Percutaneous Coronary Intervention is a common treatment for obstructive coronary artery disease, in both planned and emergency settings. Its use in the United Kingdom and elsewhere has increased dramatically in recent years due to its efficacy in the management of Acute Coronary Syndromes, increased access to PCI services, and more permissive patient selection practices. Further, a patient undergoing PCI now is likely to be treated quite differently than the same patient ten years ago, with the emergence of new interventional techniques, devices, stent types, and drugs. The widespread adoption of transradial access in favour of transfemoral access in particular has marked a new era in the delivery of PCI in the UK. Due to the rapid changes in patient and treatment characteristics, evidence generated in settings that no longer reflect the radial era is increasingly irrelevant. This thesis addresses this evidence deficit using data from the British Cardiovascular Intervention Society national PCI registry to describe contemporary trends in PCI practice and investigate the potential implications of these trends on the quality of PCI delivery. It focuses on the relationship between procedural volume, arterial access site, and short-term mortality which has not been explored in radial-era UK practice. Broadly, three research questions were posed: (1) What are the qualities and limitations of the British Cardiovascular Intervention Society PCI Registry in answering questions about routine clinical practice in the United Kingdom? (2) What is the impact on PCI outcomes of changes to the underlying patient population, changes to the selection of these patients, and changes to the treatment of these selected patients? (3) What are the consequences of these changes on the relationship of procedural volume and access site on outcomes? This thesis has showed that those centres adopting radial access more readily did not experience a decline in femoral quality, and in the most recent period were associated with better outcomes overall, particularly amongst the highest volume centres. Operator volume itself however was not associated with improved outcomes, suggesting the organisation of PCI services is not leaving operators with too few, or too many, procedures to perform competently. The current trajectory in UK practice of increasing radial adoption should continue unabated, with radial access considered as the primary access route across all clinical settings wherever possible.