In the second component, the investigators are examining whether married patients show reduced duration of ischemia compared to unmarried patients. In addition, they plan to examine whether presence of a supportive other (spouse, or friend in the case of unmarried patients) reduces the incidence and duration of ischemia in patients during daily life activities. Patients are asked to keep a detailed diary for a two week period to ascertain patterns of daily activities. Using these diaries and in consultation with patients, the investigators are selecting a two day period during which patients have a busy and varied schedule. Patients are then asked to follow the same pattern of activities for a 48 hour period on two consecutive weeks when heart rate, and the incidence and duration of ischemia are measured. During one week their spouse, in the case of married patients, or friend, in the case of unmarried patients, is present; during the other week patients are to repeat the activities alone.