Presentation on theme: "Clinical Exercise Physiology"— Presentation transcript:
1 Clinical Exercise Physiology V. Froelicher, MDProfessor of MedicineStanford UniversityVA Palo Alto HCS
2 Advances in Clinical Exercise Testing Physiology Manual SBP measurement (not automated) most important for safetyNo Age predicted Heart Rate TargetsThe BORG Scale of Perceived ExertionMETs not MinutesFit protocol to patient (RAMP)Expired Gas Analysis - ready for clinical useAvoid HV and cool down walkUse standard Exercise ECG analysisHeart rate recovery
3 Types of Exercise Isometric (Static) weight-lifting pressure work for heart, limited cardiac output, proportional to effortIsotonic (Dynamic)walking, running, swimming, cyclingFlow work for heart, proportional to external workMixed
4 Oxygen Consumption During Dynamic Exercise Testing There are Two Types to Consider:Myocardial (MO2)Internal, CardiacVentilatory (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 HRAngina 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 linepoor correlation [-0.4 to -0.6]One SD is plus/minus 12 bpmConfounded by Beta BlockersA percent value target will be maximal for some and sub-max for othersBorg scale is better for evaluating EffortDo Not Use Target Heart Rate to Terminate the Test or as the Only Indicator of Effort or adequacy of test
8 Myocardial (MO2) Systolic Blood Pressure x HR SBP should rise > 40 mmHgDrops are ominous (Exertional Hypotension)Diastolic BP should decline
9 Ventilatory (VO2)Cardiac Output x a-VO2 DifferenceVE 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 FractionVO2 = C.O.= HR x SV= HR x EDV x EFFroelicher et al. Exercise and the Heart (74)VO2 MAXEF %
12 What is a MET? Metabolic Equivalent Term 1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5 ml O2 /Kg/minActually differs with thyroid status, post exercise, obesity, disease statesBut 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 level4 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 CABS13 METs = Excellent prognosis, regardless of other exercise responses16 METs = Aerobic master athlete20 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/minuteconversion = MPH x 26.8Grade expressed as a fraction
16 METs---not Minutes (Report Exercise Capacity in METs) Can compare results from any mode or Testing ProtocolCan Optimize Test by Individualizing for PatientCan 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 EstimatedEstimated Affected by:Habituation (Serial Testing)Holding onDeconditioning and Disease StateMeasured Requires a Mouthpiece and Delicate EquipmentMeasured More Accurate and Permits measurement of Gas Exchange Anaerobic Threshold and Other Ventilatory FactorsPrognostic in CHF and Transplantation
20 MAXIMAL TREADMILL TIME (min) METS* Froelicher et al. Chest 1975 (68: 331).VO2maxml/kg(METS)30%randomerrorinEstimatedMETS706050403025MAXIMAL TREADMILL TIME (min)
21 WHY USE A BIKE ERGOMETER? WORKTREADMILLRAMPWHY 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.WORKWORKTIMETIME
24 Why Ramp?Started with Research for AT and ST/HR but clinically helpfulIndividualized test Using Prior Test, history or QuestionnaireLinear increase in heart rateImproved prediction of METsNine-minute duration for most patientsRequires 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 METsRecently found to be a predictor of prognosis after clinical treadmill testingDoes not predict angiographic CADStudies 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 METsStudies including censoring and CV mortality neededShould 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 METCan be increased by 25% by a training programWhat about Heart Rate Recovery???