These investigators also found only 70% overall agreement among readers with regard to the severity of stenosis, and this was reduced to 51% when restricted to coronary vessels rated as having some stenosis by any reader. Third, angiography in isolation provides only anatomic data and is not a reliable indicator of the functional significance of a given coronary stenosis unless a technique such as FFR (discussed below) is used to provide information about the physiological significance of an anatomic stenosis. Lastly, coronary angiography does not distinguish between a vulner- able plaque, with a large lipid core, thin fibrous cap, and increased macrophages, and a stable plaque that does not exhibit these features. Serial angiographic studies performed before and after acute events and early after MI suggest that plaques resulting in UA and MI commonly were found to be ,50% obstructive before the acute event and were therefore angiographically silent. 370,371 Diagnostic test- ing to determine vulnerable plaque, and therefore the subsequent risk for MI, remains intensely studied, but no gold standard yet has emerged.372 Despite these limita- tions of coronary angiography, the extent and severity of CAD remain very significant predictors of long-term patient outcomes (Table 13).55,70,71,373,374 For patients who are found to be at high risk of coronary events or death on the basis of clinical data and noninvasive testing, coronary angiography is often warranted to provide a more complete risk assessment even though cardiac symp- toms might not be severe. Certain clinical characteristics, though relatively infrequent in patients with IHD, have been associated with a high likelihood of severe disease, including the following: chest pain leading to pulmonary edema, chest pain associated with lightheadedness, syncope or hypoten- sion, exertional syncope, and an exercise-induced gallop sound on cardiac auscultation. 