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Because the body requires more oxygen during physical stress, the heart is forced to pump more blood. Testing a patient during stress can help determine if coronary blood flow is reduced due to CAD. Arteries affected by CAD will show restricted blood flow under stress compared with rest. Patients with abnormal resting ECG results, intermediate risk for CAD, or other indications are often referred for noninvasive stress testing. The tests discussed in this section are commonly used to evaluate patients for CAD using stress.
Exercise Treadmill Testing
Utility
In exercise treadmill testing (ETT), the patient exercises on a treadmill while undergoing ECG monitoring and blood pressure monitoring. ETT is a widely available and relatively inexpensive test that allows the correlation of symptoms with ECG changes that can indicate myocardial ischemia. ETT also provides the opportunity to assess a patient's exercise capacity, which in itself has been shown to be an independent predictor of death in women.64
Limitations
Some patients referred for ETT are unable to reach adequate exercise levels (ie, 85% of predicted maximal heart rate) for accurate testing. Some medical conditions, poor motivation, and poor physical condition can limit a patient's ability to exercise adequately for accurate testing (see Exercise vs Pharmacologic Stress). Certain patients, such as those with diabetes, obesity, and metabolic syndrome, also tend to have lower general abilities to exercise (see the Special Issues section of this Web site). Also, ETT has a lower diagnostic sensitivity and specificity in women than in men. Factors responsible for this likely include more variable exercise capacity, hormonal status (ie, menopausal status and/or hormone replacement therapy), and smaller coronary vessels.7,9
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Patient Education, Reassurance, and Motivation
Risk Factor Modification
Angina Management
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| Myocardial Perfusion Imaging
Nuclear myocardial perfusion imaging (MPI) is used to detect disease by assessing blood flow while the coronary arteries are dilated by exercise or pharmacologic stress. Healthy arteries dilate to a greater degree than diseased arteries, so perfusion will be diminished in areas distal to CAD lesions.
In MPI, a radionuclide tracer, such as thallium-201 or a technetium-labeled agent, is injected into the bloodstream. Perfusion can then be visualized using a scintigraphic camera that shows the tracer. Higher tracer concentrations indicate more blood flow, while lower concentrations indicate less blood flow.
MPI with single-photon emission computed tomography (SPECT) has proven diagnostic and prognostic value in the assessment of CAD in women.7,8 MPI SPECT adds substantial incremental diagnostic and prognostic value over ETT in women7 and has been shown to identify relatively high-risk women even more accurately than their male counterparts.8 Therefore, it can play an important role in risk stratification and management of women.
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| Echocardiography
Echocardiography (echo) allows assessment of the cardiac chambers, myocardium, valves, pericardium, and great vessels by visualizing the heart in real time using ultrasound. Echo can also identify mechanical complications of acute myocardial infarction, differentiate causes of reduced cardiac output and blood pressure, and help guide therapy. Stress echo, using either exercise or pharmacologic stress, can be used to detect the presence, location, and severity of inducible ischemia. Stress echo can be used for both diagnosis and risk stratification of patients with known or suspected CAD.
Stress echo identifies CAD by induction of reduced regional systolic wall thickening when myocardial oxygen demand exceeds myocardial blood supply.65 This occurs before chest pain and ST-T changes, which gives echo a higher sensitivity than stress electrocardiography.65
The advantages of echo include no radiation exposure, widespread availability, and the possibility of using contrast agents to improve sensitivity and specificity.66 The main disadvantages of echo are its operator dependency, lack of reproducibility, and technical difficulties in obtaining quality images in patients with high thoracic impedance.66
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| Positron Emission Tomography
Positron emission tomography (PET) is another accurate method of assessing myocardial perfusion in screening for CAD. In PET scanning, perfusion images are taken after injection of a radionuclide tracer. PET provides high spatial resolution and accuracy in diagnosis of CAD, assessment of disease severity in specific arteries or branches, and tracking of CAD progression or regression.67 PET can also detect slight differences in perfusion that reflect mild stenosis of diffuse CAD as well as abnormal endothelial function associated with early or diffuse atherosclerosis.67
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| Algorithm for Noninvasive Testing
Figure 7 shows an algorithm for CAD screening in intermediate- to high-risk women that was recommended in a report of the American Society of Nuclear Cardiology Task Force on Women and Heart Disease.7
Figure 7. Algorithm for the Evaluation of Women With Suspected or Known CAD*7
*Women with intermediate to high likelihood of CAD, with chest pain symptoms (typical or atypical), dyspnea, or reduced activities of daily living.
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