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Coarctation of the Aorta (MA49)
Coarctation of the Aorta (MA49)
Epi
-6-8% of CHD
-M>F (like most left sided obst lesions
-35% of Turner (XO) +CoAo
-Incidence peaks in late fall/winter (?environmental etiology)
Path
-Stenosis of upper Tx Ao (usually), at DA insertion (juxtaductal)
-2y to xx in the Ao media --> prominent posterior shelf (infolding), that may extend around entire Ao circumf.
-Can be long or tortuous in nature.
-Assoc: VSD, LVOTO, or diffuse hypoplasia of transverse Ao Arch/isthums
-Also can occur @ Asc Ao & Abd Ao
-DA/Lig Art inserts at same level, ant'medially, with intimal thickening/hyperplasia esp in older pts, where there is high velocity flow against the art wall. Distal to this site, infective endarteritis, intimal dissection, aneurysm occurs.
-Cystic medial necrosis- depletion/disarray of medial elastic tissue occurs next to CoAo site (can later--> aneurysm/dissection)
-Complex Coarc- = assoc with other lesion (except PDA); more common in infants (nearly half of infants w +CoAo Dx)
-large VSD- perimemb, musc, malaliagnemnt types (post deviation of conal septum and signif LVOTO)
-Subvalvar AS- common in critically ill pt w CoAo +VSD
-Bicuspid Ao Valve- +/- stenotic/hypoplastic annulus
-Mitral Stenosis- 2y to supravalvar mitral ring, thickened and dysplastic mitral leaflets, short dysplastic chordae tendineae, or single "parachute" pap muscle
-Shone Syndrome = multiple L sided obst lesion + CoAo
-Other: AVCD, d-TGA +/-TriAtresia, Taussig Bing type DORV, congen corrected TGA, HLHS
-Extracardiac xx:
-brachiocephalic artery anatomy
-collateral arterial circ (more in kids/adults)
-Ant Circ- Internal Mammary Art to External Iliac arts, via epigastric syst
-Post Circ- Thyrocervical Art and Desc Ao, via thru retrograde Q thru internal mamm.
--> dilated/tortuous--> thrills, cont. murmur, CXR rib notching
-berry aneurysm @ circle of Willis (3-5%)
-Usually the CoAo is just beyon L Subclav art, but this can vary. L subclav can be stenotic too if
-R subclav arises after L subclav in 5% cases (below the CoAo, so might have R pulses/BP <L)
-Rarely, both subclav are below the CoAo, so both have low BP/pulses
-Extracardiac NonVasc Assoc xx
-Turnur (XO)
-MSK, GU, GI, Resp in 1/4 pts; Head & Neck xx
Embryology
-Arch- week 6-8.
-Arch 3--> Comm Carotid Art
-Left Arch 4-->Tx Ao Arch & Isthmus
-Right Arch 4--> involutes
-Arch 6--> prox pulm arteries; left 6 distally --> DA
-So, CoAo = xx of Arch 4 & 6
-Ductal Tissue Theory: migration of ductal sm muscle into periductal Ao--> constriction/narrowing Ao. Coarc often occurs after ductal closure. But, this doesnt explain CoAo that occurs away fr this site
-Hemodynamic Theory: hd xx --> decr Q thru fetal AoArch. Nl fetal isthmus only gets 10% of Q (combined CO) thru it bc most goes to head or is diverted to Desc Ao via PDA, so it's diameter is smaller (75%) than rest of Ao. Explains assoc w VSD, LVOTO, hypoplastic transverse AoAr.
Hemodynamics
-bc only 10% of combined CO goes thru isthmus, there is usually no big xx as fetus
-postnatally w PDA closure, all Qs must go thru isthmus--> mild syst htn thru sev CHF shock
-Compensatory mechs: LVH- to normalize myocardial wall stress and ventric AL, and maint Nl syst fx, so that w isolated CoAo, the LVEDV is Nl and LVESV maybe low, so that EF is Nl to high (same goes for other LVOTO like AS)
-If severe or rapid CoAo, --> LV sys dysfx, then CHF. --> decr SV, incr LVEDP, incr LAP, Pulm Vn congestion, pulm art htn. If very low CO, --> decr myocard Q and dvp acidosis w decr myocardial contractility more. Usually occurs at 1st WOL.
-Compensation w Symp n sys activatn- incr HR & contractility, inc Frank Starling mech (inc LVEDV to maint Nl SV). But, neonates don't have Nl symp innerv'n bc decr beta R' density, and less compliant myocardium than adult, and less able to preserve SV via FS mech. Also w sev coarc, LVP OD occurs quickly w DA closure, so no time to dvp LVH to compensate for inc wall stress (AL)
-CoAo can also --> LV diast dysfx- swxe eRW OD Wely LV diast relax'n so abNl diast filling so that most LV filling is in late diastole. This is related to decr LV compliance due to LVH, fibrosis, and inc inotropic state of myocardium. --> inc LVEDP at any given filling vol, so LA htn and pulm vn congstn can occur, espec w inc LVEDV.
-large VSD, PDA or MR increases LVEDV and LV PL, and in concert w decr LV compliance, the increased diast vol--> incr LVEDP--> inc LAP more and then PVn congstn and PAH...
-Vascular xx- inc SBP bc of aortic constriction, and (likely) changes in vasc reactivity, art wall compliance, baroR' reflex fx (inc reactivity to arteriolar resitance vssls proximal to the coarc, resetting of baroR' reflex after repair...)
Symptoms/Signs
-infant w CHF vs child/teen w systemic htn, vs ASx child w murmur.
-Infant w sev CoAo +/- AS/VSD--> CHF/shock by 10 days old, +/-NEC/renal failure s Tx
-Infant- CHF Sx (pale, tachypnea, etc). DIfferential cyanosis = @LE only, if +R-->L shunt at PDA
-check for Turnur Sx
-Discrepant art pulses and SBP in UE vs LE
-Can be hard to tell: CHF--> decr CO so low BP/pulses at both UE and LE, R-->L PDA shunt can keep Nl Q to desc Ao, variations in brachiocephalic art anatomy can make detecting b-f delay hard (e.g. R sublcav distal to L subclav...), etc.
-Precordium Palpation- LVP and Vol OD--> prominent heaving ventric impulse at apex, prom RV impulse at LLSB/xiphoid if phtn; systolic thrill at suprasternal notch; palpable collat art pulsations at intercostal area and bn scapulae post'ly
-Nl S1S2, w loud S2 if phtn, sys ejection click at apex if bicuspid Ao; 2-3/6 SEM at LUSB, base, and L interscap area post'ly fr CoAo. It can spill into diast if bad CoAo; cont murmurs thru out chest if collaterals; also AS murmur w SEM at RUSB, VSD or MR murmur w holosys M at LLSB/apex. Mid disat rumble at apex fr MS or large L-->R shunt w VSD. Gallop if CHF. Murmurs quiet if poor CO, then hear mainly gallop.
ECG
-usually Nl, may see LVH w strain- ST/Twave depression--> c/s AS or myocardial dz; in older kids ECG shows evidence of long term LV P overload
-RVH beyond infancy--> c/s phtn fr assoc VSD
CXR
-nonspecific,
-Infants: +/- mod/sev CM, inc PVR (w LV failure/MS--> pulm vn htn, or bc inc Qp fr big VSD shunt)
-Older pt: rib notching w collaterals in older kids (>5yo), less CM, only mildly inc hrt size
- 3 Sign = indentation of Ao on AP view, w prominent desc Ao just below 3 sign. aka reverse 3/E sign on barium swallow... (indentation in esoph fr dilated Ao prox to CoAo
MRI/CTA
-Check PDA and collaterals
-MRI can also check Ao flow and P grad.
ECHO
-Suprasternal LA- see CoAo just beyond L subclav origin
-posterior shelf- thin, fibrous membrane protruding from the post aspect of Ao, oriented twd DA
-+/- isthmus hypoplasia, poststenotic dilation, decreased systolic pulsations at desc Ao
-Doppler to check hemodynamic severity- Continuous wave fr suprasternal window; see diastolic runoff
-note pk velocity 3.2m/s and diastolic runoff
CATH
-Dx and Tx
-usually not needed for Dx, but can:
-assess anatomy/severity of CoAo
-CoAo--> incr SBP (&PP) before, decr SBP (&PP) after CoAo.
-SBP gradient <20mmHg = mild CoAo
-Check anatomy w AP/Lat view, or slight LAO for Asc and Desc Ao
-assess for PDA, shunting
-assess for collaterals
-assess for intracardiac lesions
-assess LV Fx
-assess PAP/PVR
Treatment
-NHx w/o Tx- in pts who survived 1st yr of life, they died on avg at 34yo, 75% dead by 46yo- CHF, Ao rupture, bacterial endocarditis, intracranial hemorrhage
Infants:
-inotropic/diuretics PRN, PGE if critically ill to ensure open PDA for Q beyond the CoAo, then surgery
-M&M increase from LV failure if severe, even if Rx Tx given so go to OR soon.
-Surgical risk if infant presented w CHF is higher if +complex CoAo (other xx); risk is very low if isolated CoAo, but bn 2-10% if other dz...
-Sometimes fixing the CoAo alone is enough even if other xx (like small VSD or mild MS which can improve postop)
Children:
-usually ASx--> repair at 2-3yo if no signif htn bc there is a risk of late recurrence in kids <1yo, and the Ao is 55% of adult size by 3yo and signif hemodynamic obst doesn't happen till Ao is <1/2 Nl size...; but dont delay until late childhood bc of risk of athero and residual htn (30-50% if repaired at >5yo vs 6% if <5yo), best time is at 1.5yo.
Surgical Repair
-End to End anast
-Prosthetic Patch Aortoplasty
-Subclavian Flap Aortoplasty
-Bypass Grafts between Asc and Desc Ao
-Via L thoracotomy, unless repair of intracardiac lesion where ant sternotomy is done
-If it's a discrete CoAo (not a long segment of hypoplasia), then surgical repair is very effective
-Most kids have residual resting grad <20mmHg (usually <10mmHg), regardless of surgical type
-Surgical Mortality: d/o age and assoc xx- isolated lesion in older pt = 0%, but 2-10% w infant w large VSD, and worse if more complex CHD.
-Postop xx =
-postop paradoxical htn = postcoarctectomy syndrome
-POD3-5--> incr SBP and DBP, xx = mesenteric arteritis/bowel ischemia if severe, bc of rebound activation of symp n sys and renin-angiotensin sys. Prevent w b-blocker and aggressive antihtn Tx immed postop.
-spinal cd ischemia/paralysis
-if Ao cross clamp severely decr Q to desc Ao and spinal arts, rare and only in pt w poor arterial collat circ. Avoid by ensuring adequate Ao Q at cross clamp, limiting cross clamp to 30min, minimize # intercosral arteries sacrificed, avoid hypErthermia, and use hypOthermia PRN
-recurrent laryngeal/phrenic n injury, chyloTx, bleeding, infection
-Reoperationfor resid/recur CoAo is harder w higher M&M
-End to End Anast
-1st used in 1945 and still Tx of Choice if discrete CoAo, and more effective w an Extended End to End Anast w broader longitudinal incision across prox Ao for pt w isthmus/transverse Arch hypoplasia--> less risk of late stenosis.
-Advantages: remove the coarc segment and adjacent ductal tissue, avoid prosthetic materials, spares subclav arts usually,
-Disadvantages: circumferential suture line--> restenosis in early operations. Using interrupted or absorbably sutures anteriorly and using an extended anast if isthmus/arch hypoplasia--> better outcome
-Prosthetic Patch Aortoplasty
-1st done 1961--> longitudinal incision at CoAo, and at times into L subclav, and place Dacron/GoreTex patch. +/-post shelf coarc.
-Advantages: less Ao mobilization needed, preserve intercostal arts, avoid circumferential suture
-Disadvantages: prosthetic material, high rate of late aneurysm formation
-Subclavian Flap Aortoplasty
-1st done in 1966--> L subclav art ligated and divided, and longitudinal incision thru prox subclav art and beyond the coarc, then the prox sublcalv stump is turned down on the coarc to be sued as an autologous patch. The vertebral art is ligated to avoid subclav steal
-Advantages: less Ao mobilization, avoid prosthetic, growth potential, avoid circumf. anast
-Disadvantages: sacrifice L subclav. initially thought to reduce late restenosis but this was later disproven, so this isn't done often bc of risk (rare) to L arm...
Percutaneous Balloon Angioplasty & Stenting
-Balloon Angioplasty
-Accepted for recurrent CoAo, controversial for primary Tx, because surgical repair if isolated CoAo carries low risk and high success, while reoperative CoAo repair has higher risk and less success
-1st used 1982--> retrograde balloon via fem art usually (antegrade approach ok if post Norwood)
-Balloon size varies, usually use the same size as diam of Ao isthmus, but larger can be used up to diam of Ao at level of diaphragm
-works via expanding the diameter via liniear intimal/medial tears at CoAo site, rarely they can extend to adventitia. In animals, there were some medial thinning but no aneurysm several weeks post.
-Angio for Native CoAO
-1990 study- n=140pt 3days to 29yrs--> decr P and inc diam signif, BUT resid grad of >20mmHg in 14% of cases. 27% of the patients had a residual grad at f/u (59pts followed up). Thus angio for 1y CoAo not widely accepted bc of concern for resid stenosis/aneurysm. Residual gradient occurs in 8-27% of pts, but recurrent stenosis seems uncommon if it was initially successful. Aneurysm incidence varies widely by study, but is 5-10% in larger studies
-M&M: mortality rare unless newborn; xx= fem art injury/thrombosis esp if <1yo, fem art hem, CVA. Paradoxical htn is UNCOMMON post angioplasty
-Angio for Recurrent Postop CoAo
-20% had resid P grad >20mmHg in a study of 200pts; restensosis can occur...
-M&M: similar to natice Co, but reported mortality higher (5 death of 200 pts = 2.5%)
-other xx= fem art thrombosis (5%), paradoxical htn (2%), transient neuro event(1.5%)
-CoAo Stenting
-reduces risk of restenosis and late incidence of aneurysm
-very effective at reducing risk of SBP grad (to<5mmHg)
-may help some w transverse arch hypoplasia
-but they must be redilated as the child grows
Prognosis
-Good Px, expect Nl growth/dvp
-minimal phys activity restrictions
-If Nl resid grad (<10mmHg) w Nl UE BP at rest/w exercise, and no Ao aneurysm--> only rec against high impact chest collision or heavy isometric exercise. +abx ppx
-Long term Px d/o if resid/recurrent CoAo occurs regardless of if Angio or Surg was used
-Evidence to show that transverse arch will grow after CoAo repaired in infancy
-recurrent CoAo usually occurs bc inadequate growth at repair site, esp if >2yo
-If resting CoAo grad is >40mmHg following repair as infant, about 15% at 5yr & 30% at 10yr of pts need reoperation
-Recent data- extended End to End anast may substantially decrease risk of recur CoAo
-Resid and recur CoAo post angio more common when performed as infant.
-late htn may occur in 10-20%, even if repaired in infancy, due to anatomic and fxl changes in art vasculature prox to the CoAo- thickening and medial hypertrophy seen in animal studies-> decr compliance and thus changes in vascular reactivity and barR' reflex fx. Can also see dynamic SBP htn w exercise even if Nl baseline BP.
-Ao Aneurysm at repair site- highest w prosthetic patch, but also w other surgeries (24% of pts seen 1-19 yrs p patch aortoplasty
-Other xx- Ao dissection (even w/o aneurysm, inc w Turnurs), intracranial hem (maybe bc of inc berry aneurysm), diminished L arm growth post LSC flap --> arm claudication w exercise and decr growth; or subclav steal synd- if vertebral artery remains intact distally
-Bacterial endocarditis/endarteritis
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