Anatomical and Functional Targets of Stress Testing

The principle of stress under controlled conditions derives from the Industrial Revolution: metallic materials undergo endurance tests to identify the breaking load. This approach identifies structural defects that – although occult in the resting or static state – might show up under real-life loading conditions, leading to a dysfunction of the industrial product. In the same way, a patient with normal findings at rest undergoes a stress test to identify any potential vulnerability of the myocardium to ischemia, if there is clinical suspicion of ischemic heart disease. Myocardial ischemia is the final common pathway of various morphological and functional substrates. In order to describe the pathways of ischemia, the normal heart can be conveniently schematized into its three fundamental anatomical components, each a potential target of pathological conditions leading to ischemia: epicardial coronary arteries, myocardium, and small coronary vessels. Epicardial coronary artery stenoses produce selective stress-induced subendocardial hypoperfusion, which is especially important for stress echocardiography applications, since regional systolic thickening is linearly and closely related to subendocardial perfusion and only loosely related to subepicardial hypoperfusion.