During exercise, coronary blood ±ow can increase as much as Šve times above the resting value. A patient with coronary artery disease might not be able to increase coronary ±ow to the affected coronary beds, causing an imbalance between the myocardial oxygen demand and the myocardial oxygen supply. Myocardial oxygen demand increases proportionally to the product of heart rate and systolic blood pressure called the double product (DP) or rate pressure product (RPP). Angina (chest pain) at peak exercise intensity requires greater than 50-70% obstruction of a coronary artery. At rest, angina requires 90% obstruction. Factors such as coronary vasoconstriction and platelet Šbrin deposition will further decrease the coronary blood ±ow. Moderate exercise decreases and high-intensity exercise increases platelet adhesiveness. Angina at rest, triggered by emotions and silent ischemia (electrocardiographic evidence of ischemia without chest pain), is thought to have a signiŠcant vasoconstrictor component.