Coronary and Peripheral Haemodynamic Studies of Angina with No Obstructive Coronary Artery Disease - association between invasive and non-invasive investigation modalities.

This study is looking at chest pain (angina) in people whose coronary arteries appear normal or nearly normal on a heart scan — a condition called angina with no obstructive coronary artery disease (NoCAD). Despite having no major blockages, many of these patients continue having chest pain. The study will use invasive and non-invasive heart tests to understand whether problems with tiny heart blood vessels (microvascular disease) are causing the symptoms, and whether a non-invasive ultrasound test (stress echocardiography) can reliably detect these problems. You may be eligible if: - You are aged 18 to 80 years - You have been clinically diagnosed with angina (chest pain) - You have ongoing (persistent) angina symptoms - Your coronary angiogram shows no significant blockages (less than 50% narrowing) You may NOT be eligible if: - You had an acute heart attack or coronary syndrome within the past month - You have had coronary artery bypass surgery - You have a pacemaker or defibrillator - You have severe kidney or liver disease, severe asthma, or weak heart function (ejection fraction below 50%) - Your chest pain is caused by an identified blockage or other structural heart condition Talk to your doctor about whether this trial might be right for you.