Exercise Stress TestExercise Stress Test

Apiwan NuttamonwarakulThe 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 1 MET=rest; 5 MET=ADLs;10 METs=

medical therapy equivalent to CABG; 18 METS=elite athlete.

Myocardial Oxygen Consumption: 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

VO2max = (HRmax X SVmax) X (CaO2max - CvO2max)

(220 - Age)

Sinus Node Dysfunction

Drugs (e.g., B - blockers)

Genetic Factors (Heart Size)

Conditioning Factors Contractility/Afterload/Preload

Disease Factors Wall Motion/Ventricular Fxn Valve Stenosis or Regurgitation

PaO2

Hgb [ ]

SaO2

Diffusion

Ventilation

Perfusion

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. Post-

MI 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 CADAge Gender Typical/Definite

Angina PectorisAtypical/ProbableAngina Pectoris

Non-Anginal

Chest Pain

Asymptomatic

30-39 Males Intermediate Intermediate low (<10%) Very low (<5%)

30-39 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% Low = <10% Very Low = <5%

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 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

Old versus Young 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

Careful history of symptoms and past medical history; typical vs. atypical.

Risk factors Family history Informed Consent

Physical Examination 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:

Superimposition of P and T; p wave may increase in inferior leads.

PR segment: Shortens and downslopes in the inferior

leads. QRS complex:

Increases in septal q waves; slight decreases in R wave amplitude; minimal shortening of interval.

J junction: Decreases with exercise; in subjects with

resting J junction elevation, this normalizes to baseline.

ST segment: Demonstrates positive upslope that returns

to baseline by 80ms. T wave:

initially a gradual decrease in amplitude. QT interval:

Rate-related shortening.

Heart Rate Normal Heart Rate Response

Increase in HR as a result of vagal tone withdrawal. Standard deviation for peak HR determination is 15 BPM.

Chronotropic Incompetence 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 false-positive.

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 # of Studies

Total # Patients

Sens Spec Predictive Accuracy

Standard ET 147 24,047 68% 77% 73% ET Scores 24 11,788 80% Score Strategy 2 >1000 85% 92% 88%

Thallium Scint 59 6,038 85% 85% 85% SPECT 16+14 5,272 88% 72% 80% Adenosine SPECT 10+4 2,137 89% 80% 85% Exercise ECHO 58 5,000 84% 75% 80% Dobutamine ECHO 5 <1000 88% 84% 86% Dobutamine Scint 20 1014 88% 74% 81% Electron Beam Tomography (EBCT)

16 3,683 60% 70% 65%

Function is Everything!