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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.

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slide2

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.

slide3

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 PHYSIOLOGY
  • Exercise - body\'s most common physiologic stress - 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 physiology1
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
slide6

During strenuous exertion, sympathetic discharge is maximal and parasympathetic stimulation is withdrawn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
slide7

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 o 2
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.
slide9

V O2can be estimated fromtreadmillspeedandgrade

  • 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 o 2
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
  • 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
slide12

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
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
slide14

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
Calculationof METs on the Treadmill

METs = Speed x [0.1 + (Grade x 1.8)] + 3.5 3.5

Calculated automatically by Device!

exercise test modalities
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
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

slide19

Arm Ergometry

  • Bicycle Ergometry
  • Treadmill Protocol
  • Walk Test
arm ergometry
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
Treadmill Protocol s
  • Bruce
  • Modified Bruce
  • Naughton and Weber
  • ACIP (Asymptomatic cardiac ischemia pilot trial)
  • Modified ACIP
tread mill protocol bruce multistage maximal treadmill protocol
Tread mill protocolBruce 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.
slide23

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
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
Cardiopulmonary Exercise Testing
  • Involves measurements of respiratory oxygen uptake (vo2) , carbon dioxide production ( vco2  ) and ventilatory parameters during a symptom- limited exercise test
  • Patient wears a nose clip and breathes through a nonrebreathing valve
technique
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

slide27

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

slide28

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
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
lead system mason likar modification
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
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
slide33

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

slide34

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

slide35

1.PQ JUNCTION

2. J POINT

3.ST 80

upsloping st segment
Upsloping ST segment

Rapid upsloping ST segment (more than 1 mV/sec) depressed less than 1.5 mm after the J point - normal

slide37

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

slide39

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
slide40

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
t wave changes
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
Nonelectrocardiographic Observations
  • Blood pressure
  • Maximal Work Capacity
  • Heart rate response
  • Heart Rate Recovery
  • Chest discomfort
  • Rate-Pressure Product
slide44

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
slide45

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
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
slide48

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
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
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
slide51

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
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
slide53

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%
noncoronary causes of st segment depression
Noncoronary Causes of ST-Segment Depression
  •   Anaemia   Cardiomyopathy   Digitalis use   Hyperventilation   Hypokalemia   IVCD
  • LVH   MVP   Severe AS   Severe HTN   Severe hypoxia   SVT & Preexcitation
brody effect
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
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%)
exercise parameters associated with multivessel cad
EXERCISE PARAMETERS ASSOCIATED WITHMULTIVESSEL 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
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
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
duke tread mill score
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 score1
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

slide67

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

submaximal test
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
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
slide71

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
Ventriculararrhythmia
  • 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
slide73

Supraventriculararrhythmias

Premature beats are seen in 4-10%of normal persons & 40%of patients with heart disease.

Sustained arrhythmia occur in 1-2%.

Atrialfibrillation

Rapid ventricular response is seen in initial stages of exercise

Effect of digitalis & beta-blockers on attenuating this can be assessed by exercise testing

slide74

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
slide75

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.
slide76
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
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
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 exercise-induced ventricular arrhythmias

Class IIa   

  • For evaluating response to medical or ablation therapy in exercise-induced ventricular arrhythmias
cardiac pacemakers
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
slide80
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.
slide81

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
slide82

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

slide83

Elderlypatients

  • 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
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
slide85

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
slide86
MS
  • In patients with MS,

Excessive HR response to low levels of

exercise

Exercise-induced hypotension & chest pain

- Favor earlier valve repair

slide87
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
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
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
slide90

Cardiactransplantation

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
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%.
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