Treadmill Stress Testing for the Primary Care Physician

1. Treadmill Stress Testingfor the Primary Care Physician Anthony Beutler, MD Primary Care Sports Medicine

2. The Electrocardiogram

3. What is VO2max?

4. The Electrocardiographic Response

5. Objectives • Review essential Exercise Test Terminology • Describe the Performance of the Exercise Stress Test • Review Exercise Test Responses • Discuss Interpretation of the Exercise Stress Test • Discuss Special Considerations in Athletes

6. Exercise Test Terminology • The Electrocardiogram • VO2max • METs • Myocardial Oxygen Consumption

7. Maximal Oxygen Uptake (VO2max) • Greatest amount of oxygen an individual utilizes with maximal exercise (ml O2 per kilogram per minute) • “Gold Standard” for cardiorespiratory fitness • Fick Equation • VO2max = (HRmax x SVmax) x (CaO2max - CvO2max)

8. Diffusion Ventilation Perfusion FICK EQUATION (220 - Age) Sinus Node Dysfunction Drugs (e.g., B - blockers) PaO2 Hgb [ ] SaO2 • Skeletal Muscles • Aerobic Enzymes • Fiber Type • Muscle Disease • Capillary Density Genetic Factors (Heart Size) Conditioning Factors Contractility/Afterload/Preload Disease Factors Wall Motion/Ventricular Fxn Valve Stenosis or Regurgitation VO2max = (HRmax X SVmax) X (CaO2max - CvO2max)

9. The MET METS

10. Metabolic Equivalents (METs) • 1 MET = 3.5 ml O2 per kilogram of body weight per minute

11. 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

12. 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 = Ooh lah lah Aerobic athlete

13. Myocardial (MO2) • Accurate measurement requires cardiac catheterization • 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,...

14. Myocardial Oxygen Consumption • Indirectly measured as the “Double Product” • “Double Product” = HR x systolic blood pressure • A normal value is greater than 20,000 – 25,000

15. Performance of the Exercise Stress Test • Indications/Contraindications • Running the Exercise Test • Physician Responsibilities

16. ACSM’s Guidelines for Exercise Testing and Prescription ACSM. Lippincott, Williams & Wilkins 6th Edition 2000

17. Indications for Exercise Testing • Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective. • Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment. • II a: weight of evidence is in favor of usefulness/efficacy. • II b: usefulness is less well established by the evidence. • Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective and in some cases may be harmful.

18. Class I Indications for Performing an Exercise Test • To assist in the diagnosis of CAD in adult patients with an intermediate pretest probability of disease. • To assess functional capacity and to aid in assessing the prognosis of patients with known CAD. • To evaluate the prognosis and functional capacity of patients with CAD soon after an uncomplicated myocardial infarction. • To evaluate patients with symptoms consistent with recurrent, exercise-induced cardiac arrhythmias.

19. Class II Indications for Performing an Exercise Test • To evaluate asymptomatic men >40 and women >50 who: • are involved in special, high risk occupations; • plan to start a vigorous exercise program; • have multiple cardiac risk factors. • To assist in the diagnosis of CAD in adult patients with a high or low pretest probability of disease. • To evaluate patients with a Class I indication who have baseline electrocardiographic changes.

20. Class III Indications for Performing an Exercise Test • Routine screening of asymptomatic men or women. • To evaluate men or women with a history of chest discomfort not thought to be of cardiac origin. • To evaluate patients with simple PVCs on a resting ECG with no other evidence of CAD. • To assist in the diagnosis of CAD in patients with evidence of LBBB or WPW on a resting ECG.

21. Pre Test Probability of Coronary Disease by Symptoms, Gender and Age

22. Recent acute MI Unstable angina Ventricular tachycardia Dissecting aortic aneurysm Acute CHF Severe aortic stenosis Active myocarditis Thrombophlebitis or intracardiac thrombi Recent pulmonary embolus Acute infection Contraindications to GXT Testing: Absolute

23. Uncontrolled severe hypertension Moderate aortic stenosis Severe subaortic stenosis Supraventricular dysrhythmias Ventricular aneurysm Complex ventricular ectopy Cardiomyopathy Uncontrolled metabolic disease Recurrent infectious disease Complicated pregnancy Contraindications to GXT Testing: Relative

24. So What Do You Do…. • 39 yo female with risk factors and a squirrelly story….

25. Comparison of Tests for Diagnosis of CAD

26. Which Protocol? • Vast Majority (82+%) use BRUCE • So, why not you?

27. How to read an Exercise ECG • Good skin prep • PR isoelectric line • Not one beat • Three consistent complexes • Averages can help • Garbage in, garbage out • Why watch during recovery?

28. Symptom-Sign Limited Testing Endpoints – When to stop! • Dyspnea, fatigue, chest pain • Systolic blood pressure drop • ECG--ST changes, arrhythmias • Physician Assessment • Borg Scale (17 or greater) MHR=220-age...

29. 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 • A percent value target will be maximal for some and sub-max for others • Confounded by Beta Blockers • Borg scale is better for evaluating Effort • Target Heart Rate does have a place as an Indicator of Effort or adequacy of test

30. Heart Rate Recovery and Treadmill Exercise Score as Predictors of Mortality in Patients Referred for Exercise ECG Nishime EO, et al: JAMA, September 20, 2000. Vo 284, No 11, 2000.

31. Following the GXT, patients walked for 2 minutes at 1.5 mph and at a grade of 2.5%. • Heart rate recovery was the difference in heart rate at peak exercise and one minute into recovery; 12/min or less was considered abnormal. • 9454 patients were followed for a median of 5 years; 20 % had abnormal heart rate recovery; they represented 8% of deaths vs. 2%; hazard ratio of 4.16. • Heart rate recovery is an independent predictor of mortality.

32. 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

33. Heart Rate Drop in Recovery • Probably not more predictive than Duke Treadmill Score or METs • Studies including censoring and CV mortality needed

34. Heart Rate Drop in Recovery vs METs • 10 to 15% increase in survival per MET • METS can be increased by 25% by a training program • What about Heart Rate Recovery???

37. The MET METS

38. Interpretation of the Exercise Stress Test Must Contain Following Elements: • Exercise Capacity • Clinical • Hemodynamic • Electrocardiographic

39. ST Depression → or ↓ ≥ 1mm at 60msec ↑ ≥ 1.5mm at 80msec ST Elevation ≥ 1mm at 60msec ST Depression → or ↓ 0.5 - 1mm at 60msec ↑ 0.7 - 1.5mm at 80msec ST Elevation 0.5 – 1mm at 60msec Positive vs Suggestive

40. Above criteria not met and pt exercised to at least 85% MPHR Pt did not reach 85% MPHR, but no evidence of ischemia (B-Blocker??) Negative vs Inconclusive

41. DUKE Treadmill Score for Stable CAD METs - 5 X [mm E-I ST Depression] - 4 X [Treadmill Angina Index] ******Nomogram******* E-I = Exercise Induced

42. Duke Treadmill Score (uneven lines, elderly?)

43. But Can Physicians do as well as the Scores? 954 patients - clinical/TMT reports Sent to 44 expert cardiologists, 40 cardiologists and 30 internists Scores did better than all three but was most similar to the experts

44. Special Considerations in Athletes • Indications • Athletic Heart Syndrome • Test Interpretation

45. Initial ACSM Risk Stratification

46. Does the patient need a GXT? • Controversial • ACSM- Must be able to distinguish: • Moderate vs. vigorous exercise • Apparently healthy vs. higher risk • Older vs. younger

47. Low Risk Mod Risk High Risk Moderate Exercise Not Necessary Recommend Not Necessary Vigorous Exercise Recommend Recommend Not Necessary ACSM Recommendations for Medical Examination and Exercise Testing Prior to Participation

48. ACSM Initial Risk Stratification by Age and Cardiac Risk • Moderate Risk • “Older” individuals •  2 risk factors • Low Risk • Men < 45, Women <55 • No cardiac symptoms • 1 risk factor • Cardiac Risk Factors • Cigarette smoking • Fam Hx. of early CAD • LDL >130) • Hypertension • Impaired fasting gluc • (>110mg/dL) • Obesity (BMI >30) • Sedentary lifestyle “Positive” Risk Factor: High serum HDL (>60) “Positive” Risk Factor: “Positive” Risk Factor:

49. ACSM Initial Risk Stratification by Age and Cardiac Risk • Low Risk • Men < 45, Women <55 • No cardiac symptoms • 1 risk factor • Moderate Risk • “Older” individuals •  2 risk factors • High Risk • Signs or Symptoms of cardiac dz • Known cardiac, pulmonary or metabolic (DM) disease. • Signs/Sx. CV Disease • Chest pain or anginal equiv • Dyspnea w/ mild exertion • Dizziness or syncope • Orthopnea/PND • Ankle edema • Palpitations or tachycardia • Intermittent claudication • Fatigue w/ normal activities

50. Not Necessary Not Necessary Who Needs a GXT? • Athlete with known CAD • Anyone with symptoms of CAD • Moderate risk patient for vigorous exercise • Anyone with known medical disease