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. In addition to clinical signs and symptoms, findings on noninvasive studies could also suggest that certain patients are at high risk of serious cardiac events. These findings include abnormal physiological re- sponse to exercise or imaging studies that suggest extensive myocardial ischemia (Table 14). Some examples from Table 14 (high-risk category) which may suggest somewhat less extensive myocardial ischemia: CCTA 2-vessel disease, CAC score .400 Agatston units, severe resting LV dysfunction (LVEF ,35%) not readily explained by noncoronary causes, stress defects at 10% level, 2 coronary beds wall motion abnormality on stress echocardiography but only 2 segments. Coronary angiography helps to quantify risk on the basis of an anatomic prognostic index; the simplest and most widely used is the classification of disease into 1-, 2-, or 3-vessel or left main CAD.358,375 377 In the CASS registry364 of medically treated patients, the 12-year survival rate of patients with normal coronary arteries was 91%, compared with 74% for those with 1-vessel disease, 59% for those with 2-vessel disease, and 40% for those with 3-vessel disease. The probability of survival declines progressively with the num- ber of coronary arteries that are occluded. The presence of severe proximal LAD artery disease significantly reduces the survival rate. The 5-year survival rate with 3-vessel disease plus .95% proximal LAD stenosis was reported to be 59%, as compared with a rate of 79% for 3-vessel disease without LAD stenosis (Table 13). 