Role of echo with myocardial ischaemia is to identify territories affected, impact on function and identify complications.
Stress echo may identify segments which remain viable.
Anatomy
17 segment model divides LV into different regions.
Each segment is assigned to one of the coronary arteries: LAD, RAD, Cx – although there is significant overlap and individual variability..
Assess each segment in turn, preferably utilising two views.
Assign score according to motion.
Complications:
Cardiogenic shock:
Caused by AMI >90% of the time – mortality is 50-60%.
Tei index is relative independent of HR and BP and not based on geometric assumptions. Better prognostic indicator for death than EF in DCM.
Papillary muscle rupture:
Acute severe MR may be due to PM dysfunction or rupture..
Most commonly occurs in inferior MI involving postero-medial papillary muscle. Due to single blood supply, usually from RCA or Cx. Anterolateral PM has dual supply so is less likely to be affected.
Causes eccentric MR with normal LA size. Follow normal protocol for MR.
Look for evidence of flail mitral leaflet with an attached piece of papillary muscle and its chordal attachments prolapsing into LA during systole.
Patients may present with acute pulmonary oedema, cardiogenic shock and a new systolic murmur.
Requires urgent surgical intervention.
Consider alternative diagnoses e.g. post-infarction VSD.
Ischaemic mitral regurgitation:
Infarction of inferolateral/inferior LV wall can lead to progressive dysfunction of PMVL.
Calcification & retraction of the supporting apparatus leads to coaptation failure and subsequent MR directed underneath AMVL.
LV dilation and functional MR:
Rarely a cause of murmur in acute MI – will have a history of ischaemic CM/alcoholic CM.
Dilation of LV gradually pulls MV tips apart until they no long coapt.
Causes central MR of varying severity.
To diagnose – valve architecture should otherwise be normal and LV dimensions dilated.
Acute ventriculoseptal defect:
Extensive necrosis of the IVS can compromise its integrity leading to septal rupture..
Presents as a sudden deterioration in patient’s condition and a new harsh systolic murmur.
Associated with high mortality rate and requires surgical intervention.
Septum broadly split into two regions:
- Membranous – located adjacent to basal septal region forming part of the LVOT.
- Muscular – remaining wall.
VSDs classically affect the muscular septum, may be multiple and often small.
Usually secondary to anterior MI (60%). Affect thinned, dyskinetic segment
Recognised complication of posteroinferior infarction and can be associated with MV dysfunction.
Best viewed using PSAX or A4C using colour flow to identify left-to-right shunt.
May be evidence of RV volume/pressure overload – dilation/TR.
LV aneurysm:
Seen in approx 5% of patients following MI. Associated with poor prognosis.
Classified as:
- True aneurysms – most commonly located within anterior wall (80%).
- Wide neck
- Walls entirely composed of myocardium
- False aneurysms – most commonly located in interior and interolateral territories
- Narrow neck
- Full thickness necrosis of LV wall with flow of blood into a contained area within pericardium.
- If not contained – present as tamponade and sudden death usually 3 days following MI.
Ventricular rupture and cardiac tamponade:
Badness.
Uncommon – 2.7% of MIs – but devastating complication causing rapid haemorrhage into pericardial and fatal cardiac tamponade in 75% of cases.
LV mural thrombus:
Occurs where stasis of blood occurs e.g.. within LV aneurysm or akinetic segments.
Most commonly seen at the LV apex following anterior infarct.
Can be seen in RV following RV infarct.
Appear as high density structure overlying an akinetic cardiac segment.
Classically – cleavage plan is described related to the interface between endocardium and clot.
Contrast may assist in delineating potential clots.
Confirm in multiple views and grade mobility.
Dressler’s syndrome
AKA post-MI syndrome..
Combination of:
- Low-grade fever
- Pleuritic chest pain
- Features associated with pericardial effusion.
- Seen in 2-10% of patients between 2-10/52 post infarction.
Main component of echo assessment is to identify presence and consequence of any pericardial collection.
Tamponade is rare but can occur..