in 56%

AS in Neonate & Infant

Path-

-ng # of Ao cusps/dvpmt of vlv commissures - often unicupsid or bicupsid

-often thick, dysmorphic leaflets

-unicuspid- often acommissural, w only a stenotic central orifice, no commisural attchmts to Ao wall

-or, a single commissure that's eccentrically located

-bicuspid- more common in older kids - w a R & L leaflet of unequal size, separated by ant & post commissures, usually w some fusion, along w limited leaflet mobility bc the commissure is straight instead of rounded. Often bicuspid valves are actually tricuspid w a commissure that is rudimentary & fused, so it looks like just 2 leaflets

-LVOTO usually compatible w fetal dvpmt, but the incr LV AL --> LVH--> Syst & diast dysfx

-Crit AS-->signif LV dysfx w incr LAP==> L-->R shunting at PFO instead of the Nl R to L as afetus

-Qs maintained by RV ejection & the pDA

-LVH, intracavitary htn, decr coronary perfusion P --> incr risk of myocardial ischemia to LV--> EFE

-sev LVOTO--> decr Q thru L heart as fetus--> L heart hypoplasia...

-Postnatal Sx d/o degree of AS, LV dysfx, LV hypoplasia, PDA Q if critical AS

-if milder AS, then LV well enough dvpd, ASx but +SEM & then progressive LVH

-if more severe AS, --> incr LV wall tension/workload w LVH/LV dysfx

-The P gradient across the Ao vlv --> mismatch bn cor perfusion P and myocardial perfusion P--> ischemia, arrhythmia, infarct, espec at risk is subendocardium, which --> EFE, common w vlvr AS

-if critical AS, will have some cyanosis, espec lower half of body (depending on amt of Q thru native Ao vlv). As the PDA closes, pt gets shock w low BP, UOP, acidosis

Sx

...

Tx

-Indications-

-neonate- CHF or shock as PDA closes--> urgent Tx

->1mo- Sx, or mean Ao gradient >50mmHg

-Is the L Heart capable of supporting a systemic circulation?

-if severely hypoplastic or bad fx--> Norwood for SV repair or OHT

-still controversial to determine LV ability...

-echo dimensions most commonly used

-poor biventricular repair is assoc w small Ao vlv, small LV, small MV

-ref 11- small retro study- scoring sytem to determine LV adequacy

-Ao root dimension indexed to BSA,

-ratio of LV long axis dimension to heart long axis dimension,

-indexed MV area

-ref 16- presence of ategrade Q in ascending & Tx Ao is assoc w survival p biventric repair

-ref 17-19- surgical series show good BV repair even when above aren't met

-ref 6- CHSS multictr study- n=320 neonates w critical AS-

-116 w BV repair via balloon/surg Ao vlvplasty

-179 w Norwood

-5yr survival of Norwood over BV by multiple regression: age at study entry, size of Ao vlv at the sinuses, EFE amt, Asc Ao diameter, +mod-sev TR, LV length score

-but this has not ben validated in a prospective fashion

-Pre-Intervention Tx

-ventilation, inotropy, supportive care PRN

-PGE for PDA if poss critical AS

Percutaneous Balloon Valvuloplasty

-ref 20-23: = procedure of choice

-first done in 1983 (ref 24)

-ref 25-26- similar short and midterm results to valvotomy

-UA preferred in neonate, otherwise fem art, but if sev CoAo or IAA then must use carotid artery

-c/i xx: dysplastic vlv, small annulus, or Ao regurg

Surgical Valvotomy

-+/- CPB

-+/- cardioplegia

-various approaches; remains controversial

-Open Valvotomy w CPB

-Cross Clamp the Ao, arrest heart w cardioplegia

-Expose Ao vlv via vertical aortotomy twd the noncoronary cusp

-allows for detailed inspection of Ao vlv, critical to success

-Valvotomy by dividing fused commissures to 1/in 1-2mm of Ao wall, but be on the conservative side bc a small incr in orifice will drastically improve resistance across the vlv, but larger incision will--> AR

-Don't incise a false raphe in a bicuspid vlv, bc it will--> AR

-Open Valvotomy with Inflow Occlusion (no longer performed)

-allows rapid access to Ao vlv, direct visualization, without CPB

-Occlude SVC & IVC w clamp, and let heart beat 6x before cross clamping Asc Ao

-Expose Ao vlv thru verticle aortotomy

-Perform a conservative valvotomy

-Clear the heart of air by releasing IVC clap--> fill the heart and asc Ao w bld

-Clamp the side of the aortotomy, & remove the cross clamp

-Remove SVC clamp

-Rarely used today because CPB is much safer

-Closed Valvotomy

-Ao vlv opening is enlarged without direct visualization

-+/-CPB

-purse string suture around LV apex

-stab ventriculotomy in the middle of the purse string

-Use progressively larger Hegar dilators to insert thru incision to enlarge Ao vlv opening to correct diameter

-Aortic Valve Replacement

-with Pulmonary Autograft = Ross Procedure (using pts own PA vlv)

-+/- additional aortoventriculoplasty (LVOT resection) = Ross-Konno Procedure

-enlarge the LVOT w synthetic path, allograft aortic patch, or RV infundibular free wall muscular extension harvested in continuity with the PA autograft

Results-

-older studies 30-50% operative mortality, but now >90% survival (ref 20-23, 26, 36)

-the big diff is that new studies are of pts w Nl/near Nl LV size, as we do SV pathway now if pt has small LV

-4 predictors of death (ref 37): LV long axis to heart long axis ratio of 0.8 or less, indexed Ao root diam of 3.5cm/m2 or less, and LV mass index of <35g/m2

-100% mortality if pt has 2 or more r/f, 8% if 1 or no risk factors

-CHSS study (ref 6)- 70% 5yr survival vs 60% p Norwood

-Valvotomy is palliative, not curative, bc many will need reintervention

-Recurrent AS, AS & AR, or isolated AR --> reintervention (ref38-39)

-eventually will need Ao vlv replacement

-Percutaneous Balloon Valvulopasty results

-ref 25,41- same results as surgery re improving the gradient, early mortality, incidence of additional Ao vlv intervention

-Surgical Valvotomy results

-ref 43-46- expect much decr in Sx

-palliative bc most need reoperation (ref 38,47)

-high mortality in infants- 30-50%, but likely bc of inappropriate pt selection (should have gotten a Norwood), now much better results

-recent multictr study (ref 50)- open vs closed- overall survival 87.5% in-hospital survival, no diff bn the two.

-Best results w isolated valvar AS

-Signif long term mortality

-ref 51- survival decreases fr 93% at 30 days to 76% at 25yrs

-complex cardiac anomaly & EFE is assoc w incr operative mortality

-QOL for long term survivors is similar to that of gen population

AS in Older Children

-Path-

-milder than neonatal AS

-3/4 are w a bicuspid Ao vlv

-?genetic component

-not common to have severely dysmoprhic vlv or hypoplastic annulus

-incr AL--> LVH--> decr compliance--> incr LVEDP, also LVH--> incr O2 demand, decr myocardial perfusion pressure bc Ao P is Nl or low & LVEDP is high --> ischemia risk

-volume load to LV if +AR

-Sx-

-Nl growth/dvp

-usually present w ASx murmur on WCC

-Sx dvp over time- exercise intolerance, then more sev Sx- CHF, syncope, angina

-Bacterial Endocarditis incidence is 3/1000 pt-years, but doesnt correlate w surgery or AS severity

-incr risk of sudden death- 1.2-19% per pt-year, usually w severe AS and ischemia induced arrhyth

...

...

-Tx-

-Indications & Timing for Tx

-Sx + HD signif Ao vlv P gradient- peak to peak >50mmHg

-ASx + Severe vlvr stenosis w pk to pk gradient >75mmHg

-Mild-mod stenosis (pk to pk <40mmHg) in ASx pt- well tolerated

-It is progressive, but okay to follow until above are indications are met

-for P gradient of 25-75mmHg, conterversial if pt is ASx, early intervention may be beneficial

-PerQ Balloon Valvuloplasty- success rate to relive the gradient is similar to surgery (ref60-61)

-Surgical Valvotomy/Valvuloplasty- valvotomy is standard for most kids, & preferred over vlv replacement in pts w nonregurgitant trileaflet vlv

-ref 64- Ao vlv repair after prior balloon valvuloplasty had good intermediate term results w mean P gradient of 32mmHg and no more than mild AR after 22mo

-if pt had recurrent valvar AS & AR, can do an extended aortic valvuloplasty instead of replacement (Ref 65-66)

-no data on mid/longterm results

-CBP, mod hypothermia, cardioplegia- may need to give it retrograde if signif AR

-Oblique aortotomy twd noncoronary sinus of valsalva

-Augment Ao cusp by extending the commissurotomy incision into the Ao wall around the leaflet incision. The vlv cusp attchmt is mobilized at the commisssures, and then the Ao insertion of the rudimentary commissure is freed.

-w bicuspid Ao vlv, can divide the fused commissures w a knife to within1-2mm of Ao wall, but ensure you are at the true commissure and not a false raphe (common), the false raph is a rudimentary commissure but does not reach the wall of the Ao, so no lateral support, so incision would--> AR

-w unicuspid Ao vlv, do valvotomy as you would for a neonate, conservative to avoid AR

-Aortic Valve Replacement in Children

-35% need a valve replacement within 10-20yrs after initial valvotomy

-should delay replacement to enable larger sized prosthesis and delay need for anticoagulation

-mortality of valvuloplasty is higher if there's signif valvar regurg, or if the valve is not tricuspid, so Ao vlv is preferred.

-88.6% 10yr survival

-Valve choice

-Bioprosthetic- limited use:

-Porcine bioprostheses

-Allograft aortic valves

-both get accelerated Ca'ion & degeneration --> AR/AS as early as 2 yrs postop

-Mechanical

-no durability issue, but higher risk of thromboembolic xx, so need warfarin

-Pulmonary Autograft = Ross

-replace Ao w pt's PA vlv, and use a cryopreserved pulmonary allograft to replace PA

--> more durable as neo-Ao vlv than bioprosthetic on the high pressure side...

-Ross Technique:

-CPB w Ao/bicaval cannulation

-Cardioplegia

-explore Ao root thru a transverse incision

-Ao root replacement- remove leaflet & sinuses so only Ao annulus remains

-mobilize coronary ostia w generous rims

-open PA transversely b4 it's bifurcation and inspect the PA vlv

-Divide MPA

-incise RV a few mm below P vlv, leave enough cuff of RVOT muscle to suture so you don't damage PA vlv and avoid LAD cor art injury. Harvest the PA vlv

-Suture PA vlv to the Ao annulus

-Reimplant cor arts

-Place RVPA conduit

-Ross outcomes- ref 72- n=109- s/p Ross had good outcomes

- ref 73- n=301, 5yr f/u Ross had better outcome than other types of vlv replacement. QOL reflected by need for reop favors Ross- 87% free fr reop vs 55% at 9yr f/u

-85% 10yr and 61% 20yr survival after Ross (ref 74) in the original study...

-88% and 75% freedom from autograft replacement, and 89% and 80% freedom fr pulm allograft replacement at 10 and 20 yrs.

-usually need some ype of annulus enlargement, bc of mismatch to PA size

-the smallest prosthesis is 16-17mm

-Konno-Rastan to enlarge the annulus- enlarges entire LVOT in addition to annulus

-modified Konno-Rastan- limits enlargement to LVOT, exclusive of the Ao vlv annulus

-Ross-Konno combo- relieves subAS and valvar stenosis

-transect ascending aorta and resect Ao leaflets down to the Ao annulus, then longitudinal incision is made in the Ao root, twd commissure bn R and L coronary sinuses, then extend it anteriorly obliquely into the RVOT. Post'ly, the IVS is incised leftward to avoid the conduction system, to enlarge the LVOT. Augment this incision using Goretex or dacron patch, allowing for a larger autograft insertion and relieve LVOTO, then suture in the autograft. Then repair the incision into the RVOT w a patch. In smaller kids/infants, can use a muscle cuff around the RVPA conduit to enlarge the IVS by harvesting extra anteriorly.

-vey effective

-may need to also resect the EFE, and hypertrophic myocardium to improve LV fx

SUBVALVAR AORTIC STENOSIS

-usually bc of a fibromuscular structure in LVOT

-rare before 1yo, unless assoc w other CHD

-HCM causes dynamic LVOT obstruction; less common in kids

Fixed Subvalvar Stenosis & Fibromuscular Obstruction

-discrete vs diffuse - discrete =70% of cases- thin, fibromusc ring/crescent bn base of ant MV leaflet and the bottom of the Ao vlv leaflet; diffuse -12%, has long tunnel for LVOT

-Ao vlv usually Nl, might be small

-Turbulent Q can--> thick Ao vlv, and then Ao regurg

-Assoc xx in 65% pts- CoAo, IAA, VSD, AVSD; SubAS is part of Shones...

Path

-...

-etiology not exactly clear, may be bc of steep angle of Ao takeoff--> incr shear stress at LVOT--> cell prolif...

Sx

-discrete subAS rarely in isolation in infants

-+SEM, +/-diastolic murmur of AR

-ventric dysfx/AR Sx if progressed...

...

Tx

-Indications for Surgery

-+Sx due to it- CHF, angina, syncope, DOE, or progressive decompensation based on serial echo

-ASx pt- gradient >30mmHg (doesnt specify if mean or peak in this text) = indication for surgery in discrete subAS, and >50mmHg if tunnel like)

-AR, even if gradient doesnt meet above, is usually indication for Tx

-some advocate for surg at Dx bc it is progressive.... (ref 97) [[[[note other evidence much to contrary of this approach]]]]]

-Tx of Discrete Obst

-aortotomy, then remove the ring/underlying IVS muscle but dont cause heart block or VSD!

-might be able to peel it off the wall, but myectomy might reduce recurrence rate (ref 98)

-recurrence seen has high as 55% of cases....

-Tx of Diffuse Obst

-harder to Tx

-do a septal ventriculoplasty = modified Konno-Rastan- expose the IVS via incision thru pulmonar infundibulum, and open the septum longitudinally in a slightly oblique fashion fr R to L, extending to just below the commissure bn the L and R coronary cusps. Then resect the thickened septal muscle and close the VSD w a patch to enlarge the lVOT. Then close the R ventriculotomy.

-reported good results in LVOTO reduction, and "low" mortality at 2yr f/u = 6.2% (ref 99)

-may need to also have vlv Tx too if AR/small Ao diameter - Ross-Konno or prosthetic Ao vlv

Hypertrophic CM

-asymmtric ventric septal hypertrophy

-limited peds surgical experience but if fail Rx Tx, can do a Konno-Rastan

SUPRAVALVAR AORTIC STENOSIS

-Only 5-8% of LVOT obst

-Path-

-Diffuse in 23%

-medial dysplasia of entire Asc Ao/arch and beyond, and some of the branches, may also affect the PA's, to a lesser degree

-Localized in 77%

-Intimal hyperplasia, medial dysplasia, thickening w necrosis/Ca'ion at STJ in localized form

--> hourglass shape

-random arranged sm muscle cells, decreased elastin, incr collagen seen

-rarely is it just bc of a membrane above the Ao vlv

-Coronary Arteries

-xx are assoc w suprvlvr AS- intimal hyperplasia, fibrosis, dysplasia, disruption, lose internal elastic membrane, medial hypertrophy, etc

-more severe proximally than distally, espec in older pts w diffuse forms

-+/- dilation or stenosis

-if dilated/tortuous- bc of high systolic pressures prox the STJ w coronaries below the STJ

-if cor stenosis- one/both originate at or just above the STJ ridge

-focal dissection, accelerated atherosclerosis seen, sometimes get coronary ostium obstruction bc Ao vlv leaflet abNly adherent to STJ

-Valvar xx

-Ao vlv xx not uncommon- seen in 30-45% at autopsy/OR

-thick cusps, AR, which can worsen after repair of the supravalvar stenosis

-Bicuspid Ao vlv- frequent,

-17-40% of pts needed reoperation for subAS or vlvr AS

-concomittent vlv dz is ? r/f for death/reop

-my also see AbNl MV- fibrous thickening of leaflet and cords

-Myocardium xx

-LVH common, w some ischemia by childhood & onward

NHx

-ref 101- supravlvr AS tends to progress, while periph pulm stenosis spontaneously regresses over time

-bc cor arts are exposed to high SBP, --> dilate/tortuous/CAD--> sudden death at incr risk (ref 106)

Sx/Dx

-the main feature in Williams syndrome- see supravlvr AS, periph PS, elfin craniofacial features, intellectual disability, due 7q11.23 microdeletion of elastin gene

...

Tx

-Indications- gradient >50mmHg, progressive subAS or Ao vlv obst, AR, or evidence of coronary artery xx or decr perfusion to coronaries

-earlier age bc the high P's have detrimental effect on Ao vlv/cor arts

-need surgery, balloon dilation doesn help

-tailor technique to the pt...

-if localized (rare), can just remove the lesion...

-can use a Dacron patch or PTFE patch made into a tear drop shape for an aortoplasty, encompassing the entire stenotic segment as far as the Ao arch if needed

-Doty patch- inverted Y shaped incision across the constriction, and into the R and non cor sinuses. The limb of the incision is made to the L of the R cor osium --> allow more symmetric reconstruction of the Ao root than a single patch.

-if more extreme stenosis, then an alt modification is to transect the Ao completely, and make an incision longitudinally across the stenosis, to the non cor cusp. then make incision to the L and R of the cor artery --> 3 separate triangle patches are used to enlarge sinus of valsalve --> Ao vlv can coapt better, then do end to end anastomosis bn the Ao root and the Asc Ao.

-if diffuse subAS

-need deep hyopthermic circ arrest, or low flow bypass (direct perfusion of brachiocephalic vessels) so you can work on the arch.

-not much data...

-historically an LV APEX (!) to abd Ao conduit was used, but there was endocarditis and otehr xx- stenosis, prosthetic vlv dysfx, late mortality

-now, use an extended patch fr sinus of Valsalva over entire Ao arch

-THI (one of the largest series) - 3 of 11 pts w diffuse supravlv AS were treated w a combined extensive endarterectomy of Asc AO/Arch, along w patch aortoplasty --> good obst relief