Assessing cardiac function Flashcards
(45 cards)
cardiac function
maintaining the circulation, BP and perfusion of vital organs
adaptable to changing needs
what does the heart need to function properly
rate and rhythm
structures - competence of valves
efficient heart muscle contraction
what are the different ways of assessing cardiac function?
functional testing
CT angiography
cardiac MRI
invasive coronary angiography
what is functional testing?
exercise ECG
imaging stress test - ECHO or perfusion scan
what is MET?
metabolic equivalent of task
a physiological measure expressing the energy cost of physical activity
1 MET =1kcal/ kg x h = 4.13kJ/kg x h
= basal metabolic rate
what is the importance of MET?
allows activities to be graded on energy expenditure, used as a reference to see how patients can cope with the physiological stress on the heart
types of stress testing
- physiological - on treadmill or bicycle ergometer
2. pharmacological
how does stress testing work?
ECG leads and BP cuff constantly monitoring
increase stress gradually
tests for ischaemia
what is pre-test probability
looks at risk factors for ischaemia/ coronary heart disease
done before stress testing
when to and when not to use exercise testing
dependent on physical capacity of patient
NICE guidelines says not be used for primary diagnosis/ exclusion as lots of false positives and negatives
useful for seeing if there is a causal relationship between patient’s symptoms and ischaemia
what are the categories of angina?
typical
atypical
typical angina
has all 3 features of angina
atypical angina
2/3 features of angina
what does it mean if a patient only has 1/3 of the features of angina?
unlikely to be coronary disease related pain
what are the 3 features of angina?
central constricting chest pain, radiating to arms, neck or jaw
brought on by exercise or physiological stress
relieved by rest and/ or use of nitrates or vasodilator like GTN spray
when is pharmacological stress testing done?
if a patient for other reasons cannot undergo exercise testing
what happens in pharmacological stress testing?
infusion of dobutamine - beta agonist
could use infusion of vasodilator - adenosine/ dipyridamole
method varies depending on the doctor
use imaging techniques
what does dobutamine/ beta agonist do?
raises BP
increases HR
increases cardiac contractility
increases demand of heart muscle for blood supply
mimics effect of exercise
induces ischaemia - where flow is inadequate to meet needs
how does pharmacological stress testing show ischaemia?
where there are ischaemic areas vasodilation is not possible because of fixed stenosis and so they appear on imaging as hypoperfused and relatively ischaemic
when is myocardial perfusion scan used?
useful in patients with intermediate probability of coronary disease
especially if mobility limits treadmill testing of it resting ECG abnormal
how does a myocardial perfusion scan work?
thallium injected taken up by myocardium in proportion to blood flow no thallium is taken up by scar tissue detected by a gamma camera images taken under 'stress' or at rest
interpreting myocardial perfusion scan
lit up = healthy
less lit up = ischaemia
ECHO
echocardiography
what are the different types of ECHO?
transthoracic
transoesophageal
