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

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Presentation on theme: "Clinical Exercise Physiology V. Froelicher, MD Professor of Medicine Stanford University VA Palo Alto HCS."— 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 n Isometric (Static) – weight-lifting – pressure work for heart, limited cardiac output, proportional to effort n Isotonic (Dynamic) – walking, running, swimming, cycling – Flow work for heart, proportional to external work n Mixed

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

5 Myocardial (MO 2 ) n Coronary Flow x Coronary a - VO2 difference n Wall Tension (Pressure x Volume, Contractility, Stroke Work, HR) n Systolic Blood Pressure x HR n 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 n Which Regression Formula? (2YY -.Y x Age) n Big scatter around the regression line – poor correlation [-0.4 to -0.6] n One SD is plus/minus 12 bpm n Confounded by Beta Blockers n A percent value target will be maximal for some and sub-max for others n Borg scale is better for evaluating Effort n 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 n Dyspnea, fatigue, chest pain n Systolic blood pressure drop n ECG--ST changes, arrhythmias n Physician Assessment n Borg Scale

8 Myocardial (MO 2 ) n Systolic Blood Pressure x HR n SBP should rise > 40 mmHg n Drops are ominous (Exertional Hypotension) n Diastolic BP should decline

9 Ventilatory (VO 2 ) n Cardiac Output x a-VO2 Difference n VE x (% Inspired Air Oxygen Content - Expired Air Oxygen Content) n External Work Performed n ****Direct relationship with Myocardial O 2 demand and Work is altered by beta-blockers, training,...

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

11 VO2 vs. EF% F Poor correlation between VO2 (~CO) between VO2 (~CO) and Ejection Fraction and Ejection Fraction VO2 = C.O. VO2 = C.O. = HR x SV = HR x SV = HR x EDV x EF = HR x EDV x EF Froelicher et al. Exercise and the Heart 1993 (74) Froelicher et al. Exercise and the Heart 1993 (74). 1.00 EF % VO2 MAX

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) n 10 METs = As good a prognosis with medical therapy as CABS n 13 METs = Excellent prognosis, regardless of other exercise responses n 16 METs = Aerobic master athlete n 20 METs = Aerobic athlete

15 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

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

20 METS * Froelicher et al. Chest 1975 (68: 331). 7 9 11 13 15 7 9 11 13 15 706050403025 VO2maxml/kg(METS)30%randomerrorinEstimatedMETS MAXIMAL TREADMILL TIME (min)



23 METS * * Myers et al. JACC; 1991 (17: 1334). 9 13 17 21 25 9 13 17 21 25 PREDICTED VO2 (METS) MEASURED VO2 VO2(METS)overestimation of METS BRUCE-CHF RAMP-CHF UNITY

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

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

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