Echo 3: Stress echo Flashcards by Michael Amarin

What are 2 types of contrast echo?

-Bubble study
-Contrast echo

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Indications for bubble study

-Detection of left to right shunt (patent foramen ovale)
-Pericardiocentesis in pericardial effusion

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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

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Indication for contrast echo

-LV opacification
-Improve visualisation of LV (LVSD, RWMA, LV thrombus) where image quality is poor

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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

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What does this image show?

LV opacification
2D vs Contrast

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What does this image show?

Positive bubble study
Rest vs Valsalva

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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

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Purpose of stress echo

-Allows comparison of resting and stress pictures to uncover potential hidden abnormalities at rest

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Advantages and disadvantages of types of stress echo

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Indications for stress echo

-IHD
-Valve pathology
-Other

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Typical vs Atypical chest pain

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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

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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

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What does this image show?

Myocardial perfusion scan at rest and stress

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What does this image show?

CT coronary angiogram

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Pros and Cons of CTCA

Pros:
-Available
-Quick
-Non-invasive
-Minimal risks

Cons:
-Radiation
-Claustrophobic
-Requires contrast
-Artefact (HR, breathing)

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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