Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Stress Echocardiography for Detecting Coronary Ischemia
Exercise Echocardiography for the Diagnosis of Coronary Disease
Stress echocardiography—exercise or pharmacologic stress electrocardiography (ECG) coupled with echocardiography—is the most specific and sensitive method to noninvasively identify patients with inducible myocardial ischemia due to coronary artery disease (CAD) without the use of ionizing radiation. As early as 1935, Tennant and Wiggers demonstrated that coronary occlusion impairs myocardial contraction. In the 1970s, studies showed that regional wall motion abnormalities could be identified using M-mode echocardiography in canine models of coronary artery occlusion and reduced myocardial perfusion. These pivotal studies provided the basis for the development of clinical stress echocardiography.
Segmental wall motion abnormalities are more sensitive and specific for the detection of myocardial ischemia than symptoms or ECG changes. The advent of two-dimensional (2D) echocardiography improved the feasibility of stress echocardiography. In 1979, segmental wall motion abnormalities due to exercise induced by ischemia was first reported in a patient performing supine bicycle exercise. The development of digital acquisition of echocardiographic images in the 1980s enabled side-by-side comparison of resting ventricular wall motion and left ventricular (LV) wall motion at peak stress or immediately after exercise.
Digitization greatly facilitated the ability to accurately interpret stress echocardiography because it allows direct comparison of the motions of individual LV myocardial segments before and during or immediately after exercise, enhancing the sensitivity and specificity of stress echocardiography. Harmonic imaging and echocardiographic contrast further improved image resolution and identification of the LV endocardial border and the detection of segmental ventricular wall motion abnormalities.
Stress echocardiography has an excellent safety profile. The use of pharmacologic stress echocardiography is detailed in Chapter 14 . Exercise, dobutamine, and vasodilators at appropriate doses are equally effective for inducing wall motion abnormalities in the setting of a significant coronary arterial stenosis. However, exercise stress echocardiography has the added diagnostic value of providing information on inducible myocardial ischemia, functional capacity, exercise tolerance, appropriateness of heart rate response to exercise, heart rate recovery after exercise, and exercise-induced hypertension or hypotension. These data provide important prognostic information that is not evaluated with pharmacologic or pacing stress testing.
The method for stress echocardiography has evolved with improvements in imaging quality, new indications, and new ultrasound techniques, including LV echocardiographic contrast for chamber opacification and LV endocardial border definition, as well as myocardial perfusion, LV strain, three-dimensional (3D) LV volumes, and wall motion analysis. Concerns about radiation exposure with nuclear perfusion imaging and coronary computed tomography (CT) angiography have prompted a renewed interest in stress echocardiography.
Physiologic and Pathophysiologic Principles of Stress Echocardiography in Ischemic Heart Disease
The Ischemic Cascade
The primary goal of stress echocardiography is to safely induce and detect an imbalance between myocardial oxygen consumption and oxygen delivery (i.e., myocardial ischemia). The ischemic cascade is a sequence of events that occurs after the onset of myocardial ischemia. The cardinal symptom of myocardial ischemia, angina pectoris, is the last step in a series of cellular and macroscopic responses to this demand–supply imbalance.
As shown in Fig. 19.1 , the first step consists of cellular metabolic derangements, such as lactate accumulation and electrolyte disturbances within the myocytes. These cellular changes precede clinical manifestations of ischemia, lack of myocardial wall thickening, hypokinetic wall motion, ECG changes, and chest pain. Diastolic dysfunction is usually the first manifestation of myocardial ischemia. Although it is not routinely assessed, abnormal diastolic function during stress echocardiography is useful for the detection of myocardial ischemia and has incremental prognostic value.
With continuing ischemia during stress, the main echocardiographic sign of stress-induced myocardial ischemia becomes evident by a lack of myocardial segmental wall thickening and focal or global systolic dysfunction (i.e., myocardial hypokinesia, akinesia, or dyskinesia). ECG signs of ischemia occur after wall motion abnormalities can be detected, sometimes even after cessation of exercise, during the recovery period. Symptomatic angina pectoris is the last indicator of myocardial ischemia and probably the least reliable because of subjectivity in perception and variations in reporting the symptoms.
Stress-induced increases in LV filling pressures from diastolic or systolic dysfunction often cause chest pressure and dyspnea during stress testing and may be difficult to distinguish from typical angina. It is desirable to detect myocardial ischemia as early as possible to reduce the ischemic burden and the risk of complications during stress testing. The risk profile of stress echocardiography is more favorable than that of stress ECG, although it still is recommended for many patients as the first-line test for inducible ischemia. , Stress echocardiography increases test sensitivity and specificity compared with stress ECG, especially in patients with LV hypertrophy, in those with hypertension, and in women (for whom the positive predictive value of ST abnormalities is lower than for men) ; however, the cost of stress echocardiography is greater.
Determinants of Myocardial Oxygen Demand and Supply
Major determinants of myocardial oxygen demand are (1) LV wall tension, (2) heart rate, and (3) systolic blood pressure (BP). LV wall tension is influenced by myocardial wall thickness, ventricular size, and intraventricular pressure. , Examples of situations in which these three respective determinants are altered are LV and right ventricular (RV) hypertrophy, eccentric LV remodeling, and LV pressure overload from hypertension or aortic stenosis. During stress testing, the so-called double product of heart rate times systolic BP yields the external work of the heart—which is increased and reflects myocardial oxygen demand. Increased LV contractility also augments myocardial oxygen consumption ( m V.O 2 ). Other determinants of metabolic demand, including calcium handling (i.e., calcium-adenosine triphosphatase [Ca 2+ -ATPase] activity) and excitation-contraction coupling, , are harder to quantify and less well understood. Adaptation to increased oxygen demand is limited by myocardial blood flow and by oxygen extraction.
A decrease in oxygen delivery to the myocardium may also induce myocardial ischemia. Several mechanisms can lead to a diminished oxygen supply: (1) decreased oxygen carrying capacity (e.g., anemia); (2) decreased epicardial or microvascular coronary blood flow from a fixed stenosis such as atherosclerotic plaque; (3) abnormal epicardial or microvascular coronary blood flow from dynamic obstruction such as impaired vasodilatory capacity (e.g., endothelial dysfunction, endothelium-independent smooth muscle cell dysfunction) or vasospasm; (4) external systolic compression of intramural coronary arteries from myocardial bridging or increased extracellular matrix in infiltrative or hypertrophic cardiomyopathies; (5) decreased microvascular subendocardial blood flow in situations of ventricular pressure overload (e.g., hypertension, aortic stenosis, pulmonary hypertension, pulmonary embolism); (6) decreased diastolic time (e.g., tachycardia) because most coronary perfusion occurs during diastole; and (7) reduced diastolic flow gradient for myocardial perfusion, as is seen with acute severe aortic regurgitation with low diastolic aortic pressure and an elevated LV end-diastolic pressure (LVEDP). Reduction in the myocardial perfusion gradient can occur in any setting in which the LVEDP is high and aortic diastolic pressure is low (e.g., cardiogenic shock, hypotension in the setting of severe LV hypertrophy). We have even seen this occur during stress testing in a patient with pericardial constriction.
During stress echocardiography, myocardial oxygen demand increases with exercise, adrenergic stimulation with dobutamine, or incremental intracardiac or external (transesophageal) electrical pacing. The common goal of these stress modalities is to increase the myocardial work and O 2 consumption by increasing heart rate, contractility, and systolic BP during exercise to unmask coronary artery stenoses that may not be severe enough to cause symptoms or cardiac dysfunction at rest. Coronary stenoses with a reduction of the cross-sectional luminal diameter to 75% or a diameter of less than 50% can be detected with usual stress testing modalities. However, all the factors that influence supply and demand of coronary blood flow also influence the detection of significant coronary stenoses during stress echocardiography.
Indications and Contraindications for Stress Echocardiography
Table 19.1 lists general advantages, limitations, and developing areas of stress echocardiography. The most common and effective exercise stress modalities are treadmill, upright bicycle, and supine bicycle ergometers. If the patient is unable to exercise, pharmacologic stress or pacing protocols can be applied.
TABLE 19.1
Advantages, Limitations, and Developing Areas of Exercise Stress Echocardiography.
| Advantages |
| Exercise or pharmacologic stress can be used Assessment of cardiac structure Assessment of global LV and RV function Assessment of segmental wall motion at rest and with stress for location of coronary ischemia territory Prognostication for future cardiac events |
| Limitations |
| Image quality varies, depending on patient characteristics and position, equipment, and sonographer’s experience Limited time for image acquisition with treadmill exercise stress testing Inability to reach ischemic threshold with bicycle exercise |
| Developing Areas |
| Strain exercise echocardiography (tissue Doppler, speckle tracking) 3D stress echocardiography Myocardial contrast echocardiography |
Treadmill stress echocardiography is hampered by time constraints for imaging after exercise. Optimally, ultrasound images should be obtained as soon as the patient stops exercising. However, it takes time to get the patient off the treadmill and safely onto a gurney or bed so that the echocardiographic images can be obtained. The longer the delay, the lower the sensitivity of the test if the myocardial ischemia resolves. This issue is not applicable to supine bicycle stress testing, in which imaging can readily be performed during peak exercise. Bicycle testing is the preferred method at our stress laboratory.
Indications
Indications for stress echocardiography for CAD include symptoms of myocardial ischemia, chest pain in the absence of an acute coronary syndrome (ACS) or myocardial infarction, recent ACS without coronary angiography, stable CAD or a change in clinical status, and suspected risk of CAD before noncardiac surgery.
The appropriateness of stress echocardiography in various patient subsets was defined in the 2013 multimodality appropriate use criteria for detection and risk assessment of stable CAD ( Tables 19.2, 19.3, and 19.4 ). The previous appropriateness categories of testing modalities were changed from those of prior guidelines to Appropriate, May be appropriate, and Rarely appropriate by an expert panel for each of the modalities.
TABLE 19.2
Appropriateness of Noninvasive and Invasive Testing Modalities in Symptomatic Patients. a
From Wolk MJ, Bailey SR, Doherty JU, et al. ACCF/AHA/ASE/ASNC/HFSA/HRS/SCAI/SCCT/SCMR/STS 2013 Multimodality appropriate use criteria for the detection and risk assessment of stable ischemic heart disease. J Am Coll Cardiol . 2014;4:380–406.
| Indication Text | Exercise ECG | Stress RNI | Stress Echocardiography | Stress CMR | Calcium Scoring | CCTA | Invasive Coronary Angiography | |
|---|---|---|---|---|---|---|---|---|
| 1 | Low pretest probability of CAD ECG interpretable and able to exercise |
A | R | M | R | R | R | R |
| 2 | Low pretest probability of CAD ECG uninterpretable or unable to exercise |
— | A | A | M | R | M | R |
| 3 | Intermediate pretest probability of CAD ECG interpretable and able to exercise |
A | A | A | M | R | M | R |
| 4 | Intermediate pretest probability of CAD ECG uninterpretable or unable to exercise |
— | A | A | A | R | A | M |
| 5 | High pretest probability of CAD ECG interpretable and able to exercise |
M | A | A | A | R | M | A |
| 6 | High pretest probability of CAD ECG uninterpretable or unable to exercise |
— | A | A | A | R | M | A |
CAD , Coronary artery disease; CCTA , coronary computed tomography angiography; CHD , coronary heart disease; CMR , cardiac magnetic resonance; ECG , electrocardiogram; RNI , radionuclide imaging.
a Appropriate use categories: A, appropriate; M, may be appropriate; R, rarely appropriate.
TABLE 19.3
Appropriateness of Noninvasive and Invasive Testing Modalities in Asymptomatic Patients. a
From Wolk MJ, Bailey SR, Doherty JU, et al. ACCF/AHA/ASE/ASNC/HFSA/HRS/SCAI/SCCT/SCMR/STS 2013 Multimodality appropriate use criteria for the detection and risk assessment of stable ischemic heart disease. J Am Coll Cardiol . 2014;4:380–406.
| Indication Text | Exercise ECG | Stress RNI | Stress Echocardiography | Stress CMR | Calcium Scoring | CCTA | Invasive Coronary Angiography | |
|---|---|---|---|---|---|---|---|---|
| 7 | Low global CHD risk Regardless of ECG interpretability and ability to exercise |
R | R | R | R | R | R | R |
| 8 | Intermediate global CHD risk ECG interpretable and able to exercise |
M | R | R | R | M | R | R |
| 9 | Intermediate global CHD risk ECG uninterpretable or unable to exercise |
— | M | M | R | M | R | R |
| 10 | High global CAD risk ECG interpretable and able to exercise |
A | M | M | M | M | M | R |
| 11 | High global CAD risk ECG uninterpretable or unable to exercise |
— | M | M | M | M | M | R |
CAD , Coronary artery disease; CCTA , coronary computed tomography angiography; CHD , coronary heart disease; CMR , cardiac magnetic resonance; ECG , electrocardiogram; RNI , radionuclide imaging.
a Appropriate use categories: A, appropriate; M, may be appropriate; R, rarely appropriate.
TABLE 19.4
Appropriateness of Noninvasive and Invasive Testing Modalities in Various Cardiac Conditions. a
From Wolk MJ, Bailey SR, Doherty JU, et al. ACCF/AHA/ASE/ASNC/HFSA/HRS/SCAI/SCCT/SCMR/STS 2013 Multimodality appropriate use criteria for the detection and risk assessment of stable ischemic heart disease. J Am Coll Cardiol . 2014;4:380–406.
| Indication Text | Exercise ECG | Stress RNI | Stress Echocardiography | Stress CMR | Calcium Scoring | CCTA | Invasive Coronary Angiography | ||
|---|---|---|---|---|---|---|---|---|---|
| Newly Diagnosed Heart Failure (Resting LV Function Previously Assessed but No Prior CAD Evaluation) | |||||||||
| 12 | Newly diagnosed systolic heart failure | M | A | A | A | R | A | A | |
| 13 | Newly diagnosed diastolic heart failure | M | A | A | A | R | M | M | |
| Evaluation of Arrhythmias Without Ischemic Equivalent (No Prior Cardiac Evaluation) | |||||||||
| 14 | Sustained VT | A | A | A | A | R | M | A | |
| 15 | Ventricular fibrillation | M | A | A | A | R | M | A | |
| 16 | Exercise-induced VT or nonsustained VT | A | A | A | A | R | M | A | |
| 17 | Frequent PVCs | A | A | A | M | R | M | M | |
| 18 | Infrequent PVCs | M | M | M | R | R | R | R | |
| 19 | New-onset atrial fibrillation | M | M | M | R | R | R | R | |
| 20 | Before initiation of anti-arrhythmia therapy in patients with high global CAD risk | A | A | A | A | R | M | R | |
| Syncope Without Ischemic Equivalent | |||||||||
| 21 | Low global CAD risk | M | M | M | R | R | R | R | |
| 22 | Intermediate or high global CAD risk | A | A | A | M | R | M | R | |
CAD , Coronary artery disease; CCTA , coronary computed tomography angiography; CMR , cardiac magnetic resonance; ECG , electrocardiogram; PVCs , premature ventricular contractions; RNI , radionuclide imaging; VT , ventricular tachycardia.
a Appropriate use categories: A, appropriate; M, may be appropriate; R, rarely appropriate.
The 2020 American Society of Echocardiography guidelines on stress echocardiography list indications for stress testing together with recommendation class (I, IIa, IIb, or III) and level of supporting evidence (A–C) ( Table 19.5 ). In symptomatic patients, these indications include a low or intermediate likelihood of CAD in those who can exercise but have an uninterpretable ECG, and a high pretest likelihood of CAD even with an interpretable ECG. In asymptomatic patients, stress echocardiography was deemed useful only in selected cases when CAD risk is intermediate or high and the ECG uninterpretable.
TABLE 19.5
Recommendations for Stress Echocardiography in Patients With Symptoms or Suspected Stable Coronary Artery Disease.
From Pellikka PA, Arruda-Olson A, Chaudhry FA, et al. Guidelines for performance, interpretation, and application of stress echocardiography in ischemic heart disease: from the American Society of Echocardiography. J Am Soc Echocardiol . 2020;33(1):1–41 e48.
| Recommendations | Class of Recommendation | Level of Evidence |
|---|---|---|
| Recommendations for Noninvasive Testing for IHD | ||
| In patients with suspected stable CAD, intermediate pretest probability and preserved ejection fraction, stress imaging, such as stress echocardiography, is preferred as the initial test option. | I | B |
| In patients without typical angina, an imaging stress test, such as stress echocardiography, is recommended as the initial test for diagnosing stable CAD if the pretest probability is high or if LVEF is reduced. | I | B |
| In patients with suspected CAD and with resting ECG abnormalities that prevent accurate interpretation of ECG changes during stress, an imaging stress test, such as stress echocardiography, is recommended. | I | B |
| In patients with LBBB and symptoms consistent with IHD, stress echocardiography (ESE or DSE) is preferred over SPECT imaging because of its greater specificity and its versatility for detecting other cardiac conditions associated with LBBB. | I | B |
| Stress echocardiography is the preferred test for women with an indication for a noninvasive imaging test for known or suspected CAD because of its safety (absence of radiation to the breasts) and greater specificity (absence of breast attenuation artifact). | I | B |
| ESE is the preferred imaging stress test for children with suspected IHD because of the absence of radiation to developing tissues, absence of need for an intravenous line, and provision of the prognostically important assessment of exercise capacity. | I | B |
| A pharmacologic stress test, such as DSE, is recommended for patients with the above indications for a stress imaging test who are unable to exercise. | I | B |
| Stress echocardiography is the preferred test in patients with exertional dyspnea of uncertain etiology. For these patients, in addition to assessment of regional wall motion, tricuspid regurgitation velocity and diastolic function should be assessed at rest and with stress. | I | B |
| An imaging stress test, such as stress echocardiography, should be considered in patients with prior coronary artery revascularization (PCI or CABG) and new cardiac symptoms. | IIa | B |
| An imaging stress test, such as stress echocardiography, should be considered to assess the functional severity of intermediate lesions on coronary arteriography. | IIa | B |
| Recommendations for Risk Stratification Using Ischemia Testing | ||
| A stress imaging test such as stress echocardiography for risk stratification is recommended in patients with an inconclusive exercise ECG. | I | B |
| A stress imaging test, such as stress echocardiography, is recommended for risk stratification in patients with known stable CAD and a deterioration in symptoms if the site and extent of ischemia would influence clinical decision making. | I | B |
| In asymptomatic adults with diabetes, peripheral vascular disease, or a strong family history of CAD, or when previous risk assessment testing suggests a high risk of CAD (e.g., coronary artery calcium score ≥ 400), a stress imaging test, such as stress echocardiography, may be considered for advanced cardiovascular risk assessment. | IIb | B |
| Recommendation for Reassessment in Patients With Stable CAD | ||
| An exercise ECG or stress imaging test, such as stress echocardiography, is recommended in the presence of recurrent or new symptoms after instability has been ruled out. | I | C |
| In symptomatic patients with revascularized stable CAD, a stress imaging test, such as stress echocardiography, is indicated rather than stress ECG. | I | C |
| Reassessment of prognosis using a stress test, such as stress echocardiography, may be considered in asymptomatic patients after the expiration of the period for which the previous test was thought to be valid. | 2b | B |
| Recommendations for Noninvasive Stress Testing of IHD | ||
| A pharmacologic stress imaging test such as DSE is recommended before high-risk surgery in patients with more than two clinical risk factors and poor functional capacity (<4 METs). | I | B |
| A pharmacologic stress imaging test such as DSE may be considered before high- or intermediate-risk surgery in patients with suspected cardiac symptoms and poor functional capacity (<4 METs). | I | B |
CABG , Coronary artery bypass grafting; CAD , coronary artery disease; DSE , dobutamine stress echocardiography; ECG , electrocardiographic; ESE , exercise stress echocardiography; IHD , ischemic heart disease; LBBB , left bundle branch block; LVEF , LV ejection fraction; METs , metabolic equivalents; PCI , percutaneous coronary intervention; SPECT , single-photon emission computed tomography.
Indications for stress echocardiography by prior guidelines included possible ACS without ischemic ECG changes or left bundle branch block (LBBB) and normal or minimally elevated troponin levels (which is a contraindication for some practitioners). The 2013 guidelines listed stress echocardiography in patients without chest pain but with new-onset congestive heart failure or LV dysfunction, certain arrhythmias, and syncope.
Exercise Stress Echocardiography for Preoperative Risk Assessment in Noncardiac Surgery
Preoperative risk is heightened in patients with known peripheral arterial disease, ischemic heart disease, diabetes, or congestive heart failure, especially in the setting of poor functional capacity ( Table 19.6 ). It is recommended that high-risk patients with a previous history of CAD undergo stress echocardiography before noncardiac surgery.
TABLE 19.6
Stress Echocardiography: Predictors of Risk.
Adapted from Pellikka PA, Arruda-Olson A, Chaudhry FA, et al. Guidelines for performance, interpretation, and application of stress echocardiography in ischemic heart disease: from the American Society of Echocardiography. J Am Soc Echocardiol . 2020;33(1):1–41 e48.
| Very Low Risk a : Myocardial Infarction, Cardiac Events < 1%/y | Factors Increasing Risk b | High Risk c : RR > Fourfold Low Risk |
|---|---|---|
| Normal exercise echocardiogram result with good exercise capacity >7 METs men >5 METs women |
Increasing age Male sex Diabetes High pretest probability History of dyspnea or CHF History of myocardial infarction Limited exercise capacity Inability to exercise Stress ECG with ischemia Rest WMA LV hypertrophy Stress echocardiography with ischemia Reduced baseline EF No change or increased ESV with stress d No change or decreased EF with stress d Increasing wall motion score with stress |
Extensive WMA at rest (4–5 segments of LV) Baseline EF < 40% Extensive ischemia (4–5 segments of LV) Multivessel ischemia Rest WMA and remote ischemia Low ischemic threshold Ischemic WMA, no change or decrease in exercise EF d |
CAD , Coronary artery disease; CHF , congestive heart failure; ECG , electrocardiogram; EF , ejection fraction; ESV , end-systolic volume; HR , heart rate; METs , metabolic equivalents; WMA , wall motion abnormalities.
a High pretest probability of CAD, poor exercise capacity or low rate-pressure product, increased age, angina during stress, LV hypertrophy, history of infarction, history of CHF, and anti-ischemic therapy are factors known to increase risk in patients with normal stress echocardiogram results.
b The degree to which each factor increases risk varies.
c Cutoff values for high-risk group are approximate values derived from available studies. Studies have shown that increased rest and low- and peak-dose wall motion scores can identify individuals at high risk, especially those with reduced global LV function, but threshold values used to define patients at high risk have varied (e.g., peak exercise scores ranging from 1.4 to >1.7).
Although exercise testing is the preferred modality, pharmacologic stress testing can be used for those patients who are unable to exercise. Compared with myocardial perfusion scintigraphy, dobutamine stress echocardiography has been shown to be as sensitive and more specific with a better accuracy of predicting cardiac events. Table 19.7 lists advantages and disadvantages of various testing modalities for the evaluation of CAD.
TABLE 19.7
Advantages and Disadvantages of Cardiac Imaging Modalities.
Adapted from Dowsley T, Al-Mallah M, Ananthasubramaniam K, et al. The role of noninvasive imaging in coronary artery disease detection, prognosis, and clinical decision making. Can J Cardiol . 2013;29:285–296.
| Cardiac Imaging Modality | Advantages | Disadvantages |
|---|---|---|
| Stress echocardiography | Portable, inexpensive Both exercise and pharmacologic stress No radiation Concurrent structural information Future use of echocardiographic perfusion imaging |
Operator dependent Quality affected by patient body habitus, poor acoustic windows (but improved with appropriate use of contrast) |
| CT angiography | High diagnostic accuracy (particularly high sensitivity and NPV) Early detection of nonobstructive CAD (coronary calcification, noncalcified atherosclerotic plaque Future use of CT MPI may provide both anatomic and functional assessment |
Accuracy affected by high coronary calcification Involves radiation Anatomic, so unable to predict functional significance of stenotic lesion (will improve in future with CTA MPI) Use of iodinated contrast |
| MPI SPECT | Both exercise and pharmacologic stress Both perfusion and LV functional assessment with gated SPECT Robust data validating Less operator-dependent than echocardiography |
Radiation Soft tissue attenuation artifacts |
| MPI PET | Superior diagnostic accuracy compared with SPECT Absolute blood flow quantification Accurate attenuation correction |
Radiation Expensive Mainly employs only pharmacologic stress |
| Stress CMR | No radiation No soft tissue attenuation artifacts Excellent concurrent structural information |
Expensive, time consuming Contraindicated in patients with CRMD, claustrophobia, severe renal impairment |
| MR coronary angiography | No radiation No soft tissue attenuation artifacts |
Inferior spatial resolution compared with CTA |
| Exercise ECG | Added prognostic value of exercise (Duke treadmill score) Inexpensive No radiation |
Inferior diagnostic accuracy Requires ability to exercise Uninterpretable with baseline ECG abnormalities (e.g., LBBB, significant resting ST depression) |
CAD , Coronary artery disease; CMR , cardiac magnetic resonance imaging; CRMD , cardiac rhythm management device; CT , computed tomography; CTA , computed tomography angiography; ECG , electrocardiogram; LBBB , left bundle branch block; MPI , myocardial perfusion imaging; MR , magnetic resonance; NPV , negative predictive value; PET , positron emission tomography; SPECT , single-photon emission computed tomography.
Contraindications
There are no side effects associated with exercise echocardiography other than those associated with physical exercise. Absolute contraindications for exercise echocardiography are acute myocardial infarction, unstable angina, serious cardiac arrhythmias, acute pulmonary embolism, aortic dissection, a significant aortic aneurysm, active myocarditis or pericarditis, decompensated heart failure, and symptomatic severe aortic stenosis. Other contraindications include known left main coronary stenosis, severe systemic hypertension (e.g., 200/100 mmHg), severe pulmonary hypertension (e.g., 60 mmHg), and inability to adequately exercise.
Additional relative contraindications, such as hypertrophic cardiomyopathy or asymptomatic critical aortic stenosis, are readily identified from the baseline echocardiogram; therefore, a built-in safeguard exists against the inappropriate stressing of patients with these entities. Nonserious arrhythmias that may preclude adequate wall motion interpretation and poor acoustic windows that are not resolved with echocardiographic contrast can prevent accurate interpretation of segmental wall motion abnormalities and therefore are relative contraindications for exercise echocardiography. Tables 19.2, 19.3, and 19.4 list the appropriate indications for stress echocardiography in symptomatic and asymptomatic patients.
Cost-Effectiveness of Exercise Stress Echocardiography
The cost-effectiveness of stress echocardiography relates to the pretest likelihood of CAD. If there is a very low or very high pretest probability of CAD, the value of stress testing is limited. The greatest value of stress echocardiography is for patients with an intermediate probability of CAD of 20% to 80%. However, when considering stress test costs and further downstream testing from equivocal results, adding echocardiography to stress testing is cost-effective, especially if stress ECG has a high likelihood of being nondiagnostic.
Stress echocardiography has an equal or higher specificity than alternative imaging modalities. This makes it a more cost-effective method than nuclear perfusion studies, which cost more than twice as much.
Stress Protocols
General Considerations
The goal of stress echocardiography is to safely reach a workload high enough to increase myocardial oxygen demand to a level at which coronary artery stenosis can be detected with an optimal sensitivity and specificity. The exercise target at which CAD can be detected with a high level of confidence may be different for each patient, but by convention, it is 85% of the age-dependent maximal predicted heart rate.
Other exercise targets, such as a rate times pressure value (i.e., double product) of at least 20,000 or the development of symptoms, may be reasonable depending on the clinical context. For safety monitoring and for the detection of signs of myocardial ischemia or cardiac decompensation, continuous monitoring of the ECG, heart rate, BP, pulse oximetry, and symptom status, in addition to the echocardiogram, is required before, during, and after the exercise protocol.
Clinical context is particularly relevant in athletes, for whom a higher double product and greater duration and degree of exercise are often warranted to ensure that the individual will be safe during sports activities. The timing of echocardiographic imaging depends on the stress modality. However, imaging during bicycle stress testing is more sensitive and equally specific compared with treadmill protocols. Table 19.8 shows some of the advantages and disadvantages of bicycle versus treadmill exercise stress modalities.
TABLE 19.8
Advantages and Disadvantages of Bicycle Versus Treadmill Ergometry.
| Bicycle Ergometry | Treadmill Ergometry |
|---|---|
| Advantages | |
| Easier monitoring of blood pressure and pulse oximetryLess artifact on electrocardiogramContinuous/intermittent imagingAbility to maintain target heart rate for a prolonged period for comprehensive echocardiographic evaluation (e.g., diastology, valvular function) May increase sensitivity for the detection of ischemic wall motion abnormalities |
Standard exercise modality in the United StatesGreater percentage of patients achieve target heart rateMore validated data on exercise duration, workload, heart rate recovery |
| Disadvantages | |
| Some patients are not familiar with bicycle exerciseSmaller percentage of patients achieve target heart rateLess validated data on exercise duration and prognosisHigher risk of pulmonary congestion (supine position) | Noncontinuous imagingDelay between peak exercise and image acquisitionLimited time to obtain imagingGreater risk of fall/injuryMore difficult monitoring of blood pressure and pulse oximetryMore artifact on electrocardiogram |
Equipment and Personnel
Fig. 19.2 shows the setup for supine bicycle and treadmill stress echocardiographic testing in our laboratory. Whereas certain standard equipment and personnel are necessary to maximize safety and efficiency, requirements for different stress testing modalities vary. The motorized treadmill or bicycle ergometer; a lateral-tilting echocardiography table with a left lateral cutout for optimal apical imaging; stress testing equipment that can integrate workload, ECG, and vital signs for monitoring and reporting; and the echocardiography machine should be set up so that they can be controlled and inspected by the laboratory staff at any time during the test. With treadmill exercise testing, the echocardiography bed should be in immediate proximity to the treadmill so that patients can be quickly transferred for post-peak exercise imaging, which must occur within seconds of exercise cessation.
Other necessary equipment consists of a crash cart with a defibrillator and medications used during stress testing, including those to reverse or treat the adverse effects of pharmacologic stress agents. In a hospital setting, a code blue alert system should be in every stress room. It is controversial and depends on hospital or facility policy about whether a nurse or physician assistant or only a physician can directly supervise a stress test. At a minimum, a physician needs to be available without delay in case a complication occurs during or immediately after the stress test.
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here