Background:The risk of peri-procedural myocardial infarction (MI) during percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs) is reported to be low, however it may be underestimated because systematic cardiac biomarker measurement was not performed in prior studies. Methods: We retrospectively examined the incidence of peri-procedural MI among 325 consecutive CTO PCIs performed at our institution between 2006 and 2012. Creatine kinase MB fraction (CK-MB) and troponin T or I was measured before PCI and after 8-12 and 18-24 hours in all patients. Myocardial infarction was defined as CK-MB increase Ͼ3x upper limit of normal. Results: Mean age was 64 Ϯ10 years, 99 % or patients were men, 47% had diabetes, 26 % had prior coronary artery bypass graft surgery and 47% had prior PCI. The CTO target vessel was the right coronary artery (56%), left anterior descending artery (21.5%), circumflex (20.5%), and left main or bypass graft (1%). The retrograde approach was used in 26.3% of all procedures. The technical and procedural success rates were 77.2% and 76%, respectively. The mean procedural time, fluoroscopy time, radiation dose and contrast utilization was 141Ϯ72 minutes, 40Ϯ22 minutes, 4.6Ϯ2.4 Gray and 356Ϯ146 ml, respectively. Peri-procedural MI occurred in 28 of 325 patients (8.6%). Seven of those patients had ischemic symptoms. The prevalence of peri-procedural cardiac troponin elevation Ͼ3x, Ͼ10x, and Ͼ20x upper limit of normal was 57%, 24% and 7.6%, respectively. The incidence of peri-procedural MI was similar among patients with procedural failure vs. procedural success (11.8% vs. 7.6%, pϭ0.26), but was higher with the retrograde compared to the antegrade approach (13.8% vs. 6.7%, pϭ0.04). Conclusions: Systematic measurement of cardiac biomarkers post CTO PCI demonstrates that peri-procedural MI occurs in 8.6% of patients and is more common with the retrograde approach.Background: Percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs) is a rapidly evolving area of interventional cardiology. We examined the outcomes of CTO PCI from a multicenter United States registry. Methods: We retrospectively examined the procedural outcomes of 1363 consecutive CTO PCIs performed at 3 US institutions [St. Joseph Medical Center, Bellingham Washington (nϭ728), Piedmont Hospital, Atlanta Georgia (nϭ361) and VA North Texas Healthcare System, Dallas, Texas (nϭ275)] between January 2006 and November 2011. Results: Mean age was 65Ϯ10 years, 85% or patients were men, 40% had diabetes, 37% had prior coronary artery bypass graft surgery and 42% had prior PCI. The CTO target vessel was the right coronary artery (55%), circumflex (23%), left anterior descending artery (21%), and left main or bypass graft (1%). The retrograde approach was used in 34.4% of all procedures. The technical and procedural success rate was 85.5% and 84.2%, respectively. The mean procedural time, fluoroscopy time and contrast utilization was 114Ϯ63 minutes, 42Ϯ 29minutes, and 296Ϯ160 ml, respectively. A major procedural ...