Download Treadmill Stress Testing for the Primary Care Physician

Exercise Stress Test
Apiwan Nuttamonwarakul
The Supreme Patriarch Center on Aging
Ministry of Public Health
Objectives




Review essential Exercise
Stress Test (EST)
background, resources and
terminology.
Describe the performance of
the EST.
Describe common normal and
abnormal responses to
exercise testing.
Discuss interpretation of the
EST.
Exercise Stress Test Essentials
Exercise Stress Testing and Family
Physicians


Frequency of Utilization: Estimated that 13% of family physicians
perform and interpret treadmills in their office.
 American Academy of Family Physicians. Facts about Family
Practice. Kansas City, Mo: American Academy of Family
Physicians; 1998.
Credentialing: Recent guidelines suggest that a physician acquire
50 exercise stress tests to qualify for privileges, and should perform
atleast 25/yr to maintain clinical competency.
 Schlant et al: Clinical competence in exercise testing: a
statement for physicians from the ACP/ACC/AHA task force on
clinical privileges in cardiology. Circulation 1990;82;1884-1888.
Safety and Exercise Stress Testing



The risk of death during or
immediately after an exercise
test is less than or equal to
0.01%.
The risk of an acute MI during
or immediately after an exercise
test is less than or equal to
0.04%.
The risk of a complication
requiring hospitalization is less
than or equal to 0.2%.
References


ACC/AHAQ Practice Guidelines
 Fletcher GF et al: Exercise Standards: a
statement for healthcare professionals from the
American Heart Association Writing Group:
Special Report. Circulation 1995;91:580-615.
 ACC/AHA Guidelines for Exercise Testing. A
Report of the ACC/AHA Task Force on Practice
Guidelines. JACC Vol. 30 (3):260-311.
 Gibbons RJ et al: ACC/AHA 2002 guideline
update for exercise testing: a report of the
American College of Cardiology/American heart
Association Task Force on Practice Guidelines
2002. www.acc.org/clinical/guidelines
ACSM References
 ACSM’s Guidelines for Exercise Testing and
Prescription, Seventh Edition.
 ACSM’s Resource Manual for Exercise Testing
and Prescription, Seventh Edition.
The Electrocardiogram

PR segment: isoelectric line
from which the J point and ST
segment are measured from
rest. PQ junction is the point of
reference.

J Point: point that distinguishes
the QRS complex from the ST
segment; measuring point for
ST segment depression.

ST segment: ST segment is
measured relative to the PQ
junction, 80 ms from the J
point, or 60 ms in rates over
145 bpm.
Exercise Physiology

METs: oxygen uptake is conveniently
expressed in METs; 3.5 ml O2/kg/min


Myocardial Oxygen Consumption:


1 MET=rest; 5 MET=ADLs;10 METs=
medical therapy equivalent to CABG; 18
METS=elite athlete.
Double product of HRxSBP correlates with
myocardial oxygen consumption.
VO2 max:


Fick Equation: VO2max = (HRmax x SV
max) x (CaO2max – CvO2max)
Gold standard for aerobic fitness.
Metabolic Equivalents (METs)

1 MET = 3.5 ml O2 per kilogram of body weight
per minute
Key MET Values (part 1)
 1 MET = "Basal" = 3.5 ml O2 /Kg/min
 2 METs = 2 mph on level
 4 METs = 4 mph on level
 < 5METs = Poor prognosis if < 65;
 limit immediate post MI;
cost of basic activities of daily living
Key MET Values (part 2)


10 METs = As good a prognosis with medical
therapy as CABS
13 METs = Excellent prognosis, regardless of
other exercise responses

16 METs = Aerobic master athlete

20 METs = Aerobic athlete
Myocardial (MO2)



Coronary Flow x Coronary a - VO2 difference
Wall Tension (Pressure x Volume, Contractility, Stroke Work, HR)
Systolic Blood Pressure x HR
 Double product < 20,000 is low heart work load
 Double product > 29,000 indicates high heart work load




SBP should rise > 40 mmHg
Drops are ominous (Exertional Hypotension)
DBP should decline
Angina and ST Depression usually occurs at same Double
Product in an individual
** Direct relationship to VO2 is altered by beta-blockers,
training,...
The Fick Equation
(220 - Age)
PaO2
Sinus Node Dysfunction
Hgb [ ]
Drugs (e.g., B - blockers)
SaO2
Diffusion
Ventilation
Perfusion
VO2max = (HRmax X SVmax) X (CaO2max - CvO2max)
Genetic Factors (Heart Size)
Conditioning Factors
Contractility/Afterload/Preload
Disease Factors
Wall Motion/Ventricular Fxn
Valve Stenosis or Regurgitation
Skeletal Muscles
•Aerobic Enzymes
•Fiber Type
•Muscle Disease
Capillary Density
Performance of the
Exercise Stress Test
Equipment and Protocols


Equipment:
 Treadmill
 Cycle
 Arm Ergometery
 Monitor and EKG Recorder
 Thallium, Echocardiography
Protocol:
 Maximal:


Bruce Protocol is the most commonly used test. Vigorous with the
first stage commencing at 5 METs. Speed and grade is increased
every three months. Generally symptom-limited; adequate tests
reach 85% of MPHR.
Sub-Maximal:

Tests that involve termination at a pre-determined heart rate. PostMI patients generally are set at 60% of MPHR, 5 METs or 120 bpm.
Which Protocol?

Vast Majority (82+%) use BRUCE

So, why not you?
Treadmill Protocols
Indications

ACC/AHA Guidelines for
Exercise Testing



Class I: general
consensus/evidence that testing is
justified.
Class II: divergence of opinion on
utility. IIa in favor; IIb less
evidence.
Class III: agreement that testing is
not warranted.
Indications: Diagnose Obstructive CAD




Class I
 Adult patients (including those with RBBB and 1mm resting ST
depression) with an intermediate pre-test probability of disease.
Class IIa
 Patients with vasospastic angina.
Class IIb
 Patients with a high or low pre-test probability of disease.
 Patients with less than 1mm ST depression and taking digoxin.
 Patients with LVH by voltage and less than 1mm of baseline ST
depression.
Class III
 WPW; paced rhythm; >1mm ST depression; LBBB.
Pre-Test Probability of CAD
Age
Gender
Typical/Definite
Angina Pectoris
Atypical/Probable
Angina Pectoris
NonAnginal
Chest Pain
Asymptomatic
30-39
30-39
Males
Intermediate
Intermediate
low (<10%)
Very low (<5%)
Females
Intermediate
Very Low (<5%)
Very low
Very low
40-49
Males
High (>90%)
Intermediate
Intermediate
low
40-49
Females
Intermediate
Low
Very low
Very low
50-59
Males
High (>90%)
Intermediate
Intermediate
Low
50-59
Females
Intermediate
Intermediate
Low
Very low
60-69
Males
High
Intermediate
Intermediate
Low
60-69
Females
High
Intermediate
Intermediate
Low
High = >90%
Intermediate = 10-90%
Very Low = <5%
Low = <10%
ACSM Recommendations for Exercise
Testing Prior to Exercise Participation

CAD Risk Factors
 FH: MI in 1st degree male
relative before 55; female
before 65.
 Smoker or quit within 6
months.
 Hypertension
 Hypercholesterolemia:
TCHOL > 200; HDL <35;
LDL > 130.
 Impaired fasting glucose:
>110.
 Obesity: BMI >30.
 Sedentary
 HDL >60 is a negative risk
factor.

CAD Signs/Symptoms
 Pain in the chest, neck,
jaw, arms that may be due
to ischemia
 SOB at rest or exertion
 Dizziness or syncope
 Orthopnea/PND
 Ankle edema
 Claudication
 Known heart murmur
 Unusual fatigue or SOB
with usual activities
ACSM Recommendations for Exercise
Testing Prior to Exercise Participation

Initial ACSM Risk Stratification




Old versus Young


Low Risk: younger individuals who are
asymptomatic and have no more than one risk
factor.
Moderate Risk: older or those who meet the
threshold for two or more risk factors.
High Risk: individual with signs or symptoms of
CAD, or known cardiovascular, pulmonary, or
metabolic disease
Men < 45 years of age; Women < 55.
Moderate versus Vigorous Exercise


Moderate: 3-6 METs, 40 to 60% maximal oxygen
uptake.
Vigorous: >6 METs, or 60% maximal oxygen
uptake.
ACSM Recommendations for Exercise
Testing Prior to Exercise Participation
Low Risk
Moderate
Risk
High Risk
Moderate
Exercise
Not
Necessary
Not
Necessary
Recommended
Vigorous
Exercise
Not
Necessary
Recommended
Recommended
Contraindications

Absolute






Acute myocardial infarction
(within 2d)
High risk unstable angina
Uncontrolled arrhythmias
causing symptoms or
hemodynamic compromise
Symptomatic severe aortic
stenosis
Acute PE, myocarditis or
pericarditis
Acute aortic dissection
Contraindications

Relative








Left main coronary stenosis
Moderate stenotic valvular
heart disease
Electrolyte Abnormalities
Severe arterial hypertension
(200/110)
Tachy/Bradyarrhythmias
Hypertrophic cardiomyopathy
Mental or physical impairment
leading to inability to exercise
adequately
High degree AV block
Special Considerations



Medications
 Beta blockers: blunt HR response; short
acting held the day of the test; long
acting held two days.
 Calcium channel blockers: delay
ischemia, decreasing sensitivity of the
test.
 Digoxin: produces abnormal ST
depression with exercise.
 Diuretics: may cause ST depression
with hypokalemia.
Conduction Disturbances
 High degree AV block (Mobitz II and
third degree block) should not be tested.
 LBBB and WPW preclude interpretation
of ischemia and should not be tested.
Special Clinical Situations
 Severe arthritis/Obesity: consider
pharmacologic stress testing.
 Hypertension: don’t test 200/120
 Q waves: in post MI pts, ST elevation
can indicate a hypokinetic ventricle.
Physician Responsibilities During the Test

Patient Evaluation and Clearance





Physical Examination




Careful history of symptoms and
past medical history; typical vs.
atypical.
Risk factors
Family history
Informed Consent
Vital signs
Cardiovascular: murmurs, gallops
Lungs
Selection of Protocol


Maximal vs. Sub-Maximal
Treadmill vs. Cycle
Performing the Test




Preparing the Patient
Monitoring the Patient
Terminating the Test
Recovery of the Patient
Preparing the Patient




Instructions:
 No eating two hours before test;
no consumption of alcohol,
caffeine, or tobacco three hrs
before.
 Comfortable clothing.
 Medications determined by
functional vs. diagnostic testing.
Skin Preparation
 Hair shaved; abrasive rub; “tap”
test.
Appropriate Blood Pressure cuff.
Consent.
Preparing the Patient

Pre-Test Checklist








Equipment and safety check
Informed Consent
Pre-test history and physical
examination
Electrode skin preparation
Resting ECG reviewed
Standing ECG and BP
Patient Demonstration
Patient Questions
Monitoring the Patient



Pre-Test
 12 lead ECG supine and
standing.
 BP supine and standing.
Exercise
 12 lead last 15 sec of each
stage.
 BP and RPE at the end of each
stage.
Post-Test
 12 lead ECG immediately after
exercise, then every 1 to 2
minutes until return to baseline.
 BP: immediately after exercise,
then every 1 to 2 minutes until
return to baseline.
 Follow symptoms.
Borg RPE Scale
 6
 7 Very, very light
 8
 9 Very light
 10
 11 Fairly light
 12
 13 Somewhat hard
 14
 15 Hard
 16
 17 Very hard
 18
 19 Very, very hard
 20
Terminating the Test


All treadmill stress tests
should be completed to a
symptom-limited endpoint, if
possible.
85% of maximal predicted
heart rate is required to
identify a test as adequate.
Indications for Test Termination

Absolute
 Drop in SBP of >10 mmHg from
baseline, despite increased
workload, when accompanied by
other ischemia
 Moderate to severe angina
 Increasing ataxia, dizziness, or
pre-syncope
 Signs of poor perfusion
 Technical difficulties
 Subjects desire
 Sustained Vtach
 ST elevation in leads without
diagnostic Q waves
Indications for Test Termination

Relative







Drop in SBP of >10 mmHg
from baseline, despite
increased workload
ST depression >2mm from
baseline
Multifocal PVCs, triplets,
SVT, heart block
Fatigue, shortness of
breath, wheezing, leg
cramps
Bundle branch block
Increasing chest pain
Hypertensive response
Recovery of the Patient




Have the patient lie down
and continuously
observe.
Auscultate for abnormal
heart and lung sounds.
Monitor until clinically
stable and
electrocardiogram has
returned to normal.
ECG changes in
recovery just as ominous
as those occurring during
exercise.
Common Normal Responses to
Exercise Testing

Symptoms



Typical anginal symptoms can
be produced by testing and
increase the prognostic value of
a test.
Symptoms, however, do not
define a positive test, and define
a test “suggestive of ischemia.”
Opportunity for “anginal
threshold” determination and
use of Borg Scale for exercise
prescription.
Electrocardiographic Responses to Exercise

P wave:


PR segment:


Demonstrates positive upslope that
returns to baseline by 80ms.
T wave:


Decreases with exercise; in subjects with
resting J junction elevation, this
normalizes to baseline.
ST segment:


Increases in septal q waves; slight
decreases in R wave amplitude; minimal
shortening of interval.
J junction:


Shortens and downslopes in the inferior
leads.
QRS complex:


Superimposition of P and T; p wave may
increase in inferior leads.
initially a gradual decrease in amplitude.
QT interval:

Rate-related shortening.
Heart Rate

Normal Heart Rate Response



Chronotropic Incompetence



Increase in HR as a result of vagal tone withdrawal.
Standard deviation for peak HR determination is 15 BPM.
Peak heart rate less than 120 BPM.
Failure to achieve 85% of age-predicted maximum.
Heart Rate Recovery
Heart Rate Recovery and Treadmill Exercise Score as Predictors of Mortality in Patients Referred
for Exercise ECG Nishime EO, et al: JAMA, September 20, 2000.
Vo 284, No 11, 2000.
Heart Rate Drop in Recovery vs
METs
 10 to 15% increase in survival per MET
 METS can be increased by 25% by a training
program
 What about Heart Rate Recovery???
Heart Rate Recovery




Following the EST, patients walked for 2 minutes at 1.5
mph and at a grade of 2.5%.
Heart rate recovery was the difference in heart rate at
peak exercise and one minute into recovery; 12/min or
less was considered abnormal.
9454 patients were followed for a median of 5 years; 20
% had abnormal heart rate recovery; they represented
8% of deaths vs. 2%; hazard ratio of 4.16.
Heart rate recovery is an independent predictor of
mortality.
Should Heart Rate Drop in
Recovery be added to ET?
 Long known as a indicator of fitness: perhaps better for
assessing physical activity than METs
 Recently found to be a predictor of prognosis after
clinical treadmill testing
 Does not predict angiographic CAD
 Studies to date have used all-cause mortality and failed
to censor
 Probably not more predictive than Duke Treadmill Score
or METs
 Studies including censoring and CV mortality needed
Blood Pressure




Normal:
 Systolic increases during exercise; returns to baseline by five to six
minutes in recovery.
Hypotensive Response to Exercise:
 A drop in BP to baseline levels during exercise; poor prognosis.
Hypertensive Response to Exercise:
 Systolic greater than 220mmHg, or rise in diastolic of > 10mmHg, or
Stage II age predicted 95% DBP.
 Singh et al: BP response during treadmill testing as a risk factor for
new-onset hypertension. Circulation. 1999;99:1831-1836.
Blood Pressure in Recovery:
 3 Minute Systolic BP Ratio: SBP 3 min/ SBP Peak > 0.91 is abnormal.
 Taylor et al: Postexercise systolic BP response: clinical application
to the assessment of ischemic heart disease. American Family
Physician. Vol 58(5).
Common Abnormal Responses to
Exercise Stress Testing
ST Depression and Elevation



Measurement:
 Three Continuous beats
 Baseline is the junction of downsloping
PR and QRS complex
Depression:
 If ST elevated at rest c/w early
repolarization, measure from baseline.
 If ST depressed at rest, measure
deviation from the baseline
depression.
Elevation:
 ST elevation is c/w transmural
ischemia, however needs to be
classified by whether it occurs over Q
waves.
 Over Q waves: ST elevation may
occur in the presence of prior infarct,
and may or may not represent
ischemia.
Common Abnormal Responses




Isolated Inferior Depression
 Atrial repolarization has been
demonstrated to cause J point depression
in the inferior leads.
 Isolated inferior lead ST depression is
frequently a false positive.
ST Elevation
 ST segment elevation in the absence of Q
waves usually indicates transmural
ischemia.
Exercise-Induced Bundle Branch Block
 Ischemia can be interpreted in RBBB, but
not LBBB.
 The Stress test should be stopped and the
patient should have further evaluation for
structural heart disease.
Exercise-Induced Hypotension
 Always serious symptoms that warrant
further evaluation for structural heart
disease.
Common Abnormal Responses

Exercise-Induced Arrhythmias




Simple PVCs: not uncommon; low grade ectopy, unifocal,
and infrequent PVCs during exercise do not increase risk.
Complex Arrhythmias: complex arrhythmias at low levels,
in particular when associated with ischemia, warrant
further evaluation.
Ventricular Tachycardia: require termination of the test,
with prognosis based upon status of underlying heart
disease.
Paroxysmal Atrial Tachycardia/PSVT: treated as patients
who develop PSVT without exercise.
Determining Myocardial Ischemia


Diagnostic of Myocardial
Ischemia
 Horizontal or downsloping ST
depression >1.0 mm at 60ms
past the J point
 ST elevation >1.0 mm at
60ms past the J point
 Upsloping ST depression >1.5
at 80 ms past the J point
Negative for Myocardial
Ischemia
 Patient has exercised to
atleast 85% of maximal
predicted heart rate and none
of the above are present.


Suggestive of Myocardial
Ischemia
 Horizontal or downsloping ST
depression 0.5 – 1.0
 ST elevation 0.5 – 1.0
 Upsloping ST depression >.7
<1.5
 Exercise-induced hypotension
 Chest pain that seems like
angina
 High grade ventricular ectopy
 A new third heart sound
Inconclusive
 Patient does not achieve 85%
of maximum HR and has no
ischemia.
The Final Report


First Paragraph: (General Summary)
 Pt’s age, indication for testing, cardiac medications and protocol.
 Baseline heart rate, BP and resting ECG findings.
 Peak exercise data, BP, HR, peak METs, RPE and reason for
stopping.
 Description of abnormalities in ECG response, hemodynamics,
dysrhythmias, or symptoms
Second Paragraph: (Assessment)
 Presence or absence of ischemia
 Normal or abnormal HR/BP response
 Presence of dysrhythmias
 Presence of symptoms
 Maximal aerobic capacity
Interpretation of the Exercise
Stress Test
Bayes Theorem

Theory of Conditional Probability

The predictive value of a test
depends upon the descriptors of
the test accuracy as well as the
prevalence of disease in the
population being tested.



Patients with an abnormal test
and a low pre-test probability of
disease are at risk for a falsepositive.
Patients with a normal test and a
high pre-test probability of
disease are at risk for a false
negative test.
The treadmill is thought to have a
sensitivity of 70% and a specificity
of 80% for diagnosing CAD.
Pre-Test and Post-Test Probability

Diamond and Forrester Curves
Common Errors

False-Negative Tests





Failure to reach an adequate
workload
Insufficient number of leads
Single vessel disease
Good collateral circulation
Technical or observer error

False-Positive Tests














Pre-existing abnormal ECG
Cardiac hypertrophy
WPW and other conduction
abnormalities
Drugs
Cardiomyopathy
Hypokalemia
Vasoregulatory abnormalities
Mitral valve prolapse
Pericardial disorders
Pectus excavatum
Coronary spasm
Anemia
Female gender
Observer error
Predicting Severity of Disease

Electrocardiographic Responses







ST depression > 2.5mm
ST depression beginning at 5 METs or
less
Downsloping ST depression or ST
elevation
ST depression lasting more than 8
minutes into recovery
Serious dysrhythmias at a low heart rate
ST depression in more than 5 leads
Nonelectrocardiographic Response



Chronotropic incompetence
Exercise-induced hypotension
Inability to exercise past 5 METs
Determining Prognosis

Duke Treadmill Score
 Exercise Treadmill Score =
Minutes of Exercise – (5 x max
ST depression) – (4 x Anginal
Index)
 Anginal Index:
 0 – no angina;
 1 typical;
 2 – terminated test
secondary to angina.
 Scoring:
 >5 – good prognosis
with 5 yr survival of 97%
 -10 to 4 – intermediate
prognosis
 -11 < - poor prognosis 5
yr survival of 72%
DUKE Treadmill Score for
Stable CAD
METs - 5 X [mm Exercise-Induced ST
Depression] - 4 X [Treadmill Angina Index]
Duke Treadmill Score Nomogram
But Can Physicians do as well as
the Scores?
 954
patients - clinical/ETT reports
 Sent to 44 expert cardiologists, 40
cardiologists and 30 internists
 Scores did better than all three but was
most similar to the experts
How to read an Exercise ECG







Good skin prep
PR isoelectric line
Not one beat
Three consistent complexes
Averages can help
Garbage in, garbage out
Why watch during recovery?
Symptom-Sign Limited Testing
Endpoints – When to stop!

Dyspnea, fatigue, chest pain

Systolic blood pressure drop

ECG--ST changes, arrhythmias

Physician Assessment

Borg Scale (17 or greater)
Problems with Age-Predicted
Maximal Heart Rate






Which Regression Formula? (2YY - .Y x Age)
Big scatter around the regression line
– poor correlation [-0.4 to -0.6]
– One SD is plus/minus 12 bpm
A percent value target will be maximal for some and
sub-max for others
Confounded by Beta Blockers
Borg scale is better for evaluating Effort
Target Heart Rate does have a place as an Indicator of
Effort or adequacy of test
Comparison of Tests for Diagnosis
of CAD
Grouping
Standard ET
 ET Scores
 Score Strategy
Thallium Scint
SPECT
Adenosine SPECT
Exercise ECHO
Dobutamine ECHO
Dobutamine Scint
Electron Beam
Tomography (EBCT)
# of
Total #
Studies Patients
147
24,047
24
11,788
2
>1000
59
6,038
16+14 5,272
10+4
2,137
58
5,000
5
<1000
20
1014
16
3,683
Sens Spec Predictive
Accuracy
68% 77%
73%
80%
85% 92%
88%
85% 85%
85%
88% 72%
80%
89% 80%
85%
84% 75%
80%
88% 84%
86%
88% 74%
81%
60% 70%
65%
Function is
Everything!