ORBITA-SOLAR is an invasive physiological cardiac catheterisation study that aims to determine whether different coronary stenoses have different angina thresholds. The angina threshold is defined as the amount of coronary flow reduction required to reproduce symptoms. Sixty patients with symptoms of stable angina and 2 coronary artery stenoses amenable to percutaneous coronary intervention (PCI) will be recruited. This study will use intra-coronary balloon inflation during supine exercise on an ergometer to measure the fractional flow reserve (FFR) and non-hyperemic pressure ratio (NHPR) that relates to angina onset, in real time, at the location of each stenosis.

Inclusion Criteria:

1. Eligibility for PCI due to angina or angina-equivalent symptoms on exertion

2. 2 severe epicardial stenoses in a major coronary artery, defined as:

   1. ≥70% stenosis in a coronary artery with ≥2.5mm diameter, on invasive coronary angiography (ICA)
   2. Severe stenosis in a vessel with ≥2.5mm diameter, on CTCA

3. Evidence of ischaemia on an invasive or non-invasive test, including:

   1. Physiological test during invasive coronary angiography (ICA)
   2. Dobutamine stress echocardiography (DSE)
   3. Stress perfusion cardiac magnetic resonance (CMR)
   4. Myocardial perfusion scintigraphy (MPS)
   5. Fractional flow reserve computed-tomography (FFR-CT)

Exclusion Criteria:

1. Age <18 years
2. Acute coronary syndrome within 3 months
3. Previous coronary artery bypass graft
4. Significant left main stem disease
5. Single lesion amenable to PCI
6. Chronic total occlusion of the target artery
7. Moderate to severe valve disease
8. LVEF ≤40%, contraindication to PCI or drug-eluting stents
9. PCI performed with drug-eluting balloons without stenting
10. Contraindication to antiplatelet therapy
11. Contraindication to adenosine
12. Physical inability to exercise with an ergometer
13. Femoral artery access
14. Pregnancy
15. Inability to consent

During cardiac catheterisation, there will be one blinded component to verify the reproducibility of symptoms against placebo. One true and one placebo balloon inflation will be performed, in a randomised order. Both the participant and outcome assessor will be blinded to the order of true or placebo balloon inflation. The participant will be asked to report any symptoms they have.