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S4 W9-12 Congenital Heart Disease > Atrial Septal Defects > Flashcards

Atrial Septal Defects Flashcards

1
Q

ASDs: General Info

A
  • Communication between LA and RA
  • Accounts for 10% of all CHDs
  • Shunt usually L-R (LAP > RAP)
  • Dilatation of high heart (increased volume of blood to right side of heart)
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2
Q

Emybyological contribution of which structures form the IAS?

A
  1. Primum atrial septum
  2. Secundum atrial septum
  3. Endocardial cushions
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3
Q

Contribution of premium atrial septum in forming IAS?

A
  • First atrial septum to form
  • Arises from roof of the atrium and grows inferiorly towards the endocardial cushions
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4
Q

Contribution of secundum atrial septum in forming IAS?

A
  • Grows from roof of atria and overlaps with primum septum
  • Doesn’t grow far enough to lose opening = forming foramen ovale
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5
Q

Contribution of endocardial cushions in forming IAS?

A
  • Before primum fuses with cushions, septum is performed in upper part forming foramen secundum
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6
Q

What is the importance of the foramen ovale in foetal circulation?

A
  • Remains open until birth to allow oxygenated blood to be shunted to rest of the body
  • Allows blood supply to the LA
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7
Q

Overview of foetal circulation?

A
  • Oxygenated blood from maternal placenta travels to foetal heart via the IVC
  • Within RA, majority of oxygenated blood shunted across foramen ovale with help of Eustachian valve
  • Oxygenated blood in RA travels to LV and aorta, and to foetal brain
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8
Q

Modifications of Sinus Horns throughout development?

A
  • Progressive enlargement of right sinus horn develops into SVC and IVC
  • Regression of left sinus horn contributes to formation of coronary sinus
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9
Q

What are the types of ASDs from most to least common?

A
  1. Osmium secundum ASD (80% of all ASDs)
  2. Ostrium primum ASD (15% of all ASDs)
  3. Sinus Venosus (SV) ASD
    a. Superior SV ASD 5-10%
    b. Inferior SV ASD 2%
  4. Coronary Sinus (CS) ASD (<1%)
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10
Q

Secundum ASD location?

A
  • Fossa ovalis
  • Seen towards top of atria
  • Difficult to identify when IAS orientated parallel to u/s beam due to drop out of septum
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11
Q

Cause of secundum ASD?

A
  • Excessive cell death or inadequate development
  • Reabsorption of septum premium
  • Or inadequate development of septum secundum
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12
Q

Location of primum ASD?

A
  • Inferior portion of atrial septum near primitive foramen primum
  • Inferior atrial septum near the cardiac crux
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13
Q

Cause of primum ASD?

A
  • Failure of primum septum to fuse with the endocardial cushion
  • Or deficiency of endocardial cushion tissue
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14
Q

What are the two types of sinus venosus ASD?

A
  1. Superior SV ASD
  2. Inferior SV ASD
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15
Q

How to sinus venosus ASDs occur?

A

Defects result from maldevelopment of the sinus venosus and sinus horns

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16
Q

Where is the superior SV ASD located?

A
  • Located near SVC
  • Accounts for 5-10% of all ASDs
17
Q

Associated lesion with superior SV ASD?

A

Anomalous PVD (pulmonary venous drainage); RUPV to RA

18
Q

Where is the inferior SV ASD located?

A
  • Located near IVC
  • Rare, accounts for around 2% of all ASDs
19
Q

Associated lesion with inferior SV ASD?

A

Anomalous PVD; RLPV to RA

20
Q

Cause of coronary sinus ASD?

A
  • Occurs when improper development of wall of CS, so CS communicates directly with the LA
  • Defect in CS wall may be fenestrated or totally absent/unroofed
  • Communication from LA to CS to RA
21
Q

Best views for identifying secundum ASD on echo?

A
  • Best views where IAS perpendicular to ultrasound beam
  • Subcostal 4 chamber
  • Subcostal SAX
  • When defect is large, also seen from PSAX
22
Q

Best views for identifying primum ASD on echo?

A
  • Apical 4 chamber best view as this nicely shows the cardiac crux
  • Subcostal 4 chamber
  • PSAX - inferior portion of IAS
23
Q

Best views for identifying sinus venosus ASD on echo?

A
  • Located superiorly so marked anterior tilting required
  • Seen in apical 5 chamber
  • Difficult to see from 2D echo alone, CFI useful (flow from RUPV/RLPV into RA)
24
Q

Best views for identifying coronary sinus ASD on echo?

A
  • Difficult to detect with TTE in adult patients
  • Apical and subcostal 4 chamber with posterior tilt
25
Q

Clues to coronary sinus ASD?

A
  1. Dilated CS in apical view but not in PLAX: occurs as CS is unroofed therefore typical circular appearance in PLAX not present
  2. “Prominent” flow within dilated CS: flow from CS into RA is seen
26
Q

How to measure size of ASD?

A
  • Measure size with 2D echo
  • CFI useful to delineate boarders
  • Should be measured in at least 2 orthogonal planes as they are often oblong or elliptical in shape
27
Q

Normal ASD shunt direction?

A
  • Shunting usually from LA to RA as LAP > RAP
  • Marked increase in right heart pressures means shunting may be bidirectional, reversed or abolished
28
Q

What is Eisenmenger’s Syndrome?

A

Long-standing, significant L-R shunting at any level causing PHTN and secondary pulmonary vascular disease = reversal of shunt resulting in cyanosis

29
Q

Indication of ASD with a haemodynamically significant shunt?

A
  • Dilatation of right heart chambers due to increased volume of blood being shunted into the RA and RV
  • RV volume overload; abnormal septal motion, D-shaped septum
30
Q

Significance of Relative Atrial Index (RAI) in predicting if patient has ASD?

A
  • RAA:LAA
  • RAI > 0,92 predicts patients with ASDs
31
Q

What is the QP:QS ratio?

A

Calculates ratio of pulmonary venous flow (QP) to systemic venous flow (QS)

32
Q

What is QP?

A
  • Pulmonary venous volume to or from lungs
  • SV RVOT (can also be calculated from TV or MPA)
  • QP = 0.785 x d^2 x RVOT VTI
33
Q

What is QS?

A
  • Systemic volume to or from the body
  • SV LVOT (can also be calculated using MV or ascending aorta)
  • QS = 0.785 x d^2 x LVOT VTI
34
Q

What QP:QS shunt ratio is haemodynamically significant?

A

QP:QS > 1.5:1

35
Q

Calculating RVSP in ASDs?

A

Performed in usual way, RVSP = 4 x VTR^2 + RAP

36
Q

Associated lesions with osmium primum ASD?

A
  • “Cleft” anterior mitral valve leaflet (amvl looks like two hands clapping)
  • Atrioventricular canal defect (AVCD)
37
Q

Associated lesions with osmium secundum ASD?

A

Usually isolated; however MVP and/or PS may be present

38
Q

Associated lesions of coronary sinus ASD?

A
  • Persistent left SVC
  • To confirm, image left SVC from supraclavicular fossa; normally should not be able to see vertical vein draining down

S4 W9-12 Congenital Heart Disease (10 decks)

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