4 ASD 10-15% of congenital heart defects 1:1500 live births have an ASD The 2nd most common congenital lesion found in adults (bicuspid aortic valve is the most common)1:1500 live births have an ASDMale: Female ratio is 1:2Spontaneous closure is rare in children/ adultsGenerally would have closed in infancy if it was going to closeClosure only seen in 4% of patientsLife expectancy is not normal, though many patients live to advanced age.Natural survival beyond age is <50%.The attrition rate after age 40 is ~6% per yearFirst open heart closure of an atrial septal defect (ASD) on September 5th, 1952
5 Embryology Septation of the atria Septum primum arises from the superior portion of the common atria and grows caudally towards the endocardial cushions.Before the septum primum closes off the atria, it develops a fenestration called the ostium secundum.The septum secundum arises from the right atrial side of the septum primum and grows caudally.The septum secundum does not completely divide the atria and does not immediately fuse with the septum primum.
7 Types of ASDs Ostium Secundum Ostium Primum Sinus Venosus Coronary Sinus Defects
8 Secundum ASD Most common type of ASD (70-75%) ~7% of all congenital heart defectsFemale predominance (2:1)Includes all defects located in the area of the foramen ovalesMechanisms of formation:Septum secundum does not grow to cover the ostium secundum.Ostium secundum is too large for the septum secundum to cover and so is left exposed despite a fully formed septum secundum.
9 Secundum ASD Associatd findings: Specific EKG findings MVP is present in 70% of pts with this type of ASDPartial anomalous pulmonary venous connection (rare)Specific EKG findingsRight atrial abnormalityProlonged PRRight axis deviation (>100 degrees)rSR’ in v1 (incomplete RBBB)Notching of R wave peak (“crochetage sign”)
10 Secundum ASDrSR’ in v1 (incomplete RBBB) and notching of the R wave peak (“crochetage sign”)
13 Primum ASD 15-20% of all ASDs Female to Male ratio is 1:1 Simplest form of AV canal defectGenerally associated with other anomaliesCommonly have AV valve defects, most notably a cleft in the anterior mitral valve leafletDefects of the ventriular septumCommon AV canalSeen commonly in trisomy 2140-50% of pts w/ Downs syndrome have CHD. Of these pts 65% are AV canal defectsUsually not a subtle finding
14 Primum ASD Mechanism of formation: EKG findings: Failure of the septum primum to fuse with the endocardial cushions (i.e. the ostium primum remains unclosed)EKG findings:PR prolongationRight atrial enlargementLeft axis deviationrSR’ (incomplete RBBB)
15 Primum ASDLeft axis deviation, rSR’ (incomplete RBBB), and PR prolongation
18 Sinus Venosus Defect1% of all congenital heat defects in the United StatesAccount for 10% of all ASDsNot truly considered an ASD:Abnormality in the insertion of the superior or inferior vena cava (which overrides the interatrial septum)Two types:Superior sinus venosus defects, located in the atrial septum immediately below the SVCInferior sinus venosus defects (less common), located in the atrial septum immediately above the IVC
19 Sinus Venosus Defect EKG changes Associated Findings Both defects are often associated with a partial anomalous pulmonary vein connection with abnormal drainagePulmonary veins may be directed into the right atrium even if they are in the normal positionPulmonary veins may also be completely displaced and insert into either vena cavaEKG changesP wave negative in III and aVF and positive in AvlJunctional/ low atrial rhythms
22 Coronary Sinus ASD <1% of ASDs. Mechanism of formation: Loss of the common wall between the coronary sinus and the left atriumDefect of at least a portion of the common wall separating the coronary sinus and the left atrium – AKA “unroofed coronary sinus”Can be associated with a persistent left SVC draining into the coronary sinus
23 ShuntingDegree of shunt has implications as to whether to repair as ASDQp/Qs ratio correlates to the size of the ASD.This falls apart when pulmonary hypertension is presentRepair of ASD when Qp/Qs (ratio of pulmonary flow to system flow) > 2:1 although some papers argue for 1.5:1AHA recommends >1.5:1, but this excludes individuals over 21 yrs of ageCanadian Cardiac Society recommends Qp/Qs >2:1, or >1.5:1 in the presence of reversible pulmonary hypertensionRecalculation of Qp/Qs every 2-3 yrs
24 ShuntingDecreased ventricular compliance +/- increased left atrial pressure lead to an increase in shuntingDecrease ventricular compliance:Systemic hypertensionCardiomyopathyMIIncrease LA pressureMitral valve disease
25 PresentationOften asymptomatic until the 3rd or 4th decade for moderate to large ASDsPts who present in infancy usually have associated cardiac defectsFatigueDOE30% by 3rd decade75% by 5th decadeAtrial arhythmias/ SVT and R sided HF:10% by 4th decadeIncreases with ageArrhythmias present in ~20% of pts
26 Presentation Paradoxical embolus – stroke, TIA, or peripheral emboli: Transient flow reversal secondary to increased R side pressures (valsalva)PFOPulmonary hypertensionMigraine headaches:PFO > ASDPulmonary hypertension:Seen in less than 10% of pts w/ ASD at presentationSeen in 50% of individuals above the age of 40.Progression to Eisenmenger's syndrome occurs in 5 to 10% of individuals late in the disease processAltitude intoleranceIncreased decompression sickness and/or paradoxical emboliIncreased right to left shunting and decreased O2 saturations
27 Physical Findings “Left atrialization” of JVP (A=V wave) Hyperdynamic RV impulseRV heavePA tapSplit S1S2 wide/fixed splitMurmursNot hearing ASD (too little turbulance and too low velocity)Systolic:increased flow over pulmonic valveMitral regurgitationDiastolic:Pulmonary regurgitation due to PA dilatationIncreased flow across tricuspid valve
28 Echocardiographic Evaluation Subcostal view most reliable: US beam perpendicular to plane of IASOther views may have loss of signal from the atrial septum from parallel alignmentSecundum ASD: central portion of atrial septum (89% sensitivity)Primum ASD: adjacent to AV valve annuli (100% sensitivity)Sinus Venosus defects: difficult to visualize on TTE (44% sensitivity)
29 Echocardiographic Evaluation RV and RA size and functionAids in evaluation of right to left shuntPotentially the first abnormality noted on echocardiographyPW and CW Doppler to estimate RVSP and PA pressuresDrop-out of inferior portion of IAS can be seen on apical 4 or subcostal viewsTV NOT more apically positioned than MV; at same horizontal levelColor to differentiate from dilated coronary sinus
30 Echo: Identify: Coronary sinus Entrance of pulmonary veins Primum portion of atrial septumDrop-out of inferior portion of IAS can be seen on apical 4 or subcostal viewsTV NOT more apically positioned than MV; at same horizontal levelColor to differentiate from dilated coronary sinus
38 Doppler Echocardiography Color Doppler can identify left to right flowSubcostal view is bestMultiple views needed:Low-velocity flow signal between atriaSVC flow along IAS can be mistaken for shuntingTR jet directed toward IAS can also be confused as a shunt
39 Doppler Echocardiography Location and timing of flow critical (as oppsed to the velocity)Flow from L -> R atrium in both systole and diastoleMore prominent diastolic componentCan extend across open TV in diastole into RVSeen in larger shuntsFlow acceleration on side of LAAbsolute velocity of flow less important
40 Doppler Echocardiography Shunt calculation:Can be performed utilizing these equations to relate pulmonic CO and systemic COQp = TVI pulm X PULdQs = TVI lvot X LVOTdQp/Qs = shunt fractionSignificant usually if > 1.5/1.0 in ASD
41 Constast Echocardiography Microbubbles seen across IASEven if shunting predominantly L to RRA pressure transiently > LA pressure“Negative” contrast jet:Flow from LA to RA appears as area with no echo contrastRarely needed for ASD - more useful for smaller shunts (PFO’s)
42 TEENeeded when TTE images are suboptimalUsually necessary to see sinus venosus defect or partial anomalous pulmonary venous returnTo locate small secundum ASDsDevice sizing before percutaneous closureEstimation of defect size using the diameter of the Doppler color flow jet correlates with surgical findingsTEE is often used when contrast echo suggests shunting, but a defect can’t be visualized on TTE. The TEE then helps to differentiate between a PFO and a true ASD
43 MRIPhase constrast MRI compares well against the gold standard (invasive measurement)93% sensitivity and specificity for Qp/Qs > or = 1.5:1100% sensitivity and specificity for Qp/Qs > or = 1.7:1
44 MRICorrelation of PC-MRI to TEE and IVBM (invasive balloon measurement) measurements of ASD sizeSome studies have noted MR to have better correlation to balloon sizing of ASDs than TEEMR also able to provide information about shape of ASD and proximity to adjacent structuresPossible that TEE will not be able to measure the largest section of the ASD if it is not round
45 ASD Closure Percutaneous ASD closure was first performed 30 years ago First report percutaneous ASD closure of via Amplatzer septal occluder in 1997Successful closure in >80% of secundum ASDsCompared to surgical approachDecreased LOSDecreased complication rateSame success rateDetermining factors:LocationSize<30 – 40 mm by TEERimInitial studies used rim of ~5mm in all directionsSome authors have proposed that it is the posterior inferior rim in particular that must be of adequate size for successful transcatheter closure
46 ASD Closure Indications Asymptomatic in the presence of: Right-sided cardiac dilatationASD > 5mm with no signs of spontaneous closureHemodynamics reserved for “borderline” casesHD insignificant (Qp/Qs <1.5) - no closure required until later in life for embolism prevention after CVAHD significant (Qp/Qs >1.5) - should be closedIn presence of PA HTN:Defined as PAP > 2/3 systemic or PVR > 2/3 SVRClosure can be recommended IF:Net L--> R shunt of 1.5:1 or greaterPulmonary artery reactivity upon challenge with pulmonary vasodilatorLung biopsy evidence of reversibility to pulmonary arterial changes
47 ASD Closure Percutaneous indications: Only for Secundum ASD with stretch diameter < 41 mmNeed adequate rims to enable secure device deploymentCannot have anomalous pulm venous connection, be too proximal to AV valves, coronary sinus, or systemic venous drainage~2/3rds of secundum ASDs meet this criteria
48 ASD Closure Introduced in 1996. Approved for percutaneous ASD closure in 2001 by F.D.A.Over 90,000 have been manufactured and delivered to date.Consists of two round disks made of Nitinol (nickel + titanium) wire mesh linked together by a short connecting waist.
49 ASD Closure Amplatzer - advantages over other devices: Can be delivered through smaller cathetersIt is self-centering but can be repositioned easilyHas round retention disks that extend radially beyond the defect, which results in a much smaller overall size and firmer contact with the atrial septumShape enhances endothelialization and reducing the risk of residual shunting
50 ASD Closure Complications of percutaneous closure: Thrombus formation on the device leading to CVADecreased in newer devicesASA and plavix after procedure for ~6 monthsHeart block, effusion, and thrombus formation in LA (2.4%)Device embolization and/ or malposition (2.4%)Atrial fibrillation (2.4%)Erosion (0.1%):aortic to right or left atrial fistulaFree-wall perforation of the atria resulting in tamponadeFactors associated with erosion:Amplatzer Septal Occluder size greater than 4 mm larger than the unstretched ASDDevice size greater than 1.5 times the size of the unstretched ASD
51 ASD ClosureAI – anterior inferior rim, PS – posterior superior rim, PI – posterior inferior rim
52 ASD ClosureTEECan be used to evaluate suitability of transcutaneous approachMonitoring during interventional procedureMeasure stretch diameter of ASDDoppler to look for residual shunting during occlusion of the ASD with the balloonDoppler to look for residual shunting after occluder is in place
53 ASD Closure Decreased rim A more technically difficult transcutaneous procedure with higher rates of failureLong term complications are increasedErosion of device through cardiac wall and formation of fistulas.
58 ASD Closure Surgical Indications Reserved for cases that are not candidates for percutaneous closures:Non-secundum ASDsSecundum ASDs with unsuitable anatomyPrimary suture vs tissue/synthetic patchSymptomatic improvement seenDoes not prevent AF/aflutter in adults (especially >40 years old)Concomitant MAZE a consideration
59 ASD Closure Surgical outcomes: Surgery before the age of 25 yields in 30-year survival rates comparable to age- and sex-matched controls.At years of age, surgical survival is reduced, though not significantly if PA pressures are normal.If PASP > 40 mmHg, late survival is 50% less than control rates, though life expectancy in surgically treated older patients is better than that of medically treated patients.No benefit of surgery in reducing the incidence of AF, though the patient’s age at the time of closure is the most important predictor of the development of atrial arrhythmias.
60 Stroke RiskData are widely conflicting on the relationship between PFO, atrial septal aneurysm, and/or ASD and recurrent cerebral emboli.Increased prevalence of PFO and ASA in cryptogenic stroke; less clear for ASD.The role of defect closure vs. medical therapy for prevention of recurrent stroke is not well defined.Aspirin is often used in setting of PFO or an isolated atrial septal aneurysm, and especially if PFO + ASA. Role of coumadin is not as clear – coumadin recommended if patient has a documented DVT/PE. Less data available for ASDs.Surgical excision of an atrial septal aneurysm (without PFO or ASD) may be considered if aspirin or coumadin fail to prevent a recurrent embolic event.