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