Atrial Septal DefectsDr. Harshil Joshi

DM Cardiac Anesthesia ResidentUNMICRC

2

HISTORY

Leonardo da vinci describes the patent foramen ovale. “I have found from a, left auricle, to b right auricle, like perforating channel from a to b”

Sweeney and Rosenquist – normal and abnormal interatrial septum was redefined1979

Hudson described normal and abnormal interatrial septum1955

Bedford et al defined the clinical features of ASD1941

Roesler analysed 62 recorded necropsy cases of ASD in which only one was diagnosed during life

1934

Assmann described radiological features of ASD1921

Karl Von Rokitansky provided a superb account of the pathological anatomy of atrial septal defect together with its embryological basis

1875

Introduction

• An atrial septal defect (ASD) is a hole of variable size in the• atrial septumAtrial septal defect (ASD) is detected in 1 child per

1500 live births, and accounts for 5-10% of congenital heart defects.

• ASDs make up 30-40% of all congenital heart disease detected in adults (second only to bicuspid aortic valve).

• ASDs occur in women 2-3 times as often as men.

Introduction

• ASDs can occur in different anatomic portions of the atrial septum.

• ASDs can be isolated or occur with other congenital cardiac anomalies.

• Functional consequences of ASDs are related to the anatomic location of the defect, its size, and the presence or absence of other cardiac anomalies.

Embryology

Classification

• Primum ASD

• Secundum ASD

• Sinus venosus defects

• Coronary sinus defects

• Patent foramen ovale

• Common Atrium

Primum ASD• Make up ~15% of all ASDs.

• Occur if the septum primum does not fuse with the endocardial cushions, leaving a defect at the base of the interatrial septum that is usually large.

• Usually not isolated – primum ASDs are typically associated with anomalies of the AV valves (such as cleft mitral valve) and defects of the ventricular septum (VSDs) or a common AV canal.

Secundum ASD• Make up ~70% of all ASDs.

• Occur twice as often in females.

• Typically located within the area bordered by the limbus of the fossa ovalis.

• Defects vary in size, from <3 mm to >20 mm.

Secundum ASD• May be associated with other ASDs.

• Multiple defects can be seen if the floor of the fossa ovalis (AKA valve of the foramen ovale) is fenestrated.

• Ten to twenty percent have a functional mitral valve prolapse• May be related to changing LV geometry associated with RV volume overload

Sinus venosus ASD• Make up ~10% of ASDs.

• Characterized by malposition of the insertion of the SVC or IVC straddling the atrial septum.

• Often associated with anomalous pulmonary venous return – the RUL/RML pulmonary veins may connect with the junction of the SVC and RA in the setting of a superior sinus venosus ASD.

Coronary Sinus Septal Defects

• Less than 1% of ASDs• Defects in the inferior/anterior atrial septum region that

includes the coronary sinus orifice.• Defect 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.

Patent Foramen Ovale

• Not truly an “ASD” because no septal tissue is missing.

• Oxygenated blood from the IVC crosses the foramen ovale in utero.

• At birth, the flap normally closes due to

• Reduced right heart pressure and PVR• Elevated LA pressure.

• Flap fusion is complete by age two in 70-75% of children; the remainder have a PFO.

Scimitar syndrome

• rare anomaly characterized by connection of all of the right pulmonary veins into the inferior vena cava.

• The ipsilateral lung and pulmonary artery are usually hypoplastic.

• The syndrome rarely involves the left lung.• The term scimitar refers to a radiologic shadow that

resembles the shape of a Turkish sword.

15

Pathophysiology of ASD

• in utero interatrial flow is normally from right to left through a patent foramen ovale

• At birth, there is little or no shunt in either direction across an atrial septal defect because the compliance of the right and left ventricles is virtually identical.

• When the defect is restrictive, size per se determines the magnitude of the shunt

• When the defect is nonrestrictive,there is no pressure difference between the right and left atrium, so shunt volume is determined by the relative compliance of the two ventricles.

• Factors for L R shunt : R chamber compliance

1. RA COMPLIANT

2. TV - larger

3. RV –compliant, thin walled as muscle growth is less rapid than LV

4. PVR RV stroke volume.

RV tolerates extra vol load quite well as it handle large vol at low ejection

pressures

5. Qp / Qs > 3:1 --> case of PDA, AS, CoA, VSD (L A enlargement --

Foraman ovale is stretched and incompetent)

PATHOPHYSIOLOGY …. Contd ……

RV tolerates VOLUME OVERLOAD, while LV tolerates PRESSURE OVERLOAD

Changes due to left to right shunt

Hypertensive proximal pulmonary arteries dilate aneurysmally and contain mural calcification and intraluminal thrombi that can be massive and occlusive. Fibrosis of PA lead to high PAH•the right ventricle is volume overloaded and the left ventricle is volume underloaded

•volume overload of the right atrium provokes atrial fibrillation and atrial flutter, which further increase the left-to-right shunt and result in heart failure

•which displaces the ventricular septum into the left ventricular cavity, reducing its size and changing its shape from ovoid to crescentic.

•thickening and fibrosis of mitral leaflets and chordae tendineae

•Superior systolic displacement of the mitral leaflets (mitral valve prolapse) occurs because leaflets with normal area and chordal length are housed in a left ventricular cavity that is reduced in size and abnormal in shape

•coronary reserve is compromised in the volume-overloaded right ventricle if the left main coronary artery is compressed by a dilated pulmonary trunk

Patterns of shunting 1. Effect of respiration

- Inspiration : Intrathoracic negative pressure, Increases venous return to RA and decrease return to LA

In valsalva maneuvre - decrease venous return and increase

peripheral pooling

2. Effect of cardiac cycle• The shunt reaches its peak in late systole and early diastole; • it diminishes throughout diastole• In late diastole, it is supplemented by atrial contraction

3. Pattern of blood flowPulmonary blood flow that is received by the right pulmonary veins

is channelled into the right atrium because of proximity of the right pulmonary veins to the rim of the atrial septal defect.

19

4. Effect of posture

- Erect - venous pooling --> decrease IVC return

- Recumbent --> increase IVC flow --> R-L shunt

5. ASD patients have good exercise tolerance

NATURAL HISTORY

< 1 Year Spontaneous closure

Death uncommon < 0.1%

10 - 20 Years Usually asymptomatic

- 13% have Pulmonary Hypertension

- 9% have Eisenmengers

30 Years 80 - 86 % asymptomatic

4% may have Rheumatic disease of Mitral valve

> 40 Years Pulmonary Hypertension 6 – 14%

Arrhythmias

Eisenmengers

CCF

Natural History of ASDs

• Most ASDs <8mm close spontaneously in infants.

• Spontaneous closure is unusual in children and adults; defects often become progressively larger.

• Most patients with a significant shunt flow ratio (Qp:Qs > 2:1) will be symptomatic and require closure by age 40.

• Increasing size of the ASD may preclude percutaneous closure.

• Weight is more affected then height

• Association

• Holt oram syndrome

• Patau’s syndrome

• Edward’s syndrome

Natural History of ASDs

• Life expectancy is not normal, though many patients live to advanced age.

• Natural survival beyond age 40-50 is <50%.

• The attrition rate after age 40 is ~6% per year.

• Advanced pulmonary hypertension seldom occurs before the third decade.

• Atrial fibrillation is a late complication; stroke is a potential complication of ASD (ongoing investigation into this issue).

Clinical Manifestations

• Children may be asymptomatic; may have easy fatigability, exertional dyspnea. Underdeveloped, more prone to respiratory infections.

• Most patients with shunt flow ≥ 2:1 will be symptomatic and require correction by age 40.

• large left-to-right shunt is responsible for a decrease in pulmonary compliance and an increase in the work of breathing

Clinical Manifestations

• Platypnea-orthodeoxia is a rare syndrome characterized by orthostatic provocation of a right-to-left shunt across an atrial septal defect or a patent foramen ovale.Platypnea (dyspnea induced by the upright position and relieved by recumbency) and orthodeoxia (arterial desaturation in the upright position with improvement during recumbency) are features of this rare disorder

• Risk of atrial arrhythmias increases with age and PA pressure.

Physical Exam Findings

• Arterial Pulse• Jugular venous puls• Wide, fixed splitting of S2 (delayed closure of pulmonic valve with reduced respiratory variation)

• Midsystolic pulmonary flow or ejection murmur • Usually over 2nd intercostal space• Peaks in early-to-mid systole, ends before S2

• Palpable RV heave• Mid-diastolic murmurs are the result of augmented tricuspid flow.

Pregnancy and ASD

• Despite the gestational increase in cardiac output and stroke volume, young gravida with an atrial septal defect generally endure pregnancy, even multiple pregnancies, without tangible ill effects.

• However, brisk hemorrhage during delivery provokes a rise in systemic vascular resistance and a fall in systemic venous return, a combination that augments the left-to-right shunt, sometimes appreciably.

• There is also a peripartum risk of paradoxical embolization from leg veins or pelvic veins because emboli carried by the inferior vena cava traverse the atrial septal defect and enter the systemic circulation.

ECG Findings• Right atrial enlargement d/t vol overload (tall P wave)

• The P wave axis with an ostium secundum atrial septal defect is inferior and to the left with upright P waves in leads 2, 3, and aVF

• RVH – RAD, rSR’ in V1, R>S in V1.

• Atrial tachyarrhythmias – a.fib, atrial flutter

• AV delay – often with primum ASD in association with LAFB and RBBB (the rim of an ostium primum defect is near the His bundle).

• A notch near the apex of the R waves in inferior leads 2,3 and aVF of ostium secundumand sinus venosus atrial septal defects has been called crochetage.

Chest X-Ray Findings

• Dilation of RA and RV

• Enlarged main pulmonary arteries and pulmonary vessels, without redistribution to apical vessels.

• Left atrial enlargement if associated mitral regurgitation.

• Ascending aorta is seldom border forming because the intracardiac shunt does not traverse the aortic root

Echocardiography and ASDs

• Some clues to the presence of ASD:• Abrupt discontinuity of the septum, and slight thickening at its

termination• RA enlargement, RV enlargement/dilation• Dilated pulmonary arteries• Increased flow velocity in the PA and across TV• Paradoxical motion and diastolic flattening of the ventricular septum

• TTE is usually definitive in secundum ASDs.

• TEE will help with sizing defects, and identifying sinus venosus defects.

Two-Dimensional TTE

Apical four-chamber view • Can often see ostium primum

ASD in this view.• Shadowing and echo dropout

(especially in the area of the fossa ovalis) may lead to false positives.

Subcostal view• Often more reliable - can

visualize entire atrial septum.• Sensitivity for ASD detection:

• Primum ASD: 100%• Secundum ASD: 89%• Sinus venosus ASD: 44%

Color Doppler TTE

• Can confirm the presence of the ASD, estimate the defect size, and evaluate the efficacy of surgery.

• Flow extends from mid-systole to mid-diastole; second phase of flow coincident with atrial systole.

• May have brief R-L shunting.• Usually not a high velocity jet.

Contrast Echo

• Administer agitated saline contrast through IV.• Apical four-chamber view is usually optimal.• Bubbles in the LA suggests right-to-left shunting at the atrial level if 3 bubbles within 3 cardiac cycles following complete opacification of the RA. Delayed bubbles may be due to pulmonary AVMs – may be less phasic in appearance.

• Large ASDs may have nearly continuous shunting, but smaller ASDs may be more phasic with respiration.

• May see “negative contrast effect” if mainly left-to-right shunt.

Transesophageal Echo

• TEE is superior to TTE in visualizing the interatrial septum and identifying all types of ASDs.

• With contrast or Doppler, TEE can detect any brief right-to-left shunting that may occur with transient increases in right-sided pressure.

• TEE is much more sensitive than TTE for detection of left-to-right shunt as negative right atrial contrast (93% vs. 58% in one study).

• TEE can detect flow through multiple ASDs.

Transesophageal Echo

• Estimation of defect size using the diameter of the Doppler color flow jet correlates with surgical findings.

• Since ASDs are not necessarily round, TEE helps with determining both their size and shape. This is especially important when percutaneous closure is being contemplated.

• Five Rim of ASD• Posterosuperior• Posterior• AV Rim• SVC and IVC Rim

TEE

Estimation of Shunt Flow Ratio

• Operative closure of an ASD traditionally recommended when the ratio of pulmonary blood flow to systemic blood flow (Qp/Qs) is greater than 1.5:1 or 2:1.

• Can estimate Qp/Qs from TTE measurements using Pulsed Doppler echocardiography. Cardiac MR is also useful for further assessment of Qp/Qs ratio.

• Correlation between Doppler imaging and cardiac catheterization techniques for this measurement is good.

Estimation of Shunt Flow Ratio

• First measure stroke volume through each valve:Stroke Volume (Q) = CSA x VTI

• Left-sided stroke volume is measured from LVOT (diameter measured in parasternal long axis view).

• Maximum Doppler flow velocity apical to aortic valve (VTILVOT) taken in apical four-chamber view.

• Right-sided velocity time integral (VTIPA) measured in PA well before bifurcation.

• PA diameter measured at the same level as VTIPA.

Estimation of Shunt Flow Ratio

• Substitution into stroke volume ratio gives:

Qp/Qs = (PAdiam)2 x VTIPA

------------------------------------- (LVOTdiam)2 x VTILVOT

• Diameters of LVOT and PA are squared – exact measurement of these values is especially important.

• PA diameter can be difficult to assess in some patients; this is the term that is most often responsible for inaccurate estimates of the shunt ratio.

Estimation of Shunt Flow Ratio By Cath Data

Qp = O2 consumption -------------------------------------

(PVO2- PAO2) * Hb * 13.6

Qs = O2 consumption -------------------------------------

(SAO2- MVO2) * Hb * 13.6PVR = PA Pressure – LA ---------------------- QpSVR = Systemic Pressure – RA ------------------------------ Qs

Indicator Dilution Method

• More Sensitive for smaller shunts

• Cannot localize the level of left to right shunt

• Left to Right : Dye (indocyanine green) is injected into pulmonary artery and a sample is taken from the systemic artery

• Right to Left: dye injected just proximal to the presumed shunt and blood sample is taken from systemic artery

Interpretation of Indicator Dilution Method

Indications for Defect Closure

• 1.) Symptoms• Exercise intolerance, fatigue, dyspnea, heart failure• Atrial tachyarrhythmias?

• Occur in 20% and often the presenting symptom• Not an indication by itself (incidence may not be

reduced after surgery).

Indications for Defect Closure

• 2.) Defect Size and Qp/Qs• Larger ASDs impose a greater hemodynamic burden on the RV. • In the absence of pulmonary hypertension, Qp/Qs is closely correlated with the

size of the ASD.• Qp/Qs > 2:1 is a well-established indication, though many authors advocate 1.7:1

or even 1.5:1.• AHA recommends a threshold Qp/Qs ≥ 1.5:1, but these guidelines exclude

patients > 21 years of age.• Canadian Cardiac Society recommends Qp/Qs >2:1, or >1.5:1 in the presence of

reversible pulmonary hypertension.

Surgical Closure• Median sternotomy is the traditional approach• minimally invasive approaches are emerging.• Pericardial or Dacron patches are used. • Primary closure of the defect is not recommended.• Can repair other defects at the same time (such as cleft mitral valve if primum ASD).

• ANAESTHETIC MANAGEMENT

• Premedication

• Light premedication is given.

Morphine 0.1-0.2mg/kg

Fentanyle 1-2 ug/kgBenzodiazepenes can be given ( reduce dose of morphine) Midazolam 0.05-0.1 mg/kg

Avoid dehydration

Avoid 100% O2

Avoid any Air during IV injection• Connect iv line with running fluid

• Syringe should be up right

• Monitoring

• ECG, IBP, Spo2, capnography, temperature

• Invasive monitoring- -Direct arterial pressure

-CVP- measure loading conditions and means of transfusing inotropes/dilators

- Do Direct LA pressure monitoring whenever there is MR pre and post surgery.

• ANAESTHETIC MANAGEMENT

• Induction

• In left to right shunt inhlation induction will be accelerated.

• So sevoflurane up to 3-5% can be used

• Avoid halothan and isoflurane

• Or use IV inductin agents like ketamine, propofol, etomidate

• Midazolam,Narcotic( morphine 0.5mg/kg or Fentanyl 5-10 ug/kg)

• Muscle relaxants Vecuronium + Narcotics-

• Avoid atracurium- histamine release

.

• Maintainence• A balanced anesthesia that includes low concentrations

of a volatile anesthetic is desirable.Avoid halothane- arrythmogenic

• Isoflurane(tachy cardia),Sevoflurane(ideal).• Intraoperative fluid replacement must be done adequately

to maintain hydration.

WEANING FROM CPB

Deair of heart should be done properly and if possible under TEE guidance

•Before the last few stitches are pulled up, a clamp or tissue forceps is placed in the aperture, and the anesthesiologist inflates the lung to expel any air from the left atrium. The suture line is snugged while lung inflation is maintained, and an additional bite is taken with the stitch, which is then tied.

•After the right atrium is sucked dry, once again the lungs are inflated to drive through left atrial blood and thus identify any defects in the suture line.

•left atrial pressure is measured at this time (or estimated by palpation of the pulmonary artery) and noted to be 5 to 15 mmHg higher than right atrial pressure. This increase is related to small size and decreased compliance of the LV compared with that of the RV.

Post operative management

• left atrial pressure is routinely monitored intraoperatively and for about 24 hours postoperatively in older patients.

• Occasionally, when mitral regurgitation has been underestimated preoperatively and there are signs of severe pulmonary venous hypertension postoperatively, an urgent echocardiographic study may be required.

• With proper use of anesthetic agent can be extubated in OT.• All patients over age 35 years at operation receive sodium

warfarin prophylactically beginning on the evening of the second postoperative day and continuing for 8 to 12 weeks after repair.

Post-operative

Complication

• LV Dysfunction

• Air Embolism

• Pulmonary vascular disease

• Ventricular dysfunction

• Arrhythmic events

• Thromboembolism

• reintrvention

Percutaneous Closure

• An alternative to surgical closure for secundum ASDs with appropriate anatomic characteristics.

• Defect < 30mm diameter• Prefer a rim of tissue at least 5mm

around the defect to prevent obstruction of coronary sinus, R pulmonary veins, vena cavae, or AV valves.

• Approximately half to two-thirds of secundum ASDs in adults meet these criteria.

Amplatzer Occlusion Device

• 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.

Amplatzer Occlusion Device

Advantages over surgery:• Can be delivered through smaller

catheters• It is self-centering but can be

repositioned easily• Has round retention disks that

extend radially beyond the defect, which results in a much smaller overall size and firmer contact with the atrial septum

• Shape enhances endothelialization and reducing the risk of residual shunting

Amplatzer – deployment of right atrial disc

Anesthesia for Percutaneous closure

• Controlled ventilation should be preferred• Airway anesthesia• TEE guidance to cardiologist• LA Pressure measurement• Avoid any Air during IV injection

Percutaneous Closure - Complications

• Early complications• Device embolization or malposition requiring surgery (2.4%)• Atrial fibrillation (2.4%)• Heart block, effusion, thrombus in LAA (2.2%)

• Thrombus formation (both in LA and RA)• Need aspirin and plavix for at least 6 months

• Rare complications: cardiac perforation, sudden death• Long-term complication: device erosion (0.1% of cases) – risk factors include deficient aortic rim (25/28 cases), deficient superior rim, and oversized device.

Cryptogenic Stroke Risk?• Data are widely conflicting on the relationship between PFO,

atrial septal aneurysm, and/or ASD and recurrent cerebral emboli.• Increased prevalence of PFO and 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.

ACC/AHA 2008 Guidelines for the Management of AdultsWith Congenital Heart Disease

Recommendations for Transcatheter Device Closure of Secundum ASD

Thank You!