Dietary Nitrate and Nitrite to Increase Nitric Oxide in Patients With Coronary Artery Disease

This study will determine whether dietary nitrates and nitrites can produce nitric oxide in the body and dilate blood vessels in patients with coronary artery disease. Nitric oxide is normally made by endothelial cells that line blood vessels. It plays an important role in maintaining the normal function of arteries by keeping them open and preventing damage from substances such as cholesterol in the blood stream. Coronary artery disease is caused by atherosclerosis (hardening of the arteries or build-up of cholesterol and scar tissue within the walls of the arteries). Once arteries become clogged, the ability of the endothelium to produce nitric oxide diminishes considerably and may speed up the disease process, leading to shortness of breath, chest pain, and an increased risk of heart attack or stroke. Patients 21 years of age and older with coronary artery disease may be eligible for this study. Participants will have a medical history and physical examination, electrocardiogram (recording of the electrical activity of the heart), echocardiogram (ultrasound test of the heart), treadmill exercise stress test (see below), and will meet with a dietitian. They will be hospitalized at the NIH Clinical Center on two occasions. For 1 week before each admission, they will follow a diet prescribed by an NIH nutritionist. The diet before one admission will be high in nitrates and nitrites, and the diet before the other admission will be low in nitrates and nitrites. Each admission will last 4 days, during which participants will undergo the following tests: * Forearm blood flow study: Small tubes are placed in the artery and vein at the inside of the elbow of the dominant arm (right- or left-handed) and a small tube is placed in a vein of the other arm. The tubes are used for infusing saline (salt water) and for drawing blood samples. A pressure cuff is placed around the upper part of the dominant arm, and a rubber band device called a strain gauge is also placed around