Echo 3: Stress echo Flashcards
What are 2 types of contrast echo?
-Bubble study
-Contrast echo
Indications for bubble study
-Detection of left to right shunt (patent foramen ovale)
-Pericardiocentesis in pericardial effusion
How does bubble study work?
-Agitated saline solution (air bubbles) injected IV
-SCV - RA - RV - Lungs
-Normal conditions - no bubbles seen in left heart
-Abnormal - Bubbles seen in left heart suggestive of left to right shunt
-Valsalva manoeuvre often required to unmask PFO
Indication for contrast echo
-LV opacification
-Improve visualisation of LV (LVSD, RWMA, LV thrombus) where image quality is poor
How does LV opacification work?
-Contrast agent: microbubbles 1-10um pass through pulmonary capillary bed -> pulmonary veins -> LA -> LV
-Consist of outer shell enclosing a gas
-US energy causes microbubbles to resonate, emitting more US signals
What does this image show?
LV opacification
2D vs Contrast
What does this image show?
Positive bubble study
Rest vs Valsalva
What are the 3 types of stress echo?
-Exercise - treadmill, bicycle
-Pharmacological - dobutamine (inotrope), dipyridamole (vasodilator)
-Pacing - poor SA node function that would be unaffected by either alternatives
Purpose of stress echo
-Allows comparison of resting and stress pictures to uncover potential hidden abnormalities at rest
Advantages and disadvantages of types of stress echo
Indications for stress echo
-IHD
-Valve pathology
-Other
Typical vs Atypical chest pain
Why not ETT for ischaemia?
-ECG changes and angina are picked up later in the duration of ischaemia
-Echo and MRI pick up earlier signs of ischaemia
2010 vs 2016 NICE guidelines chest pain
2010:
-Test depends on pre-test probability of having CAD
2016:
-First line investigation is CTCA
-If non-conclusive, functional imaging
What does this image show?
Myocardial perfusion scan at rest and stress
What does this image show?
CT coronary angiogram
Pros and Cons of CTCA
Pros:
-Available
-Quick
-Non-invasive
-Minimal risks
Cons:
-Radiation
-Claustrophobic
-Requires contrast
-Artefact (HR, breathing)
Pros and Cons of stress echo
Pros:
-Non-invasive
-No radiation
-Only 2 people to perform
-Minimal risks
Cons:
-Does not see coronaries
-Limitations of echo
-May require contrast
-Requires consultant interpretation/input
Pros and Cons of coronary angiography
Pros:
-Direct visualisation of coronaries
-Simultaneous PCI
-Guides revasc decision (PCI vs CABG)
Stress echo service requirements
-Echo machine (probe, ECG electrodes) with stress echo software
-Exercise equipment (treadmill), drug administration equipment (infusion pump, cannulas, contrast)
-Resuscitation and safety equipment (allergic reaction, arrhythmias, physical injuries)
-Trained and experienced staff (minimum 2)
Patient preparation for stress echo
-Stop beta blocker
-Decision on stressor
-Baseline echo (screen for contraindications)
-Baseline ECG and BP
-Cannula (if required)
-Presence of PPM/ICD - settings check
Contraindications for all forms of stress echo
-Recent ACS or MI
-Ongoing unstable angina
-Acute heart failure
-LV thrombus/other mass
-Recent ventricular arrhythmia
-Severe hypertension >220/110
-High grade AV block
Contraindications for exercise stress echo
-Injury/disability
-Inappropriate footwear/clothing
-Inability to exercise efficiently
-Haemodynamically significant outflow tract obstruction (HOCM)
Contraindications for dobutamine stress echo
-LVEF<35% - arrhythmogenic properties of Dobutamine
-Glaucoma - Atropine
-Severe prostate disease - Atropine
-Difficult cannulation
-Concomitant valve disease that needs assessing with stress (exercise)
Stress echo methodology on treadmill
-Baseline imaging
-Bruce protocol exercise
-Peak imaging (within 90s)
-Recovery
What is considered a maximal test in stress echo on treadmill
-9 minutes
-10 METS
Dobutamine stress echo methodology
-5 micrograms given every 3 minutes
-Pictures taken every 3 minutes
-Repeated until 85% of MAX HR is reached or 40 micrograms
Diagnostic end points for stress echo
-Workload at least 85% predicted for age and sex
-Marked ECG positivity
-Obvious echo positivity
-Severe chest pain
Causes of test cessation in stress echo
-Intolerable symptoms
-Muscular exhaustion
-Severe hypertension (220/120)
-Symptomatic hypotension
-Arrhythmias
Abnormal test in stress echo
-Symptoms: angina, presyncope, syncope, fatigue at low workload
-Ischaemia
-Arrhythmias
-PHT
-Ischaemia mitral regurgitation
Which views are coronary territories visualised in during stress echo?
-Apical 4,3,2 chamber
-Parasternal long axis (PLAX)
-Parasternal short axis (PSAX)
How are images displayed in stress echo?
-Clear, well optimised, on-axis views of the LV where all walls can be seen
-Stress echo software package allows direct comparison between images in a quad screen format
What is hibernating myocardium?
-Body deliberately down-regulates contractility of segment
-To protect it from becoming ischaemic
-Looks hypokinetic at rest
What is a viable response?
-RWMA at rest
-When oxygen supply is increased it is still alive and can be revascularised
What is a viable/ischaemic (biphasic) response?
-Improves at low dose of dobutamine
-At higher doses segment becomes ischaemic and hypokinetic
What is infarct/scarred tissue?
-No improvement in segment at any dose
Features of normal stress echo peak pictures
-LV cavity size should reduce from baseline
-EF should increase from baseline
-All LV segments contract at same time
Features of single/multi vessel disease stress echo peak pictures
Single vessel:
-New RWMA in coronary territory
Multi vessel:
-New RWMA in several territory
-Dilation of LV cavity size with reduction in EF
Number of ischaemic segments in 17 segment model
Other applications of stress echo?
-Asymptomatic severe aortic stenosis (exercise)
-Significant mitral valve disease (exercise)
-Cardiomyopathies (exercise)
-Low gradient aortic stenosis
Purpose of low gradient/flow aortic stenosis DSE
-DSE corrects the flow by increasing contractility
-Increases flow across valve
-Determines whether issue is valve or ventricle
Outcomes of of low dose DSE for low gradient aortic stenosis
True severe AS
-<0.2cm^2 increase in AV area
-Increase in mean gradient >40mmHg
Pseudo severe AS
>0.3cm^2 increase in AV area
-Minor changes in mean gradient
-Ventricular function was the limiting factor
Indeterminate
-Contractility/flow through valve does not improve
-Can’t tell whether AS or not
Stress echo methodology on treadmill
-Ramp protocol
