A prospective, consecutive registry of patients who had undergone CTO angioplasty was created through the Iberian registry. A total of 32 sites in Spain and Portugal participated in this registry. A 2-year recruitment period from January 2015 to December 2016 was selected, during which 24 of the participating sites included patients (Table of the supplementary material). We defined CTO as angiographically proven anterograde flow obstruction of a coronary artery, known or suspected to have lasted > 3 months (with Thrombolysis In Myocardial Infarction [TIMI] flow = 0).1 The study included a total of 24 sites selected from around Spain with at least 1 operator experienced in CTO angioplasty who recorded all cases consecutively, independently, and without outside monitoring. An experienced operator was assumed to be any operator who had handled at least 50 chronic occlusions and who had been previously mentored in this intervention. Although this criterion represents a selection bias, the aim was to reflect current outcomes with this technique using a specific strategy. Once informed consent was obtained, data were obtained on clinical, anatomic (including specifically on occlusion), and procedure characteristics. Patients were considered to have a history of ischemic heart disease only if diagnosed before the procedure detecting the CTO to be treated. A total of 99% of the patients included were monitored during their hospital stay and at least once after discharge. A total of 37 procedures were excluded due to inclusion errors or duplicate data. The clinical assessment was performed by the attending clinical cardiologist according to Canadian Cardiovascular Society angina functional class (I to IV) and New York Heart Association dyspnea class (I to IV); clinical improvement was considered to be reduction of at least 1 grade on these scales. Additionally, quality of life was assessed by the EQ-5D Health Questionnaire and the Seattle Angina Questionnaire in a subpopulation. Each site entered the data using an online platform, complying with the requirements of the Law on Data Protection and accessible only to participating operators and registry coordinators. The registry is endorsed by the Cardiac Catheterization and Interventional Cardiology Section of the Spanish Society of Cardiology and was funded by an unconditional grant from Abbott Vascular Spain.

Data are expressed as absolute and percent frequency in the case of qualitative variables. Quantitative variables are expressed as mean ± standard deviation or median [interquartile range], depending on variable distribution. Group comparisons were analyzed by the Student t test or its nonparametric equivalent, the Mann-Whitney U-test, for continuous variables, and the chi-square test or Fisher's exact test for categorical variables. Statistical significance was defined as P < .05. Variables with P < .10 in the univariate analysis were included in a multivariate logistic regression model to determine the predictors of recanalization success, the predictors of complications, and the predictors of functional improvement. Survival curves during total mortality follow-up were estimated by the log-rank test based on success or failure of CTO recanalization. Predictors of mortality were not analyzed, in order to avoid any overadjustments due to a low incidence.

All analyses were performed using SPSS Statistics, version 24.0.

A total of 1000 CTO angioplasties were performed in 952 patients over a 2-year period; 83.8% were men, and the mean age was 65.5 ± 11.3 years. Most patients had symptoms (81.5%) and a history of ischemic heart disease (59.2%), with surgical revascularization in 5.6%, percutaneous revascularization in 48.4%, and previous attempts at unblocking in 15%. The mean anatomic-based SYNTAX score was 19.5 ± 10.6 (left common trunk disease in 4.1% and more than 1 chronic occlusion in 14.8%), and 17.3% had a J-score > 2. The main clinical and anatomic characteristics are summarized in Table 1.

The characteristics of the procedure, as well as the predictive factors of successful recanalization and complications, are summarized in Table 1 and Table 2, respectively. The right coronary artery was most commonly affected (50.2%; 73.7% successful), followed by the anterior interventricular artery (34.3%; 83.5% successful) and circumflex artery (14.9%; 87.3% successful). The procedure was retrograde in 92 patients (9.2%) and considered as a first option in 75%.

The overall success rate was 74.9%, higher in patients with no previous attempts (82.2% vs 75.2%; P = .001), in patients with J-score ≤ 2 (80.5% vs 69.5%; P = .002) and in procedures performed with intravascular ultrasound (IVUS) guidance (89.9% vs 76.2%; P < .001). In fact, the use of IVUS was the only modifiable factor that was an independent predictor of success (odds ratio [OR] = 2.445; 95% confidence interval [95%CI], 1.186-5.041; P < .015). Patients with worse kidney function and patients with complications during the procedure had lower success rates, and in particular, the presence of coronary perforations was associated with significantly fewer successful recanalizations (34.5% vs 79.9%; P < .001). The main factors described by the J-score, such as severe calcification, length > 20mm, and a blunt proximal cap, were also independent predictors of failed recanalization. Success varied from 68% to 91% among sites and was higher in the top quartile according to number of procedures (P = .056).

The procedure-related complication rate was 6.9%: coronary perforation (3%), cardiac tamponade (1%), myocardial infarction (1.3%), and death (0.5%). Complication-related factors are summarized in Table 2; independent predictors were a history of ischemic heart disease (OR = 2.230; 95%CI, 1.104-4.505; P = .025), blunt proximal cap (OR = 2.068; 95%CI, 1.088-3.934; P = .027), and retrograde access (OR = 3.527; 95%CI, 1.691-7.359; P < .001). The overall hospital mortality rate was 0.5%, and there were no significant differences according to PCI success or failure.

After a median follow-up of 365 [167-532] days, 78.3% of patients showed an improvement in New York Heart Association functional class for dyspnea or in Canadian Cardiovascular Society grade for angina. In 95% of patients with at least 2 years of follow-up who improved in the first year, the improvement persisted afterwards. In addition, a subpopulation of 183 patients showed significant improvement in the EQ-5D scale from 0.794 ± 0.115 to 0.869 ± 0.097 (P = .092) and in the Seattle Angina Questionnaire from 83.4 (75.4-90.0) to 95.1 (87.3-99.0) (P < .001). The main factors associated with functional improvement are shown in Table 3. Clinical improvement was significantly lower in the case of failed PCI (27.3% vs 92%; P < .001), as summarized in Figure 1. In addition to failed recanalization, the presence of other clinical conditions associated with functional impairment, such as a history of infarction or stroke and peripheral arterial disease, was associated with a lack of clinical improvement. Moreover, patients who experienced less clinical improvement had higher mortality (Table 4).

Figure 1.

Clinical progress during long-term follow-up of patients treated by revascularization of chronic coronary occlusion; total population and according to recanalization success or failure.

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Of the 877 patients who completed 1-year follow-up (92.1% of total), 14 (1.5%) died, with no significant differences according to recanalization outcome. One-year mortality curves showed some divergence in favor of patients with successful recanalization. In patients with 3 years of follow-up, the mortality rate was higher in the case of failed recanalization (28.7% vs 18.9%), although the difference was not statistically significant (P = .153) (Figure 2). The main determinants of mortality during follow-up are summarized in Table 4.

Figure 2.

Survival curves based on successful or failed treatment of chronic coronary occlusion.

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Patients with CTO were characterized by a high incidence of multiple cardiovascular risk factors and injury to other target organs, as well as multivessel disease, with a mean anatomic-based SYNTAX score of 19.5 ± 10.6, and complex lesions with J-score > 2 in 17.3% of patients. This is consistent with the data of the Canadian Multicenter CTO Registry7 and other similar registries7,16–19 indicating that isolated CTO are only present in 47% of patients. It is common for surgery to be ruled out in patients with single-vessel or multivessel disease but other comorbidities or poor distal bed visualization. In this situation, medical therapy was the first alternative for decades, but a significant percentage of patients still show evidence of ischemia or relevant symptoms8–11; in particular, up to 30% of patients included in the Iberian registry had Canadian Cardiovascular Society functional class III or IV angina. These data, along with the poor progress of patients with failed vs successful recanalization, appear to show that the indications of PCI for CTO are adequate in our setting.

Imaging techniques such as IVUS or computed tomography are not commonly used in our setting (∼11%), even though they could provide diagnostic and therapeutic benefits to patients with limited angiographic visualization. Some studies report that IVUS is mainly used in more complex CTO and that it increases the success rate. This technique was used in more than 40% of patients in the Japanese Multicenter CTO Registry20 and the Multicenter Korean CTO Registry.21 However, the European Registry of Chronic Total Occlusion10,22 had lower rates (2.9% in all; 9.2% of retrograde) and indicate, like the Iberian registry, that it is not used as often by less expert operators. Habara et al.23 has already analyzed the impact of operator experience, showing that IVUS guidance to cross the guidewire has a clear learning curve affecting the need for support from expert operators for this technique to have a positive impact.24 This could also be said of the retrograde approach which, in our series, was a predictor of complications and is another modifiable factor that could increase the success rate. The use of 2 catheters (1 for contralateral injection) is not an independent predictor of success, which might indicate that this strategy is only used in the most complex cases and not in all situations in which it may be beneficial20,21; this could also explain why the rate of successful recanalizations is higher for PCI on the circumflex artery, even though previous series have always reported lower rates.20–23 In fact, less than 15% of attempts were performed on this artery, showing that a nonnegligible percentage of patients who might benefit from percutaneous recanalization by specific techniques are using medical therapy as the first and only option. On the other hand, the fact that eventually patients with failed attempts have more complications could indicate another potentially modifiable point that might increase the success rate and identify patients at risk of complications, making it possible to halt the procedure or to change how it is being done before complications occur.

This study was not intended to demonstrate impact on mortality, as this is a controversial aspect that requires well-designed studies with a control group, although such studies are often a matter of debate in the field of CTO.25 However, there was a low rate of complications, with no cases of urgent heart surgery and with a periprocedure mortality of only 0.5%. In addition, patients clearly experienced functional benefit, which was also associated with lower mortality during follow-up (P < .001) (Table 4), confirming that there are undeniable benefits to patients treated by CTO recanalization in cases with a clear indication. Although some studies, such as SYNTAX26 or the study by Banerjee et al.,18 have compared percutaneous recanalization in CTO vs surgery with slightly more favorable results in the percutaneous recanalization arm, these cohorts are not recent and also include patients with multivessel disease, without considering that the surgical outcomes were clearly worse when saphenous vs mammary grafts were used. This explains the minimal use of surgery in patients with single-vessel disease, particular in those with occlusion of the right coronary artery, which usually cannot be revascularized with mammary graft and is actually the artery most commonly affected by CTO.27–29 The Iberian registry indicates that, although not obvious during the first year after the intervention, mortality during longer term follow-up could be significantly reduced and also indicates that percutaneous recanalization of CTO in patients with no surgical indication (due to high risk or low SYNTAX score) is an alternative to consider in our setting, particularly in patients with symptoms and ischemia no longer alleviated by medical treatment.

The main limitations of this study is that, although it was performed prospectively and systematically, the data are informative and not monitored and there is no centralized angiographic analysis. In fact, the patients included are those selected by each hospital to undergo PCI, which could lead to heterogeneity between the clinical indications. This also explains why ischemia test data are not recorded, as the indication was defined at each hospital and there were no restrictions on indication in terms of inclusion criteria. Nevertheless, the study helps provide an accurate picture of clinical practice in our setting. Additionally, complications could be underestimated because the registry did not include a systematic record of electrocardiograms and sequential measurements of necrosis markers. It is true that a strict definition of infarction or perforation may increase the overall rate of complications when compared with other, less rigorous registries. Consequently, it should be taken into account that not all complications involve the same risk burden for the patient, as seen by the fact that no patients died during the procedure or required urgent recanalization surgery. Last, the data on clinical improvement were based on dyspnea status (New York Heart Association) and angina status (Canadian Cardiovascular Society), but there was no routine use of specific questionnaires or other objective examinations.