**12. Clinical outcome data**

Successful CTO PCI and improvement in survival strongly depend on the target vessel. So far, only CTO PCI of the LAD seems to be associated with improved long-term survival [76]. From a 20-year experience of CTO PCI, Suero et al. reported improved procedural and long-term outcome [64] which was in line with more recent data from Aziz et al. who revealed CTO failure as an independent predictor of death and a higher rate of subsequent CABG (3.2 vs. 21.7%, *P* < 0.001) [140]. The result from Aziz could be confirmed by Mehran et al. (long-term clinical outcomes in 1791 patients who underwent PCI of 1852 CTOs) and Jones et al. (6996 patients underwent elective PCI for stable angina with 11.9% for CTO) who both demonstrated an association of successful CTO revascularization with reduced long-term cardiac mortality (all-cause mortality: 17.2% for unsuccessful CTO PCI vs 4.5% for successful CTO PCI [220], and 8.6 vs. 6.0%, [221] respectively) and the need for CABG surgery at a 5-year follow-up (with similar rates as Suero et al.) [220, 221]. Other studies, however, did not show a mortality benefit for successful CTO PCI compared with failed PCI [222].

In the Swedish Coronary Angiography and Angioplasty Registry (SCAAR), CTO was associated with increased overall mortality and considered to be the highest risk in patients under 60 years of age. Furthermore, the risk attributable to CTO was highest in the STEMI subgroup, and the authors reported no interaction between CTO and either diabetes or sex [223].

A metaanalysis of CTO PCI on clinical outcomes including 13 observational studies and 7288 patients with a weighted average follow-up of 6 years [77] showed a significant lower mortality, residual or recurrent angina, and subsequently CABG rate after successful CTO PCI.

Another meta-analysis of procedural effects on clinical outcomes after CTO PCI in over 12,000 patients with a mean follow-up of 3.7 ± 2.1 years [224] showed a PCI success rate of 71.2% with a significant reduction of all-cause mortality and MACE in this group. Nevertheless, successful CTO PCI was associated with a higher risk of TVR but reduction of subsequent CABG. Recently, Christakopoulos et al. reported from the largest metaanalysis, including over 28,000 patients [225] as well an improvement of clinical outcomes (mortality, MI, CABG, stroke, and angina but not TVR) after successful PCI, regardless of the revascularization technique (balloon angioplasty, BMS, or DES).
