1.3.6.5 Do not use exercise ECG to diagnose or exclude stable angina for people without known CAD. [2010] 1.3.7 Making a diagnosis following investigations Box 1 Definition of significant coronary artery disease Significant coronary artery disease (CAD) found during CT coronary angiography is 70% diameter stenosis of at least one major epicardial artery segment or 50% diameter stenosis in the left main coronary artery: Factors intensifying ischaemia Such factors allow less severe lesions (for example, 50%) to produce angina: reduced oxygen delivery: anaemia, coronary spasm increased oxygen demand: tachycardia, left ventricular hypertrophy large mass of ischaemic myocardium: proximally located lesions longer lesion length. Factors reducing ischaemia which may render severe lesions ( 70%) asymptomatic: Well-developed collateral supply. Small mass of ischaemic myocardium: distally located lesions, old infarction in the territory of coronary supply. [2016] 1.3.7.1 Confirm a diagnosis of stable angina and follow the NICE guideline on stable angina when: significant CAD (see box 1) is found during invasive or 64-slice (or above) CT coronary angiography or reversible myocardial ischaemia is found during non-invasive functional 1.3.7.2 Investigate other causes of chest pain when: significant CAD (see box 1) is not found during invasive coronary angiography or 64-slice (or above) CT coronary angiography or reversible myocardial ischaemia is not found during non-invasive functional 1.3.7.3 Consider investigating other causes of angina, such as hypertrophic cardiomyopathy or syndrome X, in people with typical angina-like chest pain if investigation excludes flow-limiting disease in the epicardial coronary arteries. [2010] Terms used in this guideline Chest pain The term 'chest pain' is used throughout the guideline to mean chest pain or discomfort. Recommendations for research In 2010, the guideline committee made the following recommendations for research. The committee's full set of recommendations for research is detailed in the full guideline. 