Exercise testing Flashcards by Michael Amarin

What factors is the physiological response to exercise dependent on?

-intensity
-duration
-frequency of exercise

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How do the requirements of skeletal muscle change during exercise?

-Increase in Oxygen and substrate requirement
-Increase in metabolite and CO2 removal

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What are the 3 types of exercise that can be applied as stress to the cardiovascular system?

-Isometric (static) - muscular contraction without movement
-Isotonic (dynamic or locomotory) - muscular contraction resulting in movement
-Resistance (combination of isometric and isotonic)

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What are the types of exercise test?

-Treadmill exercise test
-Bicycle exercise test

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What physiological stresses does exercise cause?

-Increased heart rate and BP
-Increased cardiac work
-Increased oxygen and work demand
-Alters supply and demand balance
-Produces ischaemia (chest pain/ST changes)

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What are the mechanical physiological effects of exercise on the heart and lungs?

-Vasoconstriction of vessels to increase venous return
=>Increase venous tone by autonomic reflexes
=>Blood is squeezed from large veins into right side of heart
=>This increases effective filling pressure and CO

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What are the chemical physiological effects of exercise on the heart and lungs?

-Stimulation of sympathetic nerves
-This releases catecholamines: epinephrine and norepinephrine
-These act as sympathetic agonists increasing chronotropy (HR) and inotropy (contractility)

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Cardiac output equation

CO = HR x SV

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What is normal SV?

60-80 ml

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What dictates stroke volume?

-Greater the stretch of ventricles in diastole, greater the stroke volume achieved in systole

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How is EF calculated?

SV/EDV

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What is normal EF

55%-70%

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What patient factors affect SV

-fitness
-age
-gender

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What is normal maximum HR?

~180bpm

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Why is exercise a risk for patients with AF?

-As HR increases, phases of cardiac cycle shorten
-Diastole shortens much more than systole
-LV passive filling is reduced and is more reliant on atrial contraction
-AF patients are totally reliant on passive filling due to no atrial contraction
-CO decreases

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What does Starling’s law state?

The force of contraction is a function of the degree of stretch during diastole

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How does tricuspid regurgitation link to Starling’s law?

-Tricuspid regurgitation causes increased volume of blood back into right atrium
-This stretches the right atrium more and will require a greater force of contraction to eject

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What other mechanisms affect the ability of the ventricles to pump?

-Circulating catecholamines - stimulate production of adenylyl cyclase and adenosine triphosphate -> increased force of contraction and HR
-Resistance in vascular bed and lungs (low in healthy patient)
-Systemic resistance - decreased as exercise progresses

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What is the normal respiration rate

12-15 breaths per minute

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What is the physiological effect of exercise in the lungs

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-Respiration rate increases with exercise (hyperpnea)
=>This facilitates O2 exchange

What two factors need to be overcome during breathing in exercise?

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-Elastic resistance of chest wall and muscles
-Lungs

What happens to elastic recoil of lungs with age?

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-It decreases

Advantages of exercise tests?

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-Most physiological
-Produces ischaemia
-Reproduces actual precipitants
-Gives additional diagnostic data e.g. ECG changes
-Prognostically helpful
-Widely available and inexpensive

Problems with exercise tests

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-Moderate sensitivity and specificity
-Poor performance/results in:
=>women
=>after revascularisation
=>inadequate/unable to exercise
=>resting ECG changes

What should the environment of an exercise test be like?

-well lit -well ventilated -clean -Large enough to accommodate equipment -Sufficient space for emergency/resuscitation procedures -Medical staff can reach room within 1 minute of cardiac arrest alarm being sounded

What are the requirements for staff. carrying out an ETT?

-Minimum of 2 suitably qualified healthcare professionals -Recommended that lead physiologist holds an appropriate postgraduate qualification -They should have advanced knowledge in ECG interpretation -Supervisor is responsible for safe conduct of ETT -Manager has auscultation skills to provide an aortic valve screen prior to the ETT

Describe patient setup in ETT

-Good skin prep -Hair is removed -12 lead ECG application =Limb leads in Mason Likar configuration (shoulders and hips) -Automatic/manual BP

List indications for an ETT

-Ischaemia -Induced arrhythmias (occur at different heart rates) -Syncope -Stable angina -SOB -Checking whether medication is working -DVLA -Preoperative

List contraindications for an ETT (relative vs absolute)

-LBBB (relative, depending on cause) -Hypertension (relative, up to a certain BP) -Aortic stenosis with TAVI (relative) -HOCM/HCM (relative) -Clotting/pulmonary embolism (absolute)

What are the different protocols for ETTs?

-Bruce protocol -Modified Bruce -Cornell protocol -Blake and Ware -Astrand and Rudahl -Ramp Protocol

Describe the procedure of an ETT

-Record resting ECG/BP -Calculate target heart rate -Demonstrate walking technique -Start test -Continuous monitoring of ECG -BP checked in last minute of each stage (more frequently if concerns) -Test continues to end point -Monitoring of ECG and BP continues into recovery period

How do you calculate target heart rate

Calculate max heart rate: 220 - patient's age THR = 85% of MHR

What is chronotropic incompetence associated with?

-CHD risk -Mortality

Describe BP response in ETT

Early: -Resting BP increases due to patients being anxious During: -Increase in systolic pressure with increasing workload -No significant diastolic change Late: -BP levels at peak -Then fall due to acidosis (lactic acid build up) After: -BP should return to baseline fairly rapidly

How could left mainstem/ 3 vessel disease manifest in ETT

-Drop in BP early in exercise greater than resting level WITH -Deep ST depression

How could narrowing of smaller vessels manifest in ETT

-Skin pallor -ECG changes

What would cause a physiologist to terminate the ETT

-Drop in sytolic BP > 20mmHg

What are the different types of ST depression?

Upsloping = normal Downsloping/flat = abnormal

What other factors might cause ST depression?

-Increased rate of respiration

Where should ST depression be measured?

80ms post J point -At faster heart rates, this will measure into T wave and machine will show positive ST

What scale is used for rate of perceived exertion?

-Borg -Modified Borg

What is metabolic equivalent (MET)?

-amount of oxygen consumed while sitting at rest

How long should the recovery period be after an ETT?

-Minimum 6 minutes -Recording ECG and BP recorded every minute

Why does BP decrease after exercise?

-During recovery, parasympathetic nerves are stimulated -This releases acetylcholine -Acetylcholine causes vasodilation

Why might BP be lower at peak exercise?

-Due to temporary inadequacy in cardiac pumping in relation to metabolic demand -But may rise after a minute

What is considered maximum effort in ETT?

-Test should be maximal or symptom limited (whichever comes first) -Test can be terminated when patient reaches 85% of maximum HR -Test is considered maximal when patient reaches point of bodily exhaustion

What are some causes of false positives in ETT

-LVH -Cardiomyopathy with ST segment/T wave abnormality -LVOTO (HOCM) -Hyperventilation -LBBB -Electrolyte abnormalities -Coronary artery spasms -Use of Tricyclic antidepressants

How are the results of ETTs used?

-A negative test does not rule out IHD disease -A positive test is much more likely to be false in a young person than an older person =>Testing of young, asymptomatic people is controversial

Exercise testing Flashcards

(48 cards)