Exercise stress Electrocardiography Dr.Tahsin N
Exercise physiology • Sympathetic activation • Parasympathetic withdrawal • Vasoconstriction, except- • Exercising muscles • Cerebral circulation • Coronary circulation • ↑nor epinephrine and renin
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
Exercise physiology Isotonic exercise(cardiac output) • Early phase- SV+HR • Late phase-HR
↑ Exercise work ↑ O2 usage Person’s max. O2 consumption (VO2max)reached V02 peak Oxygen consumption (liters/min) Work rate (watts)
The slope of the o2–work relationship is a measure of the biochemical efficiency of exercise • V o2max is the product of maximal arteriovenous oxygen difference and cardiac output • The V o2max depends on • Age • Men than in women • Genetic factors • Cardiovascular impairment • Physical inactivity.
The ability to deliver O2 to muscles and muscle’s oxidativecapacity limit a person’s VO2max. Training ↑ VO2max V02 peak (trained) 70% V02 max (trained) V02 peak (untrained) Oxygen consumption (liters/min) 100% V02 max (untrained) 175 Work rate (watts)
During dynamic exercise of increasing intensity, ventilation increases linearly over the mild to moderate range, then more rapidly in intense exercise • Workload at which rapid ventilation occurs is called the ventilatory breakpoint(together with lactate threshold) Respiration during exercise Lactate acidifies the blood, driving off CO2 and increasing ventilatory rate
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
Intense exerciseGlycolysis>aerobic metabolism ↑ blood lactate (other organs use some) Blood lactic acid (mM) Lactate threshold; endurance estimation Relative work rate (% V02 max)
Maximum HR HR=220 - age in years
Post exercise phase • Vagal reactivation Imp cardiac deceleration mech • ↑in well trained athletes • Blunted in CCF
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
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
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
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
Treadmill protocol • Bruce protocol • Naughton protocol • Weber protocol • ACIP(asymptomatic cardiac ischemia pilot) • Modified ACIP
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)
Procedure- Lead systems • Mason-Liker modification • RAD • ↑inf lead voltage • Loss of Q in inf leads • New Q in AVL
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 Aortic dissection
Contraindications to Exercise Testing Relative • LMCA stenosis • Moderate stenoticvalvular 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
Both MI and deaths have been reported and can be expected to occur at a rate of up to 1 per 2500 tests
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
Bayes' theorem A theory of probability ‘The post test probability is proportional to the pretest probability’
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
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.
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 ↓.
TO DIAGNOSE OBSTRUCTIVE CAD Class III • Patients with the following baseline ECG abnormalities: • Pre-excitation syndrome • Electronically paced ventricular rhythm • >1 mm of resting ST depression • Complete LBBB
in Asymptomatic PersonsWithout Known CAD 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
RISK ASSESSMENT AND PROGNOSIS IN PATIENTS WITH SYMPTOMS OR A PRIOR 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.
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.
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.
AFTER MYOCARDIAL INFARCTION 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.
Submaximal protocols • Predetermined end point • 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)
Before and After Revascularization Class I • 1. Demonstration of ischemia before revascularization. • 2. Evaluating recurrent symps suggesting ischemia after revascularization. Class IIa • After discharge for activity counseling and/or exercise training as part of rehabilitation in pts aft revascularization.
Before and After 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.
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
Investigation of Heart Rhythm Disorders Class IIb • 1. Isolated VPC in middle-aged pts without other evidence of CAD. • 2. Prolonged 1˚AV block or type I-2˚AV block , LBBB, RBBB, or VPC in young pts considering competitive sports. (C) Class III • Routine investigation of isolated VPC in young pts.
Normal ECG changes during exercise • ↓ PR, QRS, QT • ↑ P amplitude • Progressive downsloping PR in inf leads • j point depression
The Exercise ECG 1 = Iso-electric 2 = J point 3 = J + 80 msec ST 60 -- HR > 130/min ST 80 -- HR ≤ 130/min
Criteria for Reading ST-Segment Changes on the Exercise ECG ST DEPRESSION: • Measurements made on 3 consecutive ECG complexes • ST level is measured relative to the P-Q junction • When J-point is depressed relative to P-Q junction at baseline: • Net difference from the J junction determines the amount of deviation • When the J-point is elevated relative to P-Q junction at baseline and becomes depressed with exercise: • Magnitude of ST depression is determined from the P-Q junction and not the resting J point
Upsloping J point depression of 2 to 3 mm in leads V4 to V6 with rapid upsloping ST segments depressed approximately 1 mm 80 msec after the J point. The ST segment slope in leads V4 and V5 is 3.0 mV/sec. This response should not be considered abnormal.
Criteria for Abnormal and Borderline ST-Segment Depression • ABNORMAL: • 1.0 mm or greater horizontal or downsloping ST depression at 80 msec after J point on 3 consecutive ECG complexes • BORDERLINE: • 0.5 to 1.0 mm horizontal or downsloping ST depression at 80 msec after J point on 3 consecutive ECG complexes • 2.0 mm or greater upsloping ST depression at 80 msec after J point on 3 consecutive ECG complexes
Normal Rapid Upsloping Minor ST Depression Slow Upsloping
Horizontal Downsloping Elevation (non Q lead) Elevation (Q wave lead)