Exercise stress Electrocardiography

EXERCISE STRESS ELECTROCARDIOGRAPHY

Dr.Tahsin N

EXERCISE PHYSIOLOGY

Sympathetic activation

Parasympathetic withdrawal

Vasoconstriction, except-

Exercising muscles

Cerebral circulation

Coronary circulation

↑nor epinephrine and renin

EXERCISE PHYSIOLOGY

↑ventri contractility

↑O2 extraction(upto 3)

↓peripheral resistance

↑SBP,MBP,PP

DBP –no significant change

Pulm vasc bed can accommodate 6 fold CO

CO - ↑ 4-6 times

EXERCISE PHYSIOLOGY

Isotonic exercise(cardiac output)

Early phase- SV+HR

Late phase-HR

Oxygenconsumption(liters/min)

V02 peak

Work rate (watts)

↑ Exercise work ↑ O2 usage

Person’s max. O2 consumption (VO2max) reached

The slope of the o2–work relationship is a measure of

the biochemical efficiency of exercise

V o2max is the product of maximal arteriovenous

oxygen difference and cardiac output

The V o2max depends on

Age

Men than in women

Genetic factors

Cardiovascular impairment

Physical inactivity.

Oxygenconsumption(liters/min)

70% V02 max (trained) V02

peak

(trained)

V02 peak

(untrained)

100% V02 max

(untrained)

Work rate (watts)

The ability to deliver O2 to muscles and muscle’s oxidative capacity limit a person’s VO2max. Training ↑

VO2max

175

• During dynamic exercise of

increasing intensity,

ventilation increases linearly

over the mild to moderate

range, then more rapidly in

intense exercise

• Workload at which rapid

ventilation occurs is called the

ventilatory breakpoint

(together with lactate

threshold)

Respiration during exercise

Lactate acidifies the blood, driving off CO2 and increasing ventilatory rate

BLOOD PRESSURE (BP) ALSO RISES IN EXERCISE • Systolic pressure (SBP)

goes up to 150-170 mm

Hg during dynamic

exercise; diastolic scarcely

alters

• In isometric (heavy static)

exercise, SBP may exceed

250 mmHg, and diastolic

(DBP) can itself reach 180

Bloodlacticacid(mM)

Relative work rate (% V02 max)

Intense exercise Glycolysis>aerobic metabolism

↑ blood lactate (other organs use some)

Lactate threshold; endurance estimation

MAXIMUM HR

HR=220 - age in years

POST EXERCISE PHASE

Vagal reactivation

Imp cardiac deceleration mech

↑in well trained athletes

Blunted in CCF

MET

• Metabolic Equivalent Term

• 1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5

ml O2 /Kg/min

• Differs with thyroid status, post exercise, obesity, disease

states

KEY MET VALUES

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;

10 METs = same progn with medical thpy as CABG

13 METs = Excell prognosis,

regardless of othr exercise responses

KEY MET VALUES

3-5 METs:

Raking leaves,light carpentry,golf,3-4 mph

5-7 METs:

Exterior carpentry, singles tennis

>9 METs:

Heavy labour, hand ball, squash, running 6-

7 mph

CALCULATION OF METS ON THE TREADMILL

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

3.5

Calculated automatically by Device!

Note: Speed in meters/minute

conversion = MPH x 26.8

Grade expressed as a fraction

TREADMILL PROTOCOL

Bruce protocol

Naughton protocol

Weber protocol

ACIP(asymptomatic cardiac ischemia pilot)

Modified ACIP

PROTOCOL DESCRIPTION (BRUCE)

Stage Time (min) M/hr Slope

1 0 1.7 10%

2 3 2.5 12%

3 6 3.4 14%

4 9 4.2 16%

5 12 5.0 18%

6 15 5.5 20%

PROCEDURE

Standard 12 lead ECG- leads distally

Torso ECG + BP

Supine and Sitting / standing

HR ,BP ,ECG

Before, after, stage end

Onset of ischemic response

Each minute recovery(5-10 mints)

PROCEDURE- LEAD SYSTEMS

Mason-Liker modification

RAD

↑inf lead voltage

Loss of Q in inf leads

New Q in AVL

CONTRAINDICATIONS TO EXERCISE TESTING

Absolute

1) Acute MI (< 2 d)

2) High-risk unstable angina

3) Uncontrolled cardiac arrhythmias causing symptoms

or hemodynamic compromise

4) Symptomatic severe AS

5) Uncontrolled symptomatic CCF

6) Acute pulmonary embolus or pulmonary infarction

7) Acute myocarditis or pericarditis

8) Acute Aortic dissection

CONTRAINDICATIONS TO EXERCISE TESTING

Relative

1. LMCA stenosis

2. Moderate stenotic valvular heart disease

3. Electrolyte abnormalities

4. Severe HTN

5. Tachyarrhythmias or bradyarrhythmias

6. HOCM and other forms of outflow tract obstruction

7. Mental or physical impairment leading to inability

to exercise adequately

8. High-degree AV block

Both MI and deaths have been reported and can be expected to occur at a rate of up to 1 per 2500 tests

CLASSIFICATION OF CHEST PAIN

Typical angina

Atypical angina

Noncardiac chest pain

1. Substernal chest discomfort with characterstic quality and duration

2. Provoked by exertion or emotional stress

3. Relieved by rest or NTG

Meets 2 of the above characteristics

Meets one or none of the typical characteristics

‘The post test probability is proportional to the pretest probability’

BAYES' THEOREM A THEORY OF PROBABILITY

PRETEST PROBABILITY

Based on the patient's history ( age, gender, chest pain ),

physical examination and initial testing, and the clinician's

experience.

Typical or definite angina →pretest probability high - test result

does not dramatically change the probability.

Diagnostic testing is most valuable in intermediate pretest

probability category

PRE TEST PROBABILITY OF CORONARY DISEASE BY SYMPTOMS, GENDER AND AGE

Age

Gender

Typical/Definite Angina Pectoris

Atypical/Probable Angina 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%

INDICATIONS OF EXERCISE TESTING

TO DIAGNOSE OBSTRUCTIVE CAD

Class I

Adult patients (including RBBB or <1 mm of resting ST↓)

with intermediate pretest probability of CAD

Class IIa

Patients with vasospastic angina.


Class IIb

1. Patients with a high pretest probability of CAD

2. Patients with a low pretest probability of CAD

3. Patients with <1 mm of baseline ST ↓and on digoxin.

4. Patients with LVH and <1 mm baseline ST ↓.


Class III

1. Patients with the following baseline ECG

abnormalities:

• Pre-excitation syndrome

• Electronically paced ventricular rhythm

• >1 mm of resting ST depression

• Complete LBBB

IN ASYMPTOMATIC PERSONSWITHOUT KNOWN CAD

Class IIa

• Evaluation of asymptomatic T2 DM pts who plan to start

vigorous exercise ( C)

Class IIb

• 1. Evaluation of pts with multiple risk factors as a guide to

risk-reduction therapy.

• 2. Evaluation of asymptomatic men > 45 yrs and women

>55 yrs:

• • Plan to start vigorous exercise

• • Involved in occupations which impact public safety

• • High risk for CAD(e.g., PVOD and CRF)

Class III

• Routine screening of asymptomatic

RISK ASSESSMENT AND PROGNOSIS IN PATIENTS WITH SYMPTOMS OR A PRIOR HISTORY OF CAD

Class I

• 1. Initial evaluation with susp/known CAD, includingRBBB or

<1 mm of resting ST Depression

• 2.Susp/ known CAD, previously evaluated, now significant

change in clinical status.

• 3. Low-risk UA pts >8 to 12 hrs & free of active

ischemia/CCF

• 4. Intermed-risk UApts > 2 to 3 days & no active ischemia/

CCF

Class IIa

• Intermed-risk UA pts – initial markers (N),rpt ECG –no signi

change, and markers >6-12 hrs (N) & no other evidence of

ischemia during observation.

AFTER MYOCARDIAL INFARCTION

Class I

• 1. Before discharge (submaximal --4 to 6 days).

• 2. Early after discharge if the predischarge exercise test was

not done (symptom limited --14 to 21 days).

• 3. Late after discharge if the early exercise test was

submaximal (symptom limited --3 to 6 weeks).

Class IIa

• After discharge as part of cardiac rehabilitation in patients who

have undergone coronary revascularization.


Class IIb

1. Patients with the following ECG abnormalities:

• • Complete LBBB

• • Pre-excitation syndrome

• • LVH

• • Digoxin therapy

• • >1 mm of resting ST-segment depression

• • Electronically paced ventricular rhythm

2. Periodic monitoring in patients who continue to participate

in exercise training or cardiac rehabilitation.


Class III

1. Severe comorbidity likely to limit life expectancy and/or

candidacy for revascularization.

2. At any time to evaluate pts with AMI with uncompensated

CCF, arrhythmia, or noncardiac exercise limiting conditions.

3. Before discharge to evaluate pts who have already been

selected for, or have undergone, cardiac cath.

Although a stress test may be useful before or after cath

to evaluate or identify ischemia in the distribution of a

coronary lesion of borderline severity, stress imaging tests

are recommended.

Submaximal protocols

• Predetermined end point

• Peak HR 120 bpm, or

• 70% predicted max HR or

• Peak MET - 5

Symptom-limited tests

• To continue till signs or symptoms necessitating

termination (i.e., angina, fatigue, ≥ 2 mm of

ST↓,ventricular arrhythmias, or ≥10-mm Hg drop in SBP

from the resting blood pressure)

BEFORE AND AFTER REVASCULARIZATION

Class I

• 1. Demonstration of ischemia before revascularization.

• 2. Evaluating recurrent symps suggesting ischemia after

revascularization.

Class IIa

• After discharge for activity counseling and/or exercise training as

part of rehabilitation in pts aft revascularization.

BEFORE AND AFTER REVASCULARIZATION

Class IIb

• 1. Detection of restenosis in selected, high-risk

asymptomatic pts < first 12 months aft PCI.

• 2. Periodic monitoring of selected, high-risk asymptomatic

ps for restenosis, graft occlusion, incomplete coronary

revascularization, or disease progression.

Class III

• 1. Localization of ischemia for determining the site of

intervention.

• 2. Routine, periodic monitoring of asymptomatic pts after

PCI or CABG without specific indications.

STRESS TESTING

Modality Sensitivity Specificity

Exercise test 68% 77%

Nuclear Imaging 87-92% 80-85%

Stress Echo

80-85% 88-95%

INVESTIGATION OF HEART RHYTHM DISORDERS

Class I

• 1. Identification of appropriate settings in pts with rate-

adaptive pacemakers.

• 2. Evaluation of cong CHB in pts considering

↑activity/competitive sports. (C)

Class IIa

• 1. Evaluating known or suspected exercise-induced

arrhythmias.

• 2. Evaluation of medical, surgical, or ablative therapy in

exercise-induced arrhythmias

INVESTIGATION OF HEART RHYTHM DISORDERS

Class IIb

1. Isolated VPC in middle-aged pts without other evidence of

CAD.

2. Prolonged 1˚AV block or type I-2˚AV block , LBBB, RBBB,

or VPC in young pts considering competitive sports. (C)

Class III

Routine investigation of isolated VPC in young pts.

INTERPRETING TMT

NORMAL ECG CHANGES DURING EXERCISE

↓ PR, QRS, QT

↑ P amplitude

Progressive downsloping PR in inf leads

j point depression

1 = Iso-electric2 = J point3 = J + 80 msec

THE EXERCISE ECG

ST 60 -- HR > 130/minST 80 -- HR ≤ 130/min

CRITERIA FOR READING ST-SEGMENT CHANGES ON THE EXERCISE ECG

ST DEPRESSION:

Measurements made on 3 consecutive ECG complexes

ST level is measured relative to the P-Q junction

When J-point is depressed relative to P-Q junction at baseline:

Net difference from the J junction determines the amount of deviation

When the J-point is elevated relative to P-Q junction at baseline and

becomes depressed with exercise:

Magnitude of ST depression is determined from the P-Q junction and

not the resting J point

J point depression of 2 to 3

mm in leads V4 to V6 with

rapid upsloping ST segments

depressed approximately 1

mm 80 msec after the J point.

The ST segment slope in leads

V4 and V5 is 3.0 mV/sec. This

response should not be

considered abnormal.

Upsloping

CRITERIA FOR ABNORMAL AND BORDERLINE ST-SEGMENT DEPRESSION

ABNORMAL:

1.0 mm or greater horizontal or downsloping ST

depression at 80 msec after J point on 3 consecutive ECG

complexes

BORDERLINE:

0.5 to 1.0 mm horizontal or downsloping ST depression at

80 msec after J point on 3 consecutive ECG complexes

2.0 mm or greater upsloping ST depression at 80 msec

after J point on 3 consecutive ECG complexes

Normal

Rapid Upsloping

Minor ST Depression

Slow Upsloping

Horizontal

Downsloping

Elevation (non Q lead)

Elevation (Q wave lead)

• In lead V4 , the

exercise ECG result

is abnormal early in

the test, reaching

0.3 mV (3 mm) of

horizontal ST

segment depression

at the end of

exercise.

• Consistent with a

severe ischemic

response.

• The J point at peak exertion is depressed 2.5 mm, the ST segment slope is 1.5 mV/sec, and the ST segment level at 80 msec after the J point is depressed 1.6 mm.

• This “slow upsloping” ST segment at peak exercise indicates an ischemic pattern in patients with a high coronary disease prevalence pretest.

• A typical ischemic pattern is seen at 3 minutes of the recovery phase when the ST segment is horizontal and 5 minutes after exertion when the ST segment is downsloping.

• Becomes abnormal at 9:30 minutes (horizontal arrow right) of a 12-minute exercise test and resolves in the immediate recovery phase.

• This ECG pattern in which the ST segment becomes abnormal only at high exercise workloads and returns to baseline in the immediate recovery phase may indicate a false-positive result in an asymptomatic individual without atherosclerotic risk factors.

ST ELEVATION(LOCALISING)

Abnormal response

– J ↑ ≥0.10mV(1 mm)

– ST 60 ≥0.10mV(1 mm)

– Three consecutive beats

Q wave lead (Past MI)

• Severe RWMA, ↓EF, ↓Prognosis

Non Q wave lead (Past MI)

• Severe ischemic response

Non Q wave lead (No past MI)-1%

• Transmural reversible myocardial ischemia- ----

vasospasm, ↑coronary narrowing

• This type of ECG pattern is usually

associated with a full-thickness,

reversible myocardial perfusion defect

in the corresponding left ventricular

myocardial segments and high-grade

intraluminal narrowing at coronary

angiography. Rarely, coronary

vasospasm produces this result in the

absence of significant intraluminal

atherosclerotic narrowing.

ECG Patterns Indicative of Myocardial Ischaemia

ECG Patterns Not Indicative of Myocardial Ischaemia

ECG CHANGES DURING STRESS TEST

ST HEART RATE SLOPE

Maximal change in ST with heart rate calculated at the end of each

stage

Heart rate adjustment of ST segment depression - improve the

sensitivity

Calculation of the maximal ST/heart rate slope in mV/beats/min -

linear regression

An ST/heart rate slope

>2.4 mV/beats/min - abnormal

>6 mV/beats/min - three-vessel CAD.

THE ST/HEART RATE INDEX

Average change of ST segment depression with heart rate

throughout the course of the exercise test.

>1.6 - abnormal

CONFOUNDERS OF EXERCISE TREADMILL TEST INTERPRETATION

Digoxin

Abnormal ST-segment response to exercise

In 25% to 40% of healthy subjects

Related to age.

Left Ventricular Hypertrophy

Decreased specificity

sensitivity is unaffected.

Resting ST Depression

Decreased specificity

CONFOUNDERS OF EXERCISE TREADMILL TEST INTERPRETATION

Left Bundle-Branch Block

Up to 1 cm of ST depression can occur in healthy normal

subjects

Right Bundle-Branch Block

Does not reduce the sensitivity, specificity, or predictive

value of the stress ECG

Beta Blocker Therapy

Reduced diagnostic or prognostic value because of

inadequate heart rate response

EARLY REPOLARIZATION AND RESTING ST↑

Return to the PQ junction is normal

Hence ST↓ determined from PQ junction

Not from the elevated J point before exercise

DUKE TREADMILL SCORE

Treadmill Score=Exercise time

-5X (amount of ST-seg. deviation in mm) - 4X

exercise angina index

(0-no angina, 1 angina, 2 if angina stops test).

High Risk= -11, mortality >5% annually.

Low Risk= +5, mortality 0.5% annually.

Ann Intern Med 1987;106:793.

ACC/AHA GUIDELINES:

Patients with a high-risk exercise test result (mortality ≥ 4%/yr), should be referred for cardiac catheterization.

Pts. with an intermediate-risk result (mortality of 2% to

3%/yr), should be referred for additional testing, either

cardiac catheterization, or an exercise imaging study.

PSEUDO NORMALIZATION PATTERN

No prior MI

Nondiagnostic finding

Prior MI

Suggests Reversible myocardial ischemia

Needs substantiation by rev myo perfusion defect

R WAVE AMPLITUDE

LVH Voltage criteria

ST seg – less reliable to ∆ CAD even in the absence of

LV strain pattern

Loss of R wave (MI)

↓Sensitivity of ST response in that lead

U INVERSION

Occasionally in precordial leads at HR<120

Relatively nonsensitive

Relatively specific

ABNORMAL BP RESPONSE

• Failure to ↑SBP >120 mmHg

• Sustained ↓(15 secs) >10mmHg

• ↓SBP below resting BP during progressive exercise

Inadequate ↑ of CO

3VD LMCA disease

Cardiomyopathy Arrhythmias

Vasovagal LVOT obstruction

Hypovolemia Prolonged vigorous exercise

MAXIMUM WORK CAPACITY

Important prognostic measurement

Work performed in METs

Not the no: of minutes of exercise

EXERCISE CAPACITY

VO max = (mph x 26.8) x (0.1 + [% grade X 1.8] + 3.5

1 MET (metabolic equivalent) = 3.5 ml 0 /kg/min

Stage 1 = 5 METS

Stage 2 = 6 - 8 METS

Stage 3 = 8 -10 METS

2

2

EXERCISE CAPACITY

“The strongest predictor of the risk of death among both

normal subjects, and those with cardiovascular disease”.

“Each 1-MET increase in exercise capacity conferred a 12%

improvement in survival”.

NEJM 2002;346:793-801.

For each 1-MET increase in exercise capacity, the survival improved by 12 percent N Engl J Med 2002

EXERCISE CAPACITY

In pts. with CAD > 13 METS (Stage IV) prognosis excellent

regardless of whether medical or surgical therapy is selected.*

Documented CAD, ≥ 2 mm ST-segment depression. Stage IV

had a 100% 5-year survival rate.**

In the Coronary Artery Surgery Study (CASS), patients with 3-

vessel disease, and high exercise capacity (≥ 10 METS),

showed no benefit from surgery. (JACC 1986;8:741 748)

*Circ 1984;70:226.

**Circ 1982;65:482.

HEART RATE RESPONSE

Inappropriate ↑ at low work load

Anxiety (<1minute-transient)

Persisting several minutes

AF Physically deconditioned

Hypovolemia Anemia

Marginal LV function

HEART RATE RESPONSE

Chronotropic incompetence

Inability to attain THR OR

Abnormal HR Reserve(<80%)

{%HR Reserve=(HRpeak-HRrest)/(220-age-

HRrest)}

Autonomic dysfunction SN dysfuntion,

Drugs Myocardial ischemia

↑long term mortality (not on β blockers)

CHRONOTROPIC INCOMPETENCE

Circ 1996;93:1520.Framingham Heart Study

HEART RATE RECOVERY

During exercise, HR increases due to withdrawal of vagal

tone, and increase of sympathetic tone.

During recovery, there is a rapid reactivation of vagal tone

leading to a decrease in heart rate.

Delayed recovery is a marker of poor outcome

HEART RATE RECOVERY

Abnormal:

1 minute

TMT (upright) < 12 bpm

TMT (supine) < 18 bpm

An upright value <22 bpm at 2 minutes is abnormal

Poor prognosis independent of other factors

EXERCISE INDUCED CHEST DISCOMFORT

Usually after ischemic ST changes

May be associated with increased DBP

In some, only chest discomfort

In CSA, CP less freq than ST↓

Angina with no ST ↓- MPI useful to assess ischemic

severity.

ANGINA DURING STRESS TEST

Mortality

(+) ve Stress Test with angina 5%/yr.

(+) ve Stress Test, no angina 2.5%/yr.

Circ 1984;70:547-551.

MARKEDLY POSITIVE STRESS TEST

1. ECG changes in the first three minutes.

2. ECG changes that last through recovery.

3. Hypotensive response.

ADVERSE PROGNOSIS & MULTIVESSEL CAD

1. Symptom limiting exercise < 5METs

2. Abnormal BP response

3. ST↓≥2mm or downsloping ST↓

<5METs, ≥5 leads, persisting ≥5 mins

into reco

4. ST↑

5. Angina at low exercise work loads

6. Reproducible sustained/symptomatic VT

INDICATIONS FOR TERMINATING EXERCISE TESTING

Absolute indications

1. Drop in systolic BP >10 mm Hg from baseline when

accompanied by other evidence of ischemia

2. Moderate to severe angina

3. ↑ CNS sympts (ataxia, dizziness, or near-syncope)

4. Signs of poor perfusion (cyanosis or pallor)

5. Technical difficulties in monitoring ECG or systolic BP

6. Subject’s desire to stop

7. Sustained VT

8. ST ↑ (≥1.0 mm) in leads without Q-waves (other than V1 or

aVR)

INDICATIONS FOR TERMINATING EXERCISE TESTING

Relative indications

1. ↓ in systolic BP (≥10 mm Hg) in the absence of other evidence of

ischemia

2. ST or QRS changes such as excessive ST↓ (>2 mm of horizontal or

downsloping ST↓ ) or marked axis shift

3. Arrhythmias other than sustained VT, including multifocal PVCs,

triplets of PVCs, SVT, heart block, or bradyarrhythmias

4. Fatigue, shortness of breath, wheezing, leg cramps, or claudication

5. Development of BBB or IVCD that cannot be distinguished from VT

6. Increasing chest pain

7. Hypertensive response

THANK YOU

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Exercise stress Electrocardiography