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Clinical Exercise Physiology

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Presentation on theme: "Clinical Exercise Physiology"— Presentation transcript:

1 Clinical Exercise Physiology
V. Froelicher, MD Professor of Medicine Stanford University VA Palo Alto HCS

2 Advances in Clinical Exercise Testing Physiology
Manual SBP measurement (not automated) most important for safety No Age predicted Heart Rate Targets The BORG Scale of Perceived Exertion METs not Minutes Fit protocol to patient (RAMP) Expired Gas Analysis - ready for clinical use Avoid HV and cool down walk Use standard Exercise ECG analysis Heart rate recovery

3 Types of Exercise Isometric (Static) weight-lifting
pressure work for heart, limited cardiac output, proportional to effort Isotonic (Dynamic) walking, running, swimming, cycling Flow work for heart, proportional to external work Mixed

4 Oxygen Consumption During Dynamic Exercise Testing
There are Two Types to Consider: Myocardial (MO2) Internal, Cardiac Ventilatory (VO2) External, Total Body

5 Myocardial (MO2) Coronary Flow x Coronary a - VO2 difference
Wall Tension (Pressure x Volume, Contractility, Stroke Work, HR) Systolic Blood Pressure x HR Angina and ST Depression usually occurs at same Double Product in an individual ** Direct relationship to VO2 is altered by beta-blockers, training,...

6 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 Confounded by Beta Blockers A percent value target will be maximal for some and sub-max for others Borg scale is better for evaluating Effort Do Not Use Target Heart Rate to Terminate the Test or as the Only Indicator of Effort or adequacy of test

7 Symptom-Sign Limited Testing Endpoints
Dyspnea, fatigue, chest pain Systolic blood pressure drop ECG--ST changes, arrhythmias Physician Assessment Borg Scale

8 Myocardial (MO2) Systolic Blood Pressure x HR
SBP should rise > 40 mmHg Drops are ominous (Exertional Hypotension) Diastolic BP should decline

9 Ventilatory (VO2) Cardiac Output x a-VO2 Difference VE x (% Inspired Air Oxygen Content - Expired Air Oxygen Content) External Work Performed ****Direct relationship with Myocardial O2 demand and Work is altered by beta-blockers, training,...

10 VO2 = C.O. x C(a-v)O2 C(a-v)O2 ~ k VO2 THE FICK EQUATION
then, VO2 ~ C.O.

11 VO2 vs. EF% Poor correlation EF % between VO2 (~CO)
and Ejection Fraction VO2 = C.O. = HR x SV = HR x EDV x EF Froelicher et al. Exercise and the Heart (74) VO2 MAX EF %

12 What is a MET? Metabolic Equivalent Term
1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5 ml O2 /Kg/min Actually differs with thyroid status, post exercise, obesity, disease states But by convention just divide ml O2/Kg/min by 3.5

13 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

14 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

15 Calculation of METs on the Treadmill
METs = Speed x [0.1 + (Grade x 1.8)] Calculated automatically by Device! Note: Speed in meters/minute conversion = MPH x 26.8 Grade expressed as a fraction

16 METs---not Minutes (Report Exercise Capacity in METs)
Can compare results from any mode or Testing Protocol Can Optimize Test by Individualizing for Patient Can adjust test to 8-10 minute duration (aerobic capacity--not endurance) Can use prognostic power of METs



19 Estimated vs Measured METs
All Clinical Applications based on Estimated Estimated Affected by: Habituation (Serial Testing) Holding on Deconditioning and Disease State Measured Requires a Mouthpiece and Delicate Equipment Measured More Accurate and Permits measurement of Gas Exchange Anaerobic Threshold and Other Ventilatory Factors Prognostic in CHF and Transplantation

METS * Froelicher et al. Chest 1975 (68: 331). VO2max ml/kg (METS) 30% random error in Estimated METS 70 60 50 40 30 25 MAXIMAL TREADMILL TIME (min)

WORK TREADMILL RAMP WHY USE A BIKE ERGOMETER? 1. Accurate measurement of POWER. 2. Ramping protocols allow for assessment of physiologic function across all work levels. Staged protocols only assess partial physiologic function. 3. Independent of patient’s weight (Treadmill results are influenced by weight). 4. Less danger of fall and injury to patient. 5. Easier to take accurate B/P at high work rates (Patient arm is steady and there is far less noise - no treadmill motor). 6. Patient can stop at anytime. 7. Holding handle bars does not effect test (Holding treadmill handrails can significantly effect results). 8. Fits into smaller space and is portable. 9. Patients with knee or hip problems tend to perform better and report being more comfortable on the bike. 10. Bike ramp protocols are designed to last 6-10 minutes, resulting in less fatigue (yet peak work is maximized). 11. HR, Work, and VO2 (Cardiac Output) are linearly related. Bike ramp protocols produce linear increases in Work, thereby mimicking the expected physiologic response in health and disease. 12. Determination of the Anaerobic Threshold (AT) by the most popular methods (V-slope and VE/VO2 nadir) were developed and proven through the use of bike ramp protocols. To use another method means to lose AT detection accuracy. 13. Bike ramp protocols are used by many of the leading clinical and research cardiopulmonary exercise testing labs (UCLA, Duke, Mayo, Stanford, Bowman-Gray, Johns Hopkins, UAB, Temple to name a few). Recently, treadmills capable of performing ramp protocols have been developed. WORK WORK TIME TIME


* Myers et al. JACC; 1991 (17: 1334). MEASURED VO2 (METS) overestimation of METS UNITY RAMP-CHF BRUCE-CHF PREDICTED VO2 (METS)

24 Why Ramp? Started with Research for AT and ST/HR but clinically helpful Individualized test Using Prior Test, history or Questionnaire Linear increase in heart rate Improved prediction of METs Nine-minute duration for most patients Requires special Treadmill controller or manual control by operator

25 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

26 Heart Rate Drop in Recovery
Probably not more predictive than Duke Treadmill Score or METs Studies including censoring and CV mortality needed Should be calculated along with Scores as part of all treadmill tests

27 Heart Rate Drop in Recovery vs METs
10 to 15% increase in survival per MET Can be increased by 25% by a training program What about Heart Rate Recovery???

28 For CV Health Benefits Training or Activity?

29 Highest exercise level
Baseline risk Physical activity Risk Reduction Physical fitness Williams, Meta-analysis, MSSE 2001:754 8 fitness cohorts (317,908 person-yrs fu) 30 activity cohorts (>2 million person-yrs fu) Percentile activity/fitness level Highest exercise level

30 Prescription for CV Training
Mode: Dynamic Duration: 30 mins Intensity: HR, AT, BORG Frequency: 3/week

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