Truncus Arteriosus (M/A)

-usually isolated

-some assoc w 22q11del, maternal DM

Embryology:

-Embryonic TA is bn conus cordis and Aortic Sac & Ao arches distally

-TA partitioning is closely related to conal and Ao-Pulm separation

-Truncus Swellings divide the truncal lumen--> Proximal Asc Ao, & Pulmonary Trunk

-Proximal part of the truncal septum fuses w the conal septum (derived fr conal swellings), and the RV origin of the pulmonary trunk, and the LV origin of the Ao are established.

-At site of fusion bn truncus and the conal septum, valve swellings dvp fr the truncus, and form the Ao & Pulmonary Valves

-At Ao Sac, the 6th Ao Arches (primitive PA's) move leftward, and the paired 4th Ao Arches move right

-The Ao Sac roof invaginates to--> the AoPulm septum, which fuses w distal end of the truncl septum

-R & L PA's originate fr the pulmonary trunk, and the Ao Arch comes fr Asc Ao.

-The truncoaortic partition spirals to --> the Nl intertwined GA's

-Truncus Arteriosus = single art trunk fr heart

-bc defic/absent conal (=infundib) septum to --> large VSD

-bc conal septum contributes to --> ant tricuspid leaflet & med tricuspid pap muscle, they will also be malformed

-The single truncal valve may be malformed, regurgitant, or stenotic

-PA's can arise fr a short pulm trunk together, if there had been some distal truncoarotic septation, otherwise they arise separately fr the truncal root

Path:

-Single artery to --> coronaries, PA's, systemic arteries

-Single semilunar valve

-This is what DDx fr Ao & PA atresia (where 1 artery also gets both CO's)

-Types (Edwards)

-I (50-70%) = short pulm trunk fr the TArt, then --> 2 PA's

-II (29-50%) = both branch PA's arise separately fr TArt, w no MPA, and arise close to each other

-III (6-10%) = " " " " " " ", " " ", and arise far from each other

-IV = PAtresia + VSD (new type, not discussed here, see other chapter)

-Van Praagh Classification

-Type A1 = Edwards Type I

-Type A2 = Edwards Type II & III

-Type A3 = one of the PA's don't arise fr the TArt, but gets Q fr the PDA/collaterals

-Type A4 = underdvpd Ao Arch (tubular hypoplasia, discrete CoAo, or complete interruption)

-VSD

-usually large, bc absent/defic infundib septum, bn the 2 limbs of the septal band, roofed by the truncal valve cusps (see pic)

-Usually, the inf limb of the parietal band is fused--> muscular discontinuity bn the TV and the Truncal valve. Thus, the membranous septum is intact; it's an infundib VSD

-If there is no such fusion, then the tricuspud vlv is in continuity w truncal valve, and defect will involve membranous septum, and thus is both membranous & infundibular.

-Rarely is the VSD small/restrictive or even absent

-Truncal Valve

-Usually tricuspid (70%), or 4 cusps (22%), rest mainly bicuspid but some 5 cusps.

-It is in fibrous continuity w mitral valve in all pts

-It is in fibrous continuity w tricuspid valve only in some (if the septal band didn't fuse w parietal band)

-Usually biventricular origin (70%), w most of the rest fr RV, and some fr LV only

-Truncal Insufficiency

-thick/nodular dysplastic cusps, prolapse of unsupported cusps/conjoined cusps w a shallow raphe, unequal cusp size, minor commissural abNly, or annular dilation.

-Truncal stenosis

-usually w nodular/dysplastic cusps

-Truncal root often dilated, and sinuses often poorly dvp'd

-Ao Arch

-R Ao Arch in 20-35%pts (2nd only to PA+VSD)

-Arch hypoplasia +/- CoAo in 3%

-Interrupted Arch in 10-20%pts, w ductal continuity of the Desc Ao; esp w DiGeorge

-DA

-absent DA in 1/2 pts!!, but if present, 2/3 of these pts will have PDA

-Larger DA correlates to smaller Ao and vice versa (e.g. big PDA if small Ao...)

-Shiraz: presence of PDA- nearly always see an interrupted arch or a PA off the PDA

-PA's

-Usually fr L Post side of the TArt

-In type II, LPA os is usually higher than RPA os

-Rarely are their ostia stenotic

-Thus, unless you band the PA's, the lungs will be exposed to systemic pressures

-Rarely, deformed truncal valvar tissue will obstruct pulm ostia w ventric systole

-One of the PA's may be absent (16% in one series), more often on same side as the Ao Arch

-DDx- w TOF the PA is often absent on side opposite the arch

-Coronaries

-Important to know their origin/course for surgical prep; much variability

-LAD

-often small and displaced to the left, --> RCA conus branch compensates and is prominent, supplying some large branches to the RVOT (Important bc this branch might get in the way of a conduit...)

-Post Desc CA's arise from L CMX (=L cor dominant) in 1/4 pts (3x the usual rate for Nl pts)

-1/3-1/2 of pts w TArt have coronary ostial origin

-LCA tends to arise fr L post-lat truncal surface, & RCA fr the R ant-lat surface

-Single Coronary Artery

-All 3 epicardial branches fr one common site, or RCA is absent

-2 Ostia

-both might arise fr the same sinus, one may be fr a noncoronary sinus, or may be Nl...

-Often high origin, above STJ, can be slitlike

-Rarely, LCA might come fr the pulmonary trunk

-Conduction Tissue

-SA nd & AV nd are usuually Nl

-AV bundle- runs to the L of the central fibrous body,

-LBB emanates along the LV septal subendocardium, just beneath the membranous septum

-RBB runs within myocardium of ventric septal summit, stays subendocardial at level of moderator

-If the membranous septum is intact (bc VSD is infundibular), the AV conduction tissue is somewhat distant fr the rim of the defect. But, if the pt has combined membr-infundib VSD, then the conduction tissue passess along the L side of the posterior-inf rim of the defect.

-Secondary xx

-biventric hypertrophy, dilated venricles if TArt regurg, ch subendocardial ischemia if much hypertroph

-pulm htn if prolonged exposure to systemic pressures

Sx/Si:

-Usually fetal/neonatal Dx

-Initial high PVR--> mild cyanosis, and may resolve w decr PVR/weeks

-But, tachypnea/tachycardia/diaphoresis/poor PO/other pulm overcirc Sx can start as PVR drops

-W incr Qp, --> vol load on heart

-If there is natural PA stenosis (uncommon), cyanosis at birth may incr w age, but it can protect pt from pulm overcirc as PVR drops.

-Can have sev cyanosis + pulm overcirc Sx/heart failure Sx--> can present early if pt has PA stenosis and sev TArt vlv regurg.

PE

-Bounding periph pulses- bc of runoff into pulm vasc bed during diastole

-L precordial bulge

-Systolic thrill common at LSB

-"Overactive heart"

-Nl S1, w ejection click (w the maximal opening of truncal valve)

-S2 loud & single

-S3 common

-Loud pansystolic murmur, loudest at LLSB w rad all over; apical diast low pitched murmur bc of incr Q thru mitral vlv

-If TArt Regurg, usually--> diastolic high pitched murmur, loudest @ LSB

-Continuous murmur (uncommon)--> c/s PA ostial stenosis

-Consider DDx: PA+VSD bc of PDA or collaterals--> continuous murmur

-If Heart Failure--> tachypnea, rales, hepatomegaly, neck vn distention

-+Cyanosis, clubbing if decr Qp bc of PA stenosis, PA band, or pulm vlv dz

-If no TArt Regurg: Nl periph pulses and PP if there's, no diastolic murmur, and less Sx of hrt failure...

ECG:

-minimal RAD -NSR w Nl conduction times

-combined ventric hypertrophy

-Prominent LV forces if incr Qp

-LA Enlargement common

-RVH alone if Nl/decr Qp

CXR:

-moderate CM, incr pulm vasc markings

-R Ao Arch in 1/3 pts

-Thus if u see R Ao Arch + incr pulm vasc markings--> c/s TArt

-Type I- often see ~ superior LPA location prox'ly

-Dilated truncal root

Echo:

-Subcostal

-check abdominal/atrial situs, cardiac apex position

-see single GA fr heart (see pic)

-check for ASD

-check TArt vlv fx

-check Truncal root & PA branch anatomy

-PSLA

-check VSD, overriding Ao

-see continuity bn truncal vlv and mitral vlv

-see Pulm trunk origin/branches fr slightly higher view

-High PSSA

-See PA's arise directly fr post-lat side of truncus, w bifurcate to R & L branches...

-Check for a short MPA (Type I), or separate PA's fr truncus (Type II), single PA off trunc (III)

-PSSA

-Check truncal leaflet anatomy (#/morph)

-Check coronary anatomy

-Check VSD location/extension

-Suprasternal

-Check Arch anatomy- interruption/hypoplasia, R Ao Arch

-Check PA branches, r/o branch stenosis

-DDx an AP window w echo

-AP window- not assoc w VSD, RVOT and pulm vlv are in Nl positions; can see the window w high parasternal view

-Doppler- check degree of Truncal vlv stenosis, check for regurg

-If regurg+, the Doppler may overestimate amt of stenosis bc of the increase volume across the vlv

-check for flow reversal at abd Ao, bc of PA runoff or truncal vlv insuffic

Cath/Angio:

-usually not needed, but may need to check AO arch (if interrupted) or PA tree (if single PA)

-might need to check PVR

-If pulm art resistance >8unit/m2 --> higher operative risk; w late deaths due to pulm vasc dz and qy sev phtn w RV failure

MRI:

-helps assess anatomy/hemodynamics

DDx:

-TArt + incr Qp << CHD w early heart failure and cyanosis

-VSD, PDA, AP window, PA+VSD, PDA, large collats, DORV, univentric heart, TAPVR

-TArt + decr Qp<<

-PA, TA, TOF, univentric hrt w PS, DORV w PS

NHx:

-Some survive to adulthood w/o surgery, but usually most die by avg 5 weeks old; 15% survival at 1yr

-Die fr heart failure; also phtn & infective endocarditis

-rapid decline p phtn starts

-thus, Tx early!

Tx:

-Delaying OR --> ch ischemia of hypertrophied heart, (esp bc the blood in coronaries is desaturated bc of mixing, and the diast P is low bc of runoff to PA's & bc of TArt regurg)

-Thus repair at 6-12mo --> 2x mortality risk than for 6wk-6mo old

-Pulm vasc dz can dvp early, so correct at <few months old, as it plays big part in mortality

-Goal = complete repair as a neonate

-PA band may be needed but it can be risky, and a good band doesn't mean they'll make for a good surgical candidate later on...

Surgery

-1st done in 1967 w an Ao homograft bn RV to PA's

-by now, operative mortality is 5% if pt doesn't have severe assoc xx

-Pt will get conduit placed as neonate, then need replacement later on w bigger one, but replacement has a low risk

-Most surgeons prefer a valved conduit bc of the presence of phtn

-For conduit replacement, M/A Preference = Peel Operation = Autologous tissue reconstruction to reconstruct RVOT:

-Place a prosthetic roof (bovine pericardium) over the fibrous bed of the explanted conduit, and insert a prosthetic valve.

-If TArt Regerg--> usually amenable to repair, so don't need to replace as a neonate

-suture the prolapsing leaflet to adjacent leaflets (easier bc they are usually thickened)

-Late results d/o degree of TArt regurg and the need to replace the conduit

-may need to repair TArt regurg that dvps later in life...

-In one study, 25yrs post op- if there was trivial/no regurg at time of correction, they didnt need to get truncal valve replaced

-Late problem of an extracardiac conduit-

-must be replaced as pt grows; deteriorating conduit, Calcification

Long Term Issues:

-Need life long f/u

-+SBE ppx needed