Exercise Stress
Electrocardiography
Dr Bijilesh.U
Exercise is a common physiological stress used to elicit
cardiovascular abnormalities not present at rest and to
determine adequacy of cardiac function.
Exercise ecg - one of the most frequent noninvasive
modalities used to assess patients with suspected or
proven cardiovascular disease.
Estimate likelihood & extent of CAD , the prognosis ,
determine functional capacity & effects of therapy.
Exercise physiology
Exercise protocols
Electrocardiographic measurements
Nonelectrocardiographic observations
Exercise test indications
Specific Clinical Applications
Safety and risks of exercise testing
Termination of exercise
EXERCISE PHYSIOLOGY
 Exercise - body's most common physiologic stress 
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places major demands on CVS
Exercise considered most practical test of cardiac
perfusion and function
Fundamentally involves the measurement of work
Common biologic measure of total body work is oxygen
uptake
Cardiac output can increase as much as six-fold
EXERCISE PHYSIOLOGY
 Acceleration of HR by vagal withdrawal
 Increase in alveolar ventilation
 Increased venous return- sympathetic
venoconstriction.
 Early phases - cardiac output increased by
augmentation in stroke volume and heart rate
 Later phases by sympathetic-mediated increase
in HR
 During strenuous exertion, sympathetic discharge is
maximal and parasympathetic stimulation is
withdrawn
 Vasoconstriction of most circulatory body systems except in exercising muscle , cerebral and
coronary circulations
 Catecholamine release enhances ventricular
contractility
 As exercise progresses
skeletal muscle blood flow is increased
O2 extraction increases by as much as threefold
total calculated peripheral resistance decreases
systolic blood pressure, mean arterial pressure, and pulse pressure
increase
 Diastolic blood pressure does not change
significantly.
V O2
 Total body or ventilatory O2 uptake - amount of
O2 extracted from air as the body performs work
 Determinants of VO2
- cardiac output
- peripheral AV oxygen difference
 Maximal AV difference is constant 15 to 17 mL/dL
 Vo2 - estimate of maximal cardiac output.
V O2 can be estimated from treadmill speed and
grade
• Vo2 = (MPH ˣ 2.68 ) ˣ [.1 + ( Grade ˣ 1.8) ] + 3.5
• Vo2 can be converted to METS by dividing by
3.5.
M O2
 Myocardial oxygen uptake is the amount of oxygen
consumed by the heart muscle
 Determinants of M O2 – Intramyocardial wall tension
- Contractility & HR
 Mo2 - estimated by - HR & SBP (double product).
 Exercise-induced angina often occurs at the same
Mo2
 Higher double product - better myocardial perfusion
Maximum heart rate
 Maximum heart rate (MHR) : 220 – age
 Overestimate maximum heart rate in females
MHR = 206 − 0.88 (age in years)
 MHR decreased in older persons
 Age-predicted maximum heart rate is a useful
measurement for safety reasons
 Post exercise phase - hemodynamics return to
baseline within minutes
 Vagal reactivation - important cardiac deceleration
mechanism after exercise
 Accelerated in athletes but blunted in chronic
heart failure
Metabolic Equivalent
 Refers to a unit of oxygen uptake in a sitting,
resting person
 Common biologic measure of total body work is
the oxygen uptake
 One MET is equated with the resting metabolic
rate (3.5 mL of O2/kg/min)
 MET value achieved from an exercise test is a
multiple of the resting metabolic rate
 METS associated with activity = Measured Vo2 /
3.5 (both in mL O2/kg/min)
 Measured directly (as oxygen uptake) or
estimated from the maximal workload achieved using standardized equations
Calculation of METs on the Treadmill
METs = Speed x [0.1 + (Grade x 1.8)] + 3.5
3.5
Calculated automatically by Device!
Clinically Significant Metabolic
Equivalents for Maximum Exercise
1 MET
Resting
2 METs
Level walking at 2 mph
4 METs
Level walking at 4 mph
<5 METs
Poor prognosis; peak cost of basic activities of daily living
10 METs
13 METs
Prognosis with medical therapy as good as coronary artery
bypass surgery; unlikely to exhibit significant nuclear perfusion
defect
Excellent prognosis regardless of other exercise responses
18 METs
Elite endurance athletes
20 METs
World-class athletes
Exercise Test Modalities
 Isometric, dynamic, and a combination of the two.
 Isometric exercise - constant muscular contraction
without movement
 Moderate increase in cardiac output and only a small
increase in vo2 - insufficient to generate an ischemic
response.
 Dynamic exercise - rhythmic muscular activity
resulting in movement
Exercise Protocols
 Dynamic protocols are most frequently used to
assess cardiovascular reserve
 Should include a low-intensity warm-up and a
recovery or cool-down period
 Optimal for diagnostic and prognostic purposes
- Approximately 8 to 12 minutes of continuous progressive
exercise
- myocardial oxygen demand elevated to patient's maximum
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Arm Ergometry
Bicycle Ergometry
Treadmill Protocol
Walk Test
Arm Ergometry
 Involve arm cranking at incremental workloads of
10 to 20 watts for 2- or 3-minute stages
HR & BP responses to a
given workload > leg exercise
Peak vo2 and peak HR
- 70% of leg testing
Bicycle Ergometry
 Involve incremental workloads
starting at 25 – 50 watts
 Lower maximal VO2 than the treadmill
Treadmill Protocol s
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Bruce
Modified Bruce
Naughton and Weber
ACIP (Asymptomatic cardiac ischemia pilot trial)
Modified ACIP
Tread mill protocol
Bruce multistage maximal treadmill protocol
 3 minutes periods to achieve steady state
before workload is increased
 Limitation - relatively large increase in
vo2 between stages
 Modified Bruce protocol - Older individuals or
those whose exercise capacity is limited
 Modified by two 3 min warm up stages at
1.7mph % 0 % grade and 1.7mph % 5%grade.
• Naughton and Weber protocols use 1-2min
stages with 1-MET increments between
stages
• Asymptomatic cardiac ischemia pilot trial
and modified ACIP protocols use 2min
stages with 1.5mets increments between
stages - after two 1min warm up
• Functional capacity overestimated by 20% -if
handrail support is permitted
Walk Test
 A 6-minute walk test or a long-distance corridor walk
 Provide an estimate of functional capacity in patients
who cannot perform bicycle or treadmill exercise
 Older patients ,heart failure, claudication, or
orthopedic limitations
 Walk down a 100-foot corridor at their own pace cover as much ground as possible in 6 minutes
 Total distance walked is determined and the
symptoms experienced by the patient are recorded.
Cardiopulmonary Exercise Testing
 Involves measurements of respiratory oxygen
uptake (vo2) , carbon dioxide production ( vco2 )
and ventilatory parameters during a symptomlimited exercise test
 Patient wears a nose clip and breathes through a
nonrebreathing valve
Technique
No caffeinated beverages or smoke 3hr before
Wear comfortable shoes and clothes.
Unusual physical exertion should be avoided
Brief history & physical examination performed
Explain risks and benefits
Informed consent is taken
12 lead ECG is recorded with electrodes at the
distal extremities
Torso ECG is obtained in supine & standing position
If false +ve test is suspected, hyperventilation
should be performed
Room temp should be 18 –24 C & humidity < 60%
Walking should be demonstrated to the patient
HR, BP & ECG recorded at end of each stage.
Resuscitator cart, defibrillator and appropriate
cardioactive drugs should be available
Optimal patient position
in the recovery phase
? supine
 Sitting position, less space is required and patients
are more comfortable
 Supine position increases end-diastolic volume
and has the potential to augment ST-segment
changes
 Electrocardiographic
Measurements
Lead system
Mason-Likar modification
 Modification of the standard 12-lead ECG
 Extremity electrodes moved to torso to reduce motion
artefact
 Results in
right axis shift
increased voltage in inferior leads
loss of inferior Q waves
new Q waves in lead aVL
Types of ST-Segment Displacement
 J point, or junctional, depression - normal finding in exercise
 In myocardial ischemia, ST segment becomes horizontal,
 With progressive exercise depth of ST segment may increase
 In immediate post recovery phase ST segment displacement
may persist with down sloping ST segments and T wave
inversion - returning to baseline after 5-10 min
 In 10% , ischemic response may appear in recovery phase
Measurement of ST-Segment
Displacement
PQ junction is chosen as isoelectric point
TP segment is true isoelectric point but impractical choice
Abnormal ST depression
0.1mv (1mm) or > ST depression from PQ junction
with a flat ST segment slope ( <0.7-1mv /sec)
80 msec after J point (ST 80)
in 3 consecutive beats with a stable base line
When ST 80 measurement difficult at rapid heart
rates > 130/mt measure at ST 60
When ST is depressed at rest- additional 0.1mv or
more during exercise is considered abnormal
1.PQ JUNCTION
2. J POINT
3.ST 80
Upsloping ST segment
Rapid upsloping ST segment (more than 1 mV/sec) depressed
less than 1.5 mm after the J point - normal
Slow upsloping ST segment
at peak exercise
In patients with high CAD
prevalence, slow up sloping ST
,depressed > 1.5mm ST 80 is
considered abnormal
Horizontal ST-segment
depression
 ST segment elevation
 0.1mv ( 1mm) or greater of ST elevation, at ST
60 in 3 consecutive beats - abnormal
response.
 More frequently with AWMI - early after event decreases in frequency by 6 weeks
 ST elevation is relatively specific for territory of
ischemia
 In leads with abnormal Q waves - not a marker
of more extensive CAD and rarely indicates
ischemia.
 When it occurs in non q wave lead in a patient
without previous MI - transmural ischemia
 In a patient who has regenerated embryonic R
waves after AMI - significance similar
Eight typical exercise ecg
patterns at rest and at
peak exertion
T Wave Changes
 Transient conversion of a negative T wave
at rest to positive T wave in exercise –
pseudonormalisation
 Nonspecific finding in
patients without prior MI
 Does not enhance
diagnostic or prognostic
content of test
Nonelectrocardiographic Observations
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Blood pressure
Maximal Work Capacity
Heart rate response
Heart Rate Recovery
Chest discomfort
Rate-Pressure Product
Blood pressure
Normal exercise response - increase SBP progressively
with increasing workloads.
Range from 160 to 200 - higher range in older patients
with less compliant vessels
Abnormal
Failure to increase SBP > 120 mm Hg
Sustained decrease greater than 10 mm Hg
Fall in SBP below resting values
Diastolic BP doesn’t change significantly
 Conditions other than myocardial ischemia associated
with abnormal BP response
Cardiomyopathy
Cardiac arrhythmias
LVOT obstruction
Antihypertensive drugs
Hypovolemia
 An exaggerated BP increase with exercise increased risk of future hypertension
Maximal Work Capacity
 Important prognostic measurement of exercise test
 Limited exercise capacity - increased risk of fatal
and nonfatal cardiovascular events
 In one series - adjusted risk of death reduced by
13% for each 1-MET increase in exercise capacity
 Estimates of peak functional capacity for age and
gender - known for most protocols
Heart rate response
Sinus rate increases progressively with exercise.
Inappropriate increase in heart rate at low work
loads Atrial fibrillation
Physically deconditioned
Hypovolumic
Anemia
Marginal left ventricular function
Chronotropic incompetence
 Decreased heart rate sensitivity to the normal
increase in sympathetic tone during exercise
 Inability to increase heart rate to at least 85%of
age predicted maximum.
 Associated with adverse prognosis
Heart Rate Recovery(HRR)
 Abnormal HRR refers to a relatively slow
deceleration of heart rate following exercise
cessation
 Reflects decreased vagal tone - associated with
increased mortality
 Value of 12 beats/min or less - abnormal
Chest discomfort
Development of typical angina during exercise can
be a useful diagnostic finding
Chest discomfort usually occurs after the onset of
ST segment abnormality
Exercise-induced angina and a normal ECG requires
assessment using a myocardial imaging
Rate-Pressure Product
 Heart rate SBP product - indirect measure of myocardial
oxygen demand
 Increases progressively with exercise
 Normal individuals develop a peak rate pressure product
of 20 to 35 mm Hg ˣ beats/min ˣ 10−3
 With significant CAD rate-pressure product< 25
 Cardio active drug significantly influences this
Diagnostic Use of Exercise Testing
In patients with CAD - Sensitivity 68% &
specificity - 77%
In SVD -- sensitivity is 25-71%
In multivessel CAD-- sensitivity is 81%, specificity
is 66%
Left main or 3vd -- sensitivity is 86%, specificity is
53%
INDICATION FOR EXERCICE
ECG FOR DIAGNOSIS
.
ACC/AHA Guidelines 2002
Patients with intermediate pretest probability of CAD based on age, gender, and
I symptoms, including those with complete RBBB or <1 mm of ST-segment
depression at rest
IIa Patients with suspected vasospastic angina
iii 1. Patients with baseline electrocardiographic abnormalities:
a. Preexcitation (Wolff-Parkinson-White) syndrome
b. Electronically paced ventricular rhythm
c. >1 mm of ST-segment depression at rest
d. Complete left bundle branch block
2. Patients established diagnosis of CAD because of prior MI or CAG; however,
testing can assess functional capacity and prognosis
Noncoronary Causes of ST-Segment Depression
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Anaemia
Cardiomyopathy
Digitalis use
Hyperventilation
Hypokalemia
IVCD
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LVH
MVP
Severe AS
Severe HTN
Severe hypoxia
SVT & Preexcitation
Brody effect
 As exercise progress R wave amplitude increase
normally till HR around 130 , after that amplitude
decrease
 Indicates normal or minimal LV dysfunction and is
associated with normal CAG
 Increase R wave amplitude in post exercise period
indicates ischemia and LV dysfunction
 May be related to an increase in LV end-diastolic
volume due to exercise-induced LV dysfunction.
Bayes’ Theorem
 Incorporates pretest risk of disease & sensitivity
and specificity of test to calculate post-test
probability of CAD
 Clinical information and exercise test results are
used to make final estimate about probability of
CAD
 Diagnostic power maximal when pretest
probability of CAD is intermediate (30% to 70%)
PRETEST PROBABILITY
AGE (yr)
GENDER
30-39
Men
TYPICAL
ATYPICAL NONANGINAL ASYMPTOMATIC
CHEST PAIN
ANGINA
ANGINA
Intermediate Intermediate Low
Very low
Women
Intermediate Very low
Men
High
Women
Intermediate Low
Men
High
Women
Intermediate Intermediate Low
Men
High
Intermediate Intermediate Low
Women
High
Intermediate Intermediate Low
40-49
50-59
60-69
Very low
Very low
Intermediate Intermediate Low
Very low
Very low
Intermediate Intermediate Low
Very low
EXERCISE PARAMETERS ASSOCIATED WITH
MULTIVESSEL CAD
 Duration of symptom-limiting exercise < 5 METs
 Abnormal BP response
 Angina pectoris at low exercise workloads
 ST-depression ≥ 2 mm - starting at <5 METs
down sloping ST
- involving ≥5 leads,
- ≥5 min into recovery
 Exercise-induced ST- elevation (aVR excluded)
 Reproducible sustained or symptomatic VT
. Exercise Testing in Determining Prognosis
 Asymptomatic population
 Prevalence of abnormal TMT in asymptomatic
middle aged men - 5-12%.
 Risk of developing a cardiac event- approximately
nine times when test abnormal
 Future risk of cardiac events is greatest if test
strongly positive or with multiple risk factors
 Appropriate asymptomatic subjects for test estimated annual risk > 1 or 2% per year
Symptomatic patients
 Exercise ECG should be routinely performed in
patients with chronic CAD before CAG
 Patients with good effort tolerance (>10 METS)
have excellent prognosis regardless of
anatomical extent of CAD.
 Provides an estimate of functional significance
of CAG documented coronary stenoses
RISK ASSESSMENT AND PROGNOSIS in PATIENTS
WITH SYMPTOMS OR PRIOR HISTORY OF CAD
CLASS
I
INDICATION
ACC/AHAGuidelines 2002
1. Patients undergoing initial evaluation
Exceptions
a. Preexcitation syndrome
b. Electronically paced ventricular rhythm
c. >1 mm of ST-segment depression at rest
d. Complete left bundle branch block
2. Patients after a significant change in cardiac symptoms
3. Low-risk unstable angina patients 8 to 12 hr after presentation who have
been free of active ischemic or heart failure symptoms
4. Intermediate-risk unstable angina patients 2 to 3 days after presentation
who have been free of active ischemic or heart failure symptoms
III
Patients with severe comorbidity likely to limit life expectancy or prevent
revascularization
Duke tread mill score
 Developed by Mark and co-workers
 Provide survival estimates based on results from
exercise test
 Provides accurate prognostic & diagnostic
information
 Adds independent prognostic information to that
provided by clinical data & coronary anatomy
 Less effective in estimating risk in subjects > 75
Duke tread mill score
 Exercise time - (5 ˣ ST deviation) - (4 ˣ treadmill
angina index)
 Angina index
0-if no angina
1-if typical angina occurs during exercise
2-if angina was the reason pt stopped exercise
Duke tread mill score - RISK
Score
Risk
5 yr survival %
CAD
>5
Low risk
97
Nil / SVD
- 10 to +4
Moderate risk
91
< -11
High risk
72
TVD/LMCA
SPECIFIC CLINICAL
APPLICATIONS
After MI
Exercise testing is useful to determine
Risk stratification
Functional capacity for activity prescription
Assessment of adequacy of medical therapy
Incidence cardiac events with test after MI is low
Slightly greater for symptom-limited protocols
Risk Stratification Before Discharge after MI : Class I Recommendations for
exercise test
ACC/AHA Guidelines
For low-risk patients who have been free of ischemia at rest or with low-level activity
and of HF for a minimum of 12 to 24 hr
For patients at intermediate risk who have been free of ischemia at rest or with lowlevel activity and of HF for a minimum of 12 to 24 hr
SUBMAXIMAL TEST
 Performed within 3 to 4 days in uncomplicated
patients
 Low-level exercise test –
achievement of 5 to 6 METs
70% to 80% of age-predicted maximum HR
 A 3- to 6-week test - for clearing patients to return to
work in occupations with higher MET expenditure
Preoperative Risk Stratification before
Noncardiac Surgery
 Provides an objective measurement of functional
capacity
 Identify likelihood of perioperative myocardial
ischemia
 Perioperative cardiac events - significantly
increased with abnormal test at low workloads
 Consider CAG with revascularization before high
risk surgery in such patients
Cardiac arrhythmias & conduction
disturbances
VPCs are common during exercise test & increase with
age.
Occur in 0-5% of asymptomatic subjects - no increased
risk of cardiac death
Suppression of VPCs during exercise is nonspecific.
In patients with recent MI, presence of repetitive VPC is
associated with increased risk of cardiac events.
Ventricular arrhythmia
 Exercise testing provokes VPCs in most patients
with h/o sustained ventricular tachyarrhythmia.
 VPC in early post exercise phase is associated
with worse long term prognosis
 RBBB morphology was associated with increased
2-year mortality rate than LBBB
Supraventricular arrhythmias
Premature beats are seen in 4-10%of normal persons &
40%of patients with heart disease.
Sustained arrhythmia occur in 1-2%.
Atrial fibrillation
Rapid ventricular response is seen in initial stages of
exercise
Effect of digitalis & beta-blockers on attenuating this
can be assessed by exercise testing
Sinus node dysfunction
Lower heart rate response may be seen at submaximal
and maximal workloads
Atrioventricular block
In congenital AV block, exercise induced heart rate is
low
In acquired diseases, exercise can elicit advanced AV
block
LBBB
 Exercise-induced ST
depression is seen in
patients with LBBB &
cant be used as diagnostic indicator.
 New development of LBBB - 0.4%
 Relative risk of death or other major cardiac events
with new exercise-induced LBBB - increased three fold.
RBBB
 Indicators CAD in RBBB
1.new onset ST depression in V5 & V6, or L II or avF
2.reduced exercise capacity
3.inability to adequately increase systolic BP
 Exercise induced ST depression leads V1-V4
common with RBBB -non-diagnostic
Preexcitation syndrome
 WPW syndrome invalidates use of ST segment
analysis as a diagnostic method.
 False +ve ischemic changes are seen
 Exercise may normalise QRS complex with
disappearance of delta waves in 20-50%
more frequent with left sided than right sided
pathway
Exercise Testing in Heart Rhythm Disorders
Class I
 Adults with ventricular arrhythmias with
intermediate or greater probability of CAD
 In patients with known or suspected exerciseinduced ventricular arrhythmias
Class IIa
 For evaluating response to medical or ablation
therapy in exercise-induced ventricular
arrhythmias
Cardiac pacemakers
 To assess performance following CRT in patients
with heart failure and ventricular conduction delay
 Ideal pacemaker should normalize the heart rate
response to exercise
ICD
 When testing patients with ICD program detection
interval of the device should be known
 If ICD is implanted for VF or fast VT rate will
normally exceed that attainable during sinus
tachycardia
 Test terminated as the HR approaches 10 beats/min below
the detection interval
 With slower detection rates, ICD reprogrammed to
a faster rate - avoid accidental discharge during exercise testing
 Can be temporarily deactivated by a magnet.
Influence of drugs and other factors
Smoking reduces ischemic response threshold.
Hypokalemia & digoxin - exertional ST depression
Nitrates, beta blockers, CCB
Prolong the time to onset of ST depression
Increase exercise tolerance
Women
Diagnostic accuracy is less in women due to lower
prevalence of CAD.
False +ve results are common during menses or
preovulation, & in postmenopausal women on
estrogen therapy
Elderly patients
 Started at slowest speed with 0% grade and adjusted
according patient’s ability
 Frequency of abnormal results is more and risk of
cardiac events also more
 Subjects > 75 years Duke treadmill scoring system is
less useful
Diabetes mellitus
 In patients with autonomic dysfunction and sensory
neuropathy anginal threshold is increased and
abnormal HR and BP response is common
Valvular heart disease
 Provide information on timing of operative
intervention and estimate degree of incapacitation
Aortic stenosis
 With moderate to severe AS exercise testing can
be safely performed with appropriate protocols
 Hypotension during test in asymptomatic patients
with AS is sufficient to consider for valve
replacement
 In the young adult with AS with - mean gradient >
30 mm Hg or a peak velocity > 3.5 m/sec - before
athletic participation - Class IIa
 Increase in mean gradient by 18 , ecg changes,
blunted BP response – predict cardiac events
 Symptomatic patients with AS - Class III
MS
 In patients with MS,
Excessive HR response to low levels of
exercise
Exercise-induced hypotension & chest pain
- Favor earlier valve repair
HOCM
 To determine exercise capability, symptoms, ECG
changes or arrhythmias, or increase in LVOT
gradient - Class IIa
 Inability to increase BP by 20 mm Hg during
exercise is associated with adverse prognosis
 High resting gradients ,NYHA class III or IV
symptoms, h/o ventricular arrhythmias - not tested.
Coronary bypass grafting
 ST depression may persist when
revascularisation is incomplete
 Also in 5% of persons with complete
revascularisation
 After CABG Stress imaging better than exercise
ECG
 Late abnormal exercise response may indicate
graft occlusion or stenosis
Percutaneous coronary intervention
 Low detection rate of restenosis in the early
phase (< 1month)
 Early abnormal result
Suboptimal result
Impaired coronary vascular reserve in a successfully
dilated vessel
Incomplete revascularization
 6-12 month post procedure test – detect
restenosis
 Initial normal test to an abnormal result in the
initial 6 months usually associated with restenosis
Cardiac transplantation
Maximal O2 uptake & work capacity
improved as compared with pre-operative findings.
Abnormalities that may be seen are
1.resting tachycardia
2.slow HR response during mild to moderate exercise
3.more prolonged time for HR to return to baseline during
recovery
Safety and risks of TMT
 Mortality is < 0.01%, morbidity is <0.05%
 Risk of major complication is twice when
symptom limited protocol is used
 Risk is greater when test is performed soon
after an acute event.
 Early postinfarction phase risk of fatal
complication during symptom-limited testing 0.03%.
Absolute Contraindications to
Exercise Testing
ACC/AHA Guidelines
Recent significant change in the rest electrocardiogram
Acute myocardial infarction (within 2 days)
High-risk unstable angina
Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise
Symptomatic severe aortic stenosis
Uncontrolled symptomatic heart failure
Acute pulmonary embolus or pulmonary infarction
Acute myocarditis or pericarditis
Acute aortic dissection
Relative Contraindications to
Exercise Testing
ACC/AHA Guidelin
Left main coronary stenosis
Severe arterial hypertension (systolic blood pressure > 200 mm Hg and/or diastolic blood
pressure > 110 mm Hg)
Tachyarrhythmias or bradyarrhythmias
Hypertrophic cardiomyopathy and other forms of outflow tract obstruction
High-degree atrioventricular block
Neuromuscular, musculoskeletal, or rheumatoid disorders
Ventricular aneurysm
TERMINATION OF EXERCISE
Absolute indications
Moderate to severe angina
Increasing nervous system symptoms (eg, ataxia, dizziness, or near-syncope)
Technical difficulties in monitoring ECG or systolic blood pressure
Subject's desire to stop
Sustained ventricular tachycardia
ST-segment elevation (1.0 mm) in leads without diagnostic Q waves (other than V 1 or aVR)
Relative indications
Drop in systolic blood pressure of 10 mm Hg from baseline blood pressure
ST-segment depression (> 3 mm of horizontal or downsloping)
Other arrhythmias - multifocal PVCs, triplets of PVCs, SVT, heart block, or bradyarrhythmias
Fatigue, shortness of breath, wheezing, leg cramps, or claudication
Development of bundle branch block or IVCD indistinguishable from VT
Hypertensive response
( SBP > 250 mm Hg and/or a diastolic BP > 115 mm Hg)
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