cardiac stress testing Flashcards
1
Q
indications for cardiac stress testing?
A
- est a dx of CAD:
sx or asx with abnorm EKG - assessment of prognosis and functional capacity (stable angina or post MI)
- assess response to meds or revascularizatiom
- eval pre op cardiac risk
- eval asx individuals for CAD (pilots, police, firefighters, middle aged persons wanting to start vigorous exercise program)
- eval for exercise induced arrhythmias
2
Q
CIs to stress testing?
A
- acute MI
- unstable angina
- acute pericarditis
- acute systemic illness
- severe aortic stenosis
- CHF exacerbation
- severe HTN
- uncontrolled arrhythmias (V tach)
3
Q
Describe an exercise EKG
A
- treadmill or bicycle ergometer
- often combined with imaging studies: nuclear, echo or MRI
- in low risk pts without baseline ST segment abnormal or when anatomic localization isn’t necessary exercise EKG is recommended initial procedure
- various exercise protocols are used to achieve a minimum of 85% of max age predicted heart rate
- most common protocol is Bruce protocol increasing the speed and incline every 3 minutes
- EKG is monitored continuously during exercise
- BP response is noted in each stage of exercise (if it drops - marker of severe ischemia)
- sxs are noted: CP or SOB?
4
Q
What information is obtained from exercise ekG?
A
- exercise duration and tolerance
- reproducability of sxs with activity
- HR response to exercise
- BP response to exercise
- detection of stress induced arrhythmias
- assess the effectiveness of antiangial meds
- prognosis (can’t make it past 3 minutes - poor, past 6 minutes: good)
5
Q
Interpretation of exercise EKG?
A
- criteria for + test is 1 mm horizontal or downsloping ST segment depression meausre 80 ms after the J pt
- using this criteria 60-80% of pts with sig CAD will have positive test
- 10-30% of those without sig disease will also have positive test
6
Q
exercise EKG interpretation: high risk for sig ischemia
A
- BP drops during exercise
- greater than 2 mm ST depression
- ST depression that is downsloping
- ST depression or sxs at low work loads: less than 6 mkinutes or HR less than 70% of max age predicted HR
- ST depression that doesn’t resolve quickly in the recovery phase
7
Q
Risks of exercise testing?
A
- 1 MI or death/ 1000 pts
- stress induced arrhythmia
- adverse rxn to pharm stress agent
8
Q
How sensitive and specific is stress EKG?
A
- only about 68% sensitive and 77% specific
9
Q
How much does sensitivity improve with imaging? Types of imaging?
A
- up to 85%
- cardiac nuclear perfusion imaging (myocardial perfusion scintigarphy) - regular exercise stress, or pharm stress - dobutamine (positive inotropic and chronotropic agent), or adenosine or persantine (potent vasodilators): work by dilating everywhere in vessel except for where lesion is
- stress echo:
regular exercise test or pharm stress (dobutamine)
10
Q
Indications for stress imaging?
A
- when resting EKG is abnormal (LBBB, baseline ST-T changes, low voltage)
- confirmation of results of exercise EKG when results don’t align with clinical impression
- to localize region of ischemia
- distinguish ischemic from infarcted myocardium
- assessment of revascularization post stent or surgery
- eval prognosis
11
Q
What is a myocardial pefusion scintigraphy with SPECT?
A
- nuclear stress test
- myocardial uptake of radionuclide tracer is proportionate to myocardial perfusion at time of injection
- positive in about 75-90% of pts with sig CAD and 20-30% of pts without disease
- tracer won’t be take up in ischemic tissues
- nuclear images taken before and after exercise
- exercise is completed with a treadmill (same protocol as exercise EKG): if pt unable to exercise pharm stress is completed with adenosine or dobutamine
12
Q
What is stress echo used for?
A
- echo images obtained with pt supine pre and immediately post exercise
- eval of wall motion abnormalities of the LV (need blood supply, if lacking perfusion - won’t contract like it is supposed to, see on stress echo)
- exercise is completed with treadmill, if unable to exercise: pharm stress completed with dobutamine (+inotrope + chronotrope)
13
Q
Images of stress echo?
A
- images obtained are of LV (JUST LV)
- They don’t image rest of the heart
- a stress echo report will give you info regarding presence or absence of ischemia: it will not give you info on valves, chamber sizes, hypertrophy or EF
14
Q
Pros and cons of stress echo?
A
- echo images obtained before and after stress
- detect wall motion abnormalities, lack of thickening of LV with stress (LV should contract during stess), reduced EF with stress
- quicker than nuclear stress
- less expensive compared to nuclear
- slightly less sensitive but more specific for CAD
- not great for existing LBBB or previous wall motion abnormal
- may be limited by obesity or hyperinflation of the lungs
15
Q
What is a MUGA scan?
A
- multigated acquisition scan
- uses radionuclide tracers to image the LV
- evaluates the wall motion and precisely calculates the EF**
- often used for eval of EF for cancer pts on cardiotoxic drugs
