The Physiological Impact of CTO PCI on Coronary Pressure Measurements and Correlation in Donor Vessel

Inclusion Criteria: 1. Age \>18 years of age 2. Stable angina / ischaemic symptoms 3. Evidence of viability and / or ischaemia in the chronic total occlusion (CTO) territory 4. Participant is willing and able to give informed consent for participation in the study 5. Presence of a chronic total occlusion (CTO) in RCA: * Duration of the occlusion \> 3 months; * Thrombolysis In Myocardial Infarction (TIMI) (50) coronary flow grade 0; * Spontaneously visible collaterals, Rentrop classification grade 1 or 2 or 3 from contralateral donor artery 6. Presence of minor to intermediate coronary stenosis (1-70 %) in the contralateral donor artery 7. Eligible for PCI to a chronic total occlusion (CTO) Exclusion Criteria: 1. Previous CABG with patent grafts to the interrogated donor artery 2. Left main stenosis of \> 40 % 3. Presence of severe flow limiting stenosis in the contralateral donor artery (typically \> 70 % stenosis) 4. Haemodynamic instability at the time of intervention (heart rate \<40 beats per minute, systolic blood pressure \<90mmHg), balloon pump) 5. Significant contraindication to adenosine administration (e.g. heart block, severe asthma) 6. Contraindications to PCI 7. Severe hepatic or lung disease (chronic pulmonary obstructive disease) 8. Pregnancy 9. ACS within 48 hours of procedure 10. Severe valvular heart disease 11. Severe cardiomyopathy / Infiltrative heart disease 12. eGFR \< 40