William Kraus, MD Duke University

1. Durham
12 April 2024
William E. Kraus, M.D.
Duke Sudden Cardiac Death Symposium
The Role and Interpretation of Cardiopulmonary
Exercise Testing in Assessment of Exercise
Tolerance in Athletes

2. No disclosures to declare

4. CPX Indications (AHA)
• Class I indications - (good evidence)
– 1. Evaluate exercise capacity and response to therapy in
heart failure patients being considered for
transplantation.
– 2. Differentiate cardiac versus pulmonary versus peripheral
limitation for dyspnea on exertion.
• Class IIa - (weight of opinion)
– 1. Evaluate exercise capacity when indicated for medical
reasons when subjective estimates (exercise test time
or work rate) are unreliable.
• Class IIb - (efficacy less established)
– 1. Evaluate response to intervention in which improvement
of exercise tolerance is an important end point.
– 2. Determine exercise training intensity for cardiac rehab.
• Class III - (not recommended)
– 1. Routine use to evaluate exercise capacity.

5. Coupling of External to Cellular Respiration
Wasserman K. Exercise Gas Exchange in Heart Disease. Future 1996.
CO2 production O2 flow Expired
O2 consumption CO2 flow Inspired
Response: QO2 SV HR VT, f

6. CPX Testing Important Terms
• VO2 = oxygen consumption (measure of CV-R fitness)
– Absolute (L/min) vs relative (mL/kg/min)
• RER = respiratory exchange ratio (measure of effort)
– Amount of CO2 per O2 consumed
– RER > 1.0 extra CO2 produced related to lactate
production
– RER > 1.10 considered maximal effort
• Ve/VCO2 slope = vent efficiency/dead space
– Prognostic in HF: > 34 → worse prognosis
• Dyspnea index = peak exercise ventilation/MVV
– > 50% = onset of dyspnea
– > 80% = exercise ceases usually within 1 minute
– Breathing reserve = (1 – Dyspnea Index)
• O2 pulse = VO2/HR = SV x AVO2 diff
– Surrogate for stroke volume

7. Normal Study

8. CPX Test Interpretation
• Step 1: PFTs
– FVC, FEV1 , FEV1/FVC < 80% → lung limited; Is MVV ~ FEV1 x 35?
• Step 2: RER – adequacy of test
– > 1.10 = maximal test; likely limited by lactate.
– < 1.10 may or may not be max
• Step 3: VO2 and % predicted – total oxidative capacity limited
– VO2 of 14 mL/kg/min may be normal for 70 y woman.
• Step 4: O2-pulse and % predicted – cardiac limited – Panel 2
– Compare with VO2 and HR response
• Step 5: Ve/VCO2 and VE/MVV – Panel 7
– ↑ Ve/VCO2 = ↑ dead space → CHF, pulmonary vascular disease; pulmonary
limited
• Step 6: VO2 at VT; HR at VT – sk muscle limited – Panels 3, 6, 9
– Percent of predicted

9. Reason for Test:
Resting Data
Age: Height (in): Weight (lb): BMI (kg/m2): Gender: Race:
Spirometry
Ref Pre Meas. Pre % Ref
FVC L
FEV1 L
FEV1/
FVC
%
PEF L/s
MVV L/min
Measured % Predicted
Relative VO2 (mL/kg/min)
Absolute VO2 (L/min)
VE-VCO2 Slope (25-75%)
Resp. Exchange Ratio
(RER)
VT* (mL/kg/min)
VT* (L/min)
Heart Rate at VT (bpm)
VE Max (L/min) BTPS
VE/MVV Ratio
O2-Pulse (mL/beat)
Metabolic Data
Predicted VO2 (mL/kg/min):
Patient effort, understanding, cooperation:
% Pred
VO2

10. Coupling of External to Cellular Respiration
Wasserman K. Exercise Gas Exchange in Heart Disease. Future 1996.
CO2 production O2 flow Expired
O2 consumption CO2 flow Inspired
Response: QO2 SV HR VT, f

11. Cardiovascular Performance
FICK Equation
VO2 = CO  AVO2
VO2 = SV  HR  AVO2
VO2 = EDV  EF  HR  AVO2
VO2 = EDV – ESV  HR  AVO2

12. Regulation of Stroke Volume During Sub-
maximal and Maximal Upright Exercise in
Normal Men
• VO2 increase - 8 times
• Linear increase in cardiac output - 3.2 times
• Increase in AV02 difference - 2.5 times
• Increase in CO resulted from 1.4 times increase in stroke
volume and 2.5 times increase in heart rate
• Increase in stroke volume resulted from 1.1 – 1.2 times
increase in end diastolic volume (EDV) and 1.2 – 1.3 increase
in ejection fraction (EF) or decrease in end systolic volume
(ESV).
Higginbotham, Morris, Williams, McHale, Coleman, Cobb, Circ Res 58:281,
1986

13. Ventilatory threshold
• Work level above which lactate progressively increases in the
blood
• Measured by ventilatory responses
Aerobic: 1G + 6O2 36 ATP + 6 CO2 Ventilation
Anaerobic: 1G 2 ATP + 2 lactic acid
2 lactate
HCO3
H2CO3 H2O + CO2

14. Relations Between Central and Peripheral
Hemodynamics During Exercise in Normal
Subjects Patients with Heart Failure
• Upright Bicycle Exercise- Maximal effort
• Expired Gas Analysis- VO2, VCO2, VE
• Pulmonary Artery Catheter- PAP, PCWP, FICK CO, SV, AVO2
• RNA – MUGA- Rest and Exercise Ejection
Fraction
• Leg Blood Flow- Thermodilution
• Brachial Artery Catheter- Pressure, arterial gases, lactate
Higginbotham, Morris, Williams, McHale, Coleman, Cobb- Circulation Res. 58:281, 1986
Higginbotham, Morris, Williams, Coleman, Cobb- AJC 57: 1374, 1986
Sullivan, Knight, Higginbotham, Cobb – Circulation 80: 769, 1989.

15. CPX Testing - Overview
Roles of CPX testing
 Determine cause of dyspnea
o Pulmonary vs cardiac vs deconditioning vs obesity
 Objectively measure functional capacity
 Determine prognosis & measure response to therapy in (HF) patients
 Optimize settings for rate-adaptive pacemakers
 Research

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