Very complex and is a subspecialty within itself.
Can be classified as:
- New/untreated CHD – ASD/VSD/valve disease.
- Corrected CHD – simple ASD/VSD repair (cured), repaired ToF (not cured).
- Palliated CHD – fontan.
Alternative method of categorising by Kelleher in BJA Education article.
Principle of imaging is identifying site of heart and which orientation it is in.
Segmental approach to scanning:
- Atrial situs – venous connections, situs, morphology, septum.
- Atrioventricular connections: concordant(e.g. RA to RV), discordant (e.g. RA to LV) or double. ?Absent (e.g. tricuspid atresia). A-V valves.
- Ventricles – morphology, function, septum, outflow tracts.
- Ventriculo-arterial connections: concordant, discordant (TGA), double, absent, AV valves.
- Great arteries.
Normal atrial situs:
Consider scanning from subcostal view first. Parasternal views may be confusing.
Track IVC into RA – the IVC will never connect to the LA so if you can track the IVC entering RA you have identified the right side of the heart.
If IVC on LHS consider situs inversus.
Can have rotation abnormalities with abnormal veno-arterial connections (midline liver, asplenia/polysplenia). Complex and higher level scanning.
Atrioventricular connections:
Concordant – RA to RV.
Discordant – RA to LV – Congenitally corrected TGA – AV and VA discordance. Systemic RV which eventually fails. Often severe ‘TR’ but functionally is MR as regurgitation into LA not RA.
Double inlet – e.g. single ventricle.
Absent – tricuspid atresia.
A-V valves – e.g. Ebstein’s TV.
Need to clarify which ventricle is which by identifying particular characteristics.
RV – always travels with TV. TV is slightly offset towards the apex compared with MV. Chordal attachment to septum from TV – whereas MV all insert into papillary muscles. Moderator band, trabeculations – neither particularly accurate findings.
RV has separate inflow, body and outflow.
LV – adjacent inflow/outflow tracts.
Great Arteries:
Distinguishing between aorta and pulmonary artery.
PA branches early.
If GA transposed then they run parallel rather than criss-crossing.
Can be identified as early as 18/40 gestation in fetal echo.
Atrial septal defects:
Secundum ASD commonest where fossa ovalis absent.
If it is inferior septum – used to be called ‘primum’. More classically an AVSD. Different embryological origin.
All cause shunts from LA to RA. Causes RH volume overload, pulmonary hypertension and RH failure.
Potential source of embolic phenomena.
Best view for identifying is the subcostal view.
Sinus venosus ASDs are technically venous abnormalities but will behave like any ASD. Difficult to diagnose with TTE because of proximity to SVC/IVC (superior more common). Also close to the coronary sinus. Is associated with partial anomalous pulmonary venous drainage.
Use colour flow doppler to identify.
PW to assess flow. Should aim for good alignment with colour jet.
Perform shunt calculation – ratio of RV SV to LV SV:
RV SV – measure RVOT diameter and PW VTI.
LV SV – measure LVOT diameter (PLAX) and PW VTI (A5C).
For PFO – patient to perform valsalva and look for right to left flow. A4C or subcostal.
Can perform contrast echo with agitated saline if diagnostic uncertainty. If myocardial shunt – bubbles will appear in LA within 3 cardiac cycles. If intrapulmonary shunt – likely will appear after 5 cycles.
Partial AVSD (includes only atria) or complete AVSD have common embryological origin with AV valves and therefore those valves are always abnormal. Usually they have a common AV valve between the two ventricles which is only attached around the edges.
Valve abnormalities will persist after repair. Often need redo valve surgery.
Ventricular septal defects:
Perimembranous VSD – located in thin fibrous membranous septum just below AV.
Best identified in PLAX. Even if cannot see a clear defect should be able to see a high velocity colour jet.
These patients can be susceptible to very unusual patterns of endocarditis.
Muscular VSD – post MI. Can be multiple.
Inlet VSD – (canal, posterior). Posterior to TV leaflet seen in A4C.
Subpulmonary VSD – (outlet, doubly committed) Seen in between the outflow tracts below AV and PV. Seen in PSAX and A5C. Often associated AR from RCC prolapse.
Calculate shunt again. Can use Bernoulli to estimate pressure difference.
Smaller holes will have higher velocities – restrictive VSD.
Big VSDs – non-restrictive VSD.
Look for right heart and LA dilatation.
Fundamentally results in raised PA blood flow and thus PA pressure. Gradually the RV pressure will increase and shunt will reduce as ventricular pressures equilibriate. At this point flow will be bidirectional – Eisenmenger’s.
Patent Ductus Arteriosus:
Aorta to pulmonary artery pressure shunt.
In PSAX view of pulmonary arteries (can go space higher from AV PSAX) should see continuous flow into pulmonary artery.
Can also see in arch view – distal arch at transition to descending aorta.
Usually get a CT or MRI to further assess.
Coarctation of the Aorta:
Stenosis in juxtaductal region with secondary aneurysm formation due to weakness of vessel walls.
80% are associated with a bicuspid aortic valve.
Aortic root dilatation often present due to systemic connective tissue disease.
Poorly controlled hypertension which aggravates overall process.
Often see very turbulent flow. High velocity in descending aorta with unusual flow. Need to use full modified Bernoulli to estimate pressure gradient.
Tetralogy of Fallot:
Failure of cono-truncal development leading to:
- RVOTO. Often PS/PR.
- RVH
- VSD
- Overriding aorta (overrides the septum).
After repair (VSD closure, PA):
- Free PR as PV manipulated/removed.
- RVH + Right heart dilatation/dysfunction.
- Branch pulmonary stenosis.
- VT – prolonged QRS.
- May have residual VSD.
- Aortic root dilatation.
Echo follow-up focuses on RV function. Those with RV dysfunction are at risk of VT.
Also at risk of pulmonary valve endocarditis.