Isosorbide Mononitrate

The goal of this clinical trial is to learn if targeted medical therapy will improve symptoms and quality of life in patients with angina and non-obstructive coronary arteries compared to placebo, after the underlying cause of the chest pain has been ascertained by coronary function testing. Participants will be treated with either medications that target the underlying cause of their chest pain or placebo for 4 weeks after a drug titration phase of 1-3 weeks. They will be asked to complete a series of questionnaires to evaluate their quality of life at the beginning and end of the study.

Following unsuccessful CTO crossing a CTO modification procedure is sometimes performed. CTO PCI registries where plaque modification has been performed in some patients, report this to be safe, and associated with higher success rates at subsequent attempts. It has never been investigated whether a planned investment procedure, with an intention that both the initial and staged completion PCI are of shorter duration, could improve safety and efficacy. The investigators hypothesize that 1. A planned investment procedure in the treatment of CTOs will be associated with improved patient safety 2. A planned investment procedure will be associated with improved cumulative procedure success rates 3. A planned two stage procedure will be associated with improved patient experience

Background: Researchers are testing version of a system known as a magnetic resonance imagining (MRI) scanner that uses strong magnetic fields, radio waves and the like to create images of the organs in the body. It uses lower energy levels than other MRI scanners. This may help scan people with metal devices in their body, or in invasive heart procedures using metal tools. Objective: To test a new MRI scanner and software changes to create better pictures. Eligibility: People with disease and healthy volunteers, ages 18 and older. Design: Participants will be screened with blood tests. Participants may have both the new MRI and a conventional MRI or only the new one. If 2 are done, they must be within 60 days. For both MRI versions, participants lie on a table that slides into a large tube. During scans, they will hold their breath for up to 20 seconds at a time. Heart activity will be measured by wires connected to pads on the skin. A flexible belt may be used to monitor their breathing. They will be in the scanner up to 2 hours. Participants can agree to have a dye called gadolinium injected into their arm during the scan. This brightens the pictures. Participants can agree to take a drug called a vasodilator. This helps detect areas of the heart with abnormal blood supply. Scans of the heart are taken before, during, and after they get the medicine. The drug may cause temporary chest pain or shortness of breath. They may get other drugs to relieve these symptoms. Sponsoring Institution: National Heart, Lung, and Blood Institute