Protocol Number: 03-H-0312
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 the arm to measure blood flow. When the cuff is inflated, blood flows into the arm, stretching the strain gauge at a rate proportional to the flow. Maximum grip-strength of the dominant arm is measured with a dynamometer. Forearm blood flow is measured and blood samples are drawn at the following times: 20 minutes after the tubes are placed; during a hand-grip exercise; and 4 minutes after the exercise is completed. - Brachial artery reactivity study: This test measures how well the patient's arteries widen. For the procedure, the patient rests on a bed for 30 minutes. An ultrasound measuring instrument is then placed over the artery just above the elbow. The artery size and the flow of blood through it are measured before and after a pressure cuff around the forearm is inflated. Fifteen minutes later, the same measurements are taken before and 3 minutes after a nitroglycerin tablet is placed under the patient's tongue. Treadmill exercise testing: Patients exercise on a treadmill until they experience chest pain, shortness of breath, or tiredness. The patient's heart rhythm is monitored continuously and blood pressure is measured every 3 minutes. A nurse and doctor are in attendance throughout the study.
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