Transposition of the Great Arteries Flashcards
Concordance in normal heart?
- AV (atrioventricular) concordance: LA to LV; RA to RV
- VA (ventricular arterial) concordance: LV to aorta; RV to PA
Key abnormalities in complete transposition of the great arteries (d-TGA)?
- Transposed Ao and PA
- PDA
- Great arteries are transposed so there is VA discordance: LV to PA; RV to aorta
Characteristics of d-TGA?
- 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
How does d-TGA occur?
- 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
d-TGA: Circulatory Pathway
- 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
d-TGA: Associated lesions?
- VSD
- Pulmonary outflow tract obstruction
- CoAo
- Aortic arch hypoplasia
- Variations in coronary artery origin and course
d-TGA: Associated syndromes?
- DiGeorge Syndrome
- Down Syndrome
- Goldenhar Syndrome
How is d-TGA diagnosed?
- 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
Palliative procedures in d-TGA?
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
Echo in balloon septostomy?
- 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
Echo Post Balloon Septostomy?
Assess efficiency of septostomy; look at size of hole in IAS and degree of shunting through this defect
Options of surgical repair in d-TGA?
- Atrial switch (Mustard and Senning)
- Arterial switch (Jatene)
What is the Atrial Switch operation?
- 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
Circulation post atrial switch operation?
- Vana cava –> SVA –> MV –> LV –> PA –> lungs
- Pulmonary veins –> PVA –> TV –> RV –> aorta –> systemic circulation
Role of echo post atrial switch?
- Intra-atrial channel potency
- RV and LV size and systolic function
- TR severity
- PASP (LVSP from MR)
Identifying SVC channel with echo?
- 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
Identifying IVC channel with echo?
- 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
Identifying pulmonary venous channel with echo?
- 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
Visualising pulmonary valve with echo in d-TGA?
- 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
Visualising aortic valve with echo in d-TGA?
- 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
RV in d-TGA?
Morphological RV is systemic ventricle therefore ventricle almost always dilated with some degree os systolic dysfunction
TR severity of d-TGA?
- 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
Calculating PASP in d-TGA?
- 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
Most common post atrial-switch complications?
- Baffle leaks and obstruction
- RV failure
- Severe TR
Baffle leaks and obstruction post atrial-switch?
- Baffle leaks (uncommon) equivalent to ASD
- Severe baffle obstruction ≥ 2m/s
What is Arterial (Jatene) Switch operation?
- Method of choice for d-TGA
- Restores anatomic relationship between ventricles and great arteries
Key elements of arterial switch operation?
- Transection of great arteries = switched = reattached
- Coronary arteries detached = re-implanted into neo-aorta
- LeCompte Manoeuvre: PA and branches are brought forward so these arteries are anterior to the aorta
Role of echo in arterial switch?
- 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
Most common post arterial switch complications?
- Narrowing at anastomosis sites of aorta and PA
- Compression of LPA and RPA branches (post LeCompte manoeuvre)
What is the LeCompte manoeuvre?
- 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
Echo views to a assess LeCompte manoeuvre?
- 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
What is congenitally corrected TGA (cc-TGA or l-TGA)?
- 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
cc-TGA circulatory pathway?
- 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
Associated lesions of cc-TGA?
- 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
Diagnosing cc-TGA with echo?
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
“Double Switch” for cc-TGA?
- 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
