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EXERCISE STRESS TEST

EXERCISE STRESS TEST. Physiology and Protocol, Indications and Contraindications DN. Essential ET Terminology Performance of the E S T Assess Exercise Test Responses Interpretation Of The Exercise Stress Test.

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EXERCISE STRESS TEST

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  1. EXERCISE STRESS TEST Physiology and Protocol, Indications and Contraindications DN

  2. Essential ET Terminology • Performance of the E S T • Assess Exercise Test Responses • Interpretation Of The Exercise Stress Test

  3. Exercise Test Terminology • Vo2max • METs • Myocardial Oxygen Consumption

  4. Maximal Oxygen Uptake (VO2max) • Greatest amount of oxygen an individual utilizes with maximal exercise (ml O2 /kg/ min) • “Gold Standard” for cardiorespiratory fitness • Fick Equation Vo2max = (HRmax x SVmax) x (CaO2max - CvO2max)

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

  6. MET • Metabolic Equivalent Term • 1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5 ml O2 /Kg/min • inf- thyroid status, post exercise, obesity, disease states

  7. MET Values • 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;

  8. 10 METs = prognosis with med therapy = CABG 13 METs = Excellent prognosis 16 METs = Aerobic master athlete

  9. Calculation of METs on the Treadmill METs = Speed x [0.1 + (Grade x 1.8)] + 3.5 3.5 Calcul automatically by device Speed in meters/minute = MPH x 26.8 Grade expressed as a fraction

  10. Myocardial (MO2) • Accurate measurement - cardiac catheterization • Coronary Flow x Coronary (a – v)O2 diff • HR, SBP, LVEDV, CONTRACTILITY, WALL THICKNESS .

  11. Myocardial Oxygen Consumption • Indirectly measured as the “Double Product” • “Double Product” = HR x SBP • A normal value is greater than 20,000 – 25,000 • < 20,000 is low heart work load • > 29,000 indicates high heart work load • Angina & ST↓occur at the same DP for an individual

  12. Types of Exercise • Isometric (Static) -weight-lifting -pressure work for heart, limited cardiac output • Isotonic (Dynamic) -walking, running, swimming, cycling -Flow work for heart -↑CO,↓ TPR • Mixed

  13. Exercise physiology • Sympathetic activation • Parasympathetic withdrawal • Vasoconstriction, except in- • Exercising muscles • Cerebral circulation • Coronary circulation • ↑norepinephrine and renin

  14. Exercise physiology • ↑ventri contractility • ↑O2 extraction(upto 3) • ↓peripheral resistance • ↑SBP,MBP,PP • DBP –no significant change • Pulmvasc bed can accommodate 6 fold CO • CO - ↑ 4-6 times

  15. Exercise physiology Isotonic exercise(cardiac output) • Early phase- SV+HR • Late phase-HR

  16. V02 peak Oxygen consumption (liters/min) • peak oxygen consumption-age, sex, &training level of the person performing the exercise • The plateau in peak oxygen consumption-Vo2 max • Vo2 maxis limited by 1)the ability to del O2 to sk. muscles 2)muscle oxidative capacity . (VO2max) Work rate (watts)

  17. Respiration during exercise • dynamic exercise- ventilation increases linearly over the mild to moderate range, then >rapidly in intense exercise • workload at which rapid ventilation occures is called the ventilatory breakpoint(together with lactate threshold) Lactate acidifies the blood, driving off CO2 and increasing ventilatory rate

  18. BP rise in exercise • (SBP) ↑up to 150-170 mm Hg during dynamic exercise;diastolic rarely alters • isometric - SBP may ≥250 mmHg, and DBP can reach 180

  19. Intense exerciseGlycolysis>aerobic metabolism  ↑ blood lactate Blood lactic acid (mM) Lactate threshold; endurance estimation Relative work rate (% V02 max)

  20. Age Pred Max HR • APMHR=220 - age in years\ • APMHR=200-1/2 age • MHR ↓ with age • Lower/higher than actual value(+/_12beats) • Not used as an indicator of max exertion in EST/ Indi to terminate test

  21. .

  22. Post exercise phase • Vagal reactivation -Imp-cardiac deccelerationmech • ↑in well trained athletes • Blunted in CCF

  23. Exercise Stress Testing • Pathophysiology: • At rest- adequate coronary blood flow • with exercise-supply\demand mismatch -ST segment changes • 70-80%occlusion - detection by EST • Sign CAD can exist with a -VE Exercise Stress Test.

  24. Treadmill protocol EST- stand protocols to progressively ↑ cardiovascular work load in a uniform and reproducible way • Bruce protocol • Naughton protocol • Weber protocol • ACIP(asymptomatic cardiac ischemia pilot) • Modified ACIP

  25. The Bruce protocol • 1949 by Robert A. Bruce, considered the “father of exercise physiology”. • Published as a standardized protocol in 1963. • gold-standard for detection of myocardial ischemia when risk stratification is necessary.

  26. BRUCE Protocol

  27. Peak Vo2 is the same regardless of the protocol useddiff – rate at which it is achieved

  28. Procedure • Standard 12 lead ECG- leads • Torso ECG + BP • Supine and Sitting / standing • HR ,BP ,ECG • Before,after,stage • Onset of ischemic response • Each min recovery(5-10 mints)

  29. Procedure- Lead systems • Mason-Liker modification-extremity electrodes moved to torso 2 ↓ motion artifacts • RAD • ↑inf lead voltage • Loss of inf lead q • New Q in AVL

  30. Contraindications to Exercise Testing Absolute • A/c MI (< 2 d) • High-risk unstable angina • Uncontrolled cardiac arrhythmias causing symptoms or hemocompromise • Symptomatic severe AS • Uncontrolled symptomatic CCF • Acute pulmonary embolus or pulmonary infarction • A/c myocarditis or pericarditis • A/c Aodissection

  31. Contraindications to Exercise Testing Relative • LMCA stenosis • Mod- stenotic VHD • Electrolyte abnormalities • Sev HTN • Tachyarrhythmias or bradyarrhythmias • HOCM and other outflow tract obstructions • Mental or physical impairment leading to inability to exercise adequately • High-degree AV block

  32. SAFETY & RISKS In nonselected pat pop-mortality- .01% -morbidity-.05% In k/c CAD- 1 C.arrest/59000 person hours -AMI in 1.4 / 10000 tests Arrythmias-AF-Mc-9/10,000 tests -VT-6/10,000 tests -VF- .6/10,000 tests Deaths& MI estimated occur in 1 of 25000 tests

  33. Bayes' theorem A theory of probability The post test probability is proportional to the pretest probability To diagnose, test sensitivity ,specificity& prevalence in the population being tested req

  34. Sensitivity- a person with the disease having a positive test. • Specificity-person without the disease having a negative test. • Prevalence- % in the population having disease.

  35. Pretest Probability • Based on the pat's h/o ( age, gender, chest pain ), phy ex and initial testing, and the clinician's experience. • Typical or definite angina →pretest probability high - test result does not dramatically change the probability. • Diag power maximal when the pretest probability is intermediate-30-70%

  36. Classification of chest pain • Typical angina • Atypical angina • Noncardiac chest pain • Substernal chest discomfort with characterstic quality and duration • Provoked by exertion or emotional stress • Relieved by rest or NTG Meets 2 of the above characteristics Meets one or none of the typical characteristics

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

  38. INTERMEDIATE CATEGORY

  39. E T TO DIAGNOSE OBSTRUCTIVE CAD Class I • Adult (including RBBB or <1 mm of resting ST↓) with intermed pretest probability of CAD Class IIa • Patients with vasospastic angina.

  40. E T TO DIAGNOSE OBSTRUCTIVE CAD Class IIb 1. Patients - high pretest probability of CAD 2. Patients - low pretest probability of CAD 3. Patients with <1 mm of baseline ST ↓and on digoxin. 4. Patients with LVH and <1 mm baseline ST ↓. Class III • Patients with the following baseline ECG abnormalities: • Pre-excitation syndrome • Electronically paced ventricular rhythm • >1 mm of resting ST depression • Complete LBBB

  41. Exercise Testing in Asymptomatic PersonsWithout Known CAD Class I • None. Class IIa • Evaluation of asymP DM pts - plan to start vigorous exercise ( C) Class IIb • 1. Evalof pts with multiple risk factors - guide to risk-reduction therapy. • 2. Evalof asymptomatic men > 45 yrs and women >55 yrs: Plan to start vigorous exercise Involved in occupations which impact public safety High risk for CAD(e.g., PVOD and CRF) Class III • Routine screening of asymptomatic

  42. RISK ASSESS AND PROGIN PAT WITH SYMP OR APRIOR HISTORY OF CAD Class I 1. Initial evaluwith susp/known CAD +/- RBBB or <1 mm of resting ST Depression 2.Susp/ known CAD, previously evaluated-+ signichange in clinical status nw 3. Low-risk UA pts >8 to 12 hrs & free of active ischemia/CCF 4. Intermed-risk UApts > 2 to 3 days & no active ischemia/ CCF Class IIa Intermed-risk UA pts – initial markers (N),rpt ECG –no signichange, and markers >6-12 hrs (N) & no other evidence of ischemia during observation.

  43. AFTER MYOCARDIAL INFARCTION Class I • 1. Before discharge (submaximal --4 to 6 days). • 2. Early after discharge (symptom limited --14 to 21 days). • 3. Late after discharge if the early exercise test was submaximal(symptom limited --3 to 6 weeks). Class IIa • After discharge as part of cardiac rehabilitation in patients who have undergone coronary revascularization.

  44. AFTER MYOCARDIAL INFARCTION Class IIb 1. Patients with the following ECG abnormalities: • • Complete LBBB • • Pre-excitsynd • • LVH • • Dig therapy • • >1 mm of resting ST-segment dep • • paced ventricular rhythm 2. Periodic monitoring in patients who continue to participate in exercise training or cardiac rehabilitation. Class III 1. Severe comorbidity likely to limit life expectancy and/or candidacy for revascularization. 2. any time to eval pts with AMI with uncompensated CCF, arrhythmia, or noncardiac exercise limiting conditions. 3. Before discharge to evaluate pts who have already been selected for, or have undergone, cardiac cath. .

  45. Submaximal protocols • predetermined end point, often a peak HR 120 bpm, or 70% predicted max HR or peak MET – 5 Symptom-limited tests • to continue till signs or sympt needing termination (i.e., angina, fatigue, ≥ 2 mm of ST↓,v. arrhy, or ≥10-mm Hg drop in SBP from the resting blood pressure)

  46. The incidence of fatal cardiac events(inclu fatal MI & cardiac rupture)-- 0.03% • Nonfatal MI and successfully resuscitated cardiac arrest -- 0.09% • Complex arrhythmias, including VT --1.4%. • Symptom-limited protocols have an event rate that is 1.9 times that of submaximal tests

  47. High risk predischarge Present Absent Cardiac cath strategy 2 strategy3 symplim EST(14-21d) sub max (4-7d)

  48. Symplim EST(14-21 days) Markedly ab mildly ab negative Card cath Ex imaging Reversible ischemia no rev ischemia Med Rx

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