Rapid Decline of Collateral Circulation Increases Susceptibility to Myocardial Ischemia

Predictors of long-term adverse outcomes after successful chronic total occlusion intervention: physiology or morphology?

BACKGROUND

Quantitative flow ratio (QFR) and target-vessel SYNTAX score (tvSS) are novel indices used to assess lesion physiology and morphology in percutaneous coronary intervention (PCI). Their prognostic implication after successful recanalization of coronary chronic total occlusion (CTO) is unknown.

OBJECTIVES

To investigate the prognostic value of QFR measured immediately after successful CTO-recanalization in predicting vessel-oriented adverse events, and to compare it with the pre-procedural morphological tvSS.

METHODS

QFR was measured offline after successful CTO-PCIs in a single center. We grouped the patients according to a cut-off value of post-PCI QFR (0.91). The primary outcome was target-vessel failure (TVF) at 2 years.

RESULTS

Among 470 CTO lesions performed during the study period, 324 were eligible for QFR analysis (258 with QFR ≥ 0.91 and 66 with QFR < 0.91). The mean age of the study population was 68.3 ± 10.7 years. The low QFR group had a lower left ventricular ejection fraction (45.8 ± 13.9% vs. 49.8 ± 12.4%, p = 0.025) and a higher rate of atrial fibrillation (19.7% vs. 11.2%, p = 0.020). The mean tvSS was 12.8 ± 4.8, and it showed no significant difference in both groups (13.6 ± 5.1 vs. 12.6 ± 4.6, p = 0.122). Patients with low post-CTO QFR had a trend to develop more TVF at 2 years (21.2% vs. 12.4%, HR 1.74; 95% CI 0.93-3.25, p = 0.086). Low post-CTO QFR failed to predict 2-year TVF (aHR 1.67; 95% CI 0.85-3.29, p = 0.136), while pre-procedural tvSS was an independent predictor for 2-year TVF (aHR 1.06; 95% CI 1.01-1.13, p = 0.030).

CONCLUSION

We found a limited prognostic value of immediate physiological assessment using QFR after successful CTO intervention. Pre-procedure morphological characteristics of CTO lesions using tvSS can play a role in predicting long-term adverse events.

Coronary Artery Bypass Grafting versus Percutaneous Coronary Intervention in Patients with Chronic Total Occlusion

OBJECTIVES

 Mechanisms of coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) differ as CABG provides surgical collateralization and may prolong life by preventing future myocardial infarctions (MIs). However, evidence for CABG in patients with chronic total occlusion (CTO) has not been fully elucidated and the impact of PCI is discussed controversially.

METHODS

 We performed a meta-analysis of studies comparing outcomes in patients with/without multivessel disease undergoing CABG or PCI for CTO. The primary outcome was long-term all-cause mortality (≥5 years). Secondary outcomes were MIs, repeat revascularization, cardiac mortality, major adverse cardiovascular events, and stroke, as well as short-term mortality (30 days/in-hospital) and stroke. A pooled Kaplan-Meier survival curve after reconstruction analysis was generated. Random-effects models were used.

RESULTS

 Six studies totaling 12,504 patients were included. In the pooled Kaplan-Meier analysis, PCI showed a significantly higher risk of death in the follow-up compared with CABG (hazard ratio [HR]: 2.12, 95% confidence interval [CI]: 1.88-2.38, p < 0.01). During the observation period, PCI was also associated with higher rates of MI (odds ratio [OR]: 2.86, 95% CI: 1.82-4.48, p < 0.01) and more repeat revascularization (OR: 4.88, 95% CI: 1.99-11.91, p = 0.0005). The other outcomes did not show significant differences.

CONCLUSION

 CABG is associated with superior survival to PCI over time in patients with CTO who are eligible for both PCI and CABG. This survival advantage is associated with fewer events of MI and repeat revascularization.

Uric acid to high-density lipoprotein cholesterol ratio predicts adverse cardiovascular events in patients with coronary chronic total occlusion

BACKGROUND AND AIMS

Uric acid to high-density lipoprotein cholesterol ratio (UHR) is a novel index of metabolism and inflammation proposed by recent studies. The prognostic value of UHR is undetermined in patients with coronary chronic total occlusion (CTO). The aim of this study was to investigate the association of UHR with adverse cardiovascular events in patients with CTO.

METHODS AND RESULTS

In this retrospective cohort study, we enrolled 566 patients with CTO lesion in our hospital from January 2016 to December 2019. Patients were divided into three groups based on UHR level. The primary endpoint was major adverse cardiovascular event (MACE), defined as a combination of death, non-fatal MI, target vessel revascularization (TVR), and non-fatal stroke. The median follow-up time of this study was 43 months. During the follow-up, 107 (18.9%) MACEs were recorded. Kaplan-Meier survival plots show the cumulative incidence of MACE-free decreased across tertile of UHR (log-rank test, p < 0.001). In the fully adjusted model, the Hazard ratio (95% CI) of MACE was 2.16 (1.17-3.99) in tertile 3 and 2.01 (1.62-2.49) for per SD increase in UHR.

CONCLUSION

Elevated UHR predicts an increasing risk of MACE in patients with CTO. UHR is a simple and reliable indicator for risk stratification and early intervention in CTO patients.

Changes in coronary collateral function after successful chronic total occlusion percutaneous coronary intervention

BACKGROUND

Contemporary chronic total occlusion (CTO) percutaneous coronary intervention (PCI) incorporates wire escalation and dissection/re-entry recanalisation strategies.

AIMS

The purpose of the study was to investigate changes in collateral function after CTO PCI and to identify whether the mode of successful recanalisation influences collateral function regression.

METHODS

Patients scheduled for elective CTO PCI with evidence of viability in the CTO territory by noninvasive imaging were included in this study. After successful CTO PCI, the aortic pressure (Pa) and distal coronary artery wedge pressure (Pw) during balloon occlusion were measured, both in a resting state and during infusion of intravenous adenosine, allowing the calculation of the pressure-derived collateral pressure index at rest and hyperaemia (CPIrest and the collateral fractional flow reserve [FFRcoll], respectively). Measurements were repeated 3 months later during angiographic follow-up.

RESULTS

Eighty-one patients had physiological measurements at baseline and follow-up. In the final cohort the mean age was 64 years and 82% were male. The mean maximal stent diameter and total stent length were 3.2±0.5 mm and 68±31 mm, respectively. Successful strategies were antegrade wiring (64.2%), antegrade dissection re-entry (8.6%), and retrograde dissection re-entry (27.1%). Between the index procedure and follow-up, wedge pressure decreased from 34±11 mmHg to 21±8.5 mmHg (p<0.01), respectively. FFRcoll changed from 0.34±0.11 to 0.19±0.09 (p<0.01) at follow-up and CPIrest from 0.40±0.14 to 0.17±0.09 (p<0.01). Absolute maximum collateral flow decreased from 55±32 ml/min directly after PCI to 38±24 ml/min (p<0.01). There was no relation between the recanalisation technique and changes in FFRcoll.

CONCLUSIONS

There was a significant reduction in collateral flow over time, independent of the recanalisation technique.

The Role of Angiogenesis and Arteriogenesisin Myocardial Infarction and Coronary Revascularization

Surgical myocardial revascularization is associated with long-term survival benefit in patients with multivessel coronary artery disease. However, the exact biological mechanisms underlying the clinical benefits of myocardial revascularization have not been elucidated yet. Angiogenesis and arteriogenesis biologically leading to vascular collateralization are considered one of the endogenous mechanisms to preserve myocardial viability during ischemia, and the presence of coronary collateralization has been regarded as one of the predictors of long-term survival in patients with coronary artery disease (CAD). Some experimental studies and indirect clinical evidence on chronic CAD confirmed an angiogenetic response induced by myocardial revascularization and suggested that revascularization procedures could constitute an angiogenetic trigger per se. In this review, the clinical and basic science evidence regarding arteriogenesis and angiogenesis in both CAD and coronary revascularization is analyzed with the aim to better elucidate their significance in the clinical arena and potential therapeutic use.

Clinical outcomes of percutaneous coronary intervention for chronic total occlusion by treated segment length

BACKGROUND

Long lesions are known to have worse outcomes following percutaneous coronary intervention (PCI), but there are limited data assessing the association between lesion length and clinical outcomes in PCI procedures undertaken in chronic total occlusions (CTO).

METHODS AND RESULTS

We formed a longitudinal cohort (2006-2018, n = 27,205) of stable angina patients who underwent PCI to CTO in the British Cardiovascular Intervention Society (BCIS) database. Clinical, demographical, procedural, and outcome data were analyzed in three groups by treated segment length, < 30 mm (n = 11,782), 30-59 mm (n = 10,415), ≥ 60 mm (n = 5008). Prevalence of previous myocardial infarction and PCI were higher in patients in 30-59 mm group or ≥ 60 mm group compared with < 30 mm group. Following multivariable analysis, no significant difference was observed in in-patient death (OR = 30-59 mm group = 1.10, CI:0.55-2.19, p = 0.78) (OR ≥ 60 mm group = 0.82, CI: 0.33-2.05, p = 0.67), and 1-year death (OR = 30-59 mm group = 1.06, CI: 0.81-1.37, p = 0.69) (OR ≥ 60 mm group =1.01, CI: 0.70-1.43, p = 0.99) (< 30 mm group = reference) but in-patient MACE was higher in > = 60 mm group (OR: 1.52, CI: 1.15-2.01, p = 0.06) but similar in 30-59 mm group (OR: 1.16, CI: 0.91-1.48, p = 0.22) compared with < 30 mm group. The adjusted rates of procedural complications were higher in ≥ 60 mm group (OR: 1.61, CI: 1.40-1.85, p < 0.001) but were similar in 30-59 mm group (OR: 1.06, CI: 0.94-1.20, p < 0.31) compared with < 30 mm group. For every 10 mm increase, there was an increased adjusted risk of in-patient procedural complications and coronary perforation but not in-patient MACE or death.

CONCLUSION

Patients with very long CTO lesions have higher risk of procedural complications and in-patient MACE but similar risk of short or long-term mortality compared with short CTO lesions.

Coronary physiology before and after chronic total occlusion treatment: what does it tell us?

Studies performed in the last two decades demonstrate that after successful percutaneous coronary intervention (PCI) of a chronically occluded coronary artery, the physiology of the chronic total occlusion (CTO) vessel and dependent microvasculature does not normalise immediately but improves significantly over time. Generally, there is an increase in fractional flow reserve (FFR) in the CTO artery, a decrease in collateral blood supply and an increase in FFR in the donor artery accompanied by an increase in blood flow and decrease in microvascular resistance in the myocardium supplied by the CTO vessel. Analogous to these physiological changes, positive remodelling of the distal CTO artery also occurs over time, and intravascular imaging can be helpful for analysing distal vessel parameters. Follow-up coronary angiography with physiological measurements after several weeks to months can be helpful and informative in a subset of patients in order to decide upon the necessity for treatment of residual coronary artery stenosis in the vessel distal to the CTO or in the contralateral donor artery, as well as in deciding whether stent optimisation is indicated. We suggest that such physiological guidance of CTO procedures avoids unnecessary overtreatment during the initial procedure, guides interventions at follow-up, and improves our understanding of what PCI in CTO means.

Prognostic significance of occlusion length in recanalized chronic total occlusion lesion: a retrospective cohort study with 5-year follow-up

OBJECTIVES

This study sought to investigate the relationship between occlusion length and long-term outcomes of patients with recanalised chronic total occlusion (CTO) lesion.

DESIGN

A retrospective cohort study.

SETTING

Fuwai Hospital, National Center for Cardiovascular Disease, Beijing, China PARTICIPANTS: Consecutive patients with successfully recanalised CTO were included from January 2010 to December 2013.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary endpoint of the present study was a composite event of all-cause death and myocardial infarction (MI). The secondary endpoints included target lesion revascularisation (TLR) and target vessel revascularisation (TVR).

RESULTS

A total of 1987 patients were included and 1801 (90.6%) subjects completed 5-year follow-up in this study. Based on occlusion length, the patients were divided equally into two groups: short (length <15 mm, n=957) and long (length ≥15 mm, n=1030) CTO group. Kaplan-Meier survival curve showed no significant difference in the risk of the composite primary endpoint between short and long CTO groups (p=0.242). Receiver operating characteristic curve analysis also established occlusion length ≥15 mm as a cut-off value for predicting TLR and TVR, with an area under the curve of 0.604 (95% CI: 0.569 to 0.638, p<0.001) and 0.605 (95% CI: 0.572 to 0.638; p<0.001). Kaplan-Meier analysis revealed that the risks for TLR (p=0.002) and TVR (p=0.002) were higher in a patient with long CTO lesion. Multivariate Cox analysis also identified long CTO lesion as an independent predictor of TLR (HR: 1.539, 95% CI: 1.033 to 2.293; p=0.034) and TVR (HR: 1.476, 95% CI: 1.012 to 2.151; p=0.043).

CONCLUSION

Patients with long CTO lesion did not show a higher risk of death and MI after recanalisation, but had higher risks of TLR and TVR. Lesion with occlusion length ≥15 mm should be under close surveillance for restenosis after recanalisation.

Prompt and consistent improvement of coronary flow velocity reserve following successful recanalization of the coronary chronic total occlusion in patients with viable myocardium

Background

Coronary chronic total occlusion (CTO) is characterized by the presence of collateral blood vessels which can provide additional blood supply to CTO-artery dependent myocardium. Successful CTO recanalization is followed by significant decrease in collateral donor artery blood flow and collateral derecruitment, but data on coronary hemodynamic changes in relation to myocardial function are limited. We assessed changes in coronary flow velocity reserve (CFVR) by echocardiography in collateral donor and recanalized artery following successful opening of coronary CTO.

Methods

Our study enrolled 31 patients (60 ± 9 years; 22 male) with CTO and viable myocardium by SPECT scheduled for percutaneous coronary intervention (PCI). Non-invasive CFVR was measured in collateral donor artery before PCI, 24 h and 6 months post-PCI, and 24 h and 6 months in recanalized artery following successful PCI of CTO.

Results

Collateral donor artery showed significant increase in CFVR 24 h after CTO recanalization compared to pre-PCI values (2.30 ± 0.49 vs. 2.71 ± 0.45, p = 0.005), which remained unchanged after 6-months (2.68 ± 0.24). Baseline blood flow velocity of the collateral donor artery significantly decreased 24 h post-PCI compared to pre-PCI (0.28 ± 0.06 vs. 0.24 ± 0.04 m/s), and remained similar after 6 months, with no significant difference in maximum hyperemic blood flow velocity pre-PCI, 24 h and 6 months post-PCI. CFVR of the recanalized coronary artery 24 h post-PCI was 2.55 ± 0.35, and remained similar 6 months later (2.62 ± 0.26, p = NS).

Conclusions

In patients with viable myocardium, prompt and significant CFVR increase in both recanalized and collateral donor artery, was observed within 24 h after successful recanalization of CTO artery, which maintained constant during the 6 months.

Trial registration

ClinicalTrials.gov (Number NCT04060615).

Applicability and Interpretation of Coronary Physiology in the Setting of a Chronic Total Occlusion

Concurrent coronary artery disease in a vessel remote from a chronic total occlusion (CTO) is common and presents a management dilemma. While the use of adjunctive coronary physiology to guide revascularization is now commonplace in the catheterization laboratory, the presence of a CTO provides a unique and specific situation whereby the physiological assessment is more complex and relies on theoretical assumptions. Broadly, the physiological assessment of a CTO relies on assessing the function and regression of collaterals, the assessment of the microcirculation, the impact of collateral steal as well as assessing the severity of a lesion in the donor vessel (the vessel supplying the majority of collaterals to the CTO). Recent studies have shown that physiological assessment of the donor vessel in the setting of a CTO may overestimate the severity of stenosis, and that after revascularization of a CTO, the index of ischemia may increase, potentially altering the need for revascularization. In this review article, we present the current literature on physiological assessment of patients with a CTO, management recommendations and identify areas for ongoing research.

Postocclusional Hyperemia for Fractional Flow Reserve After Percutaneous Coronary Intervention

BACKGROUND

Postocclusional hyperemia caused by balloon occlusion is a potential alternative method of inducing hyperemia for measuring post-percutaneous coronary intervention fractional flow reserve (FFR). The aim of this study was to investigate postocclusional hyperemia as a method of inducing hyperemia.

METHODS AND RESULTS

FFR measured by postocclusional hyperemia (FFRoccl) caused by balloon occlusion after percutaneous coronary intervention was compared with FFR measured by drug-induced hyperemia (FFR measured by intravenous ATP; and FFR measured by intracoronary papaverine injection [FFRpap]) in 98 lesions from 98 patients. The hyperemia duration was also measured for FFRoccl and FFRpap. The correlation coefficient between FFRoccl, FFR measured by intravenous ATP (r=0.973; P<0.01), and FFRpap (r=0.975; P<0.01) showed almost identical values to those obtained for the correlation coefficient between FFR measured by intravenous ATP and FFRpap (r=0.967; P<0.01). No clear difference was observed on Bland-Altman analysis. Hyperemia duration was significantly longer with FFRoccl than with FFRpap (70±22 versus 51±25 s; P<0.01).

CONCLUSIONS

Strong correlations were found between FFRoccl and FFR measured by intravenous ATP and FFRoccl and FFRpap. Hyperemia caused by FFRoccl was significantly longer than that caused by FFRpap.

The impact of coronary chronic total occlusion percutaneous coronary intervention upon donor vessel fractional flow reserve and instantaneous wave-free ratio: Implications for physiology-guided PCI in patients with CTO

OBJECTIVE

To investigate the immediate and short term impact of right coronary artery (RCA) chronic total coronary occlusion (CTO) percutaneous coronary intervention (PCI) upon collateral donor vessel fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR).

BACKGROUND

CTO PCI influences collateral donor vessel physiology, making the indication and/or timing of donor vessel revascularization difficult to determine.

METHODS

In patients with RCA CTO, FFR, iFR, and collateral function index (FFR_coll ) were measured in LAD and LCx pre-CTO PCI, immediately post and at 4 month follow-up.

RESULTS

34 patients underwent successful PCI. In the predominant donor vessel immediately post PCI, FFR, and FFR_coll did not change (0.76 ± 0.12 to 0.75 ± 0.13, P = 0.267 and 0.31 ± 0.10 vs. 0.34 ± 0.11, P = 0.078), but iFR increased significantly (0.86 ± 0.10 to 0.88 ± 0.10, P = 0.012). At follow-up, there was a significant increase in predominant donor FFR and iFR (0.76 ± 0.12 to 0.79 ± 0.11, P = 0.047 and 0.86 ± 0.10 to 0.90 ± 0.07, P = 0.003), accompanied by a significant reduction in FFR_coll (0.31 ± 0.10 to 0.18 ± 0.07 P < 0.0001). These changes resulted in a reclassification of the predominant donor vessel from ischemic to nonischemic in 18% (FFR) and 25% (iFR) of the cases, respectively.

CONCLUSIONS

Successful recanalization of an RCA CTO resulted in a modest but statistically significant increase in the predominant donor vessel immediately post CTO PCI in the case of iFR and at 4-month follow-up for FFR and iFR compared to pre-PCI with a concomitant reduction in collateral function.

Coronary Collaterals Function and Clinical Outcome Between Patients With Acute and Chronic Total Occlusion

OBJECTIVES

This study sought to demonstrate how changes in the collateral function and its clinical significance before and after percutaneous coronary interventions (PCIs) are compared between patients with acute coronary syndrome and total or nearly total occlusions (ATOs) and chronic total occlusions (CTOs).

BACKGROUND

The functional relevance of the collateral circulation in patients with ATOs and CTOs has not been fully investigated.

METHODS

The pressure-derived collateral pressure index (CPI), myocardial fractional flow reserve (FFRmyo), and coronary fractional flow reserve (FFRcor) at maximum hyperemia induced by intravenous adenosine were evaluated in occluded vessels at baseline, after the PCI, and at 1 year in 23 ATO and 74 CTO patients.

RESULTS

The FFRmyo and FFRcor were significantly lower, but the CPI was significantly higher in the CTO than ATO patients at baseline and after the PCI. There were significant increases in the FFRmyo (p < 0.001) and FFRcor (p < 0.001), whereas there was no significant change in the CPI immediately after the PCI in both ATO and CTO patients. In the CTO patients, a post-PCI FFRmyo <0.90 (p = 0.01) and post-PCI CPI <0.25 (p = 0.033) were independent predictors of the clinical outcome. Patients with a high post-PCI CPI had better clinical outcomes in CTO patients with a low post-PCI FFRmyo (log-rank p = 0.009), but not a high post-PCI FFRmyo (log-rank p = 0.492).

CONCLUSIONS

Recruitable coronary collateral flow did not regress completely immediately after the PCI both in patients with ATOs and CTOs. Despite good collaterals in CTO patients, aggressive efforts to reduce the ischemic burden might improve the clinical outcome.

Impact of coronary collateral circulation on angiographic in-stent restenosis in patients with stable coronary artery disease and chronic total occlusion

OBJECTIVE

This study aimed to evaluate the relationship between coronary collateralization and in-stent restenosis (ISR) in stable coronary artery disease patients with chronic total occlusion (CTO) after percutaneous coronary intervention (PCI) with drug-eluting stent (DES) implantation.

METHODS

The degree of coronary collaterals supplying the distal aspect of a total occlusion from the contra-lateral vessel was graded according to Rentrop classification in 216 patients with stable angina undergoing successful DES based PCI for CTO. Univariable and multivariable logistic regression analyses were performed to assess the potential factors related to angiographic ISR during follow-up.

RESULTS

Despite similar number of diseased coronary arteries, good collateralization (Rentrop score 2 or 3) was more frequently associated with right coronary artery occlusion (60%), whereas poor collaterals (Rentrop score 0 or 1) occurred more often in left anterior descending artery occlusion (40%). Despite similar number of CTO intervened, stent length was longer in patients with good collateralization (59±27mm vs 47±23mm, p=0.001). At mean 18months, the rate of ISR did not significantly differ between patients with good collateralization and those with poor collateralization (12.7% vs 20.2%, p=0.148). At multivariable analysis, age (OR 1.058, 95%CI 1.015-1.104, p=0.008), history of diabetes mellitus (OR 2.382, 95%CI 1.109-5.116, p=0.026) and reference CTO vessel diameter (OR 0.219, 95% CI 0.051-0.951, p=0.043) were independent risk factors for ISR while Rentrop collateral grade (OR 0.795, 95% CI 0.365-1.732, p=0.414) was not associated with ISR.

CONCLUSIONS

The occurrence of ISR after successful DES based PCI for CTO may be not influenced by coronary collateralization.

[Chronic coronary occlusions : When and how should revascularization be performed?]

Chronic occlusion of coronary arteries also known as chronic total occlusions (CTO) are found in approximately 20 % of patients undergoing percutaneous coronary interventions (PCI) and in approximately 50 % of patients after coronary artery bypass grafts (CABG). As a result of technical advancements in retrograde recanalization techniques specialized centers can now achieve success rates of over 85 %, regardless of the CTO anatomy. Given the complexity of retrograde CTO techniques, a consensus paper issued by the Euro CTO Club requires interventional cardiologists to have sufficient experience in antegrade approaches (>300 antegrade CTO cases and >50 per year) with an additional training program (25 retrograde cases each as first and second operating surgeon) before becoming a qualified independent retrograde surgeon. The increased investment in time and technical resources can only be justified if the patient has a clear clinical benefit. This technical advancement and the progressively clearer evidence that complete revascularization can be achieved in patients with multivessel coronary artery disease have attracted growing interest in recent years from interventional cardiologists in the recanalization of CTO.

Localizing factors in atherosclerosis

Atherosclerotic vascular disease is the leading cause of death worldwide. Although the entire vascular bed is constantly exposed to the same risk factors, atheromatous lesions present a distinct intra-individual pattern of localization and progression, being consistently more frequent in specific segments of the arterial vascular bed. This peculiar distribution may be related to selective sensitivity of such locations to the influence of risk factors or to histopathological and flow differences, and has relevant clinical implications, as the prognosis of the disease varies according to localization. We here review the theories that have been formulated to explain such preferential locations, as its understanding can be useful to pursue diagnostic screening strategies and focused preventive measures.

Biomarkers of coronary endothelial health: correlation with invasive measures of collateral function, flow and resistance in chronically occluded coronary arteries and the effect of recanalization

OBJECTIVES

In the presence of a chronically occluded coronary artery, the collateral circulation matures by a process of arteriogenesis; however, there is considerable variation between individuals in the functional capacity of that collateral network. This could be explained by differences in endothelial health and function. We aimed to examine the relationship between the functional extent of collateralization and levels of biomarkers that have been shown to relate to endothelial health.

METHODS

We measured four potential biomarkers of endothelial health in 34 patients with mature collateral networks who underwent a successful percutaneous coronary intervention (PCI) for a chronic total coronary occlusion (CTO) before PCI and 6-8 weeks after PCI, and examined the relationship of biomarker levels with physiological measures of collateralization.

RESULTS

We did not find a significant change in the systemic levels of sICAM-1, sE-selectin, microparticles or tissue factor 6-8 weeks after PCI. We did find an association between estimated retrograde collateral flow before CTO recanalization and lower levels of sICAM-1 (r=0.39, P=0.026), sE-selectin (r=0.48, P=0.005) and microparticles (r=0.38, P=0.03).

CONCLUSION

Recanalization of a CTO and resultant regression of a mature collateral circulation do not alter systemic levels of sICAM-1, sE-selectin, microparticles or tissue factor. The identified relationship of retrograde collateral flow with sICAM-1, sE-selectin and microparticles is likely to represent an association with an ability to develop collaterals rather than their presence and extent.

Collateral donor artery physiology and the influence of a chronic total occlusion on fractional flow reserve

BACKGROUND

The presence of a concomitant chronic total coronary occlusion (CTO) and a large collateral contribution might alter the fractional flow reserve (FFR) of an interrogated vessel, rendering the FFR unreliable at predicting ischemia should the CTO vessel be revascularized and potentially affecting the decision on optimal revascularization strategy. We tested the hypothesis that donor vessel FFR would significantly change after percutaneous coronary intervention of a concomitant CTO.

METHODS AND RESULTS

In consecutive patients undergoing percutaneous coronary intervention of a CTO, coronary pressure and flow velocity were measured at baseline and hyperemia in proximal and distal segments of both nontarget vessels, before and after percutaneous coronary intervention. Hemodynamics including FFR, absolute coronary flow, and the coronary flow velocity-pressure gradient relation were calculated. After successful percutaneous coronary intervention in 34 of 46 patients, FFR in the predominant donor vessel increased from 0.782 to 0.810 (difference, 0.028 [0.012 to 0.044]; P=0.001). Mean decrease in baseline donor vessel absolute flow adjusted for rate pressure product: 177.5 to 139.9 mL/min (difference -37.6 [-62.6 to -12.6]; P=0.005), mean decrease in hyperemic flow: 306.5 to 272.9 mL/min (difference, -33.5 [-58.7 to -8.3]; P=0.011). Change in predominant donor vessel FFR correlated with angiographic (%) diameter stenosis severity (r=0.44; P=0.009) and was strongly related to stenosis severity measured by the coronary flow velocity-pressure gradient relation (r=0.69; P<0.001).

CONCLUSIONS

Recanalization of a CTO results in a modest increase in the FFR of the predominant collateral donor vessel associated with a reduction in coronary flow. A larger increase in FFR is associated with greater coronary stenosis severity.

Fatal derecruitment of occluded left anterior descending collaterals after left circumflex revascularization

Coronary arteries are not definitely functionally terminal arteries, as previously thought; indeed, they are linked and interconnected by a rich network of collaterals. Chronic total occlusions (CTOs) represent a subset of frequent lesions encountered in everyday catheterization laboratory practice, generally associated with a developed system of collateral connections. These latter have the capacity to prevent myocardial necrosis and may even uphold metabolic supply to the ischemic territory to maintain its contractile capacity. Authors have reported a rapid and progressive reduction of collateral function and their decline after antegrade flow restoration, resulting in higher myocardial susceptibility to ischemia in the CTO territory. Here, we report the case of a fatal derecruitment of collaterals for a left anterior descending CTO not reopened, after left circumflex subocclusion revascularization.

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.

The role of coronary collaterals in chronic total occlusions

A chronic total occlusion (CTO) describes a completely occluded coronary artery. This type of lesion is found in about 18% of all significant lesions in patients with coronary artery disease. A system of collateral connections are observed in almost all of these lesions, which have the capacity to prevent myocardial necrosis and may even uphold metabolic supply to the territory distal to an occlusion to maintain full contractile capacity. During exercise these collaterals are limited in their functional reserve, and more than 90% of patients with a well collateralized occlusion will experience ischemia. in the absence of ideal animal models that mimic the human collateral circulation, we need to rely on studies in man. The knowledge of collateral physiology in man has increased considerably over the past two decades with the advent of intracoronary sensors of coronary pressure and flow velocity. A number of basic physiologic questions have been answered by these studies. The blood supply through coronary arteries depends on a complex array of in general serial resistance systems, with an additional array of multiple parallel resistances on the collateral level. There seems to be a great interindividual variability in the ability to recruit preformed collateral connections in the case of an epicardial occlusion. Collateral function can develop to a similar functional level in patients post myocardial infarction with large akinetic territories as it does in patients with normal preserved regional function. The presence of viability is thus not a prerequisite for collateral development. The question of practical relevance in the era of interventional therapy of chronic occlusions is also, whether a patient with coronary artery disease will remain protected by collaterals after removing the obstruction in the collateralized artery, or whether collaterals regress and lose their functional capacity. Both developments are observed again mainly depending of individual predisposition.

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.

Does rich coronary collateral circulation distal to chronically occluded left anterior descending artery compete with graft flow?

OBJECTIVES

In coronary artery bypass grafting (CABG), graft flow distal to a mild stenosis can compete with relatively preserved native flow through the stenosis and the competition can result in graft stenosis. In chronic total occlusion (CTO), coronary collateral circulation, which is essential to maintain myocardial viability distal to CTO, varies in extent among patients and the extent can be scored by Rentrop grade in coronary angiography. We investigated whether rich collateral circulation distal to CTO competes with distally anastomosed graft flow in association with Rentrop grade.

METHODS

Of 666 patients who underwent CABG from January 2001 to December 2012, 70 patients whose left internal thoracic artery (ITA) was grafted distal to CTO in the left anterior descending artery (LAD) were divided into three groups: Poor collaterals (Rentrop grades 0 and 1, Group P, n = 22), Moderate collaterals (grade 2, Group M, n = 23) and Rich collaterals (grade 3, Group R, n = 25). The intraoperative measurements of mean graft flow (MGF) and pulsatility index (PI) of left ITA grafts, early graft patency and long-term clinical outcomes were compared.

RESULTS

The MGF and PI of left ITA grafts differed significantly among the three groups (P = 0.025 and P = 0.046, respectively). Lower Rentrop grade was associated with preferable results of higher MGF and lower PI. The graft flow pattern in Group P showed a significantly higher MGF (P = 0.020) and lower PI (P = 0.041) than those in Group R. All early postoperative coronary angiograms showed patent left ITA grafts. Serial echocardiographic evaluations, survival rates and cardiac event-free rates were comparable with the follow-up of 5.00 ± 3.11 years.

CONCLUSIONS

Rich collateral circulation distal to CTO in LADs can potentially compete with graft flow, although the competition seems not to affect clinical outcomes probably due to the regression of collaterals surmounted by the graft flow. Rentrop grade is shown to certainly reflect the degree of collateral haemodynamic circulation distal to CTO and especially important to evaluate intraoperative graft flow appropriately, considering the possible phenomenon of graft flow competition.

Evaluation of coronary steal in myocardium supplied by coronary collaterals: the role of speckle tracking analysis in resting and stress echocardiography

Coronary steal could develop in patients with chronic coronary artery disease (CAD) with collateral circulation, and adversely affect ventricular function and long-term clinical outcome. Poorly developed collaterals are more prone than well-developed collaterals to withdrawing their blood support to the collateralized myocardium due to higher collateral pathway resistance and lower vasodilatory reserve of the collateral bed. Even with well-developed coronary collaterals, coronary steal could still occur when perfusion pressure in the donor artery becomes low, or the recipient microvasculature is maximally dilated with exhaustion of vasodilatory reserve. The evaluation of distinctive coronary collateral function with or without steal provides important therapeutic and prognostic information in patients with chronic CAD. However, due to lack of reliable assessment methods, the detection and quantitative measurement of coronary steal remains a challenge. In this article, we present typical clinical scenarios to illustrate the major mechanisms underlying coronary steal in patients with chronic CAD and coronary collateral circulation, and review invasive and noninvasive methods currently available to assess coronary steal in myocardium supplied by coronary collaterals. We specifically focus on recent advances in the resting and stress echocardiography with speckle tracking techniques.

Percutaneous recanalization of chronic total occlusions: wherein lies the body of proof?

Although interventional technology and skills have markedly advanced, percutaneous coronary intervention (PCI) for coronary chronic total occlusion (CTO) lesions remains challenging. Indeed, CTO PCI is technically complex, carries the potential for a relatively high likelihood of failure and acute complications, and requires specifically skilled operators and a demanding use of resources. In addition, controversy persists surrounding appropriate indications for attempting CTO revascularization. Finally, there is a wide uncertainty on the actual benefits achieved with successful CTO recanalization. A growing number of studies have reported procedural results and/or assessed functional effects and long-term clinical outcomes of CTO PCI. We therefore sought to review and critically appraise the evidence base for procedural outcomes and potential clinical benefits of CTO PCI.

Rotational atherectomy: a "survivor" in the drug-eluting stent era

Mechanical debulking of coronary plaques with rotational atherectomy (RA) has been used for more than 20 years during percutaneous coronary interventions (PCI). Modification of plaque characteristics may be accomplished with selective ablation of inelastic fibrocalcific tissue. The use of RA, though reduced with the development of bare-metal stents (BMS) and even more with drug-eluting stents (DES), has never been completely abandoned. The present review will analyze reasons for conflicting results obtained in large series and randomized trials on this topic in the past, and will identify criteria for an appropriate use in current times.

Improvement of fractional flow reserve and collateral flow by treatment with external counterpulsation (Art.Net.-2 Trial)

BACKGROUND

Arteriogenesis (collateral artery growth) is nature's most efficient rescue mechanism to overcome the fatal consequences of arterial occlusion or stenosis. The goal of this trial was to investigate the effect of external counterpulsation (ECP) on coronary collateral artery growth.

MATERIALS AND METHODS

A total of 23 patients (age 61 +/- 2.5 years) with stable coronary artery disease and at least one haemodynamic significant stenosis eligible for percutaneous coronary intervention were prospectively recruited into the two study groups in a 2 : 1 manner (ECP : control). One group (ECP group, n = 16) underwent 35 1-h sessions of ECP in 7 weeks. In the control group (n = 7), the natural course of collateral circulation over 7 weeks was evaluated. All patients underwent a cardiac catheterization at baseline and after 7 weeks, with invasive measurements of the pressure-derived collateral flow index (CFIp, primary endpoint) and fractional flow reserve (FFR).

RESULTS

In the ECP group, the CFIp (from 0.08 +/- 0.01 to 0.15 +/- 0.02; P < 0.001) and FFR (from 0.68 +/- 0.03 to 0.79 +/- 0.03; P = 0.001) improved significantly, while in the control group no change was observed. Only the ECP group showed a reduction of the Canadian Cardiovascular Society (CCS, P = 0.008) and New York Heart Association (NYHA, P < 0.001) classification.

CONCLUSION

In this study, we provide direct functional evidence for the stimulation of coronary arteriogenesis via ECP in patients with stable coronary artery disease. These data might open a novel noninvasive and preventive treatment avenue for patients with non-acute vascular stenotic disease.

Three-year clinical outcome after primary stenting of totally occluded native coronary arteries: a randomized comparison of bare-metal stent implantation with sirolimus-eluting stent implantation for the treatment of total coronary occlusions (Primary Stenting of Totally Occluded Native Coronary Arteries [PRISON] II study)

BACKGROUND

The purpose of this study was to examine the 3-year clinical outcome in patients enrolled in the Primary Stenting of Totally Occluded Native Coronary Arteries II study.

METHODS

Patients with totally occluded coronary arteries randomized to either sirolimus-eluting Cypher stents (SESs) (Cordis, a Johnson & Joshson Company, Miami Lakes, FL) (100 patients) or bare-metal BxVelocity stents (BMSs) (Cordis) (100 patients) were followed clinically for 3 years.

RESULTS

Between 1 and 3 years, there were infrequent additional clinical events that were equally distributed between the SES and the BMS group. After 3 years, target lesion revascularization was 7% in the SES group versus 27% in the BMS group (P < .001); and target vessel revascularization was seen in 11% in the SES group versus 30% in the BMS group (P = .002). Major adverse cardiac events were noted in 10% of the SES group versus 34% in the BMS group (P < .001). There were no statistically significant differences in death, myocardial infarction, and stent thrombosis according to the Academic Research Consortium criteria between the 2 groups.

CONCLUSIONS

Clinical outcome up to 3 years after implantation of SESs for total coronary occlusions continues to demonstrate a significant reduction in adverse clinical events compared with BMSs without the evidence for either disproportionate late restenosis or late stent thrombosis.

Late Intervention on an Occluded Infarct-Related Artery: A Meta-analysis of the Randomized Controlled Trials

Context

Late intervention to open an occluded infarct-related artery (IRA) after initial acute myocardial infarction was postulated to lead to clinical benefit.

Objective

To conduct a meta-analysis of the randomized trials.

Study Selection

Eligibility criteria were: 1) randomized trials comparing percutaneous coronary intervention (PCI) in a totally occluded artery (TIMI flow 0-1) versus medical therapy, 2) in stable post myocardial infarction (MI) patients without spontaneous or low level exercise induced ischemia, 3) trials with a time from the onset of symptoms to randomization >24 hours, but <6 weeks, and 4) trials reporting mortality and recurrent MI as an endpoint. Of 961 citations reviewed, 3 disagreements were easily resolved by discussion and 6 trials were selected for inclusion.

Data Synthesis

The primary endpoint was the composite of recurrent MI or death. The secondary endpoints were the development of heart failure or recurrent myocardial infarction. In a meta-analysis of the 6 trials, which included 2642 patients, late intervention of an IRA had a RR of death or recurrent MI of 1.12 (95% CI 0.91-1.38). Data regarding the development of heart failure was available for 4 trials. In a meta-analysis of these 4 trials, which included 2527 patients, late intervention of an IRA had a RR of 0.79 (95% CI 0.58-1.08). Data regarding the occurrence of recurrent MI was available for 5 trials. In a meta-analysis of these 5 trials, which included 2598 patients, late intervention of an IRA had a RR of 1.28 (95% CI 0.91-1.79).

Conclusions

Our meta-analysis of the currently available randomized data addressing late intervention of an occluded IRA failed to reveal clinical benefit with regard to the clinical endpoints of death, heart failure or reinfarction. The trend towards an increase in reinfarction among the PCI treated patients suggested by the Open Artery Trial (OAT) investigators persisted, but did not achieve statistical significance.

Coronary Collaterals Remain Recruitable After Percutaneous Intervention

Background— Rapid loss of collateral support has been reported after percutaneous coronary intervention (PCI), leaving the myocardium susceptible to subsequent infarction. However, well-developed collaterals have been found in normal hearts, suggesting that collaterals exist even in the absence of an ischemic stimulus. We assessed the plasticity and determinants of collateral supply after PCI.

Methods and Results— Collateral flow index (CFI) was calculated in 60 patients as (P w −P v )/(P a −P v ) by measurement of aortic (P a ), central venous (P v ), and coronary wedge (P w ) pressures. CFI was reassessed during transient balloon occlusion 5 minutes and 24 hours after PCI in the first 29 patients and at 6 months in the subsequent 25 patients. We also evaluated the relationship between collateral supply, lesion characteristics, and circulating hemopoietic cells numbers before and after successful PCI. CFI at baseline was 0.23±0.10, with no change 5 minutes and 1 day later (0.21±0.12, P =0.62; and 0.22±0.11, P =0.96, respectively). At 6 months, CFI was 0.14±0.07 or 63±27% of the baseline value ( P <0.001). CFI was proportional to severity of the coronary lesion at baseline ( r =0.63, P <0.0001) but not 6 months after PCI ( r =−0.04, P =0.87). The number of circulating CD133 + and CD34 + cells was associated with CFI 6 months after PCI (CD133, r =0.59, P =0.035; CD34, r =0.63, P =0.037).

Conclusions— Coronary collateral flow remains undiminished for at least 24 hours after successful PCI. Functional collateral support subsequently declines but does not regress completely.