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s4 w9-12 congenital heart disease > Transposition of the Great Arteries > Flashcards

Transposition of the Great Arteries Flashcards

1
Q

Concordance in normal heart?

A
  • AV (atrioventricular) concordance: LA to LV; RA to RV
  • VA (ventricular arterial) concordance: LV to aorta; RV to PA
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2
Q

Key abnormalities in complete transposition of the great arteries (d-TGA)?

A
  1. Transposed Ao and PA
  2. PDA
    - Great arteries are transposed so there is VA discordance: LV to PA; RV to aorta
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3
Q

Characteristics of d-TGA?

A
  • PA arises from morphological LV and aorta arises from morphological RV
  • Communication between atria via PFO and/or communication between aorta and PA via PDA
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4
Q

How does d-TGA occur?

A
  • Occurs when coco-truncal septum fails to grow in its normal spiral course and instead runs straight down
  • As a result, aorta is anterior and rightward and arises from RV
  • PA is posterior and leftward arising from LV
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5
Q

d-TGA: Circulatory Pathway

A
  • Deoxygenated blood from IVC and SVC enters RA and flows to RV –> aorta –> systemic circulation
  • Oxygenated blood returning from pulmonary veins –> LA –> LV –> PA to lungs
  • 2 circulations, systemic and pulmonary, are in parallel rather than in series
  • In order to survive, communication between atria via PFO and/or communication between aorta and PA via PDA must also exist
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6
Q

d-TGA: Associated lesions?

A
  • VSD
  • Pulmonary outflow tract obstruction
  • CoAo
  • Aortic arch hypoplasia
  • Variations in coronary artery origin and course
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7
Q

d-TGA: Associated syndromes?

A
  • DiGeorge Syndrome
  • Down Syndrome
  • Goldenhar Syndrome
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8
Q

How is d-TGA diagnosed?

A
  • Diagnosed in PLAX by demonstrating side-by-side parallel alignment of aorta seen anteriorly and PA seen posteriorly
  • From PSAX, both great vessels are seen in their short axis wth aorta seen anterior to PA
  • Normal sausage or circle appearance of great arteries is absent from PSAX
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9
Q

Palliative procedures in d-TGA?

A

Palliative procedures such as balloon septostomy may be performed in infants with TGA when PFO inadequate and when PDA has closed, or in anticipation of ductal closure

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10
Q

Echo in balloon septostomy?

A
  • Commonly performed under echo guidance
  • Used to ensure inflated balloon is within LA and not across MV prior to jerking balloon back across IAS
  • Aim to increase size of PFO or to create a small ASD
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11
Q

Echo Post Balloon Septostomy?

A

Assess efficiency of septostomy; look at size of hole in IAS and degree of shunting through this defect

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12
Q

Options of surgical repair in d-TGA?

A
  1. Atrial switch (Mustard and Senning)
  2. Arterial switch (Jatene)
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13
Q

What is the Atrial Switch operation?

A
  • At atrial level, vena canal flow is baffled to a systemic venous atrium (SVA), across MV, to LV and ejected to PA
  • Pulmonary venous flow is baffled to a pulmonary venous atrium (PVA), across TV to RV and ejected to aorta
  • As a result, circulation is corrected
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14
Q

Circulation post atrial switch operation?

A
  • Vana cava –> SVA –> MV –> LV –> PA –> lungs
  • Pulmonary veins –> PVA –> TV –> RV –> aorta –> systemic circulation
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15
Q

Role of echo post atrial switch?

A
  • Intra-atrial channel potency
  • RV and LV size and systolic function
  • TR severity
  • PASP (LVSP from MR)
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16
Q

Identifying SVC channel with echo?

A
  • SVC channel may be imaged from slightly off-axis PLAX view
  • SVC channel runs posterior and horizontal to great arteries
    Off-axis APLAX: SVC channel courses horizontally
17
Q

Identifying IVC channel with echo?

A
  • IVC and pulmonary venous channels best seen in apical 4 chamber (CFI useful)
  • IVC Channel: blood from IVC baffles to systemic atrium –> MV –> LV to be ejected into PA
18
Q

Identifying pulmonary venous channel with echo?

A
  • Best seen in apical 4 chamber view (CFI)
  • Blood from pul. veins baffled to pulmonary venous atrium –> tV –> RV to be ejected to aorta
  • ensures oxygenated blood is being delivered to the body
  • Peak flow through baffles/channels can be determined with PW Doppler
19
Q

Visualising pulmonary valve with echo in d-TGA?

A
  • PV and flow across PV (CW) should be assessed
  • Best seen from apical views; when tilting anteriorly from apical 5 chamber, first great artery that we see is PA
  • PA posterior to aorta
20
Q

Visualising aortic valve with echo in d-TGA?

A
  • AV and flow across AV assessed from apical view
  • Best seen in apical 4 chamber with anterior tilting beyond PA
  • From PA level, transducer tilted further anteriorly to visualise aorta
21
Q

RV in d-TGA?

A

Morphological RV is systemic ventricle therefore ventricle almost always dilated with some degree os systolic dysfunction

22
Q

TR severity of d-TGA?

A
  • TR occurs due to annular dilatation and high RVSP
  • RV systemic ventricle; TV not designed to sustain high pressures
  • TR assessed normally, CFI and CW
  • TR velocity cannot be used to estimate PASP
  • RVSP estimated from TR velocity is a reflection of the systemic blood pressure
  • TR gradient + right atrial pressure = estimation of systemic systolic pressure
23
Q

Calculating PASP in d-TGA?

A
  • PASP estimated when MR
  • MR velocity = pressure difference between LV and LA during systole
  • LVSP = 4(Vmr)^2 + LAP
  • In absence of LVOTOB or PS, LVSP = PASP
24
Q

Most common post atrial-switch complications?

A
  1. Baffle leaks and obstruction
  2. RV failure
  3. Severe TR
25
Q

Baffle leaks and obstruction post atrial-switch?

A
  • Baffle leaks (uncommon) equivalent to ASD
  • Severe baffle obstruction ≥ 2m/s
26
Q

What is Arterial (Jatene) Switch operation?

A
  • Method of choice for d-TGA
  • Restores anatomic relationship between ventricles and great arteries
27
Q

Key elements of arterial switch operation?

A
  1. Transection of great arteries = switched = reattached
  2. Coronary arteries detached = re-implanted into neo-aorta
  3. LeCompte Manoeuvre: PA and branches are brought forward so these arteries are anterior to the aorta
28
Q

Role of echo in arterial switch?

A
  • LV systolic function (RWMA): myocardial ischaemia due to problems associated with re-implantation of coronary arteries
  • ? neo-aorta regurgitation: native PV, not designed to sustain high pressures therefore regurgitation is common
  • PA and aorta
29
Q

Most common post arterial switch complications?

A
  1. Narrowing at anastomosis sites of aorta and PA
  2. Compression of LPA and RPA branches (post LeCompte manoeuvre)
30
Q

What is the LeCompte manoeuvre?

A
  • Performed during arterial switch operation to avoid distortion of branch PAs when great vessels are switched
  • Aorta relocated to PA such that both branch PAs drape anteriorly to the aorta
31
Q

Echo views to a assess LeCompte manoeuvre?

A
  • PLAX of RVOT
  • PSAX of PA (difficult to visualise branches)
  • PA branches following LeCompte manoeuvre best seen in surpasternal view; seen straddling aorta
  • Branches also seen from high PLAX
32
Q

What is congenitally corrected TGA (cc-TGA or l-TGA)?

A
  • cc-TGA not cyanotic heart lesion (discussed to differentiate d-TGA)
  • AV discordance; LA to RV and RA to LV
  • VA discordance; RV to aorta and LV to PA
33
Q

cc-TGA circulatory pathway?

A
  • IVC/SVC (doxygenated blood) –> RA –> LV –> PA –> lungs
  • Pulmonary veins (oxygenated blood_ –> LA –> RV –> Ao –> body
  • Ventricles are inverted and great arteries are transposed - double discordance so circulation is correct even if anatomy is not
34
Q

Associated lesions of cc-TGA?

A
  • Anomalies present in > 90% of cc-TGA cases
    1. VSDs (usually periembranous)
    2. Pulmonary outflow tract obstruction (usually accompanied by a large VSD)
    3. TV abnormalities (E.g. Ebstein’s anomaly)
    4. CoAo
    5. Dextrocardie or mesocardia
35
Q

Diagnosing cc-TGA with echo?

A

Diagnosed on echo by recognising septal insertion of left-sided AV (atrioventricular) valve is more apically positioned than right-sided AV valve
- Identifying AV valves identifies ventricles; TV = RV, MV = LV
- Clue to identifying morphological RV = cause ventricular tribulations and moderator band within ventricle

36
Q

“Double Switch” for cc-TGA?

A
  • Anatomical repair can be achieved with double switch operation
  • Includes atrial switch plus arterial switch so systemic venous blood re-routed to RV and PA
  • Pulmonary venous return re-routed to LA and aorta
  • CA reimplanted into neo-airta
  • Vena cava –> SVA –> TV –> RV –> PA
  • Pulmonary veins –> PVA –> MV –> LV –> aorta

s4 w9-12 congenital heart disease (10 decks)

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