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SECUNDUM ASD's
-6-8% of all CHD (1/500 live births)
-F>M (2:1)
-assoc w upper limb abNly's; can be caused by TBX5 mutation
Anatomy, Embryology, Pathology
-Defect Anterior to FO = primum defect (often w MV cleft)
-Defect Post/Sup to FO = sinus venosus defects (often w anomalous R pulm vn connection)
-Interatrial communications at where cor. sinus usually is = assoc w unroofed CS & LA connection of a persistent LSVC
Embryology:
-Septum Primum- thin walled, starting at ant-inf free edge is above the AV canal, and gets lined by tissue from the sup and inf endocardial cushions (so the Ostium Premum gets closed by this tissue, so defect in endocard cushion --> primum ASD...)
-Before Ostium Premum closes, apoptosis at ant-sup aspet of septum primum --> cribiform perforations which coalesce into a large Ostium Secundum.
-Thus there is always blood flow bn the atria
-Septum Secundum- forms while Ost Secundum is formed from an ant-sup infolding of atrial roof, going post-inf as a thick walled muscular ridge --> partition overlying the Ost Secundum, and forming the limbus of the fossa ovalis, with the sept primum forming the valve of the FO. With the channel in between = foramen ovale.
PFO
-FO closes postnatally w incr LA P > RA P w valve of fossa ovalis pressing against the limbus, and then forming fibrous adhesions by 1yo to permanently seal.
-25-30% of ppl have PFO
-If there is also atrial dilation, the limbus gets stretched so that the limbus doesnt cover the entire ostium, acting like an acquired ASD.
-FO Defects - bc of xx at septum premum (valve of FO). They are considered Secundum ASDs bc the ost secundum appears enlarged or ungaurded. The intratrial comm'n is likely just valvar incompetence at a PFO and not a true ASD. can close w a stitch or in cath lab.
Effects on the Heart
-large ineratrial comm'n--> ch L-->R shunt ==> vol OD on R heart --> dilated RA and RV, but mural thrombus is uncommon
-Sev RV dil can --> RV forming apex, and IVS straightens so that both ventrics are D shaped on PSSA, and even can get L'ward bowing of IVS w crescentic LV
-+/- TV and PV annulus can dilate --> regurg, mildly thick
-+/- Central Pulm Artery dilation
-+/- mild LA dilation
-Nl LV size and mass
Effects on the Lungs
-Ch Vol OD --> dilate pulm vasc bed--> engorged vessels/medial hypertrophy at arts/vns w muscularization of arterioles, but usually reversible phtn
-Plexiform obstructive lesions
-Thrombotic obstructive lesions
-If an older pt also has a ch pulm vn htn bc of LVH or LV failure, or ch hypoxic pulm htn (bc COPD, ch interstitial dz) --> may worsen pulm vasc dz assoc w the ASD
Physiology:
-Q at ASD d/o Compliance of ventricles
-RV more compliant usually, so less resistance at RA, so more L to R shunting
-Infant: RV thick, stiff, poorly compliant, so minimal L-->R, but by first weeks of life, PVR drops so RV ore compliant and L-->R increases
-Most infant w just an ASD are ASx, but some have --> heart failure reported (!) but cath data in these pts are like Nl pt w ASD so ? why they fail... These kids often have dev delay, FTT, etc, that don't improve w ASD closure.
-->Incr Qp so that Qp is 3-4x Qs, but only slight incr PAP, with PVR still Nl usually
-Hemodynamics vary widely- pulm vasc obstructive dz in kids as young as 2mo in some reports
-one study: 6% had pum vasc obstructive dz, mostly female
-Can have sev cyanosis bc of a pulm vasc obstructive dz (uncommon)
-If large sinus venosus valve, eustachian valve, thebesian valve, may direct IVC Q accross ASD==> cyanosis; seen on echo
Sx/Si:
-Most ASx
-6-8 week old w soft SEM +/- wide split S2
-most Dx at about 6mo by echo bc of murmur heard
-Older kid w mod L-->R usually ASx
-if large L-->R, ==> tired, dyspnea
-FTT unlikely, but can have FTT, recur LRI, heart failure
-+/- precordial bulge and hyperdynamic impulse, esp in older kids w large shunt
-prominent systolic impulse on precordial palpation
-Ausc:
-wide and fixed S2 split - bc P2 delay bc prolonged RV emptying bc incr vol, and pulm vasc dil'n
-soft SEM at L 2nd IS - bc incr Q thru plm vlv; transmit to lungs bilat,
-early to mid diast murmur at LLSB - bc incr Q thru TV
-If signif phtn, then --> less ausc Sx, can have loud P2 w/o split, and shorter syst M w no diast M
CXR:
-big heart w cardiothoracic ratio >0.5, incr pulm vasc markings bc engorged PA's, esp in older pt
-if phtn, then see big MPA and oligemic periph lung fields
ECG:
-Some older pts may have SVT, aflutter
-mean QRS axis +95 to +170,
-+/- prolonged PR, esp older pt, bc intra=atrial and H-V conduction delay --> 1st deg AVB
-1/2 of these, the P waves are tall bc RAE
-usually some rsR' bc Incomplete RBBB in V1, bc RV vol OD, but QRS <0.1sec, & R' at Vi may be prolonged
Echo:
-Incr RA and RV size
-See ASD best at Subcostal
-May need TEE in older pt for Dx, esp if poss assoc PAPVR
-PW for shunting..., blood fr L-->R usually starts in midsystole, and its velocity decreases progressively until early diast, when atrial contraction accentuates teh L to R shunt
-at early ventric systole, there can be transient R to L shunt
Cath:
-not needed
-see RA sats higher than SVC/IVC
...
NHx:
-benign, unless it is a very big opening
-may be ASx through 50s or more if moderate ASD
-2nd ASD may close by self or get bigger or not change
-up to about 20% will close on their own in one older study, most that closed did so by 4yo
-Up to 24% of newborns have some AS opening at 1st week of life, but92% had closed by 1yo, more likely if it was <7-8mm and if younger at Dx
-Rec no f/u if it is <3mm bc all pts w this size had closed; but if >3mm rec f/u at 12mo & 15mo
-Some (even <3mm initially) can grow w time
-CHF rare early on, but common by >40yo, and can have afib/flutter, (13% at 40yo, 50% at 60yo)
-5-10% of pts w untreated ASD will get pulm vasc dz (mainly women), usually at >20yo
Tx:
Surgical-
-usually elective repair at 4yo (wait to see if close spont'ly)
-Close as an adult? Unsure, mixed results..., may have earlier mortality, but could be bc healthy ppl were lost to f/u..., one study found no diff w med or surg Tx...
-ASD closure is safe (0.4% mortality) for secundum or sinus ASD (9 pts, 6 were infants)
-Usually approach via median sternotomy, but a partial sternal split w limited incision may be enough...
-Late Outcomes
-97% survival at 5yrs postop, 90% at 10yrs, 74% at 30yrs, VERSUS 99%, 98%, 85% in control persons
-57% of pts >24yo had late fatal/nonfatal CVAs, compared to 15% if <24yo at Tx
Cath-
-First done in 1976 w a double umbrella, 50% success
-Then used Rashkind ASD Occluder and Lock-USCI
-Then used Clmashell Occluder, CardioSEAL device, Sideris Buttoned Device, ASD Occlusion System, Das-Angel Wings occlusion device, and teh Amplatzer Septal Occluder
-xx = residual ASD, fx of hardware, embolism of device, large delivery, too small for the ASD
-Amplatzer is only FDA approved device (since 12/2001)
-f/u p ~6yrs: complete closure, no deaths, no signif xx at 3yrs post
-other reports- erosion, thrombus formation (0.1% erosion risk in US 1/2% risk of thrombus), and temporary AV block also seen- resolved by 6mo post
SINUS VENOSUS ASD's
-5-10% of ASDs
-@ post and sup to FO
-usually a defect rimmed by atrial septal tissue only ant-inf
-Post aspect is the RA free wall, and sup border is abscent bc of SVC overriding
-assoc w R pulm vn anom return - to RA or SVC near the caval-atrial jct
-Preop ECG- 1/2 pts have frontal P wave axis <30 degrees
-so if +auscultation and +ecg, c/s SV ASD strongly
-Echo- check septum..., can be hard to see w tte, but c/s it if u see turbulent Q in SVC or a vol OD to RA or RV w/other explanation. c/s TEE if needed
-if a high SV defect w PAPVR, then must do repair w a tunnel connecting anamalous vn return with the ASD, w an autologous pericardial patch
CORONARY SINUS ASD's
-rare
-@ inf and ant to fo where CS ostium should be
-related to unroofing of CS and a persistent LSVC that joins the roof of the LA
-+/- assoc AVSD esp in asplenia syndrome
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