Chap 28	ASD
INCIDENCE	8% to 10% of CHD in children 75% ASD2 + 20% ASD1 + 5% SVASD + Coronary sinus ASD (more often seen with heterotaxy syndromes and systemic venous anomalies, and isolated CS ASDs are rare (<1%)
	F:M ratio for ASD2 is 2:1 but for the sinus venosus ASDs it is 1:1
GENETIC RISKS	A woman with ASD has 8% to 10% of having a child with any CHD
	Heterozygous mutations in TF NKX2.5/CSX were among the first found in families with auto dom ASD2 Mutations in other TFs such as TBX5, GATA4, GATA6, and TBX20 also associated with ASD2. TBX5 mutations also are responsible for Holt-Oram auto dom  with ASD2 + missing forearms + AV conduction delay A locus on chromosome 14q12 with a missense mutation in alpha-myosin heavy chain (MYH6), a structural protein expressed at high levels in the developing atria, has been linked to dominantly inherited ASD ASD2 also have been reported with cardiomyopathies from mutations in sarcomeric genes
	ASD2 also are associated with Noonan, Down, Klinefelter, Williams, Kabuki, Goldenhar, and Ellis-van Creveld.
ENVIRONMENTAL RISKS	gestational diabetes, PKU, influenza and exposure to retinoids, NSAIDs, anticonvulsants, thalidomide, smoking, and alcohol (ASD and VSD)
PATHOGENESIS AND ANATOMIC FEATURES	In the 4th week of embryonic life, the septum primum appears à 5th and 6th week of embryonic life, before complete closure of the ostium primum, tissue reabsorption occurs in the superior portion of the septum primum resulting in another opening called the ostium secundum
	The septum secundum thus forms the concave-shaped superior margin of the fossa ovalis, called the limbus of fossa ovalis (from RA side) and the septum primum forms the valve of fossa ovalis (from LA side)
Eustachian valve	IVC flow from the placenta (oxygen rich) is deflected toward the foramen ovale by the eustachian valve
4 types of ASDs	D: 1= secundum ASD, 2 = primum ASD, 3 = superior SVASD, 4 = CS ASD
ASD2	ASD2 occur in central part of the atrial septum (fossa ovalis) as a result of deficient valve tissue, ectopic or excessive resorption of septum primum, or deficient growth of septum secundum ASD2 also reported in association with noncompaction and apical hypertrophic cardiomyopathy ApHCM (a rare variant of HCM, described in Japanese, with usually no increase in sudden death, although study in Toronto found that 30% have significant cards morbidity like MI 10% or arrhythmias like A fib 12%)
SVASD	SVASD defects occur outside the margins of the fossa ovalis, in relation to the venous connections of the RA   Ectopic or incomplete resorption of sinus venosus = deficiency of wall btw right Pveins from the SVC, IVC, and RA Most commonly, SVASDs are related to SVC where blood from the RUPV or RMPV is directed into SVC or the RA. A similar defect can occur inferior to the fossa ovalis in relation to the IVC and RLPV orifice = IVC-type SVASD, although direct involvement of the IVC almost never occurs. Hence, the term RA-type SVASD is preferred
CSASD	The CS defect (unroofed CS) results from failure of the wall between the LA and CS to develop. There may be complete or partial unroofing of the CS resulting in direct communication with the LA. Almost always, this anomaly is associated with a left SVC. Rare complete absence of the CS rather than unroofing, blood from the left SVC directly enters the LA.
ASSO ANOMALIES	ASD can be crucial for survival in some such defects such as HLHS, D-TGA, tricuspid atresia, and TAPVR (all cyanotic
Lutembacher $	association of often large and unrestrictive ASD with MS of rheumatic origin à LTR shunt is augmented from MS
PATHOPHYS	After birth, the lungs expand and the PBF increases. The increased pulmonary venous return to the LA results in the left atrial pressure exceeding the right atrial pressure causing functional closure of the foramen ovale. The primary determinant of the magnitude and direction of the shunt is the relative compliance of the ventricles. During neonatal transition as the PVR drops and RV becomes thinner and more compliant à more LTR shunt Max LTR shunting occurs during diastole (all 4 cardiac chambers in communication). Atrial kicks increase shunting. During inspiration (drop intrathoracic pressure) = less blood returns to LA à decrease LTR shunt across the ASD Conversely, during expiration, gradient across ASD higher from more LTR shunting Moderate-to-large LTR shunts across an ASD à volume overload and dilation of the RA and RV à cause TR and PR + septal bowing toward the left à abnormal LV geometry à possible MVP increased flow into the lungs à pulm veins are dilated and there can be flow-related pulmonary artery HTN + medial hypertrophy of PAs and muscularization of the arterioles resulting in PVOD With severe PVOD, patients develop Eisenmenger syndrome (RTL) = resulting in cyanosis + syncope with exertion
History	Most patients with ASD are asymptomatic and may remain undiagnosed until later in life. Very rarely, some infants with ASD present with pulm overcirculation, recurrent LRIs, and FTT. Worse if MS or MR. Despite repair of ASD in these patients, there may not be any significant improvement in their symptoms
Physical Examination	In patients with long-standing large LTR shunt, there is a left precordial bulge, prominent RV impulse along LLSB In normal hearts: during inspiration, increased venous return into the right side of the heart à delayed P2 wide, fixed splitting of S2 = no variation in degree of splitting during inspiration or Valsalva S2 is “fixed” since the increased RV stroke volume does not vary much with respiration A SEM due to increased flow across the pulmonary valve (systolic ejection click means pulm valve is truly stenotic) When there is a large LTR shunt, a middiastolic murmur (short, soft, low to medium in frequency, and localized to the left lower) can be heard due to excessive flow across the tricuspid valve. cyanosis can be seen in those with pulmonary HTN, significant RV outflow tract obstruction, or in rare cases of a large eustachian valve directing IVC blood into the LA via the ASD
EKG	large ASD2 showing rSR’ pattern in lead V1 and V2 and terminal widening on S in lead V6 indicating RV volume overload
with SVASD	a frontal plane P wave axis of < 30 degrees is seen
With pulmonary HTN	the rSR’ pattern in the right precordial leads is replaced by Q waves and tall monophasic R waves with deeply inverted T waves (like in ischemia)
older ASD2 patients	usually >20s, can have junctional rhythm or atrial arrhythmias such as atrial fibrillation or atrial flutter.
EP	AV node dysfunction is less common than sinus node dysfunction. First-degree AV block can occur in older individuals as a result of intraatrial H-V conduction delay and in patients with a rare autosomal dominant form of secundum ASDs
Chest X-Ray	dilated RV - increased pulmonary vascular markings extending to the periphery are seen in patients with significant shunts. proximal branch pulmonary arteries, also are dilated, especially the RPA If pulmonary HTN develops à oligemic lung fields
Echocardiogram	defining the type of ASD, its size, the degree of shunting, its effect on the right sided chambers of the heart, associated lesions, and estimations of RV pressure.
2D + M-MODE	Subcostal views provide the best profile of the atrial septum since the ultrasound beam is perpendicular to it. In apical views, a “drop-out” may be seen = a false appearance of an ASD PFO is guarded by a flap valve on the left side and limbus of fossa ovalis to the right. Sinus venosus defects are seen superiorly at the junction of SVC with the RA large ostium of the CS is seen as an inferior interatrial communication, just above and anterior to the entry of IVC into RA overloaded RV causes diastolic flattening and paradoxical motion of the interventricular septum – shown on M-mode
DOPPLER	shunt usually is left to right, nonrestrictive = low-velocity flow Qp:Qs can be estimated = the time velocity integrals obtained by tracing the pulsed-wave Doppler of pulmonary and aortic outflow are multiplied by the area of PV and AV, respectively (unless there is RVOTO, PDA, or AR or PR) If PV flow gradient > 30, need to suspect additional pulm valve stenosis PA pressure can be estimated by PR jet + RVEDP Pulm HTN would make TR and PR worse à RVH will make RV systolic function worse
TEE	allows better spatial resolution à adjunct for operative and percutaneous closure of ASD. particularly useful to detect a SVASD, which easily can be missed using transthoracic imaging.
Contrast echo	LTR shunt is seen as a negative contrast washout into the RA when opacified with contrast (augmented with Valsalva) in unroofed CS, injection of contrast into left arm will have bubble in LA before RA
3D echo	en face view of the entire atrial septum for transcatheter device closure
ICE	device closure of ASDs, advantage of eliminating the need for general anesthesia for TEE but require large size sheath
Cath	a step-up in oxygen saturations in RA from LTR shunt (same when LV to RA shunt or a VSD + TR) When the Qp:Qs is ≥1.5, the shunt is considered significant. PVR can be calculated = (mean PA pressure – mean LA pressure or wedge)/Qp or cardiac output
CT/MRI	used to define the CS type of ASD, which can be particularly challenging to recognize using routine echo in adults Velocity-encoded, phase-difference MRI measurements of flow in the proximal great vessels has been used to noninvasively measure Qp:Qs with results comparable to those obtained by cath
Exercise Testing	Even though most patients with ASD are asymptomatic, their exercise capacity may be decreased. Closure of an ASD may improve exercise capacity in adults who were asymptomatic or mildly symptomatic helpful in documenting O2 sats during exertion if PHTN, though maximal exercise is not recommended if severe PHTN
Natural History of ASDs	most defects <5 mm recognized during infancy are likely to spontaneously close, but > 8 to 10 mm are unlikely to do so. spontaneous closure occurred in all the defects that were <3 mm at diagnosis, in 87% of defects that were 3 to 5 mm, in 80% of defects that were 5 to 8 mm, and in none of the defects that were ≥8 mm.
PVOD	young adults c ASD have 14% chance of developing progressive PHTN à PVOD à death from cardiac failure or PA thrombosis When PVOD is irreversible, closure of the ASD can result in further deterioration of the patient and decreased survival. In most of these patients there is RV failure, and the RTL shunt across ASD provides LV CO at the cost of cyanosis.
MANAGEMENT	anticongestive therapy with diuretics if symptomatic Closure of an ASD is indicated if there is a large shunt, Qp:Qs ≥1.5, diastolic flow rumble in the tricuspid area, RVH on EKG, cardiomegaly, increase pulm vascular markings, RV dilation and paradoxical septal motion If asymptomatic large shunt, closure between 2-5 yrs, to prevent complications such as atrial arrhythmias, paradoxical embolism, pulmonary HTN, severe RV dilation and dysfunction with overt symptoms of CHF, and significant MR and TR
Adults c ASD2	Late dx ASD can use a cath to determine PVR and reactivity to pulm vasodilators. While asymptomatic in 40s, reduced LV compliance from CAD, HTN, valve disease à increase of the LTR shunt Routine F/up = for atrial arrhythmias and paradoxical embolic events and an echo q2-3 yrs to evaluate RH size + pressure
Secundum ASDs	Surgical Closure: median sternotomy or newer partial lower sternotomy Small ASD = direct suture Moderate to large ASD = closure with autologous pericardial patch minimizing the risks of thrombosis and endocarditis a concomitant Maze procedure can be performed to prevent atrial arrhythmias The overall 30-year actual survival rate among survivors of the perioperative period was 74%, compared to 85% among age- and sex-matched controls. However, survival is significantly decreased in those repaired between 25 and 41 years when compared to the controls (84% and 91%, respectively). There was a further decline in late survival in those repaired after 41 years of age to 40% versus 59% in controls. Late repair was associated with significant morbidity including atrial fibrillation, stroke, and cardiac failure.   Cath closure: A: Amplatzer, B: Gore helex, C: cardioSEAL, D: BioSTAR Amplatzer septal occluder is currently the most widely used device = relatively easy deployment, easy retrievability, ability to close large defects, and the relatively larger left atrial disc to close additional atrial fenestrations complications include fracture or embolization of the device, device malalignment, residual shunts, device thrombosis, and impingement of adjacent structures such as valves, SVC, CS, pulmonary veins, or aorta (BioSTAR) made of collagen discs used in Europe since 2006 with very little foreign material left over at 6 months’ f/up fully absorbable transcatheter device (BioTREK) is under trial   ASD closure at any age was followed by improvement in symptoms and decrease in pulmonary artery pressures and right ventricular size, but the best outcome was in patients with less functional impairment and lower baseline PA pressures.
Sinus Venosus ASD   Warden procedure	in > 90% of cases, PAPVR to the SVC is present à surgical correction involves closure of ASD and baffle PVeins to LA As compared to PAPVR to RA, PAPVR connected to SVC is complex and can be associated with long-term complications such as pulmonary vein obstruction, SVC stenosis, sinus node dysfunction, and atrial arrhythmias (Afib or Aflutter) When the RPveins insertion into the SVC is high (> 2 cm above SVC/RA junction), the Warden procedure is used, in which the SVC is transected above the site of the anomalous pulmonary veins and connected to the right atrial appendage. The cardiac end of the SVC along with the anomalous pulmonary venous flow is baffled into the LA with a patch
Coronary Sinus ASD	In a partially unroofed CS defect, a roof can be created using a pericardial patch. If the left SVC is small and there is a bridging vein, LSVC can be ligated.
Postpericardiotomy Syndrome	first few weeks postoperatively, patients may present with fever, chest pain, abdominal pain, emesis, and fatigue. echocardiogram should be performed to exclude pericardial effusion and cardiac tamponade.
Pulmonary Hypertension	Despite closure of the defect, pulmonary vascular disease may progress in some patients. periodic surveillance with serial Doppler echo is recommended to estimate PA pressures + response to pulm vasodilators
Atrial Arrhythmias	< 40 years with a prevalence of <1% à Beyond 40: 15 to 60% at 60 yo = more likely to have higher PA pressure periodic f/up with ECG and Holter monitoring is recommended
Right Atrial and Ventricular Size and Function	Following ASD closure, there is regression of RA and RV size in the majority of patients, irrespective of the technique used chronic volume overload à reduced RV systolic and diastolic function in adults, which may or may not improve post closure
Left Ventricular Function	both systolic and diastolic function can be influenced adversely by severe chronic RV volume overload monitoring of both RV ad LV function during f/up is advisable.
Mitral Regurgitation	may develop MVP and MR, presumably from leftward shifting of the ventricular septum due to an enlarged RV + MV itself often is noted to be morphologically abnormal with myxomatous changes and prolapse
Bacterial Endocarditis	are NOT predisposed to endocarditis unless there is an associated valvular lesion such as cleft mitral valve with mitral valve regurgitation antibiotic prophylaxis is recommended for the first 6 months following device closure and is then discontinued
Atrial Septal Aneurysm	0.22% to 1.9% = saccular deformity or protrusion >15 mm beyond the plane of the atrial septum commonly associated with ASD, VSD, coarc, IAA, PS, and PDA, also arrhythmias and cryptogenic strokes – TEE helpful
Patent Foramen Ovale	present in up to 24% of healthy adults - similar in males and females – can get larger from stretching of the fossa ovalis over time – can be associated with cryptogenic strokes, transient ischemic attacks, and migraine headaches – can close if needed

 

These notes are for personal use.  They are not to be distributed or sold. Please read Moss and Adam book for more detail information, read this at your own risk.