STRESS TESTING
Indications, modalities
and patient selection
Dr. Kalyana Sundaram
Stress Testing
When? – Indications
What type? – Modalities
Who? – Patient selection
How often? – Frequency
How much? – Cost
Diagnostic Testing

Testing threshold

Diagnostic uncertainty

Treating threshold
The 2 x 2 (or 4 x 4) table
Test
Disease
Present
Absent
Positive
Negative
A
C
Se
A/(A+C)
B
D
Sp
D/(B+D)
PPV
A/(A+B)
NPV
D/(C+D)
Acc
(A+D)/tot
al
How “normal” is the normal curve?
The norm isn’t always the norm…
Which test is more accurate?


An exercise treadmill test (Se 80%, Sp
90%) in a population of post-CABG
patients with worsening angina?
or
The same test (Se 80%, Sp 90%) in a
population of young, healthy women
without family history of CAD?
Statistics can be tricky…
1
P 40%
1000
+
-
2
P 5%
1000
+
-
CAD
320
60
CAD
40
95
No
CAD
80
540
No
CAD
10
855
Accuracy
86%
vs.
89.5%
If there is one thing
you should think about
before ordering ANY test…
LIKELIHOOD RATIO
Stress Testing: Who?
Adults with intermediate (10-90%)
pre-test probability of CAD
Age
30-39
40-49
50-59
60-69
Sex
Typical
Atypical
Non-anginal
Asymp
Male
Intermediate
Intermediate
Low
Very low
Female Intermediate
Very Low
Very low
Very low
Male
Intermediate
Intermediate
Low
Female Intermediate
Low
Very low
Very low
Male
Intermediate
Intermediate
Low
Female Intermediate
Intermediate
Low
Very low
Male
High
Intermediate
Intermediate
Low
Female High
Intermediate
Intermediate Low
High
High
Angina
Precordial (retro-sternal) chest pain
that…



Is triggered by physical or emotional
stress
Is relieved by rest or SL NTG
Lasts for 15-20 minutes each episode
For those of you who like history…
First described in 1772 by the English
physician William Heberden in 20 patients
who suffered from "a painful and most
disagreeable sensation in the breast, which
seems as if it would extinguish life, if it were
to increase or to continue." Such patients, he
wrote, "are seized while they are walking
(more especially if it be uphill, and soon after
eating). But the moment they stand still, all
this uneasiness vanishes."
Sir William Heberden, 1710-1801
Back to contemporary times…
Classic anginal features:



Is triggered by physical or emotional
stress
Is relieved by rest or SL NTG
Lasts for 15-20 minutes each episode
2-3/3: typical angina
1/3: atypical angina
0/3: likely non-cardiac chest pain
Importance of typicality
7
6
5
4
3
Mortality
2
1
0
Typical
Atypical
Noncardiac
560 patients presenting for exercise tolerance testing (treadmill)
Prospective follow-up over 5.8 years
Jones et al. Prognostic importance of presenting symptoms in patients undergoing exercise
testing for evaluation of known or suspected coronary disease. Am J Med 2004.
Stress Testing: Who?

Patients with symptoms or prior history of
CAD
• Initial evaluation with suspected or
known CAD
• Known CAD with change in status
(crescendo)
• Low risk, unstable angina 8-12 hours
after presentation free of symptoms
(“rule out time”)
• Intermediate risk, unstable angina, 2-3
days free of active ischemia
Stress Testing: Who?

Post-MI
• Prognostic assessment
• Activity prescription
• Evaluation of medical therapy
• Before beginning cardiac rehabilitation
Stress Testing: Who?

Special Groups
• Women

Lower sensitivity, similar specificity
• Elderly (>75 years of age)

Other evaluated endpoints include
chronotropic response, exercise-induced
arrhythmias, and assessment of exercise
capacity
Chronotropic response
Stress Testing: Who?

Asymptomatic patients
• Diabetics planning to start exercise
• Guide to risk reduction therapy in a
patient with multiple risk factors*
• Men > 45 and women > 55



Starting exercise
Impact public safety
High risk due to concomitant disease (PVD,
CRF)
Stress Testing:
Absolutely Who Not!








Acute MI
High risk unstable angina
Uncontrolled arrhythmias with symptoms
Symptomatic, severe aortic stenosis*
Uncontrolled, symptomatic heart failure
Acute PE
Acute myocarditis or pericarditis
Acute aortic dissection
Stress Testing:
Maybe Who Not?*








Left main coronary stenosis
Moderate stenotic valvular heart disease
Electrolyte abnormalities
Severe hypertension (SBP > 200, DBP >
110)
Tachy or bradyarrhythmias
Outflow tract obstruction (HCM)
Mental or physical impairment (unsafe)
High-degree AV block
Stress Testing: When?


Patients with chest pain
• Change in clinical status
Acute coronary syndromes
• Low, intermediate, high risk (H&P, ECG,
markers – TIMI risk score)
• Low: 8-12 h symptom-free
• Intermediate: 2-3 days symptom-free*
• High: consider chemical imaging study
versus coronary angiography*
Stress Testing: When?

Post-MI
• Pre-discharge*

Submaximal (<70% MPHR)
• Early after discharge* (14-21 days)

Symptom limited (85% MPHR)
• Late after discharge* (3-6 weeks if early
test was submaximal)

Symptom limited (85% MPHR)
Stress Testing: When?

Before and after revascularization*
• Demonstration of ischemia
• Evaluation of post-procedure chest pain
• Evaluation of territory at risk
• Evaluation of restenosis
• Post-bypass surgery – useful later not
early
Stress Testing: How Often?


Change in clinical symptom pattern
Prognostication:
• There is no absolute guarantee


Progression of testing modality to
higher sensitivity and specificity
Depends on risk factors, their degree
of control and intensity of
modification
Two Components

Each cardiac imaging modality has
two components:
• Stressing agent: treadmill, dobutamine,
or adenosine
• Imaging agent: EKG, echo, or
radionuclide tracer (thallium or
technetium)
Stress Testing: What Type?

Exercise modality
• Treadmill

Bruce, Modified Bruce, Branching,
Naughton…
• Bicycle (recumbent)
• Chemical/Pharmacologic



Dipyridamole (Persantine®)
Adenosine (Adenoscan®)
Dobutamine
The Bruce protocol



Developed in 1949 by
Robert A. Bruce,
considered the “father
of exercise physiology”.
Published as a
standardized protocol
in 1963.
Remains the goldstandard for detection
of myocardial ischemia
when risk stratification
is necessary.
Protocol description
Stage
Time (min)
km/hr
Slope
1
0
2.74
10%
2
3
4.02
12%
3
6
5.47
14%
4
9
6.76
16%
5
12
8.05
18%
6
15
8.85
20%
7
18
9.65
22%
8
21
10.46
24%
9
24
11.26
26%
10
27
12.07
28%
Stress Testing: What Type?

Non-imaging versus imaging
• Consideration of imaging




Resting ST depression (<1 mm)
Digoxin
LVH
Women
Stress Testing: What Type?

Non-imaging vs. Imaging
• Require imaging







Intermediate risk non-imaging exercise test
Pre-excitation
Paced rhythm
LBBB or QRS > 120 ms
> 1 mm resting ST depression
Vessel localization
Improved prognostic information
Sensitivity and Specificity
Exercise EKG
Sensitivity
68%
Specificity
77%
Stress Echo
76%
88%
Nuclear
Imaging
79-92%
73-88%
Normal Myocardial Perfusion
Myocardial Ischemia
Myocardial Infarction
Stress Testing: What Type?

Choice of imaging modality is multi-factorial
• Body habitus – attenuation, COPD, etc.
• Local expertise
• Claustrophobia
• Understanding of sensitivity and specificity
• Coincident information:
 Ejection fraction
 Valvular structure
 Exercise capacity
Stressing Agents
Stressor
Pro
Con
Treadmill
Physiologic, simple,
less expensive,
good for patient
who can walk
Dobutamine
No exercise
needed
Caution in patients with
arrhythmias
Adenosine or
dipyridamole (used with
nuclear)
No exercise
needed;
uncomfortable
sensation of “heart
stoppage”
Adenosine may induce
bronchospasm – caution in
COPD and asthma!
Imaging Agents
Stressor
Pro
Con
EKG
Simple, less
expensive
Less information. May not be
able to localize the lesion. Can
not use if there are baseline
EKG abnormalities i.e. LBBB
with ST changes
Echocardiogram
Good if patient has
pre-existing EKG
abnormalities. More
info than EKG.
Less expensive
than nuclear.
Operator dependent to some
extent. May have poor
windows due to body habitus.
Pre-existing wall motion
abnormalities may make
interpretation more
challenging.
Thallium or technetium
Localizes ischemia
and infarcted
tissue.
Expensive
Sensitivity and Specificity
Exercise EKG
Sensitivity
68%
Specificity
77%
Stress Echo
76%
88%
Nuclear
Imaging
79-92%
73-88%
Exercise Testing: Contraindications






Unstable Angina
Decompensated CHF
Uncontrolled hypertension (blood
pressure > 200/115 mmHg)
Acute myocardial infarction within
last 2 to 3 days
Severe pulmonary hypertension
Relative contraindications (AS,
HCM…)
Last but not least… cost
TEST
COST - done
Hospital
COST - done
Office
ETT
$ 637
$ 239
STRESS
ECHO
$ 1600
$657
NUCLEAR
SCAN
$ 3000$4400
$937
Case Question
A 60yo man is evaluated for chest pain of 4 months’
duration. He describes the pain as sharp, located in
the left chest, with no radiation or associated
symptoms, that occurred with walking one to two
blocks and resolves with rest. Occasionally, the pain
improves with continued walking or occurs during the
evening hours. He has hypertension. Family history
does not include cardiovascular disease in any firstdegree relatives. His only medication is amlodipine.
On physical examination, he is afebrile, blood pressure
is 130/80mHg, pulse rate is 72/min, and respiration
rate is 12/min. BMI is 28. No carotid bruits are
present, and a normal S1 and S2 with no murmurs
are heard. Lung fields are clear, and distal pulses are
normal. EKG showed normal sinus rhythm.
Case Question

Which of the following is the most
appropriate diagnostic test to
perform next?
a. Adenosine nuclear perfusion stress
test.
b. Coronary angiography
c. Echocardiography
d. Exercise treadmill
Take Home Points



Stress testing is indicated for patients
with intermediate pre-test probability
Each stress test has two components: an
imaging modality and stress modality
When determining which stress test to
order, keep in mind their ability to
exercise, whether any contraindications
are present, cost by LOCATION , body
weight and specificity and sensitivity