Assessment of the ERCTO Score for Predicting Success in Retrograde Chronic Total Occlusion Percutaneous Coronary Interventions in the PROGRESS-CTO Registry.

BACKGROUND: The retrograde strategy is a common approach used in complex chronic total occlusion (CTO) percutaneous coronary intervention (PCI). The ERCTO Retrograde score is a tool that aims to predict the likelihood of technical success for retrograde CTO PCI procedures by evaluating 5 parameters: calcification, distal opacification, proximal tortuosity, collateral connection classification, and operator volume. METHODS: We evaluated the performance of the ERCTO Retrograde score using data from 2341 patients enrolled in the Prospective Global Registry for the Study of Chronic Total Occlusion Intervention (PROGRESS-CTO) at 35 centers between 2013 and 2023. RESULTS: Retrograde CTO PCI was the primary crossing strategy in 871 cases (37.2%) and a secondary crossing strategy in 1467 cases (62.8%). Technical success was achieved in 1,810 cases (77.3%). The technical success rate was higher for primary retrograde cases compared with secondary retrograde cases (79.8% vs 75.9%; P=.031). The ERCTO Retrograde score was positively associated with the likelihood of procedural success. The c-statistic of the ERCTO retrograde score was 0.636 (95% confidence intervals [CI]: .610-.662) for all cases and 0.651 (95% CI: .607-.695) for primary retrograde cases. CONCLUSIONS: The ERCTO Retrograde score has modest predictive capacity for technical success in retrograde CTO PCI.

Stress perfusion cardiovascular magnetic resonance and serial fractional flow reserve assessment of the left anterior descending artery in patients undergoing right coronary artery chronic total occlusion revascularization.

BACKGROUND: Fractional flow reserve (FFR) assessment of remote arteries, in the context of a bystander chronic total occlusion (CTO), can lead to false positive results. Adenosine stress cardiovascular magnetic resonance (CMR) evaluates perfusion defects across the entire myocardium and may therefore be a reliable tool in the work-up of remote lesions in CTO patients. The IMPACT-CTO study investigated donor artery invasive physiology before, immediately post, and at 4 months following right coronary artery (RCA) CTO percutaneous coronary intervention (PCI). The aim of this subanalysis was to assess the concordance between baseline perfusion CMR and serial FFR evaluation of left anterior descending artery (LAD) ischemia in patients from the IMPACT-CTO study. METHODS: Baseline adenosine stress CMR examinations from 26 patients were analyzed for qualitative evidence of LAD ischemia. The results were correlated with the serial LAD FFR measurements. RESULTS: The present findings demonstrated that before RCA CTO PCI, there was 62% agreement between perfusion CMR and FFR (ischemic threshold £ 0.8) in the assessment of LAD ischemia (k = 0.29; fair concordance). At 4 months after revascularization, there was 77% agreement (k = 0.52; moderate concordance) between the index CMR assessment of LAD ischemia and the follow-up LAD FFR. Concordance was improved at a LAD FFR ischemic threshold of £ 0.75. CONCLUSIONS: In this hypothesis generating study, baseline CMR assessment of LAD ischemia correlated better with the 4 months LAD FFR data (threshold £ 0.8) as compared to the FFR measurements taken prior to RCA CTO revascularization.

Echocardiographic assessment of left ventricular function recovery post percutaneous coronary intervention of chronic total occlusions in patients with low and mid-range left ventricular ejection fractions.

OBJECTIVES: Coronary chronic total occlusion (CTO) is a frequent condition encountered in cardiac catheterization laboratory with a prevalence of about 20%. Through literature, data are scarcely reported regarding the left ventricular (LV) function recovery post CTO percutaneous coronary intervention (PCI) in patients with low (<40%) and mid-range (40%-49%) LV ejection fraction (LVEF). The aim of this study was to assess the echocardiographic outcomes of CTO patients with low and mid-range LVEF successfully revascularized at 6-month follow-up. METHODS: This prospective study included 75 patients with at least one CTO of an epicardial coronary artery proved by previous diagnostic coronary angiography with PCI attempt indication, and successfully revascularized. They were equally divided according to LVEF into three groups, and echocardiographic remodeling indices were assessed at baseline and 6 months post PCI. RESULTS: Our study showed significant improvement of LVEF, S-wave velocity by tissue doppler imaging (TDI), LV wall-motion score (LVWMS), and LV systolic sphericity index (LVSIS) 6 months post CTO PCI in low LVEF group, and a significant improvement in LVEF, S-wave velocity, and LVWMS in mid-range LVEF group (P < .05). The delta change in LVEF was significantly more in low LVEF group, compared to the other two groups (F = 4.739, P < .05). CONCLUSION: Successful CTO PCI in patients with low and mid-range LVEF is associated with significant improvement of LVEF and other indices of myocardial remodeling after 6 months of follow-up.

Evaluation of Chronic Total Occlusion Recanalization: A Physiologic Assessment Perspective by Dynamic Exercise Tests.

Chronic total occlusion (CTO) recanalization and its effects on left ventricular function and patient outcomes has intrigued the interventional community over the last several years. Now that there is plenty of knowledge and experience on "how to treat" the lesion, another scientific effort should focus on "when to treat" the lesion. Physiologic assessment has altered the way we treat coronary artery stenosis to improve cardiovascular outcomes. We tend to assess the effects of CTO recanalization by evaluating resting parameters, although the effects of ischemia and concomitant left ventricular dysfunction manifest mainly during exercise. Physiologic assessment in CTOs by implementation of cardiopulmonary exercise testing, in order to indirectly assess the physiological effect of exercise-induced left ventricular dysfunction, could represent a novel approach to monitor the effects of CTO recanalization and hopefully to identify the responders after recanalization.

Coronary artery perforation during chronic total occlusion percutaneous coronary intervention: epidemiology, mechanisms, management, and outcomes.

AIMS: The aim of this study was to describe the epidemiology, mechanisms, management, and outcomes of coronary artery perforation during chronic total occlusion (CTO) percutaneous coronary intervention (PCI). METHODS AND RESULTS: We included 1,811 consecutive patients undergoing CTO PCI at five centres between 2011 and 2018. Coronary perforation was observed in n=99 (5.5%). Patients with perforation were older, had a higher J-CTO score, more often required antegrade dissection/re-entry and the retrograde approach, and had lower success rates. The frequency of Ellis type I, II, III and III "cavity spilling" perforations was 11%, 46%, 28%, and 14%, respectively. In 48% of cases, perforation involved the CTO vessel, while the retrograde approach was responsible for 46% of cases. In 53% of cases perforations required intervention. The most frequently applied management strategies included clinical observation (47%), covered stent implantation (25%), balloon occlusion (9%), and coil/fat embolisation (9%). Tamponade was observed in 20/99 (20%) perforation cases. Ellis type III perforations were most frequently observed at the CTO site. These were accountable for 16/20 tamponades and 3/5 deaths. In-hospital mortality was 5.1% vs 0.3% in patients with versus those without perforation (p<0.001). Older age, occlusion length >20 mm, rotational atherectomy, antegrade dissection/re-entry, and the retrograde approach were independently associated with coronary perforation. Patients with perforation suffered an increased incidence of target vessel failure on short-term follow-up. CONCLUSIONS: Coronary perforation is observed in a non-negligible proportion of CTO PCIs, often requires intervention, and is associated with tamponade and mortality in a minority of patients. CTO vessel-related perforations are associated with the highest burden of morbidity and mortality.

Intravascular Ultrasound Assessment of In-Stent Restenosis in Saphenous Vein Grafts.

Outcomes after percutaneous coronary interventions (PCI) in saphenous vein grafts (SVG) are inferior compared with native coronary arteries, but the mechanisms of SVG in-stent restenosis (ISR) have not been well-described. Thus, we aimed to evaluate the patterns of SVG ISR using intravascular ultrasound (IVUS) in 54 SVG ISR lesions. Stent underexpansion was defined as minimum stent area (MSA) <5 mm2. The time from stent implantation to presentation with ISR (9 BMS, 18 first-generation DES, and 27 second-generation DES) was 3.7 ± 3.0 years. IVUS-defined ISR patterns were categorized as mechanical (33%) or biological (67%). Mechanical patterns comprised 10 cases of stent underexpansion (MSA = 4.2 ± 0.9 mm2), 6 stent fractures or deformations, and 2 uncovered aorto-anastomotic lesions. Biological patterns comprised 19 cases of neoatherosclerosis, 13 excessive neointimal hyperplasia (NIH, 65 ± 11%), and 4 thrombi. Compared with biological patterns of ISR, mechanical patterns were more frequently located at the SVG anastomosis (72% vs 39%, p = 0.04) and at the SVG hinge motion site (55% vs 21%, p = 0.02). Although patients with mechanical patterns of ISR presented earlier than those with biological patterns (2.3 vs 4.4 years, p = 0.009), 61% of them were diagnosed >1 year after stent implantation. In conclusion, SVG ISR is dominated by biological patterns including neoatherosclerosis. Mechanical patterns of SVG ISR are associated with earlier presentation and location at graft anastomosis or hinge motion site.

Prospective study on the prognostic value of repeated carotid intima-media thickness assessment in patients with coronary and extra coronary steno-occlusive arterial disease.

INTRODUCTION It is debatable whether the rate of change in carotid intima­media thickness (CIMT) may be used as a risk indicator of major adverse cerebral and coronary events (MACCEs) in patients with either coronary (CAD) and peripheral artery disease (PAD). OBJECTIVES This prospective study aimed to evaluate the association between CIMT changes and the incidence of MACCEs, in patients with symptomatic CAD and PAD. PATIENTS AND METHODS The study comprised 466 patients admitted with steno­occlusive disease, in whom revascularization was performed for an index lesion. Group 1 included 305 subjects with CAD, and group 2, 161 patients with PAD. CIMT was measured at baseline and at a median of 21 and 41 months afterwards. The incidence of MACCE, cardiovascular death (CVD), myocardial infarction (MI), and ischemic stroke was recorded prospectively during 5 years. RESULTS CIMT increased with a mean (SD) progression rate of 0.027 (0.16) mm/y in group 1 and 0.026 (0.17) mm/y in group 2 (P = 0.89). CIMT regression was recorded in 112 patients (36.7%) and 61 patients (37.9%) in groups 1 and 2, respectively, at baseline (P = 0.80), and 82 patients (26.9%) and 42 patients (26.1%) in groups 1 and 2, respectively, in follow­up (P = 0.85). Maintained CIMT regression was independently associated with a reduced risk of MACCEs (hazard ratio [HR], 0.25; 95% CI, 0.15-0.42), MI (HR, 0.32; 95% CI, 0.20-0.51), ischemic stroke (HR, 0.29; 95% CI, 0.18-0.45), and CVD (HR, 0.24; 95% CI, 0.15-0.40), while the CIMT progression rate of 0.056 mm/y was associated with an increased risk of MACCEs (sensitivity, 53.2%; specificity, 72.2%; area under the receiver operating curve, 0.65). CONCLUSIONS Maintained CIMT regression is associated with 68% to 75% reduction in the risk of a cardiovascular event. However, a long­term maintained CIMT regression is achieved in one­fourth of patients with either CAD or PAD.

Intravascular Ultrasound and Angioscopy Assessment of Coronary Plaque Components in Chronic Totally Occluded Lesions.

BACKGROUND: The in vivo lesion morphologies and plaque components of coronary chronic total occlusion (CTO) lesions remain unclear.Methods and Results:We investigated 57 consecutive CTO lesions in 57 patients with stable angina pectoris undergoing elective percutaneous coronary intervention with intravascular ultrasound (IVUS) and coronary angioscopy (CAS) examination. All CTO lesions were classified according to the proximal angiographic lumen pattern; tapered-type (T-CTO) and abrupt-type (A-CTO). The differences in the intracoronary images of these lesion types were evaluated according to the location within the CTO segment. A total of 35 lesions (61.4%) were T-CTO. T-CTO lesions had higher frequencies of red thrombi (proximal 71.4%; middle 74.3%; distal 31.4%; P<0.001) and bright-yellow plaques (yellow-grade 2-3) (48.6%; 74.3%; 2.9%; P<0.001) at the proximal or middle than at the distal subsegment; A-CTO lesions showed no significant differences among the 3 sub-segments. At the middle subsegment, T-CTO lesions showed higher frequencies of positive remodeling (51.4% vs. 18.2%, P=0.01) and bright-yellow plaques (74.3% vs. 13.6%, P<0.001) compared with A-CTO lesions. Multivariate analysis identified bright-yellow plaque as an independent predictor (odds ratio, 7.25; 95% confidence interval, 1.25-42.04; P=0.03) of the occurrence of periprocedural myocardial necrosis. CONCLUSIONS: The combination of IVUS and CAS analysis may be useful for identifying lesion morphology and plaque components, which may help clarify the pathogenetic mechanism of CTO lesions.

Incremental benefit of three-dimensional transthoracic echocardiography in the assessment of left atrial appendage aneurysm leading to severe extrinsic compression of a coronary artery.

Left atrial appendage aneurysm (LAA AN) is a rare disease entity, which can be congenital or acquired in nature. We report an adult patient with LAA AN presenting with anginal chest pain in whom live/real time three-dimensional transthoracic echocardiography (3DTTE) provided incremental value over the two-dimensional (2D) technique in providing a more comprehensive assessment of the lesion. A literature review of the salient features of LAA AN is also provided in a tabular form.

Safety and efficacy of intracoronary sodium nitroprusside for the assessment of coronary fractional flow reserve.

BACKGROUND: Coronary fractional flow reserve (FFR) determination is a valuable tool for the assessment of stenosis significance in intermediate coronary obstructions. Maximal hyperemia is mandatory for this determination. Although intravenous (IV) Adenosine is the standard agent used, its use carries an elevated incidence of side effects. Intracoronary sodium nitroprusside (IC NTP) is a very well-known coronary vasodilator, but it is not routinely used for FFR determinations. OBJECTIVES: The purpose of the present study was to compare FFR determinations and side effect profile of IC NTP with IV Adenosine. METHODS: We prospectively assessed FFR determinations in a total of 20 intermediate coronary artery stenotic lesions in 18 consecutive patients with the administration of IV Adenosine (140 µg/kg/min) and IC NTP (100 µg). The appearance of side effects was registered. RESULTS: The mean age was 55.5 ±â€¯7.5 years. Fifteen (83%) of the patients were male. Mean FFR values with IC NTP were similar to those obtained with IV Adenosine (0.82 ±â€¯0.07 vs 0.82 ±â€¯0.06, respectively, r = 0.775, p < 0.0001). Intravenous Adenosine induced side effects in 45% of patients (shortness of breath 30%, flushing 5%, headache 5%, angina pectoris 5%, and transient conduction disturbances 10%). No side effects were reported with IC NTP. CONCLUSIONS: IC NTP at a dose of 100 µg is as effective as IV Adenosine for FFR assessment. Besides, it is better tolerated and should be consider as a vasodilator agent in the assessment of FFR.

Bioresorbable vascular scaffolds in coronary chronic total occlusions revascularization: safety assessment related to struts coverage and apposition in 6-month OCT follow-up.

Beneficial properties of bioresorbable vascular scaffolds (BVS) regarding to vasomotility restoration and no caging of the vessel make them attractive devices in chronic total occlusions (CTO) revascularization. However, more evidence is needed attending to their use in this specific setting. We aim to determine feasibility and safety of BVS use in CTO revascularization attending to struts coverage and apposition, as well as re-stenosis and stent thrombosis (ST) rates. 29 BVS were deployed in 9 CTO lesions revascularization (mean J-CTO score ≥3) with an acute procedural success rate of 100%. Clinical and angiographic follow-up was performed 6 months later, including intracoronary analyses from optical coherence tomography (OCT) images. 44,723 struts were analyzed within the total 636 mm of scaffolded vessel. Mean length scaffolded per lesion was 70.66 ± 31.01 mm with a mean number of 3.22 BVS. 2051 struts (4.59%) were identified as uncovered, being most of them (98.4%) neither malapposed nor disrupted. Mean thickness of struts' coverage was 0.13 ± 0.05 mm. Incomplete strut apposition (ISA) percentage was 0% as no malapposed struts were detected and 134 struts were identified as disrupted, which represents a 0.29% from the total. Mean vessel, scaffold, and lumen diameters were 3.87 ± 0.51, 2.97 ± 0.49, and 2.68 ± 0.50 mm, respectively. Neither in-stent re-stenosis nor ST was detected. During follow-up, none of our patients died, suffered from stroke or needed target lesion revascularization. Clinical and angiographic 6-month follow-up (including OCT analyses) of BVS in CTO revascularization suggests their effectiveness and safety, even in very complex chronic occluded lesions. Nevertheless, more evidence is needed.

The Outcomes, Patient Health Status, and Efficiency IN Chronic Total Occlusion Hybrid Procedures registry: rationale and design.

BACKGROUND: Patients with chronic total occlusions of a coronary artery represent a complex, yet common, clinical conundrum among patients with ischemic heart disease. Chronic total occlusion angioplasty is increasingly being used as a treatment for these complex lesions. There is a compelling need to better quantify the safety, efficacy, benefits, and costs of the procedure. METHODS: To address these gaps in knowledge, we designed the Outcomes, Patient Health Status, and Efficiency IN Chronic Total Occlusion Hybrid Procedures (OPEN CTO) study, an investigator-initiated multicenter, single-arm registry including 12 centers with a planned enrollment of 1000 patients. To ensure the accuracy of our observations, we used a unique auditing process through the National Cardiovascular Disease Registries' Cath/PCI Registry, angiographic core lab analysis, clinical events adjudication, and a systematic collection of patient-reported outcomes and costs. RESULTS: Between 21 January 2014 and 22 July 2015, 1000 patients were enrolled in OPEN CTO. A total of 28 patients either refused (N=26) or were missed by the screening process (N=2). In the National Cardiovascular Disease Registry Cath/PCI registry audit, there were 1096 chronic total occlusion-percutaneous coronary intervention procedures that were performed by participating operators during the time they enrolled in OPEN CTO. Overall, 987 of those patients could be definitively matched to an OPEN CTO enrolled patient (enrolled group). The remaining 109 were considered to be not enrolled in OPEN CTO (not enrolled group). Compared with the enrolled group, the patients in the nonenrolled group were less frequently of White race and more frequently of Hispanic origin. Procedural outcomes including National Cardiovascular Disease Registry-defined technical success, procedural success, and major adverse coronary events rates were similar. CONCLUSION: OPEN CTO is the most comprehensive and rigorously collected dataset to date that will provide unique insights into the success, safety, benefits, and the costs of chronic total occlusion-percutaneous coronary intervention using a reproducible technical approach to patients with these complex lesions.

Assessment of Inducible Myocardial Ischemia, Quality of Life, and Functional Status After Successful Percutaneous Revascularization in Patients With Chronic Total Coronary Occlusion.

The benefits of chronic total coronary occlusion (CTO) revascularization are not well established. In this prospective cohort study, 47 consecutive patients with successful percutaneous recanalization of CTO underwent adenosine stress cardiac magnetic resonance (CMR), 6-minute walk test (6MWT), and the Short Form-36 Health Survey before and 6 months after the procedure. Successful recanalization of a CTO was followed by significant improvement of (1) global physical and mental health status; (2) the distance walked in the 6MWT; (3) the incidence of chest pain at the end of the 6MWT; and (4) the score of a novel CMR ischemic burden index on the basis of the characteristics of adenosine stress perfusion defects (extension, persistence, transmurality, and induced contractile regional dysfunction). Patients with greater CMR ischemic index before percutaneous revascularization showed better improvement in the 6MWT. In conclusion, successful recanalization of a CTO leads to a concurrent improvement in ischemic burden, exercise tolerance, angina frequency, and quality of life scores. Patients with a high ischemic CMR score before CTO recanalization showed the better improvement in exercise tolerance.

Impact of microvascular obstruction on the assessment of coronary flow reserve, index of microcirculatory resistance, and fractional flow reserve after ST-segment elevation myocardial infarction.

BACKGROUND: Invasive assessment of coronary physiology (IACP) offers important prognostic insights in ST-segment elevation myocardial infarction (STEMI) but the dynamics of coronary recovery are poorly understood. OBJECTIVES: This study sought to examine the evolution of coronary flow reserve (CFR), index of microcirculatory resistance (IMR), ratio of distal coronary pressure (Pd) to mean aortic pressure (Pa), and fractional flow reserve (FFR) in patients undergoing primary percutaneous coronary intervention (PPCI). METHODS: 82 patients with STEMI underwent IACP at PPCI. Repeat IACP was performed in 61 patients (74%) at day 1 and in 46 patients (56%) at 6 months. Contrast-enhanced cardiac magnetic resonance imaging (CMR) was performed in 45 patients (55%) at day 1 and in 41 patients (50%) at 6 months. Changes in IACP were compared between patients with and without microvascular obstruction (MVO) on CMR. RESULTS: MVO was present in 21 of 45 patients (47%). Patients with MVO had lower CFR at PPCI and day 1 (p < 0.05) and a trend toward higher IMR values (p = 0.07). At 6 months, CFR and IMR were not significantly different between the groups. Baseline flow and Pd/Pa remained stable over time but FFR reduced significantly between PPCI and 6 months (p = 0.008); this reduction was mainly observed in patients with MVO (p = 0.006) but not in those without MVO (p = 0.21). CONCLUSIONS: In PPCI-treated patients with STEMI, coronary microcirculation begins to recover within 24 h and recovery progresses further by 6 months. FFR significantly reduces from baseline to 6 months. The presence of MVO indicates a highly dysfunctional microcirculation.

Quantitative assessment of magnetic resonance derived myocardial perfusion measurements using advanced techniques: microsphere validation in an explanted pig heart system.

BACKGROUND: Cardiovascular Magnetic Resonance (CMR) myocardial perfusion imaging has the potential to evolve into a method allowing full quantification of myocardial blood flow (MBF) in clinical routine. Multiple quantification pathways have been proposed. However at present it remains unclear which algorithm is the most accurate. An isolated perfused, magnetic resonance (MR) compatible pig heart model allows very accurate titration of MBF and in combination with high-resolution assessment of fluorescently-labeled microspheres represents a near optimal platform for validation. We sought to investigate which algorithm is most suited to quantify myocardial perfusion by CMR at 1.5 and 3 Tesla using state of the art CMR perfusion techniques and quantification algorithms. METHODS: First-pass perfusion CMR was performed in an MR compatible blood perfused pig heart model. We acquired perfusion images at physiological flow ("rest"), reduced flow ("ischaemia") and during adenosine-induced hyperaemia ("hyperaemia") as well as during coronary occlusion. Perfusion CMR was performed at 1.5 Tesla (n = 4 animals) and at 3 Tesla (n = 4 animals). Fluorescently-labeled microspheres and externally controlled coronary blood flow served as reference standards for comparison of different quantification strategies, namely Fermi function deconvolution (Fermi), autoregressive moving average modelling (ARMA), exponential basis deconvolution (Exponential) and B-spline basis deconvolution (B-spline). RESULTS: All CMR derived MBF estimates significantly correlated with microsphere results. The best correlation was achieved with Fermi function deconvolution both at 1.5 Tesla (r = 0.93, p < 0.001) and at 3 Tesla (r = 0.9, p < 0.001). Fermi correlated significantly better with the microspheres than all other methods at 3 Tesla (p < 0.002). B-spline performed worse than Fermi and Exponential at 1.5 Tesla and showed the weakest correlation to microspheres (r = 0.74, p < 0.001). All other comparisons were not significant. At 3 Tesla exponential deconvolution performed worst (r = 0.49, p < 0.001). CONCLUSIONS: CMR derived quantitative blood flow estimates correlate with true myocardial blood flow in a controlled animal model. Amongst the different techniques, Fermi function deconvolution was the most accurate technique at both field strengths. Perfusion CMR based on Fermi function deconvolution may therefore emerge as a useful clinical tool providing accurate quantitative blood flow assessment.

The role for adjunctive image in pre-procedural assessment and peri-procedural management in chronic total occlusion recanalisation.

Non invasive coronary angiography with multislice computed tomography has exquisite sensitivity to detect calcium and even the faintest late contrast filling of the distal vessel. Calcium burden and occlusion length are still valuable markers of duration, complexity and success of the recanalisation procedure. The ability to visualise the vessel also in the occluded segment, especially if calcified, can also help the operator to understand where to pierce the proximal cap in stumpless occlusions and to predict unusual courses, especially in very tortuous arteries. Imaging side by side CT images and angiography during the recanalisation procedure is an established practice in many active CTO laboratories and algorithms for co-registration are designed to overcome the challenges of systo-diastolic and respiratory motion. Intravascular ultrasound is used in almost all cases by the experienced Japanese CTO operators but most of the times its main use is a better identification of the diseased segment after predilatation to ensure complete stent cover and appropriate stent expansion, an application similar to other complex non occlusive lesions. The specificity of IVUS during CTO recanalisation is the identification of the vessel path in stumpless occlusions and the guidance of wire reentry especially during reverse Controlled Retrograde Anterograde Tracking. Optical coherence tomography has limitations in the setting of CTO recanalisation because of the need of forceful contrast flushing to clear blood, contraindicated in the presence of anterograde dissections, and the limited penetration. The variability in the use of both non-invasive and invasive imaging during CTO recanalisation is immense, going from more than 90% in Japan to less than 20% in Europe and intermediate penetration in the USA. Probably the explanation is almost only in availability and cost because all countries see a progressive increase of use suggesting that these methods are becoming an established tool for guidance of CTO recanalisation.