B P3 C15 Exercise Physiology and Exercise Electrocardiographic Testing Flashcards
Energy requirements at rest and for any given amount of physical activity (work rate) can be estimated from measurements of
Total-body oxygen uptake ( Vo2 )
1 MET is resting energy expenditure and is approximately _____ mL O2/kg BW/min
3.5 mL O2/kg body weight/min
________ peak oxygen uptake achieved during performance of the highest level of dynamic exercise involving large muscle groups and by definition cannot be exceeded despite increases in work rate.
VO2 max
Stroke volume in healthy persons generally plateaus at _______ of Vo 2 max.
50% to 60%
Myocardial oxygen demand is related to:
HR
BP
LV contractility (myocardial shortening per beat)
LV wall stres
LV _________ is related to LV pressure, wall thickness, and cavity size.
LV wall stress
_________ reliable index of myocardial oxygen demand and can be readily assessed clinically.
Rate-pressure product (product of HR and SBP)
_________ reliable index of myocardial oxygen demand and can be readily assessed clinically.
Rate-pressure product (product of HR and SBP)
During acute endurance (high-repetition/low-resistance) exercise (e.g., walking or cycling), ________ rises in response to the metabolic needs of the exercising muscles
Cardiac output
Diminution of _______ and a rise in sympathetic tone lead to an increase in HR and LV contractility.
Vagal tone
Stroke volume also rises because of increases in __________, and blood flow is redistributed from the renal, splanchnic, and cutaneous circulation to the exercising muscles.
Venous return of blood from exercising muscles
Accumulation of metabolites in the actively contracting muscles causes __________ of muscle arterioles, which increases skeletal muscle blood flow up to four times that of resting levels and results in a reduction in aortic outflow impedance.
Vasodilation
Systolic BP increases mostly because of the rise in cardiac output, whereas diastolic BP either remains _______ or ______ as a result of the reduction in vascular resistance.
Constant or falls
Dynamic arm exercise elicits __________ at any given work rate than does dynamic leg exercise.
Higher HR and BP responses
This type of exercise generates an increased sympathetic response, leading to an increase in HR; however, venous return, especially during straining, may decrease.
Resistance (low-repetition/high-load) exercise (e.g., weightlifting)
The rise in cardiac output is relatively small in comparison to that achieved with endurance exercise and is primarily caused by ________ in HR
Increases in HR
Muscle contraction during resistance exercise generates compressive force on muscle capillaries that leads to ______ peripheral resistance
Elevated peripheral resistance
This rise in vascular resistance coupled with an increase in cardiac output yields an increase in both ___________
Systolic and diastolic BP
In healthy persons during acute exercise, coronary arteries __________ and coronary blood flow __________ in response to the increases in myocardial oxygen demand.
Dilate and coronary blood flow rises
In general, a 50% to 70% reduction in luminal diameter will _______ reactive hyperemia, whereas 90% or greater stenosis will _______ resting flow
Peak reactive hyperemia
Reduce resting flow
Atherosclerotic arteries often _______________ thus further reducing the supply of blood in the setting of increased demand.
Fail to dilate and may actually constrict with exercise
Absolute contraindications to Exercise Testing
Acute MI within 2 days
High-risk unstable angina
Uncontrolled cardiac arrhythmia with hemodynamic compromise
Active endocarditis
Symptomatic severe AS
Decompensated HF
Acute PE or pulmonary infarction
Acute myocarditis or pericarditis
Physical disability that precludes safe and adequate testing
Relative contraindications to Exercise Testing
Known LM coronary artery stenosis
Moderate AS + uncertain relation to symptoms
Tachyarrhythmias + uncontrolled ventricular rates
Acquired complete heart block
HCM with severe resting gradient
Mental impairment with limited ability to cooperate
More common form of physiologic stress (i.e., walking) in which patients are more likely to attain a higher oxygen uptake and peak HR than during stationary cycling
Treadmill testing
_______ can be used as a surrogate measure of exercise capacity when standard treadmill or cycle testing is not available; best used in a serial manner to evaluate changes in exercise capacity and the response to interventions that may affect exercise capacity over time.
6-minute walk test
Distance walked is the primary outcome of the test; not useful in the objective determination of myocardial ischemia
Uses ventilatory gas exchange analysis during exercise to provide a more reliable and reproducible measure of Vo2
Cardiopulmonary exercise testing (CPX)
________ the most accurate measure of exercise capacity and is a useful reflection of overall cardiopulmonary health.
Peak VO2
CPX is well established as useful in the following situations:
*Evaluation of exercise capacity in selected patients with heart failure, to assist in estimation of prognosis, evaluate the response to medications and other interventions, and assess the need for cardiac transplantation.
Evaluation of exertional dyspnea.
Evaluation of the patient’s response to specific therapeutic interventions (e.g., medications; programmed pacing; cardiac rehabilitation) in which improvement in exercise tolerance is an important goal or endpoint.
_____ angina is an important clinical predictor of the presence and severity of CAD, equal to or greater than STsegment depression
Exercise-induced angina
_____ angina predicts an adverse prognosis and is worthy of further evaluation regardless of the ST-segment response or the exercise capacity.
Exercise-induced typical angina
___________ is a strong predictor of mortality and nonfatal cardiovascular outcomes in both men and women with and without CAD.
Functional capacity
Equations in estimating predicted METs
Men :
Predicted METs = 18 − (0.15 × Age)
Women :
Predicted METs = 14.7 − (0.13 × Age)
________is a fundamental physiologic parameter that provides the clinician relevant information concerning the intensity of exercise, the adequacy of the exercise test, the effect of medications that influence HR, the potential contribution to exercise intolerance, and the patient’s prognosis.
Maximum HR during exercise
Equation to estimated HRmax
HRmax = 220 − Age
Equations to generate maximum age-predicted HR (MPHR)
Men :
HRmax = 208 − (0.7 × Age)
Women :
HRmax = 206 − (0.88 × Age)
__________ is the inability of the heart to increase its rate to meet the demand placed on it.
It is considered an independent predictor of cardiac or all-cause mortality, as well as other adverse cardiovascular outcomes.
Chronotropic incompetence
A _____________ is assigned when the peak HR achieved is below the MPHR.
Submaximal study
An ________ is defined by failure to achieve a predefined goal, such as 85% of MPHR.
Inadequate study
Failure to achieve a chronotropic index higher than 80%; predicts a poor prognosis.
Chronotropic incompetence
Abnormal HR recovery (HRR) has been defined by many methods, but the most commonly accepted include
Less than 12 beats/min decrement after 1 minute with post-exercise slow walking cool-down
Less than 18 beats/min after 1 minute with immediate cessation of movement into either the supine or sitting position
Less than 22 beats/min after 2 minutes
Abnormal HRR is associated with an increase in all-cause mortality in both asymptomatic individuals and patients with established heart disease
Exercise BP responses
Increase:
* Systolic BP
* Pulse pressure (difference between systolic and diastolic BP)
* HR-BP product (also called the double product), and double-product reserve (change in double product from peak to rest) all increase steadily
Diastolic BP increases only minimally or may fall
In most normal individuals, systolic BP will increase to well above _______ and the double product to higher than ________.
140 mm Hg
20,000
Hypertensive Systolic Pressure Response
Men:
> 210 mm Hg
Women:
> 190 mm Hg
Exercise-Induced Systolic Hypotension
Systolic pressure during exercise falling below resting systolic pressure.
Another definition is a 20 mm Hg fall after an initial rise.
Absolute Indications for Terminating Exercise Test
• ST elevation (>1.0 mm) in leads without Q waves due to prior MI (other than aVR, aVL, or V1)
• Drop in systolic BP of >10 mm Hg, despite an increase in workload, when accompanied by any other evidence of ischemia
• Moderate to severe angina
• Central nervous system symptoms (e.g., ataxia, dizziness, or near syncope)
• Signs of poor perfusion (cyanosis or pallor)
• Sustained ventricular tachycardia or other arrhythmia that interferes with normal maintenance of cardiac output during exercise
• Technical difficulties monitoring the ECG or systolic BP
• Patient’s request to stop
Relative indications in terminating exercise test
• Marked ST displacement (horizontal or downsloping of >2 mm) in a patient with suspected ischemia
• Drop in systolic BP of >10 mm Hg (persistently below baseline) despite an increase in workload, in the absence of other evidence of ischemia
• Increasing chest pain
• Fatigue, shortness of breath, wheezing, leg cramps, or claudication
• Arrhythmias other than sustained ventricular tachycardia, including multifocal ectopy, ventricular triplets, supraventricular tachycardia, atrioventricular heart block, or bradyarrhythmias
• Exaggerated hypertensive response (systolic blood pressure >250 mm Hg and/or diastolic blood pressure >115 mm Hg)
• Development of bundle branch block that cannot be distinguished from ventricular tachycardia
Exercise-associated hypotension may also be seen in patients with
Cardiomyopathy
LV outflow tract obstruction
Enhanced vagal tone
Hypovolemia
Antihypertensive medications
Arrhythmias
This response occurs in patients who are anxious about the exercise study and begin exercise with a somewhat elevated systolic pressure.
Pseudo–exercise-induced hypotension
A normal rise in systolic BP is approximately _______________ increase.
10 mm Hg per MET
A blunted BP rise during exercise may be due to
Cardioactive medications
Underlying heart conditions that limit the normal increase in cardiac output during exercise
Diagnostic value of ST-segment depression has a sensitivity and specificity of ________ and ________
60% to 70%
70% to 80%
The usual criterion of ST depression applied to raw data is 1 mm or greater or 0.1 mV or greater of ____________ ST-segment depression in three consecutive beats.
Horizontal or downsloping (i.e., <0.5 mV/sec)
This assumes that the _________ (not the TP segment) is used as the isoelectric reference and that the point of STsegment measurement is _______ after the J point.
PQ point
60 to 80 milliseconds
The ____ criterion is used at HR higher than 130 beats/min.
60-millisecond post–J point
Unlike ST-segment elevation, exercise-induced ST-segment depression _______ to a precise region or vascular bed.
Does not localize ischemia
The ________ (especially lead V5) are the best for defining positive responses.
Lateral precordial leads
True or False
Positive responses are occasionally limited to the recovery period, and these have equal significance to changes that occur at peak exercise
True
True
Positive changes during exercise that resolve within 1 minute of recovery are associated with a favorable prognosis and low downstream diagnostic test yield.
True or False
Early-recovery ST changes are associated with significantly smaller summed stress scores on myocardial perfusion imaging and a lower prevalence of CAD.
True
Rapidly upsloping ST depression that resolves quickly is rarely _______ and _______ than horizontal or downsloping ST depression.
a true positive response and is less specific
Lead ______ elevation 1-mm or greater may be a significant predictor of left main CAD, proximal left anterior descending (LAD) artery disease, or at least multivessel CAD.
aVR ST elevation
The usual criterion to ST elevation applied to raw data is _______ in three consecutive beats.
1 mm or greater or 0.1 mV of STsegment elevation above the PQ point at 60 milliseconds after the J point
ST-segment elevation __________ to a particular vascular region and thus, coronary angiography is an appropriate next step
Precisely localizes the transmural ischemia
When pathologic Q waves are present, ST-segment elevation is usually indicative of an _________ or ________.
Ischemia may be involved in this process, and myocardial perfusion imaging is generally required to determine this.
LV aneurysm or significant wall motion change
______ occurring during exercise or recovery increase the likelihood of future cardiac death.
Ventricular ectopic beats
___________ are not predictive of ischemia or any cardiovascular endpoint. However, they may be a marker for the later occurrence of AF or supraVT
Exercise-induced supraventricular arrhythmias
The principal issue with digitalis has been _______ and _______
False positive results and reduced specificity
Sensitivity is not affected
Therefore, a negative ST-segment response with digitalis is still reliable.
For most patients taking digitalis, stress imaging is appropriate as an initial test if the goal of the test is to assess for myocardial ischemia.
Identification of ischemic heart disease in women can be a diagnostic challenge because of several factors:
Lower prevalence of obstructive CAD in women younger than 65
More atypical manifestations of ischemic symptoms
More frequent resting ST changes
Exercise testing has similar diagnostic characteristics in women with an _________ as it does for men
Intermediate probability of CAD
Electrocardiogram and Non-Electrocardiogram Variables Associated with an Elevated Ischemic Heart Disease Risk from Exercise Testing in Women
Exercise capacity:
<5 METs
<100% age-predicted METs = 14.7–(0.13 × age)
Exercise testing also has a role in patients with valvular heart disease who want to participate in _____________.
Competitive athletic activity
Exercise testing is combined with echocardiography to assess ________
Structural and physiologic responses
This is the preferred approach in evaluating patients with mitral stenosis and disparate clinical and resting echocardiographic data, such as severe stenosis without symptoms or symptoms with mild to moderate stenosis.
The only valve lesion in which the simple exercise ECG still has a significant role in management is ________
Aortic stenosis
Exercise testing is absolutely c cated in patients with ______________
Symptomatic severe valvular aortic stenosis
Exercise testing may be considered for patients with AS
Asymptomatic patients with severe acquired valvular aortic stenosis
Moderate stenosis but suspected symptoms
The purpose of exercise testing in this setting is to induce either _______ or an abnormal BP response, which most studies define as a lack of increase or ___________ in systolic BP
Symptoms
≤20 mm Hg increase
Exercise testing in this scenario should be performed only in those with no reported symptoms or with symptoms that are equivocal at worst, such that aortic valve surgery is not indicated on that basis.
In young or adolescent patients with congenital aortic valve stenosis that is moderate to severe
Exercise testing is done to provide advice for patients wanting to ________ as well as to evaluate asymptomatic patients with severe stenosis to
Participate in athletic activities
Assess the BP response and exercise tolerance
Exercise test in HCM carries a class I recommendation for assessing ________ using exercise echocardiography and for assessing patients with nonobstructive HCM for _______ using CPX; class IIa for determination of ________ and _______
Dynamic outflow obstruction
Possible cardiac transplantation
f\functional capacity and for risk stratification
Exercise testing in patients with HCM has clinical value in three clinical situations:
(1) defining the presence of exercise-induced outflow tract obstruction with Doppler echocardiography in patients with no gradient at rest
(2) identifying patients with coexistent CAD
(3) detecting patients with the high-risk indicator of an abnormal BP response
An _______ during upright treadmill exercise is a risk factor for SCD in patients with HCM
Abnormal BP response
It is of greater predictive value in patients younger than 50 years. An abnormal BP response is defined as either an initial increase in systolic pressure with a subsequent fall greater than 20 mm Hg, or a continuous fall from the start of exercise greater than 20 mm Hg.
The specific congenital conditions where the exercise-ECG has a role include
Repaired and unrepaired aortic coarctation
Repaired tetralogy of Fallot
Surgically and congenitally corrected transposition of the great arteries
Coronary artery anomalies.
Indications for exercise testing in AF:
When myocardial ischemia is suspected and initiation of type IC antiarrhythmic drug therapy is being considered
Assessing the adequacy of HR control across a full spectrum of activity in patients with persistent or permanent AF
Exercise testing may be used to induce possible exercise-induced AF
Exercise testing is useful to assess for exercise-induced ventricular arrhythmias in patients with ventricular arrhythmia symptoms associated with
Exertion
Suspected ischemic heart disease
Catecholaminergic polymorphic ventricular tachycardia
In symptomatic and asymptomatic patients with preexcitation, the findings of ________ during exercise testing in sinus rhythm is useful to identify patients at low risk of rapid conduction over the pathway
Abrupt loss of conduction over a manifest pathway
Catecholaminergic polymorphic VT generally appears in HRs __________ and begins with polymorphic ventricular premature beats progressing to nonsustained VT and eventually to bidirectional or polymorphic VT
above 120 to 130 beats/min
The purpose of the exercise test, therefore, is to achieve a diagnosis and determine the patient’s response to treatment, namely, beta blockade.
Changes in the QT interval with exercise can be useful in identifying and stratifying patients with LQTS
Effects of exercise testing in
LQTS1
LQTS2
LQTS3
Further prolongation of (or failure to shorten) an already prolonged QT interval with exercise is typical of LQT1
LQT2 has normal shortening
LQT3 has supranormal shortening of the QT interval with exercise
Exercise testing has no significant role in the management of these patients
Arrhythmogenic Right Ventricular Cardiomyopathy
In patients without further chest pain and no objective evidence of ischemia, an exercise test can be performed ______ of observation.
After 8 to 12 hours
Intensity of dynamic aerobic exercise is usually determined from the results of a pretraining exercise test by using either of two methods:
40% to 80% of peak exercise capacity using the HR reserve method
HR at 40% to 80% of the measured peak VO2
A simpler approach is to have individuals exercise at _________
70% to 85% of their maximal measured HR
The goal duration of exercise at the prescribed intensity is generally ________ per session at a frequency of ________ per week.
20 to 60 minutes
3 to 5 days
Exercise testing can be performed in patients with PAD to establish further the diagnosis by noninvasive techniques, particularly in patients with _______
Calf pain and borderline ankle-brachial indices (ABIs: 0.91 to 1.0)
Several diagnostic criteria to diagnosed PAD after exercise testing have been proposed and include
Greater than a 5% drop in post-exercise ABI from resting levels
Postexercise ABI lower than 0.9
Greater than a 30 mm Hg drop in systolic BP at the ankle
Recovery time to baseline ABI longer than 3 minutes
Class I indications for exercise testing for PAD
• Patients with ABI 0.91–0.99 may possibly have PAD, and should undergo exercise ABI if the clinical suspicion of PAD is significant.
• Patients with exertional non-joint-related leg symptoms and normal or borderline resting ABI (>0.90 and ≤1.4) should undergo exercise treadmill ABI testing to evaluate for PAD.
