Transcript STRESS ECHO - cardiologycmc.in

STRESS ECHO
DEEPAK NANDAN

Stress echo is a family of examinations in which
2D echocardiographic monitoring is undertaken
before , during & after cardiovascular stress
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Cardiovascular stress  exercise
pharmacological agents
PHYSIOLOGY
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Coronary blood flow – pulsatile & phasic
Precapillary arterioles – resistance vessels
* principal contributor of resistance
* main controller of coronary blood flow
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•
↑ CBF on ↑ demand occurs through
reduction in resistance at this level
CORONARY BLOOD FLOW RESERVE
Maximal CBF / basal CBF
 Magnitude of bf ↑ secondary to any
stress relative to resting flow
 In discrete stenosis – CFR begins to ↓
when stenosis reaches 50% dm
 CFR is abolished when stenosis reaches
90%
 Resting bf remains constant up
to 85- 90% of the stenosis
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Cellular Mechanism of Ischemia
Consequence(s) of Mechanical Dysfunction
Mechanical Dysfunction
•
Abnormal Contraction and Relaxation
•  Diastolic Tension
 Diastolic Wall Tension (Stiffness)
 Extravascular Compression

 Blood Flow to Microcirculation
( O2 delivery to Myocytes)
 O2 Consumption
(to maintain tonic contraction)
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 ATP Hydrolysis
 O2 Supply
 O2 Demand
Modified from: Belardinelli et al. Eur Heart 8 (Suppl. A):A10-A13, 2006
BASIC PRINCIPLES OF STRESS ECHO
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↑ Cardiac work load - ↑O2 demandsdemand supply mismatch- ischemia
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Impairment of myocardial thickening and
endocardial motion
Treadmill protocol
Stress echo-Standard-format
Supine bicycle ergometry
Supine bicycle standard format
Treadmill vs supine bicycle
advantage
 Add information
 Wide spread
availability
 Simple protocol
 High work load
 > Sensitive
Disadvantage
 Imaging post ex only
Advantage
 Image through out
the exercise- peak
 Onset of RWMA
 Better image quality
 Contrast stress echo
 > Specific
Disadvantage
 Lower work load
 Supine position
affects ex.physio
Information obtained from Exercise Stress but not
available with Pharmacological Test
Exercise Duration/Tolerance
 Reproducibility of Symptoms with Activity
 Heart rate response to exercise
 Blood Pressure response
 Detection of Stress Induced Arrhythmias
 Assess control of angina with medical
therapy
 Prognosis

Indication pharmacological stress
echocardiography
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•
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•
Inadequate exercise
Left bundle branch block
Paced ventricular rhythm
pre-excitation or conduction abnormality
Medication: beta-blocker, calcium channel
blocker
• Evaluation of patients very early after
MI(<3 days) or
angioplasty stent(<2weeks)
• Poor image degradation with exercise
• Poor patient motivation to exercise
Pharmacologic Stress Agents
Coronary vasodilator
Inotropic agents
Dipyridamole
Adenosine
Dobutamine
Arbutamine
Stress agents
DOBUTAMINE STRESS ECHO
Dobutamine- synthetic catecholamine
 Inotropic & chronotropic- β1,β2 & α
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Action: onset – 2 min
half life – 2 min: continous IV
Metabolizd by cathechol-o-methyl
transferase
 Excretion: hepatobiliary system and
kidney
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Dobut-protocol
Protocol for Dobutamine Stress
Echo.
End points to terminate
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Works by inducing myocardial ischemia
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Modest ↑ SBP and ↓DBP
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May be arrhythmogenic (0.7% rate in 8500
consecutive studies performed at Mayo Clinic)
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Usually ineffective in patients on beta blockers
High rate of side effects
 Hypotension induced does not have prognostic
value unlike TMT
 Does not interact with dipyridamole
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Dipyridamole
Potent coronary vasodilator
Provoke anginal attack in angina patients
Vasodilation effect
inhibition of reuptake of adenosine
by the endothelial cell
CBF increases 4 to 5 times in normal vessel
Reduction of subendocardial blood flow
in stenotic coronary artery
Dipyridamole
Coronary steal phenomenon
Standard protocol: 0.54 mg/kg for 4 min
High dose protocol: 0.84mg/kg
Antidote: theophylline
CORONARY STEAL
Myocardial
area
• Supplied by severe epi stenosis
• Collateral from remote cor art
Blood flow
• Depends on prefusion pressure
• Cor collaterals
Steal ischemia
• Vasodilator↓pp & flow ↓in
collaterals
• Flow through stenotic vessel↓
Dipyridamole
Contraindication
active wheezing
high degree AV block
hypotension(SBP<90 mmHg)
recent use of dipyridamole(<24 hours)
Relative contraindication
Hx of reactive airway disease
sick sinus syndrome
severe sinus bradycardia
Adenosine
Naturally occuring agent
Types of receptors
A1: slowing HR and conduction
A2a: c-AMP
– decrease calcium uptake by SR
-- smooth muscle relaxation
vasodilation
Half life: 2 seconds
need constant IV infusion
Rapidly removed from RBC and endothelial cell
Adenosine – side effect
Flushng: 37%
Dyspnea: 35%
GI discomfort: 15%
Headache:14%
Light-headedness 9%
Most side effect – short-lived and mild
Myocardial contrast in stress echo
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Left vent opacification for border enhancement
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Myocardial perfusion imaging
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Perfusion at resting state-stress is performed and
perfusion imaging is done at peak stress
Vasodilator stress echo-perfusion imaging
Stress Echo
Stress Echocardiography
Diagnosis
Prognosis
Treatment
Viability
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Exercise –preferred-add information
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> sensitive in CAD compared to dobutamine
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Treadmill >sensitive, Bicycle>specific
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Bicycle –during stress-> accurate presence and
extend of dis vs pat choice,availability etc.
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Dobutamine is limited to pats who cant exert
adequately & when the Q of viability is addressed
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In pharmaclogical stress dobutamine is the agentproduces true ischemia than a flow mismatch
INTERPRETATION OF STRESS ECHO
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Subjective assessment of regional wall motion
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Compares wall thickening & endocardial excursion
at baseline and stress
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Limitation- subjective & nonquantitative
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Measures like EF, ESV change, and strain rate to
overcome limitations
Strain rate-myocardial velocity gradient
-postsystolic shortening
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TDI/Strain imaging> sensitive
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Ischemia delays onset & rate of regional myo
relaxation
Time quantified using TDI
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QRS-onset of relaxation-350-400ms
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Interval↓ by 34+/_10% in nl segments
in response to high dose dopamine
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↓in interval is <12+/-18% in ischemic seg
Grade 1-normal
2-hypokinesis
3-akinesis
4-dyskinesis
 Nl WMSI-1 at baseline and stress
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Any score>1-abnormal
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Good prognostic value
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Hypokinesia-<5 mm of endocardial excursion
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Akinesis - -ve syst thickening & endo excursion
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Dyskinesis –systolic thinning & outward motion
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nl resp-hyperkinesis
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Absence –low work load, β blockade,
cardiomyopathy & delayed post stress imaging
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Localisation>specific in multivessel dis & in LAD
than RCA/LCX
Normal- hyperkinesis during stress test
DYSKINESIA OF THE APEX IN STRESS
Prognostic
value
A new wall motion abnormality,rest & exercise WMSI,ESV
response-correlated with risk
Chamber dilatation in resp to stress
Prognostic value of stress echo
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Independent predictors of cardiac events
a)WMSI with exercise b) ST ↓≥1 mm c) treadmill
time
Risk Index(RI)=1.02(WMSI)+1.04(ST change)−
0.14(Treadmilltime)
 RI in upper quartile(+0.66 to+2.02)– risk was
highest(30%)
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Prognostic value is comparable in women and
men
Stress echo after revascularisation
PRE-OPERATIVE RISK STRATIFICATION WITH
DOBUTAMINE STRESS ECHO
45
40
35
30
25
Ischemia at
<60% MPHR
Ischemia at
>60% MPHR
No Ischemia
20
15
10
5
0
Operative Cardiac Event Rate
*Mayo Clinic, 530 Patients
Perioperative marker of coronary event
• patients with a positive
electrocardiographic response to
treadmill stress test but no inducible wall
motion abnormality on stress
echocardiogram have a very low rate of
adverse cardiovascular events during
follow-up
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VIABILITY OF MYOCARDIUM
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That has the potential for functional recovery;either stunned/hibernating myocardium
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>6mm thickness -viable segment
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Stunned or hibernating improved contractility
with dobutamine , not in infarcted myocardium
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Biphasic response – low dose ↑contractility(10
to 20 mcg/kg), at higher dose CBF ↓-- contractility
↓
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Biphasic response is the most predictive of
the functional recovery after revascularisation
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Sustained improvement/no change-nonviable
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For viability assessment –
nuclear techniques are more sensitive
dobut stress echo more specific
PPV-similar
NPV- favours dobut stress echo
Myocardial viability-Biphasic response
Sensitivity and specificity of exercise
and pharmacologic stress test
Dobutamine Dipyridamole Exercise
Sensitivity(%) 71 – 96
43 – 74
74 – 97
Specificity(%)
92 - 100
64 - 88
66 - 83
Advantages of Stress Echocardiography
Compared to Nuclear Stress Testing
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Higher Specificity
Visualization of cardiac valves
Evaluate for presence of pericardial effusion
Ability to measure RV Systolic Pressure
More accurate assessment of LV ejection
fraction
Doppler interrogation to determine Diastolic
Function
Lower Cost
Lack of Radiation Exposure
Sensitivity Comparison of Different Testing
Modalities
100
90
80
70
60
Stress ECG
Stress ECHO
Nuclear
50
40
30
20
10
0
1 vessel
2 vessel
3 vessel
All CAD
Situations Where Stress Echo Preferred
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Younger patients with lower likelihood of symptomatic
coronary artery disease
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Pericardial Disease suspected
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Valvular heart disease needs to also be evaluated
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Need to evaluate for pulmonary hypertension
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Exertional dyspnea is the predominant complaint
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