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Treadmill Stress Testing for the Primary Care Physician

Treadmill Stress Testing for the Primary Care Physician. Francis G. O’Connor, MD,MPH,FACSM Medical Director, Human Performance Lab Professor of Military and Emergency Medicine Uniformed Services University of the Health Sciences. Objectives.

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Treadmill Stress Testing for the Primary Care Physician

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  1. Treadmill Stress Testing for the Primary Care Physician Francis G. O’Connor, MD,MPH,FACSM Medical Director, Human Performance Lab Professor of Military and Emergency Medicine Uniformed Services University of the Health Sciences

  2. Objectives • Review essential Exercise Stress Test (EST) background, resources and terminology. • Describe the performance of the EST. • Describe common normal and abnormal responses to exercise testing. • Discuss interpretation of the EST.

  3. Exercise Stress Test Essentials

  4. Exercise Stress Testing and Family Physicians • Frequency of Utilization: Estimated that 13% of family physicians perform and interpret treadmills in their office. • American Academy of Family Physicians. Facts about Family Practice. Kansas City, Mo: American Academy of Family Physicians; 1998.   • Credentialing: Recent guidelines suggest that a physician acquire 50 exercise stress tests to qualify for privileges, and should perform atleast 25/yr to maintain clinical competency. • Schlant et al: Clinical competence in exercise testing: a statement for physicians from the ACP/ACC/AHA task force on clinical privileges in cardiology. Circulation 1990;82;1884-1888.

  5. Safety and Exercise Stress Testing • The risk of death during or immediately after an exercise test is less than or equal to 0.01%. • The risk of an acute MI during or immediately after an exercise test is less than or equal to 0.04%. • The risk of a complication requiring hospitalization is less than or equal to 0.2%.

  6. References • ACC/AHAQ Practice Guidelines • Fletcher GF et al: Exercise Standards: a statement for healthcare professionals from the American Heart Association Writing Group: Special Report. Circulation 1995;91:580-615. • ACC/AHA Guidelines for Exercise Testing. A Report of the ACC/AHA Task Force on Practice Guidelines. JACC Vol. 30 (3):260-311. • Gibbons RJ et al: ACC/AHA 2002 guideline update for exercise testing: a report of the American College of Cardiology/American heart Association Task Force on Practice Guidelines 2002. www.acc.org/clinical/guidelines • ACSM References • ACSM’s Guidelines for Exercise Testing and Prescription, Seventh Edition. • ACSM’s Resource Manual for Exercise Testing and Prescription, Seventh Edition.

  7. The Electrocardiogram • PR segment: isoelectric line from which the J point and ST segment are measured from rest. PQ junction is the point of reference. • J Point: point that distinguishes the QRS complex from the ST segment; measuring point for ST segment depression. • ST segment: ST segment is measured relative to the PQ junction, 80 ms from the J point, or 60 ms in rates over 145 bpm.

  8. Exercise Physiology • METs: oxygen uptake is conveniently expressed in METs; 3.5 ml O2/kg/min • 1 MET=rest; 5 MET=ADLs;10 METs= medical therapy equivalent to CABG; 18 METS=elite athlete. • Myocardial Oxygen Consumption: • Double product of HRxSBP correlates with myocardial oxygen consumption. • VO2 MAX: • Fick Equation: VO2max = (HRmax x SV max) x (CaO2max – CvO2max) • Gold standard for aerobic fitness.

  9. The Fick Equation

  10. Performance of the Exercise Stress Test

  11. Equipment and Protocols • Equipment: • Treadmill • Cycle • Arm Ergometery • Monitor and EKG Recorder • Thallium, Echocardiography • Protocol: • Maximal: • Bruce Protocol is the most commonly used test. Vigorous with the first stage commencing at 5 METs. Speed and grade is increased every three months. Generally symptom-limited; adequate tests reach 85% of MPHR. • Sub-Maximal: • Tests that involve termination at a pre-determined heart rate. Post-MI patients generally are set at 60% of MPHR, 5 METs or 120 bpm.

  12. Treadmill Protocols

  13. Indications • ACC/AHA Guidelines for Exercise Testing • Class I: general consensus/evidence that testing is justified. • Class II: divergence of opinion on utility. IIa in favor; IIb less evidence. • Class III: agreement that testing is not warranted.

  14. Indications: Diagnose Obstructive CAD • Class I • Adult patients (including those with RBBB and 1mm resting ST depression) with an intermediate pre-test probability of disease. • Class IIa • Patients with vasospastic angina. • Class IIb • Patients with a high or low pre-test probability of disease. • Patients with less than 1mm ST depression and taking digoxin. • Patients with LVH by voltage and less than 1mm of baseline ST depression. • Class III • WPW; paced rhythm; >1mm ST depression; LBBB.

  15. Pre-Test Probability of Disease

  16. CAD Risk Factors FH: MI in 1st degree male relative before 55; female before 65. Smoker or quit within 6 months. Hypertension Hypercholesterolemia: TCHOL > 200; HDL <35; LDL > 130. Impaired fasting glucose: >110. Obesity: BMI >30. Sedentary HDL >60 is a negative risk factor. CAD Signs/Symptoms Pain in the chest, neck, jaw, arms that may be due to ischemia SOB at rest or exertion Dizziness or syncope Orthopnea/PND Ankle edema Claudication Known heart murmur Unusual fatigue or SOB with usual activities ACSM Recommendations for Exercise Testing Prior to Exercise Participation

  17. ACSM Recommendations for Exercise Testing Prior to Exercise Participation • Initial ACSM Risk Stratification • Low Risk: younger individuals who are asymptomatic and have no more than one risk factor. • Moderate Risk: older or those who meet the threshold for two or more risk factors. • High Risk: individual with signs or symptoms of CAD, or known cardiovascular, pulmonary, or metabolic disease • Old versus Young • Men < 45 years of age; Women < 55. • Moderate versus Vigorous Exercise • Moderate: 3-6 METs, 40 to 60% maximal oxygen uptake. • Vigorous: >6 METs, or 60% maximal oxygen uptake.

  18. ACSM Recommendations for Exercise Testing Prior to Exercise Participation

  19. Contraindications • Absolute • Acute myocardial infarction (within 2d) • High risk unstable angina • Uncontrolled arrhythmias causing symptoms or hemodynamic compromise • Symptomatic severe aortic stenosis • Acute PE, myocarditis or pericarditis • Acute aortic dissection

  20. Contraindications • Relative • Left main coronary stenosis • Moderate stenotic valvular heart disease • Electrolyte Abnormalities • Severe arterial hypertension (200/110) • Tachy/Bradyarrhythmias • Hypertrophic cardiomyopathy • Mental or physical impairment leading to inability to exercise adequately • High degree AV block

  21. Special Considerations • Medications • Beta blockers: blunt HR response; short acting held the day of the test; long acting held two days. • Calcium channel blockers: delay ischemia, decreasing sensitivity of the test. • Digoxin: produces abnormal ST depression with exercise. • Diuretics: may cause ST depression with hypokalemia. • Conduction Disturbances • High degree AV block (Mobitz II and third degree block) should not be tested. • LBBB and WPW preclude interpretation of ischemia and should not be tested. • Special Clinical Situations • Severe arthritis/Obesity: consider pharmacologic stress testing. • Hypertension: don’t test 200/120 • Q waves: in post MI pts, ST elevation can indicate a hypokinetic ventricle.

  22. Physician Responsibilities During the Test • Patient Evaluation and Clearance • Careful history of symptoms and past medical history; typical vs. atypical. • Risk factors • Family history • Informed Consent • Physical Examination • Vital signs • Cardiovascular: murmurs, gallops • Lungs • Selection of Protocol • Maximal vs. Sub-Maximal • Treadmill vs. Cycle

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  27. Performing the Test • Preparing the Patient • Monitoring the Patient • Terminating the Test • Recovery of the Patient

  28. Preparing the Patient • Instructions: • No eating two hours before test; no consumption of alcohol, caffeine, or tobacco three hrs before. • Comfortable clothing. • Medications determined by functional vs. diagnostic testing. • Skin Preparation • Hair shaved; abrasive rub; “tap” test. • Appropriate Blood Pressure cuff. • Consent.

  29. Preparing the Patient • Pre-Test Checklist • Equipment and safety check • Informed Consent • Pre-test history and physical examination • Electrode skin preparation • Resting ECG reviewed • Standing ECG and BP • Patient Demonstration • Patient Questions

  30. Pre-Test 12 lead ECG supine and standing. BP supine and standing. Exercise 12 lead last 15 sec of each stage. BP and RPE at the end of each stage. Post-Test 12 lead ECG immediately after exercise, then every 1 to 2 minutes until return to baseline. BP: immediately after exercise, then every 1 to 2 minutes until return to baseline. Follow symptoms. Borg RPE Scale 6 7 Very, very light 8 9 Very light 10 11 Fairly light 12 13 Somewhat hard 14 15 Hard 16 17 Very hard 18 19 Very, very hard 20 Monitoring the Patient

  31. Terminating the Test • All treadmill stress tests should be completed to a symptom-limited endpoint, if possible. • 85% of maximal predicted heart rate is required to identify a test as adequate.

  32. Absolute Drop in SBP of >10 mmHg from baseline, despite increased workload, when accompanied by other ischemia Moderate to severe angina Increasing ataxia, dizziness, or pre-syncope Signs of poor perfusion Technical difficulties Subjects desire Sustained Vtach ST elevation in leads without diagnostic Q waves Indications for Test Termination

  33. Relative Drop in SBP of >10 mmHg from baseline, despite increased workload ST depression >2mm from baseline Multifocal PVCs, triplets, SVT, heart block Fatigue, shortness of breath, wheezing, leg cramps Bundle branch block Increasing chest pain Hypertensive response Indications for Test Termination

  34. Recovery of the Patient • Have the patient lie down and continuously observe. • Auscultate for abnormal heart and lung sounds. • Monitor until clinically stable and electrocardiogram has returned to normal. • ECG changes in recovery just as ominous as those occurring during exercise.

  35. Common Normal Responses to Exercise Testing • Symptoms • Typical anginal symptoms can be produced by testing and increase the prognostic value of a test. • Symptoms, however, do not define a positive test, and define a test “suggestive of ischemia.” • Opportunity for “anginal threshold” determination and use of Borg Scale for exercise prescription.

  36. Electrocardiographic Responses to Exercise • P wave: • Superimposition of P and T; p wave may increase in inferior leads. • PR segment: • Shortens and downslopes in the inferior leads. • QRS complex: • Increases in septal q waves; slight decreases in R wave amplitude; minimal shortening of interval. • J junction: • Decreases with exercise; in subjects with resting J junction elevation, this normalizes to baseline. • ST segment: • Demonstrates positive upslope that returns to baseline by 80ms. • T wave: • initially a gradual decrease in amplitude. • QT interval: • Rate-related shortening.

  37. Heart Rate • Normal Heart Rate Response • Increase in HR as a result of vagal tone withdrawal. • Standard deviation for peak HR determination is 15 BPM. • Chronotropic Incompetence • Peak heart rate less than 120 BPM. • Failure to achieve 85% of age-predicted maximum. • Heart Rate Recovery

  38. 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. Heart Rate Recovery • 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.

  39. Blood Pressure • Normal: • Systolic increases during exercise; returns to baseline by five to six minutes in recovery. • Hypotensive Response to Exercise: • A drop in BP to baseline levels during exercise; poor prognosis. • Hypertensive Response to Exercise: • Systolic greater than 220mmHg, or rise in diastolic of > 10mmHg, or Stage II age predicted 95% DBP. • Singh et al: BP response during treadmill testing as a risk factor for new-onset hypertension. Circulation. 1999;99:1831-1836. • Blood Pressure in Recovery: • 3 Minute Systolic BP Ratio: SBP 3 min/ SBP Peak > 0.91 is abnormal. • Taylor et al: Postexercise systolic BP response: clinical application to the assessment of ischemic heart disease. American Family Physician. Vol 58(5).

  40. Common Abnormal Responses to Exercise Stress Testing

  41. ST Depression and Elevation • Measurement: • Three Continuous beats • Baseline is the junction of downsloping PR and QRS complex • Depression: • If ST elevated at rest c/w early repolarization, measure from baseline. • If ST depressed at rest, measure deviation from the baseline depression. • Elevation: • ST elevation is c/w transmural ischemia, however needs to be classified by whether it occurs over Q waves. • Over Q waves: ST elevation may occur in the presence of prior infarct, and may or may not represent ischemia.

  42. Common Abnormal Responses • Isolated Inferior Depression • Atrial repolarization has been demonstrated to cause J point depression in the inferior leads. • Isolated inferior lead ST depression is frequently a false positive. • ST Elevation • ST segment elevation in the absence of Q waves usually indicates transmural ischemia. • Exercise-Induced Bundle Branch Block • Ischemia can be interpreted in RBBB, but not LBBB. • The Stress test should be stopped and the patient should have further evaluation for structural heart disease. • Exercise-Induced Hypotension • Always serious symptoms that warrant further evaluation for structural heart disease.

  43. Common Abnormal Responses • Exercise-Induced Arrhythmias • Simple PVCs: not uncommon; low grade ectopy, unifocal, and infrequent PVCs during exercise do not increase risk. • Complex Arrhythmias: complex arrhythmias at low levels, in particular when associated with ischemia, warrant further evaluation. • Ventricular Tachycardia: require termination of the test, with prognosis based upon status of underlying heart disease. • Paroxysmal Atrial Tachycardia/PSVT: treated as patients who develop PSVT without exercise.

  44. Diagnostic of Myocardial Ischemia Horizontal or downsloping ST depression >1.0 mm at 60ms past the J point ST elevation >1.0 mm at 60ms past the J point Upsloping ST depression >1.5 at 80 ms past the J point Negative for Myocardial Ischemia Patient has exercised to atleast 85% of maximal predicted heart rate and none of the above are present. Suggestive of Myocardial Ischemia Horizontal or downsloping ST depression 0.5 – 1.0 ST elevation 0.5 – 1.0 Upsloping ST depression >.7 <1.5 Exercise-induced hypotension Chest pain that seems like angina High grade ventricular ectopy A new third heart sound Inconclusive Patient does not achieve 85% of maximum HR and has no ischemia. Determining Myocardial Ischemia

  45. The Final Report • First Paragraph: (General Summary) • Pt’s age, indication for testing, cardiac medications and protocol. • Baseline heart rate, BP and resting ECG findings. • Peak exercise data, BP, HR, peak METs, RPE and reason for stopping. • Description of abnormalities in ECG response, hemodynamics, dysrhythmias, or symptoms • Second Paragraph: (Assessment) • Presence or absence of ischemia • Normal or abnormal HR/BP response • Presence of dysrhythmias • Presence of symptoms • Maximal aerobic capacity

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