Assessing Cardiac Function Flashcards
why is maintaining cardiac function important?
- circulation
- blood pressure
- perfusion of vital organs and adaptability to change to emotions/stress
The hearts function as a pump
- regulates HR and rhythm
- Chambers and valves/structures
- contraction (regularity and strength)
what does MET stand for
Metabolic equivalent of Task
what is MET measure of
a physiological measure expressing the energy cost of physical activity
1MET =
1Kcal/kg/h
The reference metabolic rate is set by convention to
3.5 ml O2·kg−1·min−1
what is the average expenditure of energy at rest?
3.5 ml O2·kg−1·min−1
1MET
resting
2MET
Eat, move and go to the toilet
4MET
light house work
still a dangerous group dot be in if its the max
10MET
safe level, good functional level - can do light sport
stress testing includes
treadmill and bicycle egonometer
stress testing is putting the body under
physiological stress - moving/excersising
how would you test for ischaemia
- exercise using the treadmill stress test
what would you test before heart surgery to work out how healthy/fit a person is?
ECG leads, cardiopulmonary testing, testing gases/saturationin the blood, total energy used during the activity
- try and get the patient to 5MET
what is the excersise treadmill test looking for
looking for any abnormalities, CHD with the ECG
where do you put the ECG leads?
over the main coronary arteries
what would you see on the ECG when the patient is starting to struggle and want to stop exercising?
the STZ wave drops down
what are you looking for on the ECG of the
- looking for changes at the peak of exercise
- T wave inversion
(V2 and V3 leaders have inversion of the T wave)
T wave inversion is typical of
impairment of the blood vessels in the heart
what would some of us with the healthy people in the low risk group have with the treadmill test
false positive tests - this test should be carried out on people who have chest pains etc - more of a discriminator then
what test would have low false positives?
coronary angiogram
If patient is UNLIKELY to have disease to start with, an abnormal test has greater chance of being a
false positive
- influences pre-test probability of CAD on post test probability of CAD
what other factor influence pre-test probability of CAD
age sex and symptoms
Any tests are most likely to be most useful in those whose age, sex and symptoms put them in a
higher risk group
what 2 ways can you test for Ischaeima by stress testing?
physiological and pharmacological
what is dobutamine?
a beta antagonist
which raises BP and HR, increases cardiac contractility and demand of heart muscle for blood supply
how is dobutamine used during stress testing?
Induces ischaemia, where flow is inadequate to meet needs
what are adenosine and dipyridamole?
vasodilators
how do adenosine and dipyridamole work as to show ischaemia?
Relative ischaemia where vasodilatation not possible because of fixed stenoses >75% lumen area
what does dobutamine mimic?
excersise stress test
What is the myocardial perfusion scan useful in?
- patients with intermediate probability of CHD
- Particularly useful if mobility limits treadmill testing or if resting ECG is abnormal
how is myocardial perfusion scan carried out
Thallium is taken up by myocardium in proportion to blood flow. Not by scar tissue.
Detected by a gamma camera.
Images taken under “stress” or at rest.
“Stress”: pharmacological
what are you looking for myocardial perfusion scan images?
- impaired bloood supply (ischaemia)
- change in the colouring on the images - gaps
- stress when blue - coronary arteries not supplying enough blood
what is the first sign that a piece of heart muscle is becoming ischemic?
stops contracting well
what changes do you see in a piece of heart muscle that is becoming ischaemic?
- stops contracting well
- change in systolic function
- changes in ECG
- symptoms
thallium is taken up into the heart muscle in proportion to
the blood flow
radioisotope that is visualised by a gamma gun
with the myocardial perfusion scan which is the donut scan?
cutting a horizontal cross section through the heart
Myocardium perfusion scan with problem in circumflex artery
big branch across the lateral wall - can see that under stress you – dark blue part of the lateral part - not got a good blood supply – area of ischemia
what is Echocardiography
Imaging at rest
what is Echocardiography looking at
Chamber size Muscle contractility Can also be stressed pharmacologically Valve function stenosis or regurgitation Doppler
can you remember some of the measured chamber dimensions?
Aortic Root Diameter (ED) 2.0 – 3.6cm Left Atrial Dimension (ED) 1.9 – 4.0 RV Internal Dimension (ED) 0.7 – 2.3 LV Internal Dimension (ED) 3.7 – 5.6 LV Internal Dimension (ES) 2.5 – 4.1 IV Septal Thickness (ED) 0.7 – 1.2 LV Post Wall Thickness (ED) 0.7 – 1.1)
TOE/TEE
Transoesophageal echocardiography
what is Transoesophageal echocardiography used for?
When clear view of valves is needed (infective endocarditis)
When clear view of inter-atrial septum and atrial appendages needed (cryptogenic stoke)
what is CT scan and what is it used for?
Radiation
Excellent for structure of heart and great vessels
3 D reconstruction
what is CT coronary angiogram used as?
1st line investigation of cardiac sounding chest pain
what is the cardiac MRI used for?
Excellent for structure, and for muscle function ( right and left heart)
Excellent for detailed muscle structure (fibrosis)
No radiation, repeatable.
what is a hotter ECG?
24h ambulatory monitoring
Frequently recurring (daily)
Palpitations, dizzy spells, blackouts.
Automatic detection and patient triggered events
