EXERCISE ELECTROCARDIOGRAMDR SUHAILKIMS,TRIVANDRUM

ROBERT A. BRUCE, CONSIDERED THE “FATHER OF EXERCISE PHYSIOLOGY”.

INTRODUCTION

• Non- invasive tool to evaluate the cardio vascular system's response to exercise under carefully controlled conditions.

• Exercise is the body’s most common physiologic stress- most practical test of cardiac perfusion and function.

• During exercise body increases its metabolic rate to greater than 20 times that of rest; cardiac out put as much as six fold.

(depends on age,sex,type of exercise,size etc)

MASON-LIKAR LEAD PLACEMENT 9 TAKEN FROM WELINDER (2004).

EXERCISE PHYSIOLOGYPHYSIOLOGIC PRINCIPLE & PATHOPHYSIOLOGIC PRINCILE

• Total body oxygen up take and myocardial o2 uptake are distinct.

• Total body o2 uptake: amount of o2 that is extracted from inspired air as the body performs work.

• Determinants are cardiac out put and peripheral arterio venous o2 difference.

• Myocardial o2 uptake: amount of o2 consumed by the heart muscle.

• Determinants include LV pressure& EDV, contractility and HR.

• EXERCISE INDUCED ISCHEMIA CAN CAUSE CARDIAC DYSFUNCTION ,WHICH RESULTS IN EXERCISE IMPAIRMENT AND AN ABNORMAL SYSTOLIC BP RESPONSE

METS- METABOLC EQUIVALENT OF THE TASK

• Used to express the o2 requirement of the work rate during an exercise test on a treadmill or cycle ergometer.

• One MET is equated with the resting metabolic rate- 3.5 ml of O2 / kg / min.

• MET value achieved from an exercise test is a multiple of the resting metabolic rate.

1 MET Resting

2 METs Level walking at 2 mph

4 METs Level walking at 4 mph

< 5 METs Poor prognosis; peak cost of basic activities of daily living

10 METs Prognosis with medical therapy as good as CABG;unlikely to exhibit significant nuclear perfusion defect.

13 METs Excellent prognosis regardless of other exercise response.

18 METs Elite endurance athletes

20 METs World-class athletes.

• Most important factor that influences HR response to heart is AGE - decline in maximal HR occurs with age.

• Age related maximal HR estimates are poor index of maximal effort- high variability.

• So exercise should be symptom limited and not targeted on achieving a certain HR.

• Of all HR measurements, most studies show that HR increase at peak exercise is the most powerful predictor of cardiovascular prognosis.

• Maximal HR is very little changed after a program of training; resting HR is frequently changed.(vagal).

• Initial response to exercise (100-120) is attributable to withdrawal of vagal tone; later by augmented sympathetic.

CENTRAL DETERMINANTAS OF O2 UPTAKE

Cardiac out put

Stroke volume

End diastolic volume

End diastolic volume

PERIPHERAL DETERMINANTS OF O2 UPTAKE

EXERCISE:

. Withdrawal of vagal tone-initial.sympathetic stimulation- later in moderate to severe exercise.:HR at peak exercise is powerful prognostic marker.

RECOVERY:

.Reactivation of parasympathetic initially- decline in HR. (first 2 minutes)..sympathetic withdrawal-later..Delay in HR recovery is a powerful prognostic marker..plasma NE concentration increase/remain constant in 1st minute of recovery (decline late).

SAFETY PRECAUTIONS &PRE TEST PREPARATIONS• tread mill should have front and side rails.

• Should be caliberated monthly

• No automated BP measurements- but manually.

• Pt should not eat,drink, smoke at least 2 hour prior.

• Proper foot wear.

• To establish pt’s usual level of exercise activity prior***.

• Proper medical history / examination- to r/o CI.

• Pre test standard 12-lead ECG in supine & standing position.

• Good skin preparation- esp. in elderly as they have higher skin resistance.

MODIFIED LIMB LEAD PLACEMENTS

• Arm electrodes on the shoulders.

• Rt leg electrode on the back out of cardiac field.

• Lt leg electtrode below the umbilicus.

• Record baseline ecg in supine with this- keep as reference

• Hyper ventilation should be avoided before testing- hyper ventilation to identify false positive responders is no longer considered.

• (ST changes can occur in nl / diseased)

DURING THE TEST….• ECG, BP, history, examination; assess the appearance.

• Pt can rest hands on the rail; but should not grasp/hang on- decreases he work performed/ over estimates the capacity.

• Target HR based on age should not be used ; wide scatter exists- unrealistic goal.

• Borg scale excellent means to quantify.

DANGEROUS SITUATIONS!• Pt exhibits ST elevation without baseline Q- associated

with dangerous arrythmias and tnfarction. More in V2 /aVF.

• Pt with ischemic cardiomyopathy exhibits severe angina- do cool down walk.

• Pt develops exertional hypotension accompanied by angina / ST depression or occurs in pt with CHF, cardiomyopathy or recent MI.

• Pt with h/o sudden collapse during exercise develops frequent pVCs – cool down walk is advisable.

RECOVERY….

CONTRAINDICATIONS

ABSOLUTE RELATIVE

High risk unstable angina Lt main coronary stenosis

Symptomatic severe Aortic stenosis Moderate stenotic valvular d/s

Uncontrolled symptomatic heart failure

Tachy / brady arrythmias

Uncontrlled arrythmias causing symptoms/ hemodyn.compromise

HOCM/ out flow tract obstructions

Acute pulmonary embolism/infarctn Electrolyte abnormalities

Acute myocarditis/pericarditis Severe arterial hypertension (>200/110 mm hg)

Acute aortic dissection High degree AV block

Mental/physical impairement

INDICATIONS FOR TERMINATING TESTABSOLUTE RELATIVE

Moderate to severe angina Drop in BP>10 mm hg from base line despite an increase in work load

Sustained VT Excessive ST depression (>2mm of horizontal/down sloping) or marked axis shift.

ST elevation(>1mm) in leads without diagnostic Q waves (other than v1,aVR)

Arrythmias other than sustained VT (SVT, Multifocal PVCs,triplets,hrt block,bradyarrythmias)

Signs of poor perfusion (cyanosis/pallor) Development of BBB/intra ventricular conduction delay (that cannot be distinguished from VT)

Increase in nervous system symptoms (ataxia,dizziness,near syncope)

Fatigue,shortness of breath, wheezing, leg cramps, or claudication

Subject’s desire to stop Increase in chest pain

Technical difficulties in measuring ECG / BP

Hypertensive response (>250/115 )

BENEFITS OF EXERCISE TESTING POST MIPre –discharge submaximal test:

Maximal test for return to normal activity:

Optimizing discharge Determining limitations

Altering medical therapy prognostication

Triaging for intensity of follow up

Reassuring employers

Reassuring spouse Determining level of disability

First step in rehabilitation-assurance,encouragement

Triaging for invasive studies

Recognizing exercise induced ischemia and dysrhythmias

Deciding on medication

Exercise prescription

Continued rehabilitation

RULES• Report exercise capacity in METs, not minutes of exercise

• Hyperventilation prior to testing is not indicated.

• ST –segment measurements should be made at J-junction,and ST-depression should be considered abnormal only if horizontal or downsloping.

• Raw ECG waveforms should be considered first and then supplemented by computer-enhanced (filtered&averaged) waveforms when the raw data are accepatable.

• In testing for diagnostic purposes,pt should be placed supine as soon as possible after exercise ,with a cool-down walk avoided.

• The 3 min recovery period is critical to include in analysis of the ST segment response.

• Measurement of systolic BP during exrecise is extremely important and exertional hypotension is omnious; manual BP preferred.

• Age predicted HR targets are largely useless because of the wide scatter for any age;exercise tests should be symptom limited.

• Protocol should be adjusted to the pt; one protocol is not appropriate for all pts.

• Tread mill score should be calculated for every pt.

PROGNOSTIC SCORES

• TM AP SCORE:

0 : if no angina

1: angina during test.

2: if angina was the reason for stopping.

• Change in SBP score: from 0 for rise greater than 40 mm hg to 5 for drop below rest.

• DUKE SCORE= METs- 5 * (mm E-I ST depression) –

4*(TM AP index).

• VA SCORE= 5 * (CHF/dig) + mm E-I ST depression+

change in SBP score-METs.