These studies suggest that the higher mortality rate of patients with multivessel disease could occur because they have more mildly stenotic or nonstenotic plaques that are potential sites for acute coronary events than do patients For many years, it has been known that patients with severe stenosis of the left main coronary artery have a poor progno- sis when treated medically. A gradation of worsening risk also has been found with increasing degrees of stenosis of the left main in medically managed patients.380 382 Angiographic determination of the significance of left main disease can be difficult, with suboptimal intraobserver agreement with re- gard to the degree of severity of any given stenosis.381,383,384 However, multiple other modalities are available to the angiographer to assist in accurately determining the signifi- cance of a left main lesion (ie, FFR and intravascular ultrasound). Despite the challenges posed by angiographic determination of left main disease, it remains the best option for the diagnosis and reevaluation of left main disease if concern exists about progression of previously diagnosed disease because of the inability to consistently detect and evaluate this condition with noninvasive testing or clinical 4.1. Definition of Successful Treatment The paramount goals of treating patients with SIHD are to minimize the likelihood of death while maximizing health and function. The more specific objectives are to: Table 14. Noninvasive Risk Stratification High risk (3% annual death or MI) 1. Severe resting LV dysfunction (LVEF 35%) not readily explained by noncoronary causes 2. Resting perfusion abnormalities 10% of the myocardium in patients without prior history or evidence of MI 3. Stress ECG findings including 2 mm of ST-segment depression at low workload or persisting into recovery, exercise-induced ST-segment elevation, or exercise-induced VT/VF 4. 