Timing and triggers of transient myocardial ischemia. Use of exercise tolerance testing and new techniques of ambulatory electrocardiographic monitoring to more objectively measure myocardial ischemia have enabled clinicians to better recognize the magnitude, timing and variable characteristics of transient ischemic events. These commonly occurring events in patients with coronary artery disease have a diurnal pattern strikingly similar to that reported for catastrophic cardiovascular events such as myocardial infarction, sudden cardiac death and stroke. Whether those factors that contribute to reversible ischemic events are similar to those causing infarction and sudden death has not been resolved. However, the parallel increase in morning activity for these related phenomena suggests that a better understanding of the triggers of reversible myocardial ischemia may help improve understanding of the causes of myocardial infarction and sudden cardiac death. 