ICL 5.8: Intro to Cardiac Stress Testing Flashcards
(35 cards)
what are the different stress tests you can do?
making sure the heart has proper cardiac perfusion during stress
- treadmill only
- treadmill with MPI (Myocardial Perfusion Imaging {Nuclear})
- lexiscan (regdenosine) stress/MPI
- treadmill stress echo
- dobutamine stress MPI
- dobutamine stress echo
- cardiac PET
how does a nuclear scanner work?
radio tracer is injected into a vein and emits game radiation as it decays
gamma camera scans and creates an image
how does echocardiography work?
take images before then stress the patient and take more images
you get images of how the let ventricle is contracting
what does cardiac stress testing evaluate for?
- diagnosis of CAD
- prognosis of CAD
- efficacy of treatment of CAD
what are the indications to get stress testing done?
- chest pain (yet to determine if angina)
- angina in those known to have CAD
- post MI
- exercise prescription for cardiac rehab
- preop eval for noncardiac surgery
- new cardiomyopathy
why would you use stress testing post-MI?
these are all treadmill only
1. before discharge for prognostic assessment, activity prescription, or evaluation of medical therapy done submaximal at about 4 to 7 days after the MI
- early after discharge for prognostic assessment, activity prescription, evaluation of medical therapy, and cardiac rehabilitation if the predischarge exercise test was not done –> symptom-limited/about 14 to 21 days
- late after discharge for prognostic assessment, activity prescription, evaluation of medical therapy, and cardiac rehabilitation if the early exercise test was submaximal –> symptom-limited/about 3 to 6 weeks
what are the absolute contraindications for getting stress testing done?
- within 2 days of an MI
- if the patient is 100% pacing or they have chronotropic incompetence with a pacemaker = they can’t get a heart rate good enough to even walk on a treadmill like someone with heartblock
- unstable angina not previously stabilized by medical therapy
- uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise
- symptomatic severe aortic stenosis
- uncontrolled symptomatic heart failure
- acute pulmonary embolus or pulmonary infarction
- acute myocarditis or pericarditis
- acute aortic dissection
what are the relative contraindications for stress testing?
- left main coronary stenosis
- moderate stenotic valvular heart disease
- electrolyte abnormalities
- severe arterial hypertension
- tachyarrhythmias or bradyarrhythmias
- hypertrophic cardiomyopathy and other forms of outflow tract obstruction
- mental or physical impairment leading to inability to exercise adequately
- high-degree atrioventricular block
- LVH w repolarization changes
what are the cons of stress testing?
- expensive
- time consuming (3 hours)
- we can predict the probability of CAD without it
do women and men develop CAD at the same time?
no
women are delayed in developing CAD about 1 decade compared to men
when is a treadmill EKG stress test indicated?
if you suspect CAD, a normal EKG and the patient can use a treadmill
if the EKG has LBBB, paced rhythm, resting ST depression or preexcitation then don’t do an EKG treadmill stress test
how do you do an EKG treadmill stress test?
goal HR = (220-age) x 0.85
BRUCE Protocol
1. start flat for 3 minutes
- increase speed and incline every 3 minutes
- assess symptoms during test
- assess what stopped the test = chest pain, dyspnea on exertion, fatigue, leg pain, etc
- evaluate EKG
it’s only 60-75% sensitive in diagnosing CAD and is better in males
what is the EKG criteria for a positive EKG treadmill stress test according to the Bruce Protocol?
EKG criteria for a positive stress test:
measure the ST depression 80ms from the J point (junction of QRS & ST segment)
- if there is 2mm horizontal or downslopping ST depression in anterior or lateral leads for more than 2 QRS complexes in a row = ischemia
- if there is 1mm horizontal or downslopping ST depression in inferior leads for more than 2 QRS complexes in a row= ischemia
what’s the formula for target HR for an EKG stress test?
goal HR = (220-age) x 0.85
this makes sure the coronary artieries are maximally dilated
what is the Duke treadmill score nomogram?
once you do an EKG treadmill stress test, this is how you assess the results
- asses if there was ST segment deviation during exercise
- assess if there was any exercise angina
if there was neither then you get a flat line and this means there was no ischemia! if either of these changes there will be a sloped line and you’ll cross the ischemia line at various degrees indicating ischemia
- assess duration of exercise to assess prognosis of 5-year survival rate and average annual mortality
which leads do you look at to know if the axis is normal?
II, III and aVf all need to be upright to have a normal axis!
what does MPI stand for?
MPI = myocardial perfusion imaging
what are the pros and cons of MPI?
adds sensitivity & specificity (90+ & 90+)to ECG treadmill stress test
but more $$$, use appropriately!
what are MPI? how does it work?
the heart is imaged in slices much like a CT scan
Tc-sestamibi is a lipophilic isotope taken up by myocardial cell in proportion to blood flow of the coronary arteries –> this passive mechanism is drive by negative membrane potential
you have to wait 4-6 hours after injection and the isotope remains fixed in myocardial cells
then you compare images of tissue perfusion of isotope after exercise compared to at rest images
since you know which coronary arteries supply specific areas of the heart, you can look at which tissues are getting perfused or not perfused to tell which artery is causing the CAD!
these images are timed with the EKG to get overall systolic function and wall motion analysis!
if there is NO perfusion to an area of the LV on BOTH rest and stress images, then that area has NO cellular membrane activity and it’s considered necrosed = infarcted
what are the 3 axises that MPI looks at?
- short axis = cut the heart axially like a loaf of bread in donut shapes –> anterior, inferior, lateral and septal walls of LV visible
- horizontal axis = flip the heart upside down like it’s on a hinge so that the apex is at the top then cut coronally down the middle vertically –> lateral and septal walls of LV visible
- vertical long axis = slice coronally if you’re looking at the heart straight on –> anterior and inferior walls of LV visible
slide 32 and 33
what’s the order that the results of an MPI are presented?
top row is motion
then stress
then rest
so compare the stress to the rest!
what stress test do you do if the patient is unable to do the treadmill? what patients would qualify as unable to use the treadmill?
use nuclear/echo/PET Imaging ~only (no target heart rate-ECG not helpful) –> lexiscan/regadenosine stress/MPI, dobutamine stress MPI, dobutamine stress echo or cardiac PET
- inability to walk
- uses cane or walker
- wheelchair bound
- deconditioned states
- severe COPD
- severe heart failure
what is regadenosine? how is it used for stress testing?
it’s a coronary vasodilator used to mimic vasodilation that occurs with treadmill testing at target heart rates
so first take at rest imaging then
administer denosine analog = Regadenosine injection then repeat stress testing
a blocked artery won’t be able to vasodilate to the same caliber of normal artery because that artery has already been vasodilated by ‘our own’ local ‘dilators’ since it has a blockage – thus no change w/ regadenosine
evaluate for lack of tissue (myocardial cell) perfusion which indicates ischemia
what does of regadenosine is given during stress testing?
it has a half-life 9 seconds but it can block the AV node if dose is high enough
so a lower dose is useful in nuclear testing
