Transient myocardial ischemia and its relation to determinants of myocardial oxygen demand. Because of conflicting data and a clear need to establish the relative role of increase in myocardial oxygen demand versus reduction in coronary blood flow in the causation of transient ischemia, the role of heart rate and blood pressure changes immediately preceding and during the transient ischemic events observed during daily life were evaluated in 25 patients with coronary artery disease. Elevations in heart rate before onset of ischemia were observed in 61% of the episodes. Similarly, 73% of the ischemic events were preceded by an increase in arterial pressure. These data provide evidence for a significant role of increased myocardial oxygen demand in the genesis of transient myocardial ischemia. 