Question 3 : Complications of myocardial infarction

Discuss the use of Echocardiography/Doppler in the assessment of the complications of acute myocardial infarction

Acute/subacute complications

Chronic

Assessment using ECHO

Regional wall abnormalities

Will depend on size and coronary artery vessels affected. Need to do full cardiac views to evaluate properly

Cardiogenic shock :

Poor LV function on
EF : 2D ECHO using fractional shortening (inaccurate if RWA present , requires good PLAX views which are not oblique)
EF : Using Simpson’s Method ( (ED vol – ES vol) / EDvol X 100) ( requires good apical 4 chamber and 2 chamber views , takes time)
SV : LVOT VTI (cm) X Area of LVOT (requires good 3 or 5 chamber views for LVOT VTI and good PLAX view to measure diameter of LVOT) Need to get an average of 3 measurements if patient is in AF
Measure contractility of LV dP/dt Nomal 1200mmHg /sec , reduced < 800 mmHg/sec Measure the slope of the regurgitatant MR signal between 1 and 3 m/s (disadvantage need MR, inexact)
Size of LV : Normal if less than 5.5 cm but dependent on size of patient. Athletes may have 6cm – normal
Eye ball contractility of LV in PLAX and PSAX views and in 4 cardiac windows

Thrombus formation:

2D ECHO to look for thrombus. Need to put the focus in the area of interest. Early on thrombi are completely anechoic and may not be seen
Put colour Doppler to check that thrombus does not perfuse
Visible in > 1 plane
Measure size to monitor treatment effects

Myocardial rupture

Pericardial effusion and tamponade
Pericardial effusion with associated tamponade
Echo can assess and measure the effusion and assess haemodynamic effects of tamponade
RV/RV collapse/LA collapse/Tricuspid inflow inspiratory E wave changes > 40% and inflow changes on expiration >25% through mitral valve

Papillary muscle rupture

Rupture of postero papillary muscle is more common than the anterolateral one which had a dual blood supply
Severe mitral regurgitation :
May have a lack of distinct mitral regurgitation jet due to a large regurgitant orifice and low flow velocity mitral regurgitation – need TEE
Triangular shape of mitral regurgitation because of low systolic blood pressure in shock and pressure equilibrium between the left ventricle and the left atrium
Flail papillary muscle
Left ventricular overload with dilatation of LV

Ischaemic ventricular septum rupture

Can see a disrupted interventricular septum (usually distal anterior or basal inferior)
Colour Doppler shows flow from LV to RV in systole
CW Doppler velocity depends on the size of the rupture and the pressure gradient between the right and left ventricles
Elevated pulmonary flow velocities across the pulmonary valve
Acute pulmonary hypertension

Aneurysm

Right heart failure

Late mitral regurgitation due to remodelling of the heart assess