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The pathophysiology of myocardial ischemia involves a series of progressive changes from the cellular level through perfusion abnormalities, contractile dysfunction, electrocardiographic abnormalities, and finally symptoms. In clinical practice, it has multiple potential manifestations, with atherosclerotic coronary disease being the most important underlying etiology. Uncovering these abnormalities or their underlying causes requires selection of the most appropriate stress method depending on the question being asked, and the clinical status of the patient. A sound understanding of the principles of imaging will contribute to informed interpretation of test results. Only by integrating knowledge of the pathophysiology of myocardial ischemia, the role of the various stress modalities, and the strengths and weaknesses of the available imaging technologies will the best possible test be selected for each patient.

Echocardiography is an important tool for patients with CAD. It can be used to differentiate regional myocardial ischemia from other etiologies of chest pain, can be used to evaluate the extent of myocardial dysfunction, at rest and with stress, and to ascertain the presence of complications in patients with acute myocardial infarction. With the prospect of identifying myocardial perfusion defects, echocardiography is clearly an approach that can provide a “one-stop” strategy for assessing cardiac anatomy, function, and perfusion.

Stress echocardiography and MPS are clinically useful tools for selection of patients with known or suspected CAD who are likely to benefit from revascularization. Both imaging modalities are the mainstay tests for the diagnosis of in-stent stenosis and graft disease and are integral parts of the investigative strategies recommended by both European and American guidelines. However, CMR and multislice computed tomography are increasingly used for this purpose in centers with access to these techniques. Myocardial perfusion and wall motion abnormalities after myocardial revascularization are predictive of cardiac events and the risk associated with these abnormalities is not related to symptoms.

Consider a linear time-invariant system with the following dynamics: where () ∈ ℝ is the state vector at time , ∈ ℝ is the initial state, and is a constant known matrix with appropriate dimension. The stability of this class of systems has been extensively studied and many interesting results can be used to check the stability of a given system of this class. Lyapunov equations or equivalent LMI conditions are often used to check stability.

Stress echocardiography and MPS are clinically useful tools for selection of patients with known or suspected CAD who are likely to benefit from revascularization. Both imaging modalities are the mainstay tests for the diagnosis of in-stent stenosis and graft disease and are integral parts of the investigative strategies recommended by both European and American guidelines. However, CMR and multislice computed tomography are increasingly used for this purpose in centers with access to these techniques. Myocardial perfusion and wall motion abnormalities after myocardial revascularization are predictive of cardiac events and the risk associated with these abnormalities is not related to symptoms.

EBCT is a highly sensitive technique for detection and measurement of coronary artery calcification and thus noninvasive estimation of atherosclerotic plaque burden. It offers a high spatial resolution with low acquisition time and has good reproducibility and interobserver agreement with optimized ECG triggering. EBCT is a mature technique for calcium detection with a continuously expanding literature. With growing technological advances, cardiac CT has a promising role in clinical practice as well as research.

The ability of CT imaging to visualize and measure disease process in the coronary arteries has increased our knowledge of atherosclerosis and coronary heart disease. Beyond feasibility studies, further well-designed, prospective single or multicenter studies are required to assess the diagnostic performance of MS-CT in various patient populations with different levels of prevalence of coronary artery disease and to establish the diagnostic role of MS-CT in cardiology before we embrace this promising technique as a clinically acceptable new diagnostic tool. Moreover, the fundamental characteristics of MS-CT such as the X-Y spatial resolution, slice thickness, and temporal resolution need to be further optimized to consider MS-CT coronary angiography as a reliable clinical diagnostic tool to detect coronary atherosclerotic obstructions. In particular, the temporal resolution needs improvement to meet the challenges of motion-free imaging also during faster heart rates.

Cardiovascular risk estimates can be improved by several noninvasive imaging techniques, collectively called atherosclerosis imaging. Clinically useful techniques currently include coronary calcium imaging and carotid ultra sound. Both these tests are most valuable in intermediate-risk patients, in whom a significant proportion will be reassigned into either a higher- or lower-risk category. However, before widespread adoption of any of these techniques takes place, studies to establish treatment protocols based on atherosclerosis imaging tests and to determine the cost-effectiveness of atherosclerosis imaging tests are needed.

Echocardiography provides useful information for high-risk asymptomatic patients. When combined with stress, a powerful prognostic tool is available that can unmask previously undiagnosed CAD. The application of this to screening is constrained by overall low disease probability in unselected asymptomatic patients, but the use of clinical tools, such as the Framingham risk score, can define a subgroup, which will be enriched with high-risk individuals.

We have examined the role of SE and other imaging modalities in various high-risk subgroups. Overall, SE seems to have a good predictive value comparable to that of MPS and in certain cases may avoid the need for coronary angiography. For those who have abnormalities on a noninvasive imaging test and are asymptomatic, a management plan needs to be defined. This includes a choice of addressing cardiac risk factors, or invasive assessment of coronary anatomy by angiography with a view to possible revascularization if necessary. In many of the high-risk subgroups we have discussed, the decision to proceed to revascularization is hampered by the lack of large randomized trials to support this approach. Although SE and MPS can provide prognostic data in high-risk subgroups, further clarification with multicenter studies is required to assess under what circumstances revascularization can alter prognosis in high-risk patients who are truly asymptomatic.

Echocardiography provides useful information for high-risk asymptomatic patients. When combined with stress, a powerful prognostic tool is available that can unmask previously undiagnosed CAD. The application of this to screening is constrained by overall low disease probability in unselected asymptomatic patients, but the use of clinical tools, such as the Framingham risk score, can define a subgroup, which will be enriched with high-risk individuals.

We have examined the role of SE and other imaging modalities in various high-risk subgroups. Overall, SE seems to have a good predictive value comparable to that of MPS and in certain cases may avoid the need for coronary angiography. For those who have abnormalities on a noninvasive imaging test and are asymptomatic, a management plan needs to be defined. This includes a choice of addressing cardiac risk factors, or invasive assessment of coronary anatomy by angiography with a view to possible revascularization if necessary. In many of the high-risk subgroups we have discussed, the decision to proceed to revascularization is hampered by the lack of large randomized trials to support this approach. Although SE and MPS can provide prognostic data in high-risk subgroups, further clarification with multicenter studies is required to assess under what circumstances revascularization can alter prognosis in high-risk patients who are truly asymptomatic.