The myocardium supplied by a chronic total occlusion is a persistently ischemic zone

Arterialized collateral capillaries progress from nonreactive to capable of increasing perfusion in an ischemic arteriolar tree

OBJECTIVE

CCA, outward remodeling of capillaries that anastomose 2 arteriolar trees with different parent feed arteries, may represent a therapeutic target for patients who lack collaterals. ACCs can reperfuse an ischemic tree, but their functional capacity is unknown. Therefore, we determined whether ACCs mature into resistance vessels that regulate blood flow following arterial occlusion.

METHODS

We ligated the lateral spinotrapezius feed artery in Balb/C mice, which induces CCA. At days 7 and 21 following occlusion, we measured vasodilation of ACCs using intravital microscopy and blood flow in the ischemic tree using LSF. We determined the presence of ACCs and neurovascular alignment with immunofluorescence.

RESULTS

At day 7, ACCs do not vasodilate following muscle contraction and have reduced responses to endothelial- and smooth muscle-dependent agents. By day 21, ACCs exhibit normal vasodilation, accompanied by normalized increases in relative blood flow to the ischemic zone. Although functioning as resistance vessels by regulating blood flow, ACCs do not appear to be innervated.

CONCLUSIONS

ACCs mature into resistance vessels that regulate blood flow to the downstream tissue. Therefore, induction of mature ACCs may be a target for reducing ischemia in patients who lack collateral networks.

Recovery of myocardial perfusion after percutaneous coronary intervention of chronic total occlusions is comparable to hemodynamically significant non-occlusive lesions

Background

The benefits of chronic coronary total occlusion (CTO) percutaneous coronary intervention (PCI) are being questioned. The aim of this study was to assess the effects of CTO PCI on absolute myocardial perfusion, as compared with PCI of hemodynamically significant non‐CTO lesions.

Methods

Consecutive patients with a preserved left ventricular ejection fraction (≥50%) and a CTO or non‐CTO lesion, in whom [¹⁵O]H₂O positron emission tomography was performed prior and after successful PCI, were included. Change in quantitative (hyperemic) myocardial blood flow (MBF), coronary flow reserve (CFR) and perfusion defect size (in myocardial segments) were compared between CTOs and non‐CTO lesions.

Results

In total 92 patients with a CTO and 31 patients with a non‐CTO lesion were included. CTOs induced larger perfusion defect sizes (4.51 ± 1.69 vs. 3.23 ± 2.38 segments, P < 0.01) with lower hyperemic MBF (1.30 ± 0.37 vs. 1.58 ± 0.62 mL·min⁻¹·g⁻¹, P < 0.01) and similarly impaired CFR (1.66 ± 0.75 vs. 1.89 ± 0.77, P = 0.17) compared with non‐CTO lesions. After PCI both hyperemic MBF and CFR increased similarly between groups (P = 0.57 and 0.35) to normal ranges with higher hyperemic MBF values in non‐CTO compared with CTO (2.89 ± 0.94 vs. 2.48 ± 0.73 mL·min⁻¹·g⁻¹, P = 0.03). Perfusion defect sizes decreased similarly after CTO PCI and non‐CTO PCI (P = 0.14), leading to small residual defect sizes in both groups (1.15 ± 1.44 vs. 0.61 ± 1.45 segments, P = 0.054).

Conclusions

Myocardial perfusion findings are slightly more hampered in patients with a CTO before and after PCI. Percutaneous revascularization of CTOs, however, improves absolute myocardial perfusion similarly to PCI of hemodynamically significant non‐CTO lesions, leading to satisfying results.

Outcomes of Percutaneous Antegrade Intraluminal Coronary Intervention of Chronic Total Occlusion With Remote Surgical Backup

Percutaneous coronary intervention (PCI) of chronic total occlusion (CTO) is not favored in facilities without on-site surgical backup. We reviewed outcomes of patients who had CTO intervention with remote surgical backup in our institution. All patients who underwent attempted antegrade intraluminal CTO PCI from January 2013 to July 2017 were analyzed. Twenty cases (18 patients, 58.1 ± 7.0 years, 70% males) were identified. Procedure was successful in 85% (17 of 20). There were 2 nonflow limiting dissections and 1 wire perforation. Two patients had post-PCI myocardial infarction. There was no cardiac death, myocardial infarction, target vessel revascularization, or stroke at 30 days and at mean follow-up of 19.5 ± 13.7 months. There were 4 rehospitalizations for angina requiring repeat angiogram in 3 cases: 2 without intervention, and 1 referred for coronary artery bypass grafting. Careful attempt at antegrade intraluminal CTO intervention done at a center with remote surgical backup is feasible in selected patients.

Chronic Total Occlusion Coronary Intervention: In Search of a Definitive Benefit

Percutaneous coronary intervention (PCI) of chronic coronary total occlusion is the latest frontier in percutaneous intervention. There are vast improvements in the initial success and safety of the procedure as well as a better understanding of appropriateness and benefits. Advances in technology and skill allow for increased utilization of PCI in cases of chronic coronary total occlusion, with benefits regarding symptoms and quality of life. Percutaneous coronary intervention for chronic coronary total occlusion can correct ischemia and achieve complete revascularization while avoiding traditional coronary bypass grafting, although survival benefits remain unclear.

Impact of Coronary Artery Chronic Total Occlusion on Arrhythmic and Mortality Outcomes: A Systematic Review and Meta-Analysis

OBJECTIVES

This study aimed to examine the relationship between chronic coronary artery total occlusion (CTO) status and the occurrence of ventricular tachycardia (VT)/ventricular fibrillation (VF) or appropriate implantable cardioverter-defibrillator (ICD) therapy.

BACKGROUND

CTO is a significant problem in patients with ischemic heart disease. However, the extent to which it predisposes affected individuals to VT/VF and whether these arrhythmic events could be prevented by revascularization are unclear. Therefore, a systematic review and meta-analysis were conducted to examine the relationship between CTO status and the occurrence of VT/VF or appropriate ICD therapy.

METHODS

PubMed and Embase databases were searched until November 16, 2017, identifying 137 studies.

RESULTS

Seventeen studies involving 54,594 subjects (mean age, 61 ± 21 years of age, 81% male) with a mean follow-up of 43 ± 31 months were included. The presence of CTO was associated with higher risk of VT/VF or appropriate ICD therapy (adjusted hazard ratio [aHR]: 1.99; 95% confidence interval (CI): 1.53 to 2.59; p < 0.0001, I² = 3%) but not in cardiac mortality (aHR: 2.59; 95% CI: 0.64 to 10.59; p = 0.18, I² = 86%) or in all-cause mortality (aHR: 1.70; 95% CI: 0.84 to 3.46; p = 0.14; I² = 64%). Compared to patients with non-infarct-related CTOs, those with infarct-related CTOs have a higher risk of VT/VF or appropriate ICD therapy (aHR: 2.47; 95% CI: 1.76 to 3.46; p < 0.0001; I² = 14%), cardiac mortality (aHR: 2.73; 95% CI: 1.02 to 7.30; p < 0.05; I² = 79%) and higher all-cause mortality (aHR: 1.69; 95% CI: 1.19 to 2.40; p < 0.01; I² = 40%). Nonrevascularization of CTOs tended to be associated with an increased risk of all-cause mortality compared to successful revascularization (unadjusted HR: 1.52; 95% CI: 0.96 to 2.43; p = 0.08; I² = 76).

CONCLUSIONS

CTOs, especially infarct-related, are associated with high risk of VT/VF or appropriate ICD therapy and mortality. ICD implantation could be beneficial. However, it is not clear that revascularization has an impact on the outcome of patients with CTOs.

Prevalence of ischaemia in patients with a chronic total occlusion and preserved left ventricular ejection fraction

Aims

Previous studies on invasive assessment of collateral function in patients with a chronic total occlusion (CTO) have displayed only a limited increase in collateral flow and high occurrence of coronary steal during pharmacological stress. This could question the necessity for ischaemia testing prior to revascularization of CTOs in the presence of myocardial viability. The purpose of the present study was to determine the prevalence of perfusion impairments in patients with a CTO as assessed by [15O]H2O positron emission tomography (PET).

Methods and results

Seventy-six consecutive patients (60 men, 62 ± 10 years) with a documented CTO and preserved left ventricular ejection fraction (LVEF) were included. All patients underwent PET to assess (hyperaemic) myocardial blood flow (MBF) and coronary flow reserve (CFR). Collateral connection score was 0 in 7 (9%), 1 in 13 (17%), and 2 in 56 (74%) of the cases, with predominantly a high Rentrop grade (96% ≥2). MBF of the target area during hyperaemia was significantly lower when compared with the remote area (1.37 ± 0.37 vs. 2.63 ± 0.71 mL min-1 g-1, P < 0.001). Target to remote ratio during hyperaemia was on average 0.54 ± 0.13, and 73 (96%) patients demonstrated a significantly impaired target to remote ratio (≤0.75). Only 7 (9%) patients displayed a preserved CFR of ≥2.50, whereas coronary steal (CFR <1.0) was observed in 10 (13%) patients.

Conclusions

Even in the presence of angiographically well-developed collateral arteries, the vast majority of CTO patients with a preserved LVEF showed significantly impaired perfusion. These results suggest that collateral function during increased blood flow demand in viable myocardium is predominantly insufficient.

Meta-Analysis of Risk of Ventricular Arrhythmias and All-Cause Mortality in Patients With Chronic Total Occlusion of a Coronary Artery and/or Implantable Cardioverter-Defibrillator

Implantable cardioverter-defibrillator (ICD) has been increasingly used to prevent sudden death in patients with high risk of ventricular arrhythmias (VAs). Chronic total occlusion (CTO) is a severe condition of coronary artery disease. However, the prognostic impact of CTO in ICD recipients remains controversial. We systematically searched the PubMed, EMBASE, and Cochrane databases for documents published before October 1, 2017 to identify studies that investigated the prognostic impact of CTO on VAs and all-cause mortality (ACM) in ICD recipients. The effect size was expressed by hazard ratio (HR) and 95% confidence interval (CI). Overall, 6 studies with 1,423 patients were included. We found that CTO independently predicted the occurrence of VAs in the global population (HR 1.77, 95% CI 1.14 to 2.76, p = 0.01). Subgroup analysis revealed that CTO only predicted VAs in patients receiving ICD as secondary prevention (HR 1.96, 95% CI 1.55 to 2.48, p <0.01). However, CTO was not associated with ACM in the global population (HR 1.51, 95% CI 0.99 to 2.32, p = 0.06). Further subgroup analysis still showed no association between CTO and ACM in patients receiving ICD as primary prevention (HR 1.49, 95% CI 0.43 to 5.21, p = 0.53) or secondary prevention (HR 1.56, 95% CI 0.87 to 2.78, p = 0.13). In conclusion, CTO is an independent predictor of VAs in patients with secondary-prevention ICD, but not for ACM. Our study provided additional evidence for improving the risk stratification and management of VAs in ICD recipients.

Robustness of Percutaneously Completed Coronary Revascularization in Stable Coronary Artery Disease: Obstructive Versus Occlusive Lesions

Our study sought to assess long-term outcomes of percutaneously completed coronary revascularization (CCR) in patients with obstructive coronary artery disease (CAD) comprising chronic total occlusions (CTOs). Between 2010 and 2014, percutaneous coronary interventions (PCIs) of the CTOs were attempted in 213 patients: the CCR was achieved in 125 patients (group 1), while the PCI failed in 88 patients (group 2). They were matched against 252 patients (group 3) with the CCR obtained by the non-CTO PCIs. In the 5-year follow-up, more adverse cardiovascular (CV) events occurred in group 2 (29.5% vs 4.8% in group 1 vs 3.5% in group 3, P = .0001), mainly due to recurrent severe symptoms and additional revascularization of the CTOs; CV mortality did not seem to be significantly affected. Survival curves for the successful CTO and non-CTO PCIs appeared indistinguishable. Stent thromboses were infrequent in the CCR groups. In conclusion, long-term outcomes of the patients with the obstructive CAD containing the CTOs showed a favorable outcome if the CCR had been achieved percutaneously.

Percutaneous coronary interventions of chronic total -occlusions; a review of clinical indications, treatment strategy and current practice

Chronic total occlusions (CTOs) are commonly encountered in patients undergoing coronary angiography, but percutaneous coronary intervention (PCI) for CTO is currently infrequently performed owing to the perception of limited clinical benefit, high complexity and cost of intervention, and perceived risk of complications. Numerous observational studies have demonstrated that successful CTO revascularization is associated with better cardiovascular outcomes and enhanced quality of life (QOL). However, in the absence of randomized trials, its prognostic benefit remains debated. Nevertheless, over the past decade the interest in CTO-PCI has exponentially grown due to important developments in dedicated equipment and techniques, resulting in high success and low complication rates. A number of factors must be taken into consideration in selecting patients for CTO-PCI, including presence of symptoms attributable to the CTO, extent of ischaemia distal to the occlusion, and degree of myocardial viability. In this review, we focus on the impact of CTO revascularization on clinical outcomes and QOL and on appropriate patient selection. Data regarding efficacy and safety of recent advances in PCI-CTO techniques will be discussed. Steps involved in setting up a dedicated CTO program will be outlined and the current CTO landscape in Belgium will be briefly highlighted. The overall aim of this review is to promote a more balanced approach to management of patients with a CTO.

Utility of adjunctive modalities in Coronary chronic total occlusion intervention

Coronary chronic total occlusion (CTO) intervention remains one of the most challenging domains in interventional cardiology. Due to the technical challenges involved and potential procedural complications, CTO percutaneous coronary intervention (PCI) attempt and success rates remain less than standard PCI. However, the use of several adjunctive tools such as intravascular ultrasound, optical coherence tomography, rotational atherectomy, orbital atherectomy, excimer laser coronary atherectomy and percutaneous left ventricular assist device may contribute to improved CTO PCI success rates or provide better hemodynamic assessment of CTO lesion (i.e., using fractional flow reserve). In this review we present the current literature describing the utility and efficacy of these adjunctive modalities in CTO intervention.

Approach to CTO Intervention: Overview of Techniques

OPINION STATEMENT

Successful percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs) has been associated with significant clinical benefits, but remains technically demanding. Failure to cross the CTO with a guidewire is the most common cause of CTO PCI failure. CTO crossing can be achieved in the antegrade or retrograde direction and can be accomplished by maintaining true lumen position throughout or via subintimal dissection/reentry techniques. A procedural plan should be created prior to the procedure through careful angiographic review of four key parameters: (a) morphology of the proximal occlusion cap; (b) length of the occlusion; (c) quality of the distal vessel and presence of bifurcation at the distal cap; and (d) suitability of collateral circulation for retrograde crossing. Dual coronary injection is recommended in all cases with contralateral collaterals for detailed characterization of the lesion. If one approach fails to progress, a quick transition to the next approach is encouraged to maximize efficacy and efficiency. Procedural complications, including vessel perforation, may occur more frequently in CTO as compared with non-CTO PCI; hence, availability of necessary equipment and expertise in treating such complications are essential.

Noninvasive Discrimination of Coronary Chronic Total Occlusion and Subtotal Occlusion by Coronary Computed Tomography Angiography

OBJECTIVES

The aim of this study was to investigate whether noninvasive discrimination of chronic total occlusion (CTO), a complete interruption of coronary artery flow, and subtotal occlusion (STO), a functional total occlusion, is feasible using coronary computed tomography angiography (CTA).

BACKGROUND

CTO and STO may be different in pathophysiology and clinical treatment strategy.

METHODS

We included 486 consecutive patients (median age 63 years, 82% male) who showed a total of 553 completely occluded coronary arteries in coronary CTA. The length of occlusion, side branches, shape of proximal stump, and collateral vessels were measured as anatomical findings. Transluminal attenuation gradient, which reflects intraluminal contrast kinetics and functional extent of collateral flow, was measured as a physiological surrogate. All patients were followed by invasive coronary angiography.

RESULTS

Coronary arteries with CTO showed longer occlusion length (cutoff ≥ 15 mm), higher distal transluminal attenuation gradient (cutoff ≥-0.9 Hounsfield units [HU]/10 mm), more frequent side branches, blunted stump, cross-sectional calcification ≥ 50%, and collateral vessels compared with arteries with STO (p < 0.001, all). The combination of these findings could distinguish CTO from STO (c-statistics = 0.88 [95% confidence interval: 0.94 to 0.90], sensitivity 83%, specificity 77%, positive predictive value 55%, negative predictive value 93%; p < 0.001). Percutaneous coronary intervention (PCI) was attempted in 342 arteries and was successful in 279 arteries (82%). The computed tomography findings could predict the unsuccessful PCI (c-statistics = 0.70 [95% confidence interval: 0.65 to 0.75], sensitivity 63%, specificity 73%, positive predictive value 91%, negative predictive value 31%; p < 0.001).

CONCLUSIONS

Noninvasive coronary CTA could discern CTO from STO, and also could predict the success of attempted PCI.

Fractional flow reserve based on computed tomography: an overview

Computed tomography coronary angiography (CTCA) is a technique proved to provide high sensitivity and negative predictive value for the identification of anatomically significant coronary artery disease (CAD) when compared with invasive X-ray coronary angiography. While the CTCA limitation of a ionizing radiation dose delivered to patients is substantially overcome by recent technical innovations, a relevant limitation remains the only anatomical assessment of coronary stenoses in the absence of evaluation of their functional haemodynamic significance. This limitation is highly important for those stenosis graded as intermediate at the anatomical assessment. Recently, non-invasive methods based on computational fluid dynamics were developed to calculate vessel-specific fractional flow reserve (FFR) using data routinely acquired by CTCA [computed tomographic fractional flow reserve (CT-FFR)]. Here we summarize methods for CT-FFR and review the evidence available in the literature up to June 26, 2016, including 16 original articles and one meta-analysis. The perspective of CT-FFR may greatly impact on CAD diagnosis, prognostic evaluation, and treatment decision-making. The aim of this review is to describe technical characteristics and clinical applications of CT-FFR, also in comparison with catheter-based invasive FFR, in order to make a cost-benefit balance in terms of clinical management and patient's health.

The collateral circulation of coronary chronic total occlusions

AIMS

Despite advances in understanding the physiological role of collaterals in coronary chronic total occlusions (CTOs), collateral anatomy remains poorly defined. Our aim was to define the anatomy and interventional utility of collaterals within a large population of patients with CTOs.

METHODS AND RESULTS

We studied the coronary angiograms of 481 patients with 519 CTOs at six centres in the U.K. over four years. Detailed angiographic analysis was performed by interventional cardiologists specialising in CTO percutaneous coronary intervention (PCI). All visible collaterals with a collateral connection (CC) grade ≥1 were recorded. A subgroup of CTOs (n=277) was assessed for interventional capability, defined as whether the collateral supply was able to facilitate retrograde access. We described 45 different collateral patterns: 20 in right coronary artery (RCA), 13 in left anterior descending (LAD), and 12 in circumflex artery CTOs. Septal collaterals from the LAD to the right posterior descending artery (RPDA), and from the posterior descending artery to the LAD were most common, and most often considered as having "interventional capability".

CONCLUSIONS

This is the largest analysis of collateral circulation anatomy in a population of patients with CTOs. We anticipate that these data will be of significant benefit in angiographic analysis and procedure planning for CTO PCI.

Association of blood pressure and coronary collateralization in type 2 diabetic and nondiabetic patients with stable angina and chronic total occlusion

OBJECTIVE

We investigated whether and to what extent blood pressure (BP) affects coronary collateralization in type 2 diabetic and nondiabetic patients with stable angina and chronic total occlusion.

METHODS

Brachial BP was measured using an inflatable cuff manometer in 431 diabetic and 287 nondiabetic patients with stable angina and angiographic total occlusion of at least one major coronary artery. They were classified according to the SBP (<100, 100-119, 120-139, 140-159, 160-179, and ≥180 mmHg), DBP (<60, 60-69, 70-79, 80-89, 90-99, and ≥100 mmHg), and pulse (<40, 40-49, 50-59, 60-69, 70-79, and ≥80 mmHg) BP ranges. The degree of coronary collaterals supplying the distal aspect of a total occlusion from the contralateral vessel was graded as poor (Rentrop score of 0 or 1) or good collateralization (Rentrop score of 2 or 3).

RESULTS

In diabetic patients, the incidence of poor collateralization was related to the DBP in a U-shaped pattern, with the lowest risk at 80-89 mmHg. In nondiabetic patients, an optimal DBP range was 90-99 mmHg for good collaterals, but no U-shaped relation between DBP and coronary collateralization was observed. After adjusting for the baseline characteristics in the logistic regression models, the increased risk of poor collateralization persisted for low or high DBP ranges in diabetic [odds ratio (OR) 2.02-7.29, P ≤ 0.04] and nondiabetic patients (OR 3.62-5.98, P ≤ 0.02). No such relations were observed between collateral grades and SBP and pulse BP.

CONCLUSION

This study demonstrates that 80-89 and 90-99 mmHg are the optimal ranges for DBP in diabetic and nondiabetic patients with stable angina and chronic total occlusion, within which the risk of poor collateralization is low.

Influence of Total Coronary Occlusion on Clinical Outcomes (from the Bypass Angioplasty Revascularization Investigation 2 DiabetesTrial)

Our aim was to evaluate the influence of chronic total occlusions (CTOs) on long-term clinical outcomes of patients with coronary heart disease and diabetes mellitus. We evaluated patients with coronary heart disease and diabetes mellitus enrolled in the Bypass Angioplasty Revascularization Investigation 2 Diabetes, who underwent either prompt revascularization (PR) with intensive medical therapy (IMT) or IMT alone according to the presence or absence of CTO. Of 2,368 patients enrolled in the trial, 972 patients (41%) had CTO of coronary arteries. Of those, 482 (41%) and 490 (41%) were in the PR with IMT versus IMT only groups, respectively. In the PR group, patients with CTO were more likely to be selected for the coronary artery bypass grafting stratum (coronary artery bypass grafting 62% vs percutaneous coronary intervention 31%, p <0.001). Compared to the non-CTO group, patients with CTO had more abnormal Q wave, abnormal ST depression, and abnormal T waves. The myocardial jeopardy score was higher in the CTO versus non-CTO group (52 [36 to 69] vs 37 [21 to 53], p <0.001). After adjustment, 5-year mortality rate was significantly higher in the CTO group in the entire cohort (hazard ratio [HR] 1.35, p = 0.013) and in patients with CTO managed with IMT (HR 1.46, p = 0.031). However, the adjusted risk of death was not increased in patients managed with PR (HR 1.26, p = 0.180). In conclusion, CTO of coronary arteries is associated with increased mortality in patients treated medically. However, the presence of a CTO may not increase mortality in patients treated with revascularization. Larger randomized trials are needed to evaluate the effects of revascularization on long-term survival in patients with CTO.

Predicting ischemic mitral regurgitation in patients with acute ST-elevation myocardial infarction: Does time to reperfusion really matter and what is the role of collateral circulation?

BACKGROUND/OBJECTIVES

Ischemic mitral regurgitation (MR) is an adverse prognostic factor. We aimed to assess the role of time delay from symptom onset to reperfusion, and the impact of collateral circulation to incidence of MR in relation to established echocardiographic and clinical risk factors.

METHODS

Patients with STEMI presenting within 12 h from symptom onset and treated with primary percutaneous coronary intervention (PPCI) at Hospital of Lithuanian University of Health Sciences were enrolled. Echocardiography was performed after PPCI. Based on MR grade, patients were divided into no significant MR (NMR, grade 0-I MR, N = 102) and ischemic MR (IMR, grade ≥ 2 MR, N = 71) groups. Well-developed collaterals were defined as grade ≥ 2 by Rentrop classification. Continuous variables were compared by independent samples Student's T-test. Multivariate logistic regression analysis was used to identify independent predictors of ischemic MR.

RESULTS

Time to reperfusion, MI localization, TIMI flow before/after PCI was similar between the groups. IMR group patients were elder, more often females and non-smokers, had lower body mass index, higher prevalence of multi-vessel coronary artery disease (CAD), better-developed collateral supply, greater left ventricular end-diastolic diameter index, left atrial index, pulmonary artery systolic pressure and lower ejection fraction. Multivariate logistic regression analysis revealed that ischemic MR is predicted by female gender, well-developed collateral supply, presence of multi-vessel CAD, and lower EF.

CONCLUSION

In acute STEMI significant MR is unrelated to ischemic time and is predicted by female gender, lower EF, multi-vessel CAD and well-developed collateral supply to the infarct region.

The haemodynamic effects of collateral donation to a chronic total occlusion: Implications for patient management

Physiological lesion assessment in the form of Fractional Flow Reserve (FFR) is now well established for the purpose of guiding multi-vessel revascularization. Chronic total coronary occlusions are frequently associated with multi-vessel disease and the collateral dependent myocardium distal to the occlusion is often supplied by a collateral supply from another epicardial coronary artery. The haemodynamic effect of collateral donation upon collateral donor vessel flow may have important implications for the vessel's FFR; rendering it unreliable at predicting ischaemia should the CTO be revascularized. As a consequence, in the setting of multi-vessel disease, optimal revascularization strategy might be altered. There is a paucity of work in the medical literature directly examining this phenomenon. We endeavoured to review the existing literature related to it, to summarise from current knowledge of coronary physiology what is known about the potential effects of CTO revascularization on both collateral flow and collateral donor vessel physiology, and to highlight where further studies might inform practice.

Physiologic significance of coronary collaterals in chronic total occlusions

Chronic total occlusions (CTOs) are commonly found in patients with coronary artery disease, and a system of collateral connections are found in almost all of these patients. These collateral vessels serve to prevent myocardial necrosis but are not sufficient to prevent myocardial ischemia during exercise. Unfortunately, the presence of well-developed collaterals has been used as argument against CTO revascularization. Many continue to falsely believe that these patients are "protected" by collaterals and, therefore, CTO recanalization is not indicated. Our knowledge of the physiologic significance of coronary collaterals has increased significantly over the past several years. Studies utilizing coronary pressure and flow velocity have answered a number of basic physiologic questions. We therefore sought to review the evidence for coronary collateral flow and their clinical significance in patients with CTOs.

Ventricular tachycardic storm with a chronic total coronary artery occlusion treated with percutaneous coronary intervention

A 66-year-old man with a history of coronary artery disease was evaluated due to ventricular tachycardic (VT) storm. The patient continued to have frequent recurrences of VT despite treatment with amiodarone and lidocaine. Since the ventricular arrhythmia could be related to myocardial ischemia related to a chronic total occlusion (CTO) of the right coronary artery, the patient underwent successful percutaneous coronary intervention of the CTO, followed by implantable cardioverter defibrillator implantation. He had no further episodes of VT during his hospital stay. After 9 months of follow-up, he had no further chest pain or clinically apparent recurrent ischemia. Interrogation of his defibrillator has shown brief nonsustained episodes of ventricular tachycardia, but the patient has not required delivery of a shock. The temporal association between treatment of the CTO and resolution of the VT, as well as the lack of recurrence of sustained VT, suggest a causative link between underlying ischemia produced by a chronically occluded coronary artery and provocation of VT and lend supportive evidence to this treatment approach.

Meta-analysis on the impact of percutaneous coronary intervention of chronic total occlusions on left ventricular function and clinical outcome

BACKGROUND

Percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs) may have a beneficial effect on survival through a better-preserved or improved LVEF. Current literature consists of small observational studies therefore we performed a weighted meta-analysis on the impact of revascularization of CTOs on left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV) and long-term mortality.

METHODS

We conducted a meta-analysis evaluating LVEF before and after CTO PCI and long-term mortality. No language or time restrictions were applied. References from the identified articles and reviews were examined to find additional relevant manuscripts.

RESULTS

Of the 812 citations, 34 studies performed between 1987-2014 in 2243 patients were eligible for LVEF and 27 studies performed between 1990-2013 in 11,085 patients with success and 4347 patients that failed CTO PCI were eligible for long-term mortality. After successful CTO PCI, LVEF increased with 4.44% (95% CI: 3.52-5.35, p<0.01) compared to baseline. In a small cohort of ~70 patients, no significant difference in LVEF was observed after non-successful CTO PCI or reocclusion. Additionally, 8 studies reported the change in left ventricular end-diastolic volume (LVEDV) in a total of 412 patients. LVEDV decreased with 6.14 ml/m(2) (95% CI: -9.31 to -2.97, p<0.01). Successful CTO PCI was also associated with reduced mortality in comparison with failed CTO PCI (OR: 0.52, 95% CI: 0.43-0.62, p-value<0.01).

CONCLUSIONS

The current meta-analysis revealed that successful recanalization of a CTO resulted in an overall improvement of 4.44% absolute LVEF points, reduced adverse remodeling and an improvement of survival (OR: 0.52).

Impact of a chronic total occlusion in an infarct-related artery on the long-term outcome of ventricular tachycardia ablation

INTRODUCTION

In patients with a prior myocardial infarction (MI), angiographic predictors of ventricular tachycardia (VT) recurrence after ablation are lacking. Recently, a proarrhythmic effect of a chronic total occlusion (CTO) in a coronary artery has been suggested.

METHODS AND RESULTS

A total of 191 patients with prior MI were referred to our Hospital between 2010 and June 2013 for a first ablation of VT. Of these, 84 patients (44%) with stable coronary artery disease that underwent a coronary angiography during the index hospitalization were included in this study. A CTO in an infarct-related artery (IRA-CTO) was present in 47 patients (56%). Patients with and without IRA-CTO did not differ in terms of comorbidities, severity of heart failure, presentation of VT or acute outcome of ablation, that was completely successful in 93% of cases. At electroanatomic mapping, IRA-CTO was associated with greater scar and especially with greater area of border zone (34 cm(2) vs. 19 cm(2) , P = 0.001). Median follow-up was 19 months (IQR 18). At follow-up, patients with IRA-CTO had a significantly higher rate of VT recurrence (47% vs. 16%, P = 0.003). At multivariate analysis, IRA-CTO resulted to be an independent predictor of VT recurrence after ablation (HR 4.05, P = 0.004).

CONCLUSIONS

IRA-CTO is an independent predictor of VT recurrence after ablation and identifies a subgroup of patients with high recurrence rate despite a successful procedure. IRA-CTO is associated with greater scars and border zone area; however, this association does not completely justify its proarrhythmic effect.

Percutaneous Treatment of Coronary Chronic Total Occlusions Part 1: Rationale and Outcomes

Coronary chronic total occlusions (CTOs) are commonly encountered in patients with coronary artery disease. Compared to patients without coronary CTOs, those with CTO have worse clinical outcomes and lower likelihood of complete coronary revascularisation. Successful CTO percutaneous coronary intervention (PCI) can significantly improve angina and improve left ventricular function. Although currently unproven, successful CTO PCI might also reduce the risk for arrhythmic events in patients with ischaemic cardiomyopathy, provide better tolerance of future acute coronary syndrome, and possibly improve survival. Evaluation by a heart team comprised of both interventional and non-interventional cardiologists and cardiac surgeons is important for determining the optimal revascularisation strategy in patients with coronary artery disease and CTOs. Ad hoc CTO PCI is generally not recommended, so as to allow sufficient time for (a) discussion with the patient about the indications, goals, risks, and alternatives to PCI; (b) careful procedural planning; and (c) contrast and radiation exposure minimisation. Use of drug-eluting stents is recommended for CTO PCI, given the lower rates of angiographic restenosis compared to bare metal stents.

Contemporary overview and clinical perspectives of chronic total occlusions

Chronic total occlusions (CTOs) are often detected on diagnostic coronary angiograms, but percutaneous coronary intervention (PCI) for CTO is currently infrequently performed owing to high technical difficulty, perceived risk of complications, and a lack of randomized data. However, successful CTO-PCI can significantly increase a patient's quality of life, improve left ventricular function, reduce the need for subsequent CABG surgery, and possibly improve long-term survival. A number of factors must be taken into account for the selection of patients for CTO-PCI, including the extent of ischaemia surrounding the occlusion, the level of myocardial viability, coronary location of the CTO, and probability of procedural success. Moreover, in patients with ST-segment elevation myocardial infarction, a CTO in a noninfarct-related artery might lead to an increase in infarct area, increased end-diastolic left ventricular pressure, and decreased left ventricular function, which are all associated with poor clinical outcomes. In this Review, we provide an overview of the anatomy and histopathology of CTOs, perceived benefits of CTO-PCI, considerations for patient selection for this procedure, and a summary of emerging techniques for CTO-PCI.