Exercise Testing

1
Exercise Testing

• Theodore D. Fraker, Jr., MD
• Associate Division Director, Cardiovascular
  Diseases
• Ohio State University Medical Center

2
Why do an exercise test?

• To diagnose coronary artery disease
• To assess the response to therapy
• For CAD
• For Hypertension
• For atrial fibrillation
• To establish prognosis
• To elicit arrythmias

3
Criteria for a Positive Stress Test

• gt 1mm (0.1mV) of ST depression or elevation
  (compared to baseline) at 60-80 msec after the
  j-point
• Downsloping ST segments
• Horizontal or upsloping ST segments adds to
  sensitivity but decreases specificity

4
Criteria for a Positive Stress Test
5
The Problem Stress ECG

• Uninterpretable ECGs
• Ventricular Pre-excitation
• Paced Rhythms
• LBBB
• Resting ST depression gt 1 mm
• Problematic ECGs
• Digoxin
• LVH
• Resting ST depression lt 1 mm

6
Pretest Probability of CAD
Gibbons, et al. JACC 2002401531
7
Pretest Probability of CAD

• Framingham 10 year CAD risk calculator
• http//hp2010.nhlbihin.net/atpiii/calculator.asp?u
  sertypeprof
• http//www.mdcalc.com/framingham-cardiac-risk-scor
  e

8
Pretest Probability of CAD

• ACC/AHA 2013 risk calculator
• http//my.americanheart.org/professional/Statement
  sGuidelines/Prevention-Guidelines_UCM_457698_SubHo
  mePage.jsp
• Individuals with gt 7.5 10-year risk of cardiac
  events should be recommended for moderate or
  high-dose statin therapy
• No specific LDLc target in this recommendation

9
Atherosclerosis Risk

• Major Risk Factors
• LDL-cholesterol
• Low HDL-cholesterol
• Family History (malelt55 femalelt65)
• Hypertension
• Smoking
• Diabetes
• LVH by ECG

10
Atherosclerosis Risk

• Lesser Risk Factors
• Age
• Male Sex
• Elevated Insulin levels
• Elevated triglycerides
• Physicial inactivity
• Postmenopausal status
• Obesity (especially central obesity)
• Stress Depression

11
Atherosclerosis Risk

• Thrombogenic Factors
• Lipoprotein (a) Lp(a)
• Homocysteine
• Fibrinogen
• C-reactive protein
• Plasminogen Activator Inhibitor
• Chlamydia pneumoniae infection

12
Pretest Probability of CAD
Gibbons, et al. JACC 2002401531
13
Pretest Probability of CAD
Gibbons, et al. JACC 2002401531
14
Diagnostic Accuracy of the ETT
Gibbons, et al. JACC 2002401531
15
Useful Data from Stress Testing

• Electrocardiographic
• Maximum ST depression or elevation
• ST-depression slope (downsloping vs horizontal)
• Number of leads with ST depression
• Exercise-induced arrythmias
• Time to ST deviation

16
Useful Data from Stress Testing

• Hemodynamic
• Maximum heart rate
• Maximum systolic blood pressure
• Maximum double product (HR x systolic BP)
• Total exercise duration
• Exercise-induced hypotension
• Chronotropic incompetence

17
Useful Data from Stress Testing

• Symptomatic
• Symptoms of angina or severe SOB
• Time to exercise-induced angina
• Time to exercise-induced SOB

18
The Rate-Pressure Product

• Low lt 200 x 100
• Moderate 200-300 x 100
• High gt 300 x 100

The rate-pressure is a surrogate for maximum
oxygen uptake
19
Borg Scale Rate of Perceived Exertion
20
Indications for Terminating ETT

• Fall in BP gt 10 mm Hg when accompanied by signs
  of ischemia
• Moderate to severe angina
• Ataxia, dizziness or near syncope
• Technical difficulties with ECG monitoring
• Sustained V-tach
• ST elevation in leads w/o Q-waves (not aVR or V1)

21
Duke Treadmill Score

• Treadmill Score Exercise time 5 x (amount of
  ST depression in mm) 4 x (exercise angina
  index) index 0 for no angina 1 if angina
  occurred 2 in angina was the reason to stop the
  test
• Risk Assessment
• High risk (score lt -11 annual mortality gt 5
• Low risk (score gt 5 annual mortality of 0.5

22
Duke Treadmill Score
23
Exercise Protocols

• Bruce
• Most commonly used protocol
• Abundant prognostic information
• Balke
• Developed in the military
• Ramp
• More physiologic approach to achieving maximum VO2

24
Exercise Protocols
25
(No Transcript)
26
Ramp Protocol
27
Overview of Exercise Physiology

• During exercise CV system must deliver increased
  blood flow by increasing cardiac output (Q)
• CAD impairs the ability to achieve a peak Q and
  maximal oxygen uptake (VO2 max)
• Signs and symptoms of CAD are proportional to the
  relative intensity (VO2max) and/or duration of
  exercise

28
Normal cardiovascular responses to exercise

• During exercise VO2 increases linearly and
  plateaus at VO2 max
• The anaerobic threshold (AT) is an important
  clinical endpoint for patients with cardiac
  disease
• Increasing dyspnea and muscle fatigue are
  symptoms experienced at exercise intensities
  which exceed the AT

29
Oxygen uptake (VO2) versus treadmill exercise
intensity
30
Exercise capacity expressed as VO2 max METs

• VO2 max in normal subjects varies from 20 to 80
  ml/kg/min
• Patients with CAD range from 3 to 30 ml/kg/min
• Exercise capacity is expressed in METs with 1
  MET resting VO2 (3.5 ml/kg/min)
• Activities are described as multiples of
• 1 MET (Metabolic EquivalenT)

31
MET Cost of Common Activities
32
Max VO2 in sedentary, normal, conditioned
endurance athletes
33
Maximum Recorded VO2
34
Maximum Recorded VO2
35
Maximum Recorded VO2
36
Determination of maximal oxygen uptake (VO2 max)

• In the absence of pulmonary limitations, anemia
  or hypoxia, VO2 max is a function of maximal Q
  and (a-V)O2 difference.
• VO2 max HR x SV x (a-v)O2
• VO2 max HR x EF x EDV x (a-v)O2

37
Cardiac output response to dynamic exercise

• Increases in a linear relationship to VO2 and
  percent of VO2 max
• At submaximum exercise intensities Q is mediated
  by combined increases in HR and SV
• At higher intensities SV is maximal and further
  increases in Q are due to HR

38
Heart rate response to dynamic exercise

• HR increase is initially determined by withdraw
  of vagal tone
• Increases in HR above 100 BPM are mediated by
  additional sympathetic drive
• Peak HR usually occurs near VO2 max
• Maximum heart rate is estimated by
• Maximum HR 220 - age (years)

39
HEART RATE PATTERNS WITH EXERCISE
Maximum predicted heart rate
Heart Rate Recovery
VAGAL RECOVERY
Exercise
Heart Rate
SYMPATHETIC ACTIVATION
Recovery
SYMPATHETIC WITHDRAWAL
VAGAL WITHDRAWAL
Resting heart rate
Rest
Peak Exercise
40
Stroke volume response to dynamic exercise

• SV increases due to increased LVEDV (preload)
  which is dependent on increased venous return and
  increased LV contractility which enhances LV
  emptying which reduces LVESV
• Maximal SV is usually achieved at 50 of VO2 max
  and usually does not increase at higher exercise
  intensities

41
Relationship of systolic and diastolic time to HR

• At higher heart rates, stroke volume may actually
  decrease because of the disproportionate
  shortening in diastolic filling time

42
Stroke volume response to dynamic exercise

• SV increases due to increased LVEDV (preload)
  which is dependent on increased venous return and
  increased LV contractility which enhances LV
  emptying which reduces LVESV
• Maximal SV is usually achieved at 50 of VO2 max
  and usually does not increase at higher exercise
  intensities

43
Ejection fraction response to dynamic exercise

• LVEF EDV - ESV / EDV x 100
• Or
• LVEF SV / EDV x 100
• Resting LVEF is 55 - 65 and increases to 75 or
  more during maximal exercise
• EDV increases 5-10 ESV decreases 5-10

44
Changes in SV from rest to maximal exercise
45
Arterial blood pressureresponse to dynamic
exercise

• Reflects balance between increased Q and
  decreased SVR
• SBP increases substantially due to higher SV and
  LV ejection force
• DBP is moderately reduced due to lowering of SVR
  during diastole
• This combination of responses provide a moderate
  increase in MAP

46
(a-v) O2 Response to Dynamic Exercise

• A typical (a-v)O2 difference at rest is 5 mL
  O2/dL (arterial of 20 - mixed venous of 15)
• During maximal exercise the mixed venous O2
  content falls to 5 ml O2/dL, thus widening the
  (a-v)O2 difference from 5 to 15 ml O2/dL
• Maximal (a-v)O2 difference of normals subjects,
  athletes and cardiac patients is very similar
  (15-17 vol)

47
Systemic vascular resistance response to dynamic
exercise

• SVR decreases in an exponential pattern
  proportional to Q and VO2 max
• SVR is determined by the balance between marked
  metabolic vasodilation in exercising muscle and
  increases in regional sympathetic tone in
  nonexercising muscle and visceral organs
• Overall SVR decreases 50 from rest

48
Acute Response to Exercise
49
Acute Blood Pressure Response to Exercise
50
Changes in resistance to flow during exercise
51
Coronary blood flow and myocardial VO2 during
exercise

• Coronary blood flow (CBF) increases
  proportionately to myocardial VO2 (MVO2)
• Determinants of MVO2 include HR, preload,
  afterload and contractility state
• HR X SBP (Rate Pressure Product, RPP) correlates
  with MVO2 CBF during EX
• RPP is a clinical index of MVO2

52
Correlation of CBF MVO2 with RPP during
exercise
53
Unravelling the Mysteries of the Metabolic Stress
Test

• What is actually measured?
• Heart Rate
• Respiratory Rate
• Duration of Exercise
• Expired Tidal Volume
• FiO2 (percent of oxygen in inspired air)
• FeO2 (percent of oxygen in expired air)
• FiCO2 (percent of CO2 in inspired air)
• FeCO2 (percent of CO2 in expired air)

54
Unravelling the Mysteries of the Metabolic Stress
Test

• What is calculated?
• VE (minute ventilation) respiratory rate x
  tidal volume (L/min)
• VO2 (oxygen uptake) FF x (FiO2-FeO2) x VE
• VCO2 (CO2 produced) VE x FeCO2

(FF fudge factor)
55
Unravelling the Mysteries of the Metabolic Stress
Test

• What is calculated?
• RER (respiratory exchange ratio) VCO2/VO2
• Roughly 75 of consumed O2 is converted to CO2
  thus the resting RER is 0.75-0.85
• More O2 is required to burn fat than to burn
  carbs (RER for fat metabolism 0.7)
• With exercise, more CO2 is produced than O2
  consumed RER gt 1.2 good effort
• Hyperventilation will raise the RER

56
Unravelling the Mysteries of the Metabolic Stress
Test

• What is calculated?
• Ventilatory Efficiency VE/VCO2
• Ventilatory requirement to eliminate CO2
• Metabolic CO2 is a strong stimulus for
  ventilation
• VE/VCO2 drops in early exercise and normally
  rises very little with exercise
• In chronic CHF, VE/VCO2 is shifted upward
• VE/VCO2 gt 34 signifies severe CHF (or COPD)

57
Unravelling the Mysteries of the Metabolic Stress
Test

• What is calculated?
• Oxygen Pulse VO2/Heart rate
• Normal values of 4-6 at rest 10-20 at peak
  exercise
• Higher values reflect better conditioning
• Reduced in CHF or severe deconditioning

58
Unravelling the Mysteries of the Metabolic Stress
Test

• What is calculated?
• Breathing Reserve VE max/MVV (at rest)
• MVV is determined by hyperventilation at rest
• VE max is minute ventilation at peak exercise
• Healthy subjects achieve VE max of 60-70 of MVV
• Breathing reserve lt 30 signifies severe COPD

59
Unravelling the Mysteries of the Metabolic Stress
Test

• Interpretation of the MST
• Refer for CHF management
• Peak VO2 lt 16 ml/kg/min (especially lt 12)
• Peak VO2 lt 50 of predicted
• VE/VCO2 gt 34
• Consider Pulmonary Disease
• Consider Deconditioning

60
Unravelling the Mysteries of the Metabolic Stress
Test

• Interpretation of the MST
• Refer for CHF management
• Consider Pulmonary Disease
• Breathing Reserve lt 30
• Fall in O2 saturation with exercise
• Respiratory rate over 60/min
• Consider Deconditioning

61
Unravelling the Mysteries of the Metabolic Stress
Test

• Interpretation of the MST
• Refer for CHF management
• Consider Pulmonary Disease
• Consider Deconditioning
• RER lt 1.0 poor effort
• Failure to reach anaerobic threshhold

62
Oxygen uptake (VO2) versus treadmill exercise
intensity