Flashcards in cardiac stress testing Deck (23)
indications for cardiac stress testing?
- 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
CIs to stress testing?
- acute MI
- unstable angina
- acute pericarditis
- acute systemic illness
- severe aortic stenosis
- CHF exacerbation
- severe HTN
- uncontrolled arrhythmias (V tach)
Describe an exercise EKG
- 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?
What information is obtained from exercise ekG?
- 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)
Interpretation of exercise EKG?
- 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
exercise EKG interpretation: high risk for sig ischemia
- 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
Risks of exercise testing?
- 1 MI or death/ 1000 pts
- stress induced arrhythmia
- adverse rxn to pharm stress agent
How sensitive and specific is stress EKG?
- only about 68% sensitive and 77% specific
How much does sensitivity improve with imaging? Types of imaging?
- - 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)
Indications for stress imaging?
- 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
What is a myocardial pefusion scintigraphy with SPECT?
- 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
What is stress echo used for?
-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)
Images of stress echo?
- 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
Pros and cons of stress echo?
- 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
What is a MUGA scan?
- 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
Cardiac CT - CT angiography
- useful in eval pts with low likelihood of sig disease
- IV contrast given and images of coronary arteries are obtained
- very rarely done, only if you want pics of arteries, save them from going into cath lab if no abnormal findings
Cardiac CT - EBCT
- quantifies coronary artery calcification
- coronary calcification is highly correlated with atherosclerotic plaques
- doesn't determine the degree of stenosis
- uses MRI VI contrast medium: gadolinium
- perfusion images post pharm stress can be obtained: dobutamine or adenosine
- still in early stages of technology
Pt comes in and cannot exercise, pt has LBBB (or pacemaker or afib). What test should be done?
- nuclear test with adenosine (pharm stress)
Pt comes in, cant exercise, pt doesn't have LV wall motion abnormalities, test that should be done? What if pt did have LV wall motion abnormalities?
- no LV wall abnorm: stress echo with dobutamine
- LV wall abnorm: nuclear with adenosine
Pt comes in for stress test, can exercise, doesnt have any arrhythmias, LVH, or abnorm ST seg, what test should be done?
- exercise EKG
PT comes in for stress test with abnorm ST seg (or LBBB, pacemaker, arrhythmia) and left ventricle wall abnormalities, what test should be done?
- nuclear (with exercise)
- if pt had LBBB or pacemaker - nuclear with pharm stress (adenosine)
- if pt didnt have pacemaker or LV wall abnorm - could do stress echo