Although medical therapy and revascularization procedures are effective for relief of chest pain symptoms in many patients with coronary artery disease (CAD), others either do not respond to or tolerate medical therapies, or have failed attempts at revascularization. For this growing number of patients, there is a need for novel therapeutic approaches. The purpose of this protocol is to test the effectiveness of nitric oxide (NO) inhalation for the relief of inducible myocardial ischemia in patients with CAD who have failed conventional attempts at medical and revascularization management. Our hypothesis is that enriched NO transport in blood from the lungs and delivery to the coronary vasculature with NO inhalation will improve blood flow to the myocardium during stress by dilating coronary arteries and arterioles. The primary end-point of this study is improvement in treadmill exercise duration during NO inhalation compared with exercise duration during room air breathing, with secondary end-points selected to provide mechanistic insight as to relief of inducible ischemia by NO, including effects on: 1) arterial delivery and myocardial extraction of NO transport molecules, 2) myocardial perfusion, and 3) global and regional myocardial contractility. This clinical trial is randomized, double-blind, and placebo (room air)-controlled in design, with CAD patients treated with NO (or room air) breathing for approximately1 hour before each stress test, followed by crossover to the alternate therapy after two days of testing. Demonstration of benefit from NO inhalation could result in an important therapeutic option for CAD patients with few alternatives for the relief of myocardial ischemia.
