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

Chronic total coronary occlusions, distal collateral supply and implications of recanalisation

The optimal treatment for patients with a chronic total coronary occlusion (CTO) is controversial, both in terms of the decision whether to revascularise and with respect to the physiological effect of recanalisation on revascularisation strategy.Physiological lesion assessment in the form of fractional flow reserve (FFR) is now well established for the purpose of guiding multi-vessel revascularisation. CTOs 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. 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 revascularised. These haemodynamic changes along with the changes in the target vessel after recanalisation of the occlusion are not well described.The ability to form a functional collateral supply varies considerably between individuals. As arteriogenesis is an endothelium dependent process we hypothesised that biomarkers of endothelial health might be associated with the degree of functional collateralisation measured invasively in the coronary vessel segment distal to a CTO.In this series of studies, I first compare long-term outcomes between patients with a chronic total coronary occlusion treated electively by medical therapy or CTO PCI. I go on to study the haemodynamic changes associated with CTO PCI. Firstly, the associated changes in physiology in the non-CTO vessels and how these changes might influence best revascularisation strategy. Secondly, the haemodynamics in the recently recanalised CTO vessel and the effect that might have on physiological optimization of the PCI result. Finally, I compare coronary haemodynamics taken at the time of CTO PCI with biomarkers of endothelial health to investigate a link between their levels and degree of functional collateralisation. The over-arching goal of this thesis is to add to our understanding of how best to manage patients with a chronic total coronary occlusion

Medical therapy, percutaneous coronary intervention and prognosis in patients with chronic total occlusions

Objective There is little published data reporting outcomes for those found to have a chronic total coronary occlusion (CTO) that is electively treated medically versus those treated by percutaneous coronary intervention (PCI). We sought to compare long-term clinical outcomes between patients treated by PCI and elective medical therapy in a consecutive cohort of patients with an identified CTO. Methods Patients found to have a CTO on angiography between January 2002 and December 2007 in a single tertiary centre were identified using a dedicated database. Those undergoing CTO PCI and elective medical therapy to the CTO were propensity matched to adjust for baseline clinical and angiographic differences. Results In total, 1957 patients were identified, a CTO was treated by PCI in 405 (20.7%) and medical therapy in 667 (34.1%), 885 (45.2%) patients underwent coronary artery bypass graft surgery. Of those treated by PCI or medical therapy, propensity score matching identified 294 pairs of patients, PCI was successful in 177 patients (60.2%). All-cause mortality at 5 years was 11.6% for CTO PCI and 16.7% for medical therapy HR 0.63 (0.40 to 1.00, p=0.052). The composite of 5-year death or myocardial infarction occurred in 13.9% of the CTO PCI group and 19.6% in the medical therapy group, HR 0.64 (0.42 to 0.99, p=0.043). Among the CTO PCI group, if the CTO was revascularised by any means during the study period, 5-year mortality was 10.6% compared with 18.3% in those not revascularised in the medical therapy group, HR 0.50 (0.28–0.88, p=0.016). Conclusions Revascularisation, but not necessarily PCI of a CTO, is associated with improved long-term survival relative to medical therapy alone

Microvascular dysfunction in the immediate aftermath of chronic total coronary occlusion recanalization

Objectives The aim of this study was to compare microvascular resistance under both baseline and hyperemic conditions immediately after percutaneous coronary intervention (PCI) of a chronic total occlusion (CTO) with an unobstructed reference vessel in the same patient. Background Microvascular dysfunction has been reported to be prevalent immediately after CTO PCI. However, previous studies have not made comparison with a reference vessel. Patients with a CTO may have global microvascular and/or endothelial dysfunction, making comparison with established normal values misleading. Methods After successful CTO PCI in 21 consecutive patients, coronary pressure and flow velocity were measured at baseline and hyperemia in distal segments of the CTO/target vessel and an unobstructed reference vessel. Hemodynamics including hyperemic microvascular resistance (HMR), basal microvascular resistance (BMR), and instantaneous minimal microvascular resistance at baseline and hyperemia were calculated and compared between reference and target/CTO vessels. Results After CTO PCI, BMR was reduced in the target/CTO vessel compared with the reference vessel: 3.58 mm Hg/cm/s vs 4.94 mm Hg/cm/s, difference −1.36 mm Hg/cm/s (−2.33 to −0.39, p = 0.008). We did not detect a difference in HMR: 1.82 mm Hg/cm/s vs 2.01 mm Hg/cm/s, difference −0.20 (−0.78 to 0.39, p = 0.49). Instantaneous minimal microvascular resistance correlated strongly with the length of stented segment at baseline (r = 0.63, p = 0.005) and hyperemia (r = 0.68, p = 0.002). Conclusions BMR is reduced in a recanalized CTO in the immediate aftermath of PCI compared to an unobstructed reference vessel; however, HMR appears to be preserved. A longer stented segment is associated with increased microvascular resistance

Timing of invasive strategy in non-ST-elevation acute coronary syndrome: risk and reward?

This commentary refers to ‘Timing of invasive strategy in elevation acute coronary syndrome: a meta-analysis of randomized controlled trials’, by T.A. Kite et al., https://doi.org/10.1093/eurheartj/ehac213 and the discussion piece ‘Timing of early invasive strategy in patients with non-ST-elevation acute coronary syndrome’, by A.I. Aladin et al., https://doi.org/10.1093/eurheartj/ehac466

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

Timing of invasive strategy in non-ST-elevation acute coronary syndrome: a meta-analysis of randomized controlled trials

AIMS: The optimal timing of an invasive strategy (IS) in non-ST-elevation acute coronary syndrome (NSTE-ACS) is controversial. Recent randomized controlled trials (RCTs) and long-term follow-up data have yet to be included in a contemporary meta-analysis. METHODS AND RESULTS: A systematic review of RCTs that compared an early IS vs. delayed IS for NSTE-ACS was conducted by searching MEDLINE, Embase, and Cochrane Central Register of Controlled Trials. A meta-analysis was performed by pooling relative risks (RRs) using a random-effects model. The primary outcome was all-cause mortality. Secondary outcomes included myocardial infarction (MI), recurrent ischaemia, admission for heart failure (HF), repeat re-vascularization, major bleeding, stroke, and length of hospital stay. This study was registered with PROSPERO (CRD42021246131). Seventeen RCTs with outcome data from 10 209 patients were included. No significant differences in risk for all-cause mortality [RR: 0.90, 95% confidence interval (CI): 0.78-1.04], MI (RR: 0.86, 95% CI: 0.63-1.16), admission for HF (RR: 0.66, 95% CI: 0.43-1.03), repeat re-vascularization (RR: 1.04, 95% CI: 0.88-1.23), major bleeding (RR: 0.86, 95% CI: 0.68-1.09), or stroke (RR: 0.95, 95% CI: 0.59-1.54) were observed. Recurrent ischaemia (RR: 0.57, 95% CI: 0.40-0.81) and length of stay (median difference: -22 h, 95% CI: -36.7 to -7.5 h) were reduced with an early IS. CONCLUSION: In all-comers with NSTE-ACS, an early IS does not reduce all-cause mortality, MI, admission for HF, repeat re-vascularization, or increase major bleeding or stroke when compared with a delayed IS. Risk of recurrent ischaemia and length of stay are significantly reduced with an early IS

Wire-based antegrade dissection re-entry technique for coronary chronic total occlusions percutaneous revascularization: Experience from the ERCTO Registry

Background: The recent development and widespread adoption of antegrade dissection re-entry (ADR) techniques have been underlined as one of the antegrade strategies in all worldwide CTO consensus documents. However, historical wire-based ADR experience has suffered from disappointing long-term outcomes.Aims: Compare technical success, procedural success, and long-term outcome of patients who underwent wire-based ADR technique versus antegrade wiring (AW).Methods: One thousand seven hundred and ten patients, from the prospective European Registry of Chronic Total Occlusions (ERCTO), underwent 1806 CTO procedures between January 2018 and December 2021, at 13 high-volume ADR centers. Among all 1806 lesions attempted by the antegrade approach, 72% were approached with AW techniques and 28% with wire-based ADR techniques.Results: Technical and procedural success rates were lower in wire-based ADR than in AW (90.3% vs. 96.4%, p < 0.001; 87.7% vs. 95.4%, p < 0.001, respectively); however, wire-based ADR was used successfully more often in complex lesions as compared to AW (p = 0.017). Wire-based ADR was used in most cases (85%) after failure of AW or retrograde procedures. At a mean clinical follow-up of 21 & PLUSMN; 15 months, major adverse cardiac and cerebrovascular events (MACCEs) did not differ between AW and wire-based ADR (12% vs. 15.1%, p = 0.106); both AW and wire-based ADR procedures were associated with significant symptom improvements.Conclusions: As compared to AW, wire-based ADR is a reliable and effective strategy successfully used in more complex lesions and often after the failure of other techniques. At long-term follow-up, patient's MACCEs and symptoms improvement were similar in both antegrade techniques

Very early invasive angiography versus standard of care in higher-risk non-ST elevation myocardial infarction: study protocol for the prospective multicentre randomised controlled RAPID N-STEMI trial

Background: There are a paucity of randomised data on the optimal timing of invasive coronary angiography (ICA) in higher-risk patients with non-ST elevation myocardial infarction (N-STEMI). International guideline recommendations for early ICA are primarily based on retrospective subgroup analyses of neutral trials. Aims: The RAPID N-STEMI trial aims to determine whether very early percutaneous revascularisation improves clinical outcomes as compared with a standard of care strategy in higher-risk N-STEMI patients. Methods and analysis: RAPID N-STEMI is a prospective, multicentre, open-label, randomised-controlled, pragmatic strategy trial. Higher-risk N-STEMI patients, as defined by Global Registry of Acute Coronary Events 2.0 score ≥118, or &gt;90 with at least one additional high-risk feature, were randomised to either: very early ICA±revascularisation or standard of care timing of ICA±revascularisation. The primary outcome is the proportion of participants with at least one of the following events (all-cause mortality, non-fatal myocardial infarction and hospital admission for heart failure) at 12 months. Key secondary outcomes include major bleeding and stroke. A hypothesis generating cardiac magnetic resonance (CMR) substudy will provide mechanistic data on infarct size, myocardial salvage and residual ischaemia post percutaneous coronary intervention. On 7 April 2021, the sponsor discontinued enrolment due to the impact of the COVID-19 pandemic and lower than expected event rates. 425 patients were enrolled, and 61 patients underwent CMR. Ethics and dissemination: The trial has been reviewed and approved by the East of England Cambridge East Research Ethics Committee (18/EE/0222). The study results will be submitted for publication within 6 months of completion. Trial registration number: NCT03707314; Pre-results