Following unsuccessful CTO crossing a CTO modification procedure is sometimes performed. CTO PCI registries where plaque modification has been performed in some patients, report this to be safe, and associated with higher success rates at subsequent attempts.

It has never been investigated whether a planned investment procedure, with an intention that both the initial and staged completion PCI are of shorter duration, could improve safety and efficacy.

The investigators hypothesize that

1. A planned investment procedure in the treatment of CTOs will be associated with improved patient safety
2. A planned investment procedure will be associated with improved cumulative procedure success rates
3. A planned two stage procedure will be associated with improved patient experience

Inclusion Criteria:

• Ability to provide written informed consent
• Comply with the procedural and study follow-up schedule
• Planned CTO PCI in accordance with the European and American appropriateness criteria.
• CTO defined as high-risk

Exclusion Criteria:

• Non-high risk CTO
• Occlusion within a stent
• Flush aorto-ostial occlusion of RCA and Left Main (LMS)
• Limited arterial access precluding repeat procedure
• Baseline non invasive testing showing non-viable target vessel territory
• Contra-indication to dual antiplatelet therapy
• Pregnancy
• Prior radiation skin injury
• Lack of informed consent