PDA & AP Window (M/A)

PDA & AP Window (MA33)

PATENT DUCTUS ARTERIOSUS

Anatomy:

-fr distal L 6th Ao Arch, connects MPA to Desc Ao, 5-10mm distal to LSCA origin

-if R Ao Arch, PDA may insert on R, joining the RPA and R Ao Arch just distal to RSCA, but usually it's on the L, joining the LPA and prox part of the LCSA

-PDA's media layer is made of smooth muscle arranged spirally in both L and R directions, w incr amts of hyaluronic acid, while the Ao/PA have more elastic fibers at medial layer

-PDA's intimal layer is thicker than the arteries, w incr amt of mucoid substance, and there are small subendothelial vessels in the PDA

Physiology:

-Fetal Role- dvpd by 6wks GA, carrying most of the RV output. RV ejects 2/3 of the combined CO bc the Qp is only 6-8%, so the DA carries 55-60% of the combined cardiac output

--> divert flow away fr lungs (high resistance) to Desc Ao and low resistance placenta

--> reduce total workload bc fetus doesn't waist energy pumping to lungs

-Prostaglandin (PGE2) and Prostacyclin (PGI2) --> relaxation

-Postnatal Closure- 2 phases:

-Immediately postnatally (<12hrs old)- contraction & cellular migration of med sm muscles in DA--> shorten it w incr wall thickness, thickened intima protrudes into lumen w cushions--> fx'l closure

-Then, by 2-3 weeks old, endothelial infolding, internal elastic lamina disruption/fragmentation, subintimal layer prolif and hemorrhage/necrosis, cushions enlarge and CT formation replaced muscle fibers--> permanently seal the lumen--> form Ligamentum Arteriosum

-? exact mech for closure

-there is incr pO2 in PDA postnatally (as GA increases, the fetus is more responsive to pO2)

-ACH, bradykinin, endog NE/E may also --> closure

-Prostaglandins- COX mediated product of Arachidonic Acid metab

-PGE1, PGE2, PGI2 dilate DA's, while inhibitors of these constrict DA's

-PGE1 is made 10x more than PGE2 but PGE2 is 1000x more powerful to relax PDA

-PGE is made by placenta w higher [ ] as fetus, so at birth w loss of placental PGE, and w incr Qp (allows for removal of PGE2 in circulation), tips toward closure...

-Indomethacin- constricts rings of DA, more effective in premies (in lambs)

Persistent Patency of the DA:

Physiology of maintaining patency

-DA Sn to PGE2 decreases as GA increases, and lost shortly after birth at term; pulm metab important bc it clears PGE2

Physiology of L-->R Shunt

-d/o: PDA diameter, PDA length, and P difference bn Ao & PA & PVR/SVR

-Postnatally, SVR is high and PVR dropping as ventilation starts, so syst art BP > PAP

-w small PDA--> high resistance so only small L-->R shunting, even if big P gradient

-w large PDA--> Pressures equalize and the amt of shunting is determined by the PVR:SVR

-bc SVR doesn't change much postnatally, PDA shunting d/o PVR mainly, esp @ 0-2mo

-LV output is initially high postnatally, but increases even more bc the Q goes in part to lungs and back to LA--> increased LV preload (LV vol OD)--> incr LV stroke volume (Frank Starling mech) & LV dilation which --> incr LVEDP which then incr LAP--> L heart failure w LA dilation and pulm edema. RV failure if large PDA w phtn or pulm edema and incr LAP (via high PVR)--> pressure OD R heart

-L-->R at PFO fr big LA commonly seen

-Compensation:

-Frank Starling mech

-sympathetic adrenal stim (local nerves within myocardium and adrenal glands)

--> incr HR and force of contraction (and also diaphoresis seen)

-myocardial hypertrophy

-these mechs are less well dvpd in younger/less term infants (e.g. symp stim matures at term), same w Frank Starling mech; premies have lower [Ca] serum, which may affet performance, SO premies w PDA get LV failure earlier than older/term pts

-myocardial perfusion- cor Q is mainly at diastole, d/o P grad bn systemic arteris and intramyocardial diastolic P, and the duration of diastole.

-so, -decr in Ao diastolic P bc of a large PDA w big shunt to lungs

-incr LVEDP bc of LV vol OD--> incr subendocardial intramyocardial P

-incr HR so less diastolic time

all contribute to decr Q coronaries

-also, coronary DO2 d/o O2 content in arterial blood. low Hgb (e.g. physiologic anemia of newborn), espec if premie or blood draws..., and bc of fetal Hgb has higher O2 affinity so less delivery

-Effects on Pulm Circ & Lungs

-if large shunting, then systemic and pulm art P will be =

-the high Q and high P --> small pulm arts don't mature correctly, so the medial sm muscle doesn't regress as rapidly as Nl or as much as Nl, so the PVR drop is slower & less complete

-initially the high PVR is bc of the incr amt of medial sm muscle, but then true pulm vasc dz sets in which = intimal damage w cell prolif, hyalinization, and then thrombosis/fibrosis of small pulm art

-w more small pulm art xx, the PVR increases so less L-->R, and then you get R-->L

-w severe pulm vasc dz, Arteriovenous Malformations form, can --> hemoptysis

-Pulm Edema common in premie infants w even just a moderate shunt and not sev heart failure

-cap permeability is higher in newborn, ?espec premies, so small incr in pulm vn P--> edema

PDA in Preterm Infants

-common issue as premies get younger GA

-45% of pt <1750gm BW have clinically evident PDA, 80% if <1200gm BW

Sx/Si:

-PDA in Preterm pt w Little/No Lung Disease

-hear murmur at 24-72 HOL, as L-->R increases it gets louder/longer, extending to S2 or beyond

-@LSB 2nd-3rd IS

-instead of hearing the continuous machinery murmur as w older kids, in premies- hi freq "rocky" M

-P2 moderately accentuated

-mid diastolic rumble bc incr diast Q at MV, heard at apex

-incr precordial activity, incr PP, so bounding periph pulses

-if large shunt, may see LV failure w incr HR, RR, rales fr pulm edema, decr art PaO2, then apnea and sev bradycardia, and also big liver (late)

-ECG-eventually would show LC and LA hypertrophy, CXR show big heart fr LA and LV w bigger shunts, and incr pulm vascularity.

-on echo check LA:Ao ratio (Nl 0.8-1) if >1.2 c/s LA enlargement, usually = signif L-->R (unless LH obstructive lesion...)

-Many pts can be managed w Rx to constrict the DA (indomethicin) and w CHF Rx- diuretics, fluid restriction, Hct>45%; surgical need is rare. Left alone, the PDA usually closes by 2-3mo old.

-PDA in Preterm Infant Recovering from Lung Disease

-s/p moderately sev to sev resp idstress, usually weigh 1000-1500gm at birth

-the postnatal RDS improved by DOL 3-4 usually. As it improves the the L-->R shunt thru PDA becomes more apparent. Also at this age we start to incr amt of fluid intake for caloric intake, worsening the volume OD on the LV. During the acute RDS, PVR was high, and now as it drops w recovering lungs, there is more L-->R at PDA. As lung dz improves, oxygenation (PaO2) should improve--> constrict PDA, but espec in premies, it doesn't in many pts.

-Note that you might not hear the murmur if pt is on a vent or CPAP (SO TAKE THEM OFF W EXAM)

-murmur may be intermittent over a few days as lungs get better/worse and PVR changes

-may hear only systolic murmur, then continue to diastole

-may hear S3

-P2 will already be loud usualy bc of the pulm dz, then louder as shunt increases

-precordial activity increases--> indicates magnitude of shunting

-see incr in HR, PP, and decr in diastolic P as L-->R increases

-Rales are not reliable for pulm edmea and L failure bc the CPAP can suppress rales

-apnea w bradycardia common

-deteriorating resp status may be bc of worsening PDA shunt, though must PTx, sepsis, etc

-echo helps ddx Sx fr PDA vs lungs

-see incr LA:Ao ratio

-PDA in Preterm pt w Associated Lung Disease

-sev RDS fr birth, many VLBW (<1000gm), so very high chance of PDA (>80%)

-Sx of L-->R common

-failure to improve at an age when they should have recovered fr the lung dz

-very Sn to small incr in Na and fluid intake

-incr vent/CPAP need then expected

-often incr pCO2

-murmurs often hard to hear, may have no murmur w fully patent PDA

-increasing precordial activity, bounding pulses, and widening PP fr L-->R

-if +murmur, usually systolic only, w P2 loud and a gallop

-Tx:

-Confirm Dx:

-check echo, r/o other CHD

-retrograde Ao Q --> decr Qs--> moderate hypotension common, can --> decr Q to organs

-decr Q cerebral--> IVH; renal fx, myocardial Q espec subendocardial Q

-NEC fr bowel ischemia a big issue (?if true connection, not proven)

-Ensure H&H appropriate for best DO2 (goal Hct>45%)

-HgbF is problematic, but w all the bld tests you often get rid of much of it (?really?)

-Maint elecs, glucose, nutrition. caloric intake can be a big issue, but be careful to avoid volume overload which can --> LV failure, also avoid Na intake...; diuretics PRN

-Surgical closure at <10 days old--> decr ventilation support duration and hosp stay, and morbidity

-Indomethacin--> constrict PDA - best if <10 days old, and better in less mature infant

-commonly give 0.2mg/kg NG or IV x1

-if initial Tx is at <48HOL, then give 2 doses of 0.1mg/kg for next 2 days

-if initial dose is at DOL2-7, give 0.2mg/kg for next 2 days

-if initial dose is at DOL>7, give 0.25mg/kg for next 2 days

-give total of 3 doses, spaced q12-24 hours, d/o UOP- if UOP decr then may c/s fewer doses or incr time bn doses

-c/s a second course of indomethacin if initial improvement and then Sx recur

-Contraindications: Renal fail w Cr>1.6, BUN>20, bleeding, shock, NEC, or any suspicion of these

-or evidence of myocardial ischemia by echo

-Side xx- oliguria, hyponatremia (both usually transient), more severe if signif fluid restriction

-Motrin may be just as good as indomethacin on recent meta-analysis w less renal xx, but may incr phtn risk

-Usually go to OR if fail Rx Tx by 48-72hrs of Tx--> ligation, not division of PDA

PDA in Term Infant

-fx'l closure usually complete by end of DOL1, it could be delayed a few days, w L-->R as PVR drops, so you might hear a murmur within hours of birth

-cresc syst murmur or cont murmur w cresc systolic and diminuendo diastolic parts

-both gr 1-2/6, both incr w inspiration

-both at 2nd L IS, without wide radiation

-P2 is Nl bc PAP is Nl

-As the PDA closes, the diastolic part of the murmur isn't heard, and then the systolic part stops by DOL 2-3.

-ECG- Nl

-Echo- see the PDA, Doppler shows flow pattern, see NO retrograde Ao Q (bc it's L-->R)

-anything that drops PaO2 or incr PGE2 may delay closure until true closure is achieved

-e.g. asphyxial state (meconium aspiration), high altitude, etc.

-(PDA incidence is 30x more likely at high altitude (5000m) than sea level)

-initial constriction occurs more at PA side, then extends inward, so you see a cone shaped small PDA.

-Even if pulm end closed completely, the Ao end may stay open for weeks, w a ductal ampulla

-Sx/Si:

-Small PDA

-high resistance to Q so limited shunting at PDA, thus often ASx, and only Dx p Murmur

-Nl growth, full periph pulses and slightly incr PP, Nl precordial activity

-short syst murmur which can become continuous in older kids, loudest at 2nd L IS, incr w supine or w inspiration, or w things that incr SVR; starts just after S1, gets louder at late systole, and continues into early diast

-Nl or slightly prominent MPA and periph PAs on CXR

-Moderate PDA

-poor feeding, irritable, tachypnea, slow weight gain

-Sx incr until 2-3mo

-if LV failure doesn't --> signif Sx by then, then pt gets LVH to compensate, and so Sx improve much. Though on exam, pt may be smaller than expected and easily tired, incr HR, bounding pulses w incr PP, low DPB, hyperdynamic precordium, apical impulse fr LV enlargement, +/- systolic thrill at LUSB; +/-S2 at apex. Progresses faster fr syst murmur to continuous murmur; harsher and lower freq than w a small PDA, bc there's more Q so more turbulence; machinery like bc eddy sounds vary w each beat

-Hrt Failure--> murmur may stop being continuous, and only be at systole; and hear middiastolic low freq rumble at apex, with early P2. +/-soft ejection murmur bc of increased stroke vol of LV relative to Ao size

-if much L-->R shunt at PFO (now stretched) in the setting of LH failure w big LA, then can have RVH and also RV outflow murmur like w an ASD (relative PS)

-ECG will eventually show LVH w deep Q and tall R at II, III, aVF, and L precordials V5-6, may also have upright T wave in these leads w tall amp. May have LBBB, widened P wave fr LAE, RVH if phtn w tall R waves in R precordials, and tall P wave if RAE

-CXR- big heart, prominent LV and LAE, prominent MPA, pulm vasc markings incr, prominent Asc Ao

-Large PDA

-all +Sx - irritable, poor feeding, FTT, tired, diaphoresis, incr WOB, incr RR, worse w feeds, recurrent resp infections fr LH failure w pulm edema...

-rales w pulm edema, bounding pulses, wide PP unless sev LV failure w narrow PP, very hyperdynamic precordium, "thrusting" apical impulse fr LV, L parasternal impulse if RV big, +systolic thrill common, loud S1&2, +S3 at apex

-if sev LV fail, maybe no murmur at all

-hear mod-loud murmur that pks at late systole, prolongs into diastole, often ends w S3, sometimes hear the typical continuous murmur of a sm-mod PDA; +middiastolic rumble at apex

-ECG- LVH w deep Q, tall R, diphasic or inverted T waves, +/-RVH w upright T waves at R precordials and incr R wave amplitude in R precordials. LA enlargement w wide P waves

-CXR- big heart w LA and LV enlarged, MPA big, incr pulm vasc markings...

-most need Tx to survive, but some do well enough that phtn then dvps w less L-->R so improved Sx by 8-15mo, murmur shorter w/o diastolic component and middiastolic rumble stops as does S3. Decr bounding pulses, decr precordial activity, CXR improves.

-Then worsening phtn/pulm vasc dz that becomes irreversible; murmur stops, then S2 gets louder w ejection click and faint early diastolic regurg fr PR at LUSB. ECG then shows RVH w dominent R wave at R precordials, and pk'd P wave fr RAE, and CXR shows big RV, large MPA, decr pulm vasc markings. THen pt can get R-->L shunt at PDA w cyanosis (often worse at lower limbs)- first w exertion then continuously, w incr precordial activity fr RV, Nl/small PP, blowing systolic murmur fr TR at LLSB, ECG shows RAD and RVH w T wave inversion as pt ages..

-Cath- ...

-Angio- AP camera at RAO caudal

-DDx of PDA on Exam

-Venous Hum--> continuous bruit fr large venous flow in neck, but the hum varies w neck position and respiration; can be stopped w firm pressure over the neck or turning head to one side or lying flat

-TAPVR - to innominate vein can --> cont murmur like a venous hum

-Ruptured Sinus of Valsalva - into RA or RV--> cont murmur, but Sx/Si are abrupt, and often p chest trauma. murmur loudest lower in precordium than PDA

-AV Fistula- w coronary, intercostal artery, interna mammary art- can--> continuous murmur, but usually more superficial, and sound extracardiac. Also c/s hemitruncus (one PA fr Ao) or lobar sequestration (anomalous art fr Ao goes to a lung lobe), or pulmonary AV fistula but if large enough to cause murmur usually also cause cyanosis

-ALCAPA - retrograde Q fr RCA can cause continuous murmur (rare)

-Absent Pulm Valve- massively dilated PAs, w VSD; "sawing wood" murmur that's not really continuous but more to-and-fro...

-AI Assoc w VSD - w prolapse of a cusp into VSD, not really continuous but hear the syst mrumru of a VSD and the blowing regurg diastolic murmur fr AI

-PPS - soft, continuous murmur loudest at infraclavicular areas and conducted to axillae

-can be unilateral if unilateral PPS

-hard to DDx fr PDA sometimes

-Truncus Arteriosus - might not have cyanosis initiallly. W low PVR and incr Qp, may have cont murmur. C/s if you don't see the PA segment on the PA CXR, espec if +RAoARch (common w Truncus)

-AP Window - very hard to DDx fr PDA, w cont. murmur loudest lower on chest at LSB

-Pulm Atresia - would see very big bronchial arts w a continuous murmur, but usually see cyanosis and no bounding periph pulses like w a PDA...

Complications:

-Bacterial Endarteritis- less common w correction of the PDA..., fr S viridans and S aureus most often

-Aneurysm/Calcification Formation- w ampulla dilation after PDA closed, uncommon

Tx in Term Infants:

-Early correction if +Sx or complications..., soon bc minimal risk

-cath coil/device closure, or surgery; indomethacin doesn't work in term infants/older kids so don't try it

-Coil occlusion if more than a few mo old in duct <3mm diameter

-0 mortality, 97% success (using 1-2 coils)

-Device closure if larger PDA <12mm

-Amplatzer ductal occluder

-0 mortality, >98% success w closure by 6mo after placement

-Device for PDA >12mm

-AGA septal occluder, VSD device, Cardioseal device, or covered stent (?)

-Surgery Tx of choice for premies and kids w very large PDA

-divide or transsect DA thru lat thoracotomy or due via thoroscopy but ? risk of tearing and hemorrhage of large PDA espec in adults where PDA may be calcified so still limited use to date, also risk of laryngeal nerve injury

-If mod to sev incr PVR complicated decision to close PDA- should get cath first and test occlude it and see response to pulm vasodilators. If good response to either, then close the PDA. IF poor/equivocal response, then c/s not closing PDA bc it is a pop-off for phtn crisis...

AORTOPULMONARY WINDOW

-rare

-1/2 w other xx- Ao origin of RPA, type A interptd. Ao arch, TOF, RCA or LCA anom origin fr PA, RAoArch

-AP septum is made fr 2 opposing truncal cushions that enlarge and fuse to divide the TA into separate Ao and pulm channels, influenced by the neural crest cells

-Defect usually at proximal AP septum, midway bn semilunar vlvs and the pulmonary bifurcation

-size varies, but all --> large continuous L-->R shunt as PVR (like PDA or TA)

-all pts will die by teens fr phtn xx w/o Tx

Path:

-Vol OD to LV and LA, incr branch PA size fr incr Qp, small Asc Ao espec if it's very proximal

-See pic for classifications

-Type I most common- small defect bn vlvs and PA bifurcation

-Type II more distal, distal to PA bifurcation - assoc more w RPA origin off Ao

-Type III large, confluent defect of ~entire AP septum (rarest)

Sx/Si:

-Sx of large L-->R like VSD or PDA w CHF Sx by 1 WOL, no cyanosis unless very large defect causing bidirectional shunting and mixing at arterial level

-Metabolic acidosis as DA closes if Ao Arch anomalies (e.g. interrupted arch)

-PE: tachypnea, incr WOB, incr RV impulse at LSB, bounding pulses bc Ao runoff to PA, oud S2 w narrow split bc of pulm htn, +/- ejection click at P region fr phtn, or machinery like murmur like a pDA, often middiastolic rumble at apex fr incr Q thru MV

-if small defect often ASx, then Nl S2 w only a SEM and +/- middiastolic murmur at apex, w picture like a small VSD

ECG- BVH if signif size..., RVH w rsR' at R precordials

CXR- big heart, prominent pulm vasc markings, big MPA; Ao knuckle not prominent, pulm edema

Echo- Dx by echo, also in fetal echo able to see it

-dilate LA and LV, +/-RVH, Nl semilunar valves, PAs are big, AP window seen directly but don't confuse dropout for it - DDx bc APW has a "T" artifiact at edges of the defect, then check Doppler...

-Doppler- see continuous abNl fw Q in PA to indicate AP communication, not PDA bc you see fw flow in distal MPA and branch PAs (would be retrograde w a PDA...)

-see phtn, check TR jet...

Cath- not usually needed...

DDx- large VSD, large PDA, persistent truncus arteriosus; hard to DDx by exam though PDA sx are uncommon in first weeks of life, and pt w TA usually has more desaturations than w AP window and also some CHF, and at times regurg murmur during diastole fr truncal vlv regurg; VSD murmur often heard more at bottom of sternum and there's no bounding pulses