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Exercise stress electrocardiography

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  1. Exercise stress electrocardiography • Physiology and Protocol, • Indications and Contraindications • Frijo Jose A

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

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

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

  5. ↑ exercise work à ↑ O2 usage à Person’s max. O2 consumption (VO2max) reached V02 peak Oxygen consumption (liters/min) Work rate (watts)

  6. V02 peak Oxygen consumption (liters/min) • The peak oxygen consumption is influenced by the age, sex, and training level of the person performing the exercise • The plateau in peak oxygen consumption, reached during exercise involving a sufficiently large muscle mass, represents the maximal oxygen consumption • Maximal oxygen consumption is limited by the ability to deliver O2 to skeletal muscles and muscle oxidative capacity (mucle mass and mitochondirial enzymes activity). (VO2max) Work rate (watts)

  7. The ability to deliver O2 to muscles and muscle’s oxidative capacity limit a person’s VO2max. Training à ↑ VO2max V02 peak (trained) 70% V02 max (trained) V02 peak (untrained) Oxygen consumption (liters/min) 100% V02 max (untrained) 175 Work rate (watts)

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

  9. Blood Pressure (BP) also rises in exercise • systolic pressure (SBP) goes up to 150-170 mm Hg during dynamic exercise;diastolic scarcely alters • in isometric(heavy static) exercise, SBP may exceed 250 mmHg, and diastolic (DBP) can itself reach 180

  10. Intense exercise à Glycolysis>aerobic metabolism à ↑ blood lactate (other organs use some) Blood lactic acid (mM) Lactate threshold; endurance estimation Relative work rate (% V02 max)

  11. Maximum HR • HR=220 - age in years

  12. Post exercise phase • Vagal reactivation • Imp cardiac deceleration mech • ↑in well trained athletes • Blunted in CCF

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

  14. Key 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; • 10 METs = same progn with medical thpy as CABG • 13 METs = Excell prognosis, • regardless of othr exercise responses

  15. Key MET Values • 3-5 METs: • raking leaves,light carpentry,golf,3-4 mph • 5-7 METs: • exterior carpentry, singles tennis • >9 METs: • heavy labour, hand ball, squash, running 6-7 mph

  16. Estimated Energy Requirements for Various Activities

  17. Estimated Energy Requirements for Various Activities

  18. 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

  19. Treadmill protocol • Bruce protocol • Naughton protocol • Weber protocol • ACIP(asymptomatic cardiac ischemia pilot) • Modified ACIP

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

  21. Protocol description

  22. 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

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

  24. Procedure- Lead systems • Mason-Liker modification • RAD • ↑inf lead voltage • Loss of inf lead q • New Q in AVL

  25. Contraindications to Exercise Testing • Absolute • Acute MI (< 2 d) • High-risk unstable angina • Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise • Symptomatic severe AS • Uncontrolled symptomatic CCF • Acute pulmonary embolus or pulmonary infarction • Acute myocarditis or pericarditis • Acute Ao dissection

  26. Contraindications to Exercise Testing • Relative • LMCA stenosis • Moderate stenotic valvular heart disease • Electrolyte abnormalities • Severe HTN • Tachyarrhythmias or bradyarrhythmias • HOCM and other forms of outflow tract obstruction • Mental or physical impairment leading to inability to exercise adequately • High-degree AV block

  27. Both MI and deaths have been reported and can be expected to occur at a rate of up to 1 per 2500 tests

  28. Bayes' theorem A theory of probability ‘The post test probability is proportional to the pretest probability’

  29. 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

  30. Pretest Probability • Based on the patient's history ( age, gender, chest pain ), physical examination and initial testing, and the clinician's experience. • Typical or definite angina →pretest probability high - test result does not dramatically change the probability. • Diagnostic testing is most valuable in intermediate pretest probability category

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

  32. Pre-test Probability of CAD by Age, Gender, and Symptoms • Typical/Definite Angina Pectoris • Age 30-39 • Men Intermediate (10-90%) • Women Intermediate • Age 40-49 • Men High (>90%) • Women Intermediate • Age 50-59 • Men High • Women Intermediate • Age 60-69 • Men High • Women High

  33. Pre-test Probability of CAD by Age, Gender, and Symptoms • Atypical/Possible Angina Pectoris: • Age 30-39 • Men Intermediate • Women Very Low (<5%) • Age 40-49 • Men Intermediate • Women Low (<10%) • Age 50-50 • Men Intermediate • Women Intermediate • Age 60-69 • Men Intermediate • Women Intermediate

  34. Pre-test Probability of CAD by Age, Gender, and Symptoms • Nonanginal Chest Pain: • Age 30-39 • Men Low • Women Very Low • Age 40-49 • Men Intermediate • Women Very Low • Age 50-59 • Men Intermediate • Women Low • Age 60-69 • Men Intermediate • Women Intermediate

  35. Pre-test Probability of CAD by Age, Gender, and Symptoms • Asymptomatic: • Age 30-39 • Men Very Low • Women Very Low • Age 40-49 • Men Low • Women Very Low • Age 50-59 • Men Low • Women Very Low • Age 60-69 • Men Low • Women Low

  36. EXERCISE TESTING TO DIAGNOSE OBSTRUCTIVE CAD • Class I • Adult patients (including RBBB or <1 mm of resting ST↓) with intermediate pretest probability of CAD • Class IIa • Patients with vasospastic angina.

  37. EXERCISE TESTING TO DIAGNOSE OBSTRUCTIVE CAD • Class IIb • 1. Patients with a high pretest probability of CAD • 2. Patients with a 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

  38. Exercise Testing in Asymptomatic PersonsWithout Known CAD • Class I • None. • Class IIa • Evaluation of asymptomatic T2 DM pts who plan to start vigorous exercise ( C) • Class IIb • 1. Evaluation of pts with multiple risk factors as a guide to risk-reduction therapy. • 2. Evaluation of 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

  39. RISK ASSESSMENT AND PROGNOSISIN PATIENTS WITH SYMPTOMS OR APRIOR HISTORY OF CAD • Class I • 1. Initial evaluation with susp/known CAD, includingRBBB or <1 mm of resting ST Depression • 2.Susp/ known CAD, previously evaluated, now significant change in clinical status. • 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 signi change, and markers >6-12 hrs (N) & no other evidence of ischemia during observation.

  40. AFTER MYOCARDIAL INFARCTION • Class I • 1. Before discharge (submaximal --4 to 6 days). • 2. Early after discharge if the predischarge exercise test was not done (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.

  41. 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 symptoms necessitating termination (i.e., angina, fatigue, ≥ 2 mm of ST↓,ventricular arrhythmias, or ≥10-mm Hg drop in SBP from the resting blood pressure)

  42. 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

  43. AFTER MYOCARDIAL INFARCTION • Class IIb • 1. Patients with the following ECG abnormalities: • • Complete LBBB • • Pre-excitation syndrome • • LVH • • Digoxin therapy • • >1 mm of resting ST-segment depression • • Electronically 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. At any time to evaluate 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. • Although a stress test may be useful before or after cath to evaluate or identify ischemia in the distribution of a coronary lesion of borderline severity, stress imaging tests are recommended.

  44. Strategy 3 Clinical indications of high risk at pre-discharge

  45. Cardiac cath Clinical indications of high risk at pre-discharge

  46. Exercise Testing Before and After Revascularization • Class I • 1. Demonstration of ischemia before revascularization. • 2. Evaluating recurrent symps suggesting ischemia aft revascularization. • Class IIa • Aft discharge for activity counseling and/or exercise training as part of rehabilitation in pts aft revascularization. • Class IIb • 1. Detection of restenosis in selected, high-risk asymptomatic pts < first 12 months aft PCI. • 2. Periodic monitoring of selected, high-risk asymptomatic ps for restenosis, graft occlusion, incomplete coronary revascularization, or disease progression. • Class III • 1. Localization of ischemia for determining the site of intervention. • 2. Routine, periodic monitoring of asymptomatic pts after PCI or CABG without specific indications.

  47. Stress Testing

  48. Investigation of Heart Rhythm Disorders • Class I • 1. Identification of appropriate settings in pts with rate-adaptive pacemakers. • 2. Evaluation of cong CHB in pts considering ↑activity/competitive sports. (C) • Class IIa • 1. Evaluating known or suspected exercise-induced arrhythmias. • 2. Evaluation of medical, surgical, or ablative therapy in exercise-induced arrhythmias