Angina and heart attacks are caused by narrowings in the coronary arteries (blood vessels) supplying the heart. These narrowings can be opened using a balloon and stent (angioplasty). Traditionally, stents are constructed from metal and are permanent. However, newer stents are being constructed from carbohydrate polymers (scaffolds), which allow them to reabsorb over time leaving no permanent implant. New data has suggested that these scaffolds appear to reduce recurrent angina and may alter the blood flow down the artery. However, it is not known whether this is due to the scaffolds themselves or the way the scaffolds are inserted. In this study we hope to measure the blood flow to the heart and assess changes in that flow during stent and scaffold insertion. It is also important to know whether these effects are durable and thus, a cohort of patients will return at 3-months to be restudied. These data are important to help us understand why blood flow is affected by stent/scaffold selection or device implantation technique and whether this results in better long-term outcomes.

Inclusion Criteria:

1. Patient age >18 years, <75 years.
2. Lesion suitability for BVS deployment: target vessel calibre >2.3mm and <3.8mm reference diameter, without significant tortuosity or calcification.
3. Listed for single-vessel PCI procedure.
4. Lesion length≤28mm (to accommodate single BVS/DES)
5. Preserved left ventricular ejection fraction (EF≥50%).

Exclusion Criteria:

1. Patients with confirmed myocardial infarction within the preceding 2 months.
2. Allergy or intolerance to aspirin, clopidogrel, prasugrel or ticagrelor or contraindication to 12 months' dual antiplatelet therapy.
3. Contraindication to use of adenosine (asthma/chronic lung disease with documented bronchoreactivity).
4. Significant known comorbidity or terminal condition with life expectancy <6 months.
5. Pregnancy.
6. Coagulopathy or warfarin treatment.
7. Significant renal impairment (baseline creatinine>130 mmol/l).
8. Other comorbid condition that may affect microcirculatory function or troponin release (eg. Seropositive inflammatory conditions).
9. Inability to comply with follow-up requirements.
10. Target lesion in left mainstem, saphenous vein or arterial grafts.
11. Chronic total occlusion.