In clinical practice the non-invasive diagnosis of "coronary heart disease" is based on the clinical findings, the detection of ischemia at rest or during exercise, and elevations of cardiac enzymes. However, due to the compensatory enlargement of the vessel diameter at the beginning of plaque growth, the so-called Glagov effect, early stages of plaque development are missed by the angiography. By means of coronary angiography, changes of the coronary arteries become visible only in patients with angiographically recognizable lumen narrowing compared to the reference vessel segment. Thus, early or diffuse stages of atherosclerosis cannot be detected by ECG, stress-tests or coronary angiography. This limitation explains discrepancies, like positive troponin-test and even transmural ischemia, without angiographic visible coronary lumen narrowing. Diagnostic procedures such as intravascular ultrasound, optical coherence tomography, measurements of vasomotion and computed tomography can, in contrast, detect earlier stages of coronary artery disease and thus contribute to clarification in these patients. In addition, plaque rupture and plaque-erosion lead to acute or recurrent microembolism to distal myocardium with subsequent myocardial necrosis. In patients with formerly unexplained cardiovascular events, intravascular ultrasound, optical coherence tomography, and measurements of vasomotion help to understand the underlying pathophysiology. In the report after cardiac catheterization, the term "ruled out coronary heart disease" should be replaced by "No signs of obstructive coronary heart disease" and additional testing should be performed as necessary.
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