WHAT IS STRESS TESTING
Tests used in Medicine to measure the heart’s ability
to respond to external stress in a controlled clinical
TYPES OF STRESS TESTING
INDICATIONS OF EXERCISE TESTING
• Elicit abnormalities not present at rest
• Estimate functional capacity
• Estimate prognosis of CAD
• Likelihood of coronary artery disease
• Extent of coronary artery disease
• Effect of treatment
INDICATIONS OF PHARMACOLOGICAL
Patients inability to exercise adequately because of
physical or psychological limitations.
The chosen test cannot be performed readily with
exercise (e.g. PET scanning).
METHODS OF DETECTING ISCHEMIA
DURING STRESS TESTING
Myocardial perfusion imaging
Positron emission tomography
Magnetic resonance imaging
(American College of Cardiology/
Indications for exercise testing to
diagnose obstructive coronary artery
Adult patients with right bundle branch block or less
than 1mm of resting ST depression with an
intermediate pretest probabilty CAD on the basis of
gender , age and symptoms.
Indications in patients with prior
history of coronary heart disease
Patients undergoing initial evaluation with suspected or
known CAD, including those with complete right bundle
branch block or less than 1mm of resting ST depression.
Patients with suspected or known CAD , previously
evaluated , now presenting with significant change in
clinical status .
Low risk (on pretest probability), unstable angina patients
8 – 12 hours after presentation who have been free of
active ischemia or heart failure symptoms.
Intermediate risk (on pre test probability),unstable angina
patients 2 to 3 days after presentation who have been
free of active ischemic or heart failure symptoms.
Indications in patients with Valvular
1. In Chronic Aortic Regurgitation for assessment
of functional capacity and symptomatic responses
in patients with a history of equivocal symptoms.
2. Aortic stenosis – role of exercise testing in
asymptomatic AS patients , with recommendations
that aortic valve replacement be considered in
those with exercise induced symptoms or abnormal
blood pressure response.
Indications in patients with Valvular
Mitral stenosis – class 1 reommendation for stress
echocardiography in patients with MS and
discordance between symptoms and stenosis
Threshold values proposed for consideration of
a. Mean transmitral pressure gradient >15 mm Hg
b. A peak pulmonary artery systolic pressure > 60 mm
Hg during exercise.
Indications in patients with Valvular
Mitral regurgitation – In asymptomatic patients with
severe MR, exercise stress echo helps identify:
a. Patients with subclinical latent LV dysfunction
b. Worsening of MR severity
c. Marked increase in pulmonary arterial pressure
d. Impaired exercise capacity
Indications in patients with Valvular
Prosthetic heart valves – Stress echocardiography
used in confirming or excluding the presence of
hemodynamically significant prosthetic valve
stenosis or Patient prosthesis mismatch (PPM).
Evaluation of congenital complete heart block in
patients considering increased physical activity or
participation in competitive sports .
CONTRAINDICATIONS FOR STRESS
Acute myocardial infarction ( within 2 days )
High risk(on pretest probability) unstable angina
Uncontrolled cardiac arrthymias causing symptoms
or hemodynamic compromise
Symptomatic severe aortic stenosis
Acute pulmonary embolus or pulmonary infarction
Acute myocarditis or pericarditis
Acute aortic dissection
• Patient position – supine or upright.
• At rest CO and SV more in supine position than in
• Change from supine to upright position causes
, CO as a result of in SV and HR.
• The net effect on exercise performance is an approx.
10 % increase exercise time cardiac index, heart
rate, and rate pressure product at peak exercise in
the upright as compared with the supine position.
The main types of exercise are isotonic or dynamic
exercise, isometric or static exercise, and resistive
(combined isometric and isotonic) exercise.
a. Holding a static pushup position;
b. Holding a dumbbell in one hand;
c. Pushing against an immovable object, such as a
a. Weight lifting
c. Rock climbing
• Involves measurements of respiratory oxygen uptake
(VO2),carbon dioxide production (VCO2), and ventilatory
parameters during a symptom-limited exercise test.
• VO2 max is the product of maximal arterial-venous oxygen
difference and cardiac output and represents the largest amount
of oxygen a person can use while performing dynamic exercise
involving a large part of total muscle mass.
• The VO2 max decreases with age, is usually less in women
than in men, and diminished by degree of cardio-vascular
impairment and by physical inactivity.
• Peak exercise capacity is decreased when the ratio of
measured to predicted VO2 max is less than 85 to 90 percent.
• Metabolic equivalent (MET) refers to a unit of
oxygen uptake in a sitting, resting person.
• 1 MET is equivalent to 3.5 VO2 ml 02/kg/min of body
weight. Measured VO2 in ml 02/kg/min divided by 3.5
ml 02/kg/min determines the number of METs
associated with activity.
• Work activities can be calculated in multiples of
METs; this measurement is useful to determine
exercise prescriptions, assess disability, and
standardize the reporting of submaximal and peak
exercise workloads when different protocols are used.
General concerns prior to performing an exercise
test include –
• Safety precautions and equipments needs.
• Patient preparation
• Choosing a test type
• Choosing a test protocol
• Patient monitoring
• Reasons to terminate a test
• Post test monitoring
SAFETY PRECAUTIONS AND EQUIPMENT
The treadmill should have front and side rails for
subjects to steady themselves.
It should be calibrated monthly.
An emergency stop button should be readily
available to the staff only.
Exercise test should be performed under the
supervision of a physician who has been trained to
conduct exercise tests.
Any history of light headed or fainted while
exercising sholud be asked.
The physician should also ask about family history
and general medical history, making note of any
considerations that may increase the risk of sudden
A brief physical examination should always be
performed prior to testing to rule out significant
Preparation for exercise testing include
1. The subject should be instructed not to eat or smoke
atleast 2 hours prior to the test .
2. Unusual physical exertion should be avoided before
3. Specific questioning should determine which drugs
are being taken. The labeled medications should be
brought along so that medications can be identified
4. Because of a greater potential for cardiac events
with the sudden cessation of -blockers , they should
not be automatically stopped prior to testing but
done so gradually under physician guidance, only
after consideration of the purpose of the test.
Dynamic protocols most frequently are used to
assess cardiovascular reserve, and those suitable
for clinical testing should include a low intensity
In general, 6 to 12 minutes of continuous
progressive exercise during which the myocardial
oxygen demand is elevated to the patient's maximal
level is optimal for diagnostic and prognostic
purposes. The protocol should include a suitable
recovery or cool-down period.
c. Balke ware
In healthy individuals, the standard Bruce
protocol is normally used.
The Bruce multistage maximal treadmill
protocol has 3-minute periods to allow
achievement of a steady state before work-load
is increased for next stage.
In older individuals or those whose exercise
capacity is limited by cardiac disease, the
protocol can be modified by two 3-minute warm
-up stages at 1.7 mph and 0 percent grade and
1.7 mph and 5 percent grade.
The 6-Minute Walk Test
Used for patients who have marked left
ventricular dysfunction or peripheral arterial
occlusive disease and who cannot perform bicycle
or treadmill exercise.
Patients are instructed to walk down a 100-foot
corridor at their own pace, attempting to cover as
much ground as possible in 6 minutes.
At the end of the 6-minute interval, the total
distance walked is determined and the symptoms
experienced by the patient are recorded.
a. A flat or downsloping depression of the ST
segment > 0.1 mV below baseline (i.e the PR
segment ) and lasting longer than 0.08s
b. Upsloping or junctional ST segment changes are
not considered characteristic of ischemia and do
not constitute a positive test.
a. Target heart rate (85% of maximal predicted heart
for age and sex ) is not achieved .
The normal and rapid upsloping
ST segment responses are
normal responses to exercise.
Minor ST depression can occur
occasionally at submaximal
workloads in patients with
The slow upsloping ST
segment pattern often
demonstrates an ischemic
response in patients with known
coronary disease or those with a
high pretest clinical risk of
Downsloping ST segment
depression represents a severe
ST segment elevation in an
infarct territory (Q wave lead)
indicates a severe wall motion
abnormality and, in most cases, is
Bruce protocol. lead V4, the exercise
electrocardiographic (ECG) result is
abnormal early in the test, reaching
0.3mV (3mm) of horizontal ST segment
depression at the end of exercise.
The ischemic changes persist for at least
1 minute and 30 seconds into the
The right panel provides a continuous
plot of the J point, ST slope, and ST
segment displacement at 80msec after
the J point (ST level) during exercise and
in the recovery phase. Exercise ends at
the vertical line at 4.5 minutes (red
arrow). The computer trends permit a
more precise identification of initial onset
and offset of ischemic ST segment
This type of ECG pattern, with early
onset of ischemic ST segment
depression, reaching more than 3mm
of horizontal ST segment displacement
and persisting several minutes into the
recovery phase, is consistent with a
A 48-year-old man with
several atherosclerotic risk
factors and a normal resting
result, developed marked ST
segment elevation (4 mm
[arrows]) in leads V2 and V3
with lesser degrees of ST
segment elevation in leads
V1 and V4 and J point
depression with upsloping
ST segments in lead
II, associated with angina.
This type of ECG pattern is
usually associated with a
myocardial perfusion defect
in the corresponding left
segments and high-grade
intraluminal narrowing at
False positive :
a. In asymptomatic men
< 40 years.
b. In patients taking
c. In patients with
, abnormal potassium
False negative :
a. In patients with
limited to circumflex
portion is not well
represented on the
surface 12 lead ECG.)
Bruce protocol. The exercise
electrocardiographic (ECG) result
is not yet abnormal at 8:50 minutes
but becomes abnormal at 9:30
minutes (horizontal arrows, right)
of a 12-minute exercise test and
resolves in the immediate recovery
This ECG pattern in which the ST
segment becomes abnormal only
at high exercise workloads and
returns to baseline in the
immediate recovery phase may
indicate a false-positive result in an
asymptomatic individual without
atherosclerotic risk factors.
Vertical arrow indicates
termination of exercise.
T WAVE CHANGES
Pseudonormalisation of T wave:
Usually non-diagnostic and consider ancillary
imaging in such cases.
Pseudonormalization of T waves in
a 49-year-old man referred for
The resting electrocardiogram in
this patient with coronary artery
disease shows inferior and
anterolateral T wave inversion, an
adverse long-term prognosticator.
The patient exercised to 8
METs, reaching a peak heart rate
of 142 beats/min and a peak
systolic blood pressure of 248 mm
Hg. At that point, the test was
stopped because of hypertension.
exercise, pseudonormalization of T
waves occurs, and it returns to
baseline (inverted T wave) in the
postexercise phase. Transient
conversion of a negative T wave at
rest to a positive T wave during
exercise is a nonspecific finding in
patients without prior myocardial
infarction and does not enhance
MAXIMAL WORK CAPACITY
In patients with known or suspected CAD, a limited
exercise capacity is associated with an increased
risk of cardiac events and in general the more
severe the limitation, the worse the CAD extent and
In estimating functional capacity the amount of work
performed (or exercise stage achieved) expressed in
METs and not the number of minutes of
exercise, should be the parameter measured.
Major reduction in exercise capacity indicates
significant worsening of cardiovascular status.
BLOOD PRESSURE RESPONSE
The normal exercise response is to increase systolic
blood pressure progressively with increasing
workloads to a peak response ranging from 160 to
200mmHg with the higher range of the scale in older
patients with less compliant vascular systems.
Failure to increase systolic blood pressure beyond
120mmHg or a sustained decrease greater than
10mmHg repeatable within 15 seconds or a fall in
systolic blood pressure below standing resting
values during progressive exercise when the blood
pressure has otherwise been increasing
appropriately, is abnormal .
HEART RATE RESPONSE
Peak HR > 85% of maximal predicted for age
HR recovery >12 bpm (erect)
HR recovery >18 bpm (supine)
Chronotropic incompetence is determined by decreased
heart rate sensitivity to the normal increase in
sympathetic tone during exercise and is defined as
inability to increase heart rate to atleast 85 percent of
age predicted maximum.
Heart rate reserve is calculated as follows –
% HRR used = (HRpeak- HRres) / (220-age-HRres)
Abnormal heart rate recovery refers to a relatively slow
deceleration of heart rate following exercise cessation.
This type of response reflects decreased vagal tone and
is associated with increased mortality.
PROGNOSTIC VALUE OF STRESS TESTING
Parameters associated with adverse prognosis or multi-
vessel disease :
Duration of symptom-limiting exercise <5 METs
Failure to increase sBP ≥120mmHg, or a sustained
decreased ≥ 10mmHg, or below rest levels, during
ST segment depression ≥2mm, downsloping ST
segment, starting at <5 METs, involving ≥5
leads, persisting ≥5 min into recovery
Exercise-induced ST segment elevation (aVR excluded)
Angina pectoris at low exercise workloads
Reproducible sustained (>30 sec) or symptomatic
LIMITATIONS OF TREADMILL STRESS
Non-diagnostic ECG change
Women – false positives
Elderly – more sensitive/less specific
Diabetics – autonomic dysfunction
Inability to exercise
Drugs – digoxin; anti-anginals
NON-CORONARY CAUSES OF ST
Intraventricular conduction disturbance
Mitral valve prolapse
Severe aortic stenosis
Severe volume overload (aortic or mitral rgurgitation)
Sudden excessive exercise
LIMITATIONS OF TREADMILL
Dipyridamole or Adenosine can be given to create a
coronary "steal" by temporarily increasing flow in
nondiseased segments of the coronary vasculature
at the expense of diseased segments.
Alternatively, a graded incremental infusion of
dobutamine may be administered to increase MVO2
STRESS ECHO - LIMITATIONS
Factors which effect image quality:
THALLIUM- 201 SCAN
Myocardial perfusion problems are separated from
non viable myocardium by the fact that thallium
eventually washes out of the myocardial cells and
back into the circulation .
If a defect detected on initial thallium imaging
disappears over a period of 3-24 hours , the area is
presumably viable .
A persistent defect suggests a myocardial scar.
TECHNETIUM – 99M(sestamibi)
The technetium – 99m(sestamibi) based agents take
advantage of the shorter half - life ( 6 hours; thallium
201’s is 73 hours)
This allows for use of a larger dose , which results in
higher energy emissions and higher quality images.
Technetium 99m’s higher energy emissions scatter
less and are attenuated less by chest wall
structures, reducing the number of artifacts.
POSITRON EMISSION TOMOGRAPHY
Is a technique using tracers that simultaneously emit
two high energy photons .
A circular array of detectors around the patient can
detect these simultaneous events and accurately
identify their origin in the heart.
This results in improved spatial resolution
, compared with SPECT .
PET can be used to assess myocardial perfusion
and myocardial metabolic activity separately by
using different tracers coupled to different
Oxygen 15(half time 2mins)
Nitrogen -13(half life 10 mins)
Carbon -11(half time 20 mins)
Flourene -18(half 110 mins)
Because Rubidium – 82 with a half life of 75 seconds
, does not reqiure a cyclotron and can be generated
on site , it is frequently used with PET scanning
, especially for perfusion images.