EXERCISE STRESS ELECTROCARDIOGRAPHY Dr.Tahsin N

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Exercise stress Electrocardiography

• Dr.Tahsin N

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Exercise physiology

• Sympathetic activation
• Parasympathetic withdrawal
• Vasoconstriction, except-
• Exercising muscles
• Cerebral circulation
• Coronary circulation
• ?nor epinephrine and renin

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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

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Exercise physiology

• Isotonic exercise(cardiac output)
• Early phase- SVHR
• Late phase-HR

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? Exercise work ? ? O2 usage ? Persons max. O2
consumption (VO2max) reached
V02 peak
Oxygen consumption (liters/min)
Work rate (watts)
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• The slope of the    o2work 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.

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The ability to deliver O2 to muscles and muscles
oxidative capacity limit a persons VO2max.
Training ? ? VO2max
V02 peak (trained)
70 V02 max (trained)
V02 peak (untrained)
Oxygen consumption (liters/min)
100 V02 max (untrained)
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Work rate (watts)
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• 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
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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

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Intense exercise ? Glycolysisgtaerobic
metabolism ? ? blood lactate (other organs use
some)
Blood lactic acid (mM)
Lactate threshold endurance estimation
Relative work rate ( V02 max)
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Maximum HR

• HR220 - age in years

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Post exercise phase

• Vagal reactivation
• Imp cardiac deceleration mech
• ?in well trained athletes
• Blunted in CCF

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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

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Key MET Values

• 1 MET "Basal" 3.5 ml O2 /Kg/min
• 2 METs 2 mph on level
• 4 METs 4 mph on level
• lt 5METs Poor prognosis if lt 65
• 10 METs same progn with medical thpy as CABG
• 13 METs Excell prognosis,
• regardless of othr
  exercise responses

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Key MET Values

• 3-5 METs
• Raking leaves,light carpentry,golf,3-4 mph
• 5-7 METs
• Exterior carpentry, singles tennis
• gt9 METs
• Heavy labour, hand ball, squash, running 6-7
  mph

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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
  

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Treadmill protocol

• Bruce protocol
• Naughton protocol
• Weber protocol
• ACIP(asymptomatic cardiac ischemia pilot)
• Modified ACIP

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Protocol description (BRUCE)
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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)

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Procedure- Lead systems

• Mason-Liker modification
• RAD
• ?inf lead voltage
• Loss of Q in inf leads
• New Q in AVL

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Contraindications to Exercise Testing

• Absolute
• Acute MI (lt 2 d)
• High-risk unstable angina
• Uncontrolled cardiac arrhythmias causing
  symptoms or hemodynamic compromise
• Symptomatic severe AS
• Uncontrolled symptomatic CCF
• Acute pulmonary embolus or pulmonary infarction
• Acute myocarditis or pericarditis
• Acute Aortic dissection

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Contraindications to Exercise Testing

• Relative
• LMCA stenosis
• Moderate stenotic valvular heart disease
• Electrolyte abnormalities
• Severe HTN
• Tachyarrhythmias or bradyarrhythmias
• HOCM and other forms of outflow tract obstruction
• Mental or physical impairment leading to
  inability to exercise adequately
• High-degree AV block

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

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Classification of chest pain

• Typical angina
• Atypical angina
• Noncardiac chest pain

• Substernal chest discomfort with characterstic
  quality and duration
• Provoked by exertion or emotional stress
• Relieved by rest or NTG

Meets 2 of the above characteristics
Meets one or none of the typical characteristics
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Bayes' theorem A theory of probability
The post test probability is proportional to
the pretest probability
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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

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Pre Test Probability of Coronary Disease by
Symptoms, Gender and Age
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INDICATIONS OF EXERCISE TESTING
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TO DIAGNOSE OBSTRUCTIVE CAD

• Class I
• Adult patients (including RBBB or lt1 mm of
  resting ST?) with intermediate pretest
  probability of CAD
• Class IIa
• Patients with vasospastic angina.

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TO DIAGNOSE OBSTRUCTIVE CAD

• Class IIb
• 1. Patients with a high pretest probability of
  CAD
• 2. Patients with a low pretest probability of CAD
  
• 3. Patients with lt1 mm of baseline ST ?and on
  digoxin.
• 4. Patients with LVH and lt1 mm baseline ST ?.

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TO DIAGNOSE OBSTRUCTIVE CAD

• Class III
• Patients with the following baseline ECG
  abnormalities
• Pre-excitation syndrome
• Electronically paced ventricular rhythm
• gt1 mm of resting ST depression
• Complete LBBB

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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 gt 45 yrs and
  women gt55 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

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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 lt1 mm of resting ST Depression
• 2.Susp/ known CAD, previously evaluated, now
  significant change in clinical status.
• 3. Low-risk UA pts gt8 to 12 hrs free of active
  ischemia/CCF
• 4. Intermed-risk UApts gt 2 to 3 days no active
  ischemia/ CCF
• Class IIa
• Intermed-risk UA pts initial markers (N),rpt
  ECG no signi change, and markers gt6-12 hrs (N)
  no other evidence of ischemia during observation.

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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.

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AFTER MYOCARDIAL INFARCTION

• Class IIb
• 1. Patients with the following ECG abnormalities
• Complete LBBB
• Pre-excitation syndrome
• LVH
• Digoxin therapy
• gt1 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.

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AFTER MYOCARDIAL INFARCTION

• 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.

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• 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)

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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.

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Before and After Revascularization

• Class IIb
• 1. Detection of restenosis in selected, high-risk
  asymptomatic pts lt 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.

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Stress Testing
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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

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Investigation of Heart Rhythm Disorders

• Class IIb
• 1. Isolated VPC in middle-aged pts without other
  evidence of CAD.
• 2. Prolonged 1AV block or type I-2AV block ,
  LBBB, RBBB, or VPC in young pts considering
  competitive sports. (C)
• Class III
• Routine investigation of isolated VPC in young
  pts.

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Interpreting TMT
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Normal ECG changes during exercise

• ? PR, QRS, QT
• ? P amplitude
• Progressive downsloping PR in inf leads
• j point depression

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The Exercise ECG
1 Iso-electric 2 J point 3 J 80 msec
ST 60 -- HR gt 130/min ST 80 -- HR 130/min
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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

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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

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Normal
Rapid Upsloping
Minor ST Depression
Slow Upsloping
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Horizontal
Downsloping
Elevation (non Q lead)
Elevation (Q wave lead)
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• 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.

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• 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.

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• Becomes abnormal at 930 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.

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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

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• 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.

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ECG Patterns Indicative of Myocardial Ischaemia
ECG Patterns Not Indicative of Myocardial
Ischaemia
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ECG changes during stress test
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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
• gt2.4 mV/beats/min - abnormal
• gt6 mV/beats/min - three-vessel CAD.

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The ST/heart rate index

• Average change of ST segment depression with
  heart rate throughout the course of the exercise
  test.
• gt1.6 - abnormal

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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

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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

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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

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Duke Treadmill Score

• Treadmill ScoreExercise 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 gt5 annually.
• Low Risk 5, mortality 0.5 annually.
• Ann Intern Med 1987106793.

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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.

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Pseudo normalization pattern

• No prior MI
• Nondiagnostic finding
• Prior MI
• Suggests Reversible myocardial ischemia
• Needs substantiation by rev myo perfusion defect

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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

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U inversion

• Occasionally in precordial leads at HRlt120
• Relatively nonsensitive
• Relatively specific

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Abnormal BP Response

• Failure to ?SBP gt120 mmHg
• Sustained ?(15 secs) gt10mmHg
• ?SBP below resting BP during progressive exercise
• Inadequate ? of CO
• 3VD LMCA disease
• Cardiomyopathy Arrhythmias
• Vasovagal LVOT obstruction
• Hypovolemia Prolonged vigorous exercise

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Maximum work capacity

• Important prognostic measurement
• Work performed in METs
• Not the no of minutes of exercise

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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

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2
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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 2002346793-801.
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For each 1-MET increase in exercise capacity, the
survival improved by 12 percent N Engl J Med 2002
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Exercise Capacity

• In pts. with CAD gt 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 19868741 748)
• Circ 198470226.
• Circ 198265482.

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Heart rate response

• Inappropriate ? at low work load
• Anxiety (lt1minute-transient)
• Persisting several minutes
• AF Physically deconditioned
• Hypovolemia Anemia
• Marginal LV function

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Heart rate response

• Chronotropic incompetence
• Inability to attain THR OR
• Abnormal HR Reserve(lt80)
• HR Reserve(HRpeak-HRrest)/(220-age- HRrest)
• Autonomic dysfunction SN dysfuntion,
• Drugs Myocardial ischemia
• ?long term mortality (not on ß blockers)

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Chronotropic Incompetence
Framingham Heart Study
Circ 1996931520.
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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

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Heart Rate Recovery

• Abnormal
• 1 minute
• TMT (upright) lt 12 bpm
• TMT (supine) lt 18 bpm
• An upright value lt22 bpm at 2 minutes is abnormal
• Poor prognosis independent of other factors

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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.

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Angina during Stress Test

• Mortality
• () ve Stress Test with angina 5/yr.
• () ve Stress Test, no angina 2.5/yr.

Circ 198470547-551.
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Markedly Positive Stress Test

• ECG changes in the first three minutes.
• ECG changes that last through recovery.
• Hypotensive response.

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Adverse prognosis multivessel CAD

• Symptom limiting exercise lt 5METs
• Abnormal BP response
• ST?2mm or downsloping ST?
  lt5METs, 5 leads,
  persisting 5 mins into reco
• ST?
• Angina at low exercise work loads
• Reproducible sustained/symptomatic VT

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Indications for Terminating Exercise Testing

• Absolute indications
• Drop in systolic BP gt10 mm Hg from baseline when
  accompanied by other evidence of ischemia
• Moderate to severe angina
• ? CNS sympts (ataxia, dizziness, or
  near-syncope)
• Signs of poor perfusion (cyanosis or pallor)
• Technical difficulties in monitoring ECG or
  systolic BP
• Subjects desire to stop
• Sustained VT
• ST ? (1.0 mm) in leads without Q-waves (other
  than V1 or aVR)

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Indications for Terminating Exercise Testing

• Relative indications
• ? in systolic BP (10 mm Hg) in the absence of
  other evidence of ischemia
• ST or QRS changes such as excessive ST? (gt2 mm
  of horizontal or downsloping ST? ) or marked axis
  shift
• Arrhythmias other than sustained VT, including
  multifocal PVCs, triplets of PVCs, SVT, heart
  block, or bradyarrhythmias
• Fatigue, shortness of breath, wheezing, leg
  cramps, or claudication
• Development of BBB or IVCD that cannot be
  distinguished from VT
• Increasing chest pain
• Hypertensive response

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