matthew schumaecker, md, facc assistant professor of medicine vtc school of medicine
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INTRODUCTION TO CARDIAC STRESS TESTING
Matthew Schumaecker, MD, FACC
Assistant Professor of Medicine
VTC School of Medicine
Objectives
Review and be familiar with:
1. the importance of cardiac stress testing
2. imaging modalities of stress testing
3. stress modalities of stress testing
4. Relative specificity and sensitivity of each modality
Overview of Stress ModalitiesStress Modality Imaging Modality
Exercise Treadmill Bicycle
Pharmacological Dobutamine Atropine
Adenosine Dipyridamole
Surface electrocardiography
Echocardiography Myocardial Perfusion
Imaging: SPECT PET
Stress Modality: ExerciseAdvantages: Least expensive stress
modality Lowest concern for
adverse reaction Produces physiologic
ischemia in CAD Threshold of reproduction
of ischemic symptoms Derived functional data
is strongly predictive of cardiac mortality
Disadvantages: Cannot perform in
patients with significant functional limitations
ECG uninterpretable in LBBB, LVH, resting ST abnormalities, WPW, PPM and SPECT can be false positive in LBBB and patients with PPM
Stress Modality: Exercise-Treadmill Treadmill is most commonly used for
exercise Bicycle is used mostly in echo lab for
valve cases (i.e., mitral stenosis) and to assess for exercise-induced pulmonary hypertension.
Patients are put on a standardized protocol which can predict performance based on age and gender (i.e., Bruce, Cornell, Naughton)
Stress Modality: Exercise-TreadmillBruce Protocol -
Treadmill Most commonly used
protocol. Very well-studied and
validated with good prognostic data.
Each stage lasts three minutes
Patient exercises to symptomatic maximum
Stage
Speed (mph)
Gradient (%)
I 1.7 10
II 2.5 12
III 3.4 14
IV 4.2 16
V 5.0 18
VI 5.5 20
Stress Modality: Exercise
MET = Metabolic equivalent 1 MET = amount of energy expended at
supine rest 1 MET ≈ (kcal/hour)/kg 1 MET ≈ 3.5 ml/kg/min VO2
Average maximum exercise threshold in healthy middle-aged male ~ 10 METS
Stress Modality: Exercise-Treadmill
Stress Modality: Exercise-Treadmill
Stress Modality: Exercise - Bicycle
Advantages More direct measurement of
work (i.e., watts) Echocardiographic images
obtained during exercise Useful for evaluating mitral
stenosis and exercise induced pulmonary hypertension
Can complement vasodilator stress by producing better images and minimizing symptoms
Can obtain respiratory data if
equipped
Disadvantages Can be cumbersome to set up. Takes longer to reach MPHR Not widely used in US for
cardiac stress testing
Stress Modality: Dobutamine
Beta agonist Simulates exercise by positive chronotropy
and inotropy. Can be difficult to achieve 85% MPHR with
dobutamine alone May need to augment chronotropic
response with atropine up to 1 mg. Can cause SAM and LVOT obstruction in
patients with significant septal hypertrophy.
Stress Modality: Vasodilator
Slide by Dr. Robert Hendel. ASNC 7/07
Stress Modality: Vasodilator
Slide by Dr. Robert Hendel. ASNC 7/07
Stress Modality: Adenosine Causes coronary arteriolar vasodilation Extremely short half life Given in a four or six minute infusion Tracer is injected halfway through the
protocol Can cause flushing, diaphoresis,
chest pain. Usually resolves within minutes after infusion
Stress Modality: Adenosine
Causes mast cell degranulation and histamine release in asthmatic patients.
Can cause atrioventricular block
Stress Modality: Dipyridamole
Trade Name: Persantine Acts by blocking the cellular uptake of
adenosine Four to ten times less expensive than
adenosine Comparable to adenosine with respect to
sensitivity; specificity may be lower Much longer half life so adverse reactions
tend to be more severe
Imaging Modalities
Slide by Dr. Robert Hendel. ASNC 7/07
Imaging Modalities:Sensitivity and Specificity
Tread
mill
ECG
Planar
Tha
llium
SPECT MPI
Tread
mill
Echo
PET0%
10%20%30%40%50%60%70%80%90%
100%
SensitivitySpecificity
Surface ECG Obtained during every stress modality. Determine underlying rhythm Assess for arrhythmic response to stress Assess for ischemic response to stress
ST segment is monitored during all phases of stress to look for significant deviation.
Sensitivity and specificity alone are lower than other modalities (especially in women) but can be complementary to other modalities.
ECG Positivity
Tak and Gutierrez. Postgraduate Medicine Online June 2004
Treadmill Echo
Lower sensitivity than other tests Get additional prognostic data with
exercise Technically challenging – images should
all be aqcuired within 90 seconds and within 10% of peak heart rate
Dobutamine Echo
Dobutamine Echo Dobutamine is infused at 20, 30, 40 and 50
mcg/kg/min Dobutamine can test for viability (i.e., biphasic
response) Dobutamine images are collected in real time Dobutamine can give information about aortic
stenosis Sensitivity of 84%; specificity of 87% Robust transplant literature surrounding DSE
SPECT
New Frontiers
PET Adenosine MRI Adenosine Echo Echo microbubble perfusion imaging
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