Exercise Stress Testing Flashcards
What is the formula for max HR during stress testing?
220-age
What occurs during the initial stage of exercise?
increased ventricular HR, SV, and CO d/t vagal withdrawal and SNS stimulation Epi and Norepi release increases ventricular contractility at peak exertion Alveolar ventilation and venous return increase due to vasoconstriction
What happens physiologically during exercise progression?
Increased skeletal muscle blood flow Increased oxygen extraction Decreased peripheral resistance SBP, MAP, and PP usually increase DBP remains unchanged or may increase or decrease by approx 10 mmHg
What is defined as an inadequate SBP during exercise? What conditions cause this?
Inadequate rise in SBP is <20-30 mmHg or drop in SBP Results from aortic outflow obstruction, severe LV dysfunction, myocardial ischemia, BB’s
What occurs physiologically in the late phase of exercise?
Increased cardiac output due to primarily increased ventricular HR
What occurs physiologically during the post exercise phase?
Hemodynamics return to baseline within 6 minutes and often remain lower than pre-exercise for several hours, abrupt termination of exercise may cause precipitous drop in SBP d/t venous pooling and delayed immediate increase in SVR to match reduction in CO
What HR indicates a good result in a stress test?
80% max HR = good result, 90% max HR = excellent result
What is age-predicted max HR used to estimate?
The adequacy of stress to evoke inducible ischemia
What is a MET?
Metabolic equivalent, referring to the resting volume of oxygen consumption per minute for 70 kg, 40 y/o man
What does one MET equal?
VO2 3.5 mL/min/kg
What does a mean exercise capacity = 5 indicate?
high mortality risk
What is the double product?
Estimate of myocardial oxygen uptake during clinical exercise testing Calculated using HR x SBP Also known as a rate pressure product 10th percentile - 25000 90th percentile - 40000
What is Bruce protocol?
3- minute periods to allow achievement of steady state before workload is increased in an exercise stress test.
What is a modified Bruce protocol?
Two 3 minute warm up stages at 1.7 mph and 0% grade and 1.7 and 5% grade (used in older individuals or those who’s exercise capacity is limited by cardiac disease)
What is a stress test indicated for the evaluation of?
CP Prognosis and severity of CV disease Eval of therapy Screening for latent coronary disease Early detection of labile HTN Evaluation of CHF Evaluation of arrhythmia Pre-participation examination for sports Eval of congenital heart disease Stimulus to motivate change in lifestyle
What are the absolute CI of exercise stress testing?
AMI within 2 days, high-risk UA, uncontrolled arrhythmia, sx HF, acute PE or pulmonary infarct, acute myocarditis or pericarditis, acute aortic dissection, severe anemia, acute illness/infection, hyperthyroidism, symptomatic severe AS (moderate to severe defined as valve area between 0.5-1.5 cm2 and a mean gradient of 18-64mmHg)
What are the relative contraindications of exercise stress test?
LM coronary stenosis, moderate stenotic valvular heart disease, electrolyte abnormality, severe arterial hypertension (SBP >200, DBP >110), tachyarrhythmia or bradyarrhythmia, hypertrophic cardiomyopathy or other form of outflow obstruction, mental or physical impairment, high-degree AV block, CHD, severe ST-segment depression in at-rest “ischemia”
What is specific to HF patients undergoing cardiac stress testing?
ETT adds significant clinical info, impaired exercise capacity is a high prognostic indicator
What is specific to patients with hypertension in cardiac stress testing?
Exaggerated BP response is predictive of future HTN and potentially predictive of future mortality secondary to MI; associated with angiographic CAD
Why does a person with dilated cardiomyopathy need stress testing?
Determine exercise capacity, assess pulmonary response to LV dysfunction, determine grace of VE, evaluated effectiveness of treatment; often in this situation SV and CO cannot continue to meet exercise demands
Why would you stress test a person with HOCM?
It is not ideal to stress test someone with HOCM, can cause sudden death secondary to arrhythmia; may have CP, abnormal resting ECG, and exercise induced ST depressions are frequent; however ETT may be specially helpful to demonstrate the level at which significant events occur
What instructions does a patient receive in preparation for a stress test?
No eating or smoking 3 hours prior Water is fine Dress to exercise No unusual physical efforts for at least 12 hours prior to testing
What medication should you consider removing prior to stress testing?
Beta blocker - will attenuate exercise responses and limit test interpretation *potential for rebound tachycardia in pts with recent ACS
What should you be aware of when reviewing a patient’s daily medications prior to a stress test?
Potential for electrolyte abnormalities, hemodynamic effects
Why should the patient only grip the bar of the treadmill lightly?
It reduces workload and supports body weight when gripped tightly
Why is perceived exertion important?
It is generally a sound indication of relative fatigue which helps clinicians judge the degree of fatigue using the Borg scale
Why do patients not do a cool down period?
Cool down periods can eliminate the appearance of ST segment depression
What is an indication of a positive stress test?
J-point and ST80 depression of 1mV/1mm or more and/or ST segment slope within +/- 1mV/s in 3 consecutive beats
What is defined as an inadequate rise in SBP?
<20-30 mmHg or a drop Typically caused by aortic outflow obstruction, severe LV dysfunction, MI, or beta blockers
What is exercise induced hypotension indicative of?
In conjunction with other indicators of ischemia it is a poor prognostic indicator with 50% PPV of LM or triple vessel disease Also indicative of serious arrhythmias in patients with CAD, valvular HD, cardiomyopathy Can also occur in dehydration, patients on antihypertensives, or prolonged strenuous exercise
What are some reasons for tachycardia during submaximal exercise or recovery?
Deconditioning, prolonged bed rest, anemia, metabolic disorders, or any other cause of decreased vascular volume or peripheral resistance
What are the reasons for a low heart rate during submaximal exercise?
Exercise training, enhanced SV, drugs (beta blockers)
Define chronotropic incompetence
Failure to achieve 85% of age-predicted max HR or a low chronotropic index (HR adjusted to MET level), associated with increased mortality risk in pts with known CVD
What are the absolute indications for terminating an exercise stress test?
Drop in SBP >10mmHg when accompanied by other evidence of ischemia Moderate to severe angina Increasing nervous system symptoms (ataxia, dizziness, near syncope) Signs of poor perfusion (cyanosis, pallor) Technical difficulties in monitoring ECG or SBP Pt wants to stop Sustained VT ST elevation >/= 1 mm in leads without diagnostic q waves other than V1 or aVR
What are the relative indications for terminating an exercise stress test?
Drop in SBP >/= 10 mmHg from baseline with absence of other evidence of ischemia ST or QRS changes such as excessive ST depression (>2mm of horizontal or downsloping ST segment depression or marked axis shift Arrhythmias other than sustained VT Fatigue, SOB, wheezing, leg cramps, or claudication Development of BBB or IVCD that cannot be distinguished from VT Increasing CP Hypertensive response (SBP >250 mmHg and/or DBP >115 mmHg) Decreased skin temp, light perspiration, peripheral cyanosis (may indicate poor tissue perfusion due to inadequate CO with secondary vasoconstriction)
What parameters can be used to diagnose an ECG from exercise stress testing in a patient with baseline ST segment depression?
2mm additional ST segment depression or downsloping depression of 1mm or more in recovery (dx of CAD)
Why is Digoxin a confounder in stress ECG interpretation?
Produces ST segment response to exercise in 25-40% of healthy patients Directly related to age Requires two weeks off med to alleviate repolarization pattern
Why is LVH a stress ECG confounder?
If repolarization abnormalities are present it decreases specificity
What about LBBB makes it an stress ECG confounder?
Causes exercise induced ST-segment depression and is unrelated to ischemia, even up to 1 cm (therefore no level of ST depression that is diagnostic) *must do nuclear imaging without exercise* Rate dependent blocks typically precede chronic blocks that occur at rest LBBB occurring at a HR <125 bpm in pts with typical angina is frequently associated with CAD LBBB occurring at a HR >125 bpm occurrs more frequently in pts with normal coronary arteries Presence of intraventricular blocks at rest that disappear during exercise are rare
Why are RBBB confounders of stress ECG interpretation?
Exercise induced ST depression usually occurs with RBBB in anterior chest leads (V1-3) and is not associated with ischemia In L chest leads (V5-6) or inferior leads (II, aVF), test characteristics are similar to those of a normal resting ECG
What are the the potential changes seen in exaggerated atrial repolarization during a stress ECG?
Downsloping ST-segment depression in the absence of ischemia High peak exercise HR Absence of exercise-induced chest pain Markedly downsloping PR segments in inferior leads
Why is beta blocker therapy a confounder in stress ECG interpretation?
Inadequate HR response, sudden discontinuation may cause rebound effect leading to accelerated angina and HTN
Why are nitrates a confounder in stress ECG interpretation?
Can attenuate angina and ST depression associated with myocardial ischemia
Why is flecainide a stress ECG confounder?
Associated with exercise-induced VT
What changes does a torso placement of ECG leads cause?
Shifts axis to the R Increased voltage in inferior leads Disappearance of Q waves
True or false: electrode placement affects ST segment slope and amplitude?
True
Which leads have the highest diagnostic value?
Lateral precordial leads (V4-6) are capable of detecting 90% of all ST depression observed in multiple leads and are by themselves reliable markers for CAD Lead II has a high false-positive rate Inferior leads are of little value in identifying CAD during stress tests
What are the ideal diagnostic properties in abnormal ST segment changes in a stress ECG?
ST level measured relative to P-Q junction 3 consecutive beats in the same lead with stable baseline Measure at 60-80 ms after the J point (60 ms optimal with upsloping ST segment) HR >130
What is the most common ECG manifestation of ischemia?
ECG depression Downsloping > horizontal at predicting CAD; both more predictive than upsloping, but if slowly upsloping with a slope <1mV there is increased probability of CAD Positive: ST depression horizontal or downsloping >/= 1 mV for 60-80 ms