No-reflow phenomenon after acute myocardial infarction is associated with reduced clot permeability and susceptibility to lysis

Intracoronary thrombolysis in ST-elevation myocardial infarction: a systematic review and meta-analysis

BACKGROUND

Despite restoration of epicardial blood flow in acute ST-elevation myocardial infarction (STEMI), inadequate microcirculatory perfusion is common and portends a poor prognosis. Intracoronary (IC) thrombolytic therapy can reduce microvascular thrombotic burden; however, contemporary studies have produced conflicting outcomes.

OBJECTIVES

This meta-analysis aims to evaluate the efficacy and safety of adjunctive IC thrombolytic therapy at the time of primary percutaneous coronary intervention (PCI) among patients with STEMI.

METHODS

Comprehensive literature search of six electronic databases identified relevant randomised controlled trials. The primary outcome was major adverse cardiac events (MACE). The pooled risk ratio (RR) and weighted mean difference (WMD) with a 95% CI were calculated.

RESULTS

12 studies with 1915 patients were included. IC thrombolysis was associated with a significantly lower incidence of MACE (RR=0.65, 95% CI 0.51 to 0.82, I2=0%, p<0.0004) and improved left ventricular ejection fraction (WMD=1.87; 95% CI 1.07 to 2.67; I2=25%; p<0.0001). Subgroup analysis demonstrated a significant reduction in MACE for trials using non-fibrin (RR=0.39, 95% CI 0.20 to 0.78, I2=0%, p=0.007) and moderately fibrin-specific thrombolytic agents (RR=0.62, 95% CI 0.47 to 0.83, I2=0%, p=0.001). No significant reduction was observed in studies using highly fibrin-specific thrombolytic agents (RR=1.10, 95% CI 0.62 to 1.96, I2=0%, p=0.75). Furthermore, there were no significant differences in mortality (RR=0.91; 95% CI 0.48 to 1.71; I2=0%; p=0.77) or bleeding events (major bleeding, RR=1.24; 95% CI 0.47 to 3.28; I2=0%; p=0.67; minor bleeding, RR=1.47; 95% CI 0.90 to 2.40; I2=0%; p=0.12).

CONCLUSION

Adjunctive IC thrombolysis at the time of primary PCI in patients with STEMI improves clinical and myocardial perfusion parameters without an increased rate of bleeding. Further research is needed to optimise the selection of thrombolytic agents and treatment protocols.

Coronary No-Reflow after Primary Percutaneous Coronary Intervention-Current Knowledge on Pathophysiology, Diagnosis, Clinical Impact and Therapy

Coronary no-reflow (CNR) is a frequent phenomenon that develops in patients with ST-segment elevation myocardial infarction (STEMI) following reperfusion therapy. CNR is highly dynamic, develops gradually (over hours) and persists for days to weeks after reperfusion. Microvascular obstruction (MVO) developing as a consequence of myocardial ischemia, distal embolization and reperfusion-related injury is the main pathophysiological mechanism of CNR. The frequency of CNR or MVO after primary PCI differs widely depending on the sensitivity of the tools used for diagnosis and timing of examination. Coronary angiography is readily available and most convenient to diagnose CNR but it is highly conservative and underestimates the true frequency of CNR. Cardiac magnetic resonance (CMR) imaging is the most sensitive method to diagnose MVO and CNR that provides information on the presence, localization and extent of MVO. CMR imaging detects intramyocardial hemorrhage and accurately estimates the infarct size. MVO and CNR markedly negate the benefits of reperfusion therapy and contribute to poor clinical outcomes including adverse remodeling of left ventricle, worsening or new congestive heart failure and reduced survival. Despite extensive research and the use of therapies that target almost all known pathophysiological mechanisms of CNR, no therapy has been found that prevents or reverses CNR and provides consistent clinical benefit in patients with STEMI undergoing reperfusion. Currently, the prevention or alleviation of MVO and CNR remain unmet goals in the therapy of STEMI that continue to be under intense research.

Association Between Thrombogenicity Indices and Coronary Microvascular Dysfunction in Patients With Acute Myocardial Infarction

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Our study supports the feasibility of measuring thrombogenicity in patients with acute myocardial infarction, with intent to predict periprocedural and long-term clinical events, in real-world clinical practice.

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Preprocedural assessment of ex vivo thrombogenicity (eg, platelet-fibrin clot strength by thromboelastography) was significantly associated with the risk of coronary microvascular dysfunction.

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A combined risk stratification with coronary microvascular dysfunction and platelet-fibrin clot strength increased the prognostic implication to predict the rates of long-term clinical outcomes.

The association between thrombogenicity and coronary microvascular dysfunction (CMD) has been poorly explored in patients with acute myocardial infarction (AMI). In our real-world clinical practice (N = 116), thrombogenicity was evaluated with thromboelastography and conventional hemostatic measures, and CMD was defined as index of microcirculatory resistance of >40 U using the invasive physiologic test. High platelet-fibrin clot strength (P-FCS) (≥68 mm) significantly increased the risk of postprocedural CMD (odds ratio: 4.35; 95% CI: 1.74-10.89). Patients with both CMD and high P-FCS had a higher rate of ischemic events compared to non-CMD subjects with low P-FCS (odds ratio: 5.58; 95% CI: 1.31-23.68). This study showed a close association between heightened thrombogenicity and CMD and their prognostic implications after reperfusion in acute myocardial infarction patients.

Quantitative analysis of clot density, fibrin fiber radius, and protofibril packing in acute phase myocardial infarction

INTRODUCTION

Coronary artery disease is associated with impaired clot structure. The aim of this study was to investigate acute phase myocardial infarction (AMI) and provide detailed quantitative analysis of clot ultrastructure.

MATERIALS AND METHODS

Clot formation and breakdown, pore size, fiber density, fiber radius and protofibril packing were investigated in plasma clots from AMI patients. These data were compared to those from healthy controls.

RESULTS

Analysis on clot formation using turbidity showed increased lag time, suggesting changes in protofibril packing and increased fiber size for AMI patients compared to healthy controls. Additionally, increased average rate of clotting and decreased time to maximum absorbance in AMI patients suggest that clots formed more quickly. Moreover, we observed increased time from max OD to max rate of lysis. Increased fibrinogen and decreased plasminogen in AMI patients were accounted for in represented significant differences. AMI samples showed increased time to 25% and 50% lysis, but no change in 75% lysis, representative of delayed lysis onset, but expediated lysis once initiated. These data suggest that AMI patients formed less porous clots made from more densely packed fibers with decreased numbers of protofibrils, which was confirmed using decreased permeation and increased fiber density, and decreased turbidimetry.

CONCLUSIONS

AMI plasma formed clots that were denser, less permeable, and lysed more slowly than healthy controls. These findings were confirmed by detailed analysis of clot ultrastructure, fiber size, and protofibril packing. Dense clot structures that are resistant to lysis may contribute to a prothrombotic milieu in AMI.

[The no-Reflow Phenomenon During Primary Percutaneous Coronary Intervention in Patients With ST-Segment Elevation Myocardial Infarction due to Massive Coronary Thrombosis. Pathogenesis and Predictors of no-Reflow]

Despite successful and timely revascularization of the infarct-related artery, myocardial tissue remains underperfused in some patients. This condition is known as the no-reflow phenomenon, which is associated with a worse prognosis. The first part of the systematic review on no-reflow focuses on description of the no-reflow pathogenesis and predictors. This phenomenon has a complicated, multifactorial pathogenesis, including distal embolization, ischemic injury, reperfusion injury, and a component of individual predisposition. Meanwhile, this phenomenon undergoes spontaneous regression in some patients. Several studies have demonstrated the role of definite biomarkers and clinical indexes as risk predictors for no-reflow. The significance of each pathogenetic component of no-reflow is suggested to be different in different patients, which may warrant an individualized approach in the treatment.

Epicardial Surface Area of Infarction: A Stable Surrogate of Microvascular Obstruction in Acute Myocardial Infarction

BACKGROUND

Microvascular obstruction (MO) is a pathophysiologic complication of acute myocardial infarction that portends poor prognosis; however, it is transient and disappears with infarct healing. Much remains unknown regarding its pathophysiology and whether there are predictors of MO that could function as stable surrogates. We tested for clinical and cardiovascular magnetic resonance predictors of MO to gain insight into its pathophysiology and to find a stable surrogate.

METHODS

Three hundred two consecutive patients from 2 centers underwent cardiovascular magnetic resonance within 2 weeks of first acute myocardial infarction. Three measures of infarct morphology: infarct size, transmurality, and a new index-the epicardial surface area (EpiSA) of full-thickness infarction-were quantified on delayed-enhancement cardiovascular magnetic resonance.

RESULTS

Considering all clinical characteristics, only measures of infarct morphology were independent predictors of MO. EpiSA was the strongest predictor of MO and provided incremental predictive value beyond that of infarct size and transmurality (P<0.0001). In patients with 3-month follow-up cardiovascular magnetic resonance (n=81), EpiSA extent remained stable while MO disappeared, and EpiSA was a predictor of adverse ventricular remodeling. After 20 months of follow-up, 11 died and 1 had heart transplantation. Patients with an EpiSA larger than the median value (≥6%) had worse outcome than those with less than the median value (adverse events: 6.4% versus 1.9%, P=0.045).

CONCLUSIONS

The EpiSA of infarction is a novel index of infarct morphology which accurately predicts MO during the first 2 weeks of MI, but unlike MO, does not disappear with infarct healing. This index has potential as a stable surrogate of the presence of acute MO and may be useful as a predictor of adverse remodeling and outcome which is less dependent on the time window of patient assessment.

Role, Laboratory Assessment and Clinical Relevance of Fibrin, Factor XIII and Endogenous Fibrinolysis in Arterial and Venous Thrombosis

Diseases such as myocardial infarction, ischaemic stroke, peripheral vascular disease and venous thromboembolism are major contributors to morbidity and mortality. Procoagulant, anticoagulant and fibrinolytic pathways are finely regulated in healthy individuals and dysregulated procoagulant, anticoagulant and fibrinolytic pathways lead to arterial and venous thrombosis. In this review article, we discuss the (patho)physiological role and laboratory assessment of fibrin, factor XIII and endogenous fibrinolysis, which are key players in the terminal phase of the coagulation cascade and fibrinolysis. Finally, we present the most up-to-date evidence for their involvement in various disease states and assessment of cardiovascular risk.

Effect of coronary flow on intracoronary alteplase: a prespecified analysis from a randomised trial

OBJECTIVES

Persistently impaired culprit artery flow (

METHODS

In T-TIME (trial of low-dose adjunctive alTeplase during primary PCI), patients ≤6 hours from onset of ST-elevation myocardial infarction (STEMI) were randomised to placebo, alteplase 10 mg or alteplase 20 mg, administered by infusion into the culprit artery, pre-stenting. In this prespecified, secondary analysis, coronary flow was assessed angiographically at the point immediately before drug administration. Microvascular obstruction, myocardial haemorrhage and infarct size were assessed by cardiovascular magnetic resonance (CMR) at 2-7 days and 3 months.

RESULTS

TIMI flow was assessed after first treatment (balloon angioplasty/aspiration thrombectomy), immediately pre-drug administration, in 421 participants (mean age 61±10 years, 85% male) and was 3, 2 or 1 in 267, 134 and 19 participants respectively. In patients with TIMI flow ≤2 pre-drug, there was higher incidence of microvascular obstruction with alteplase (alteplase 20 mg (53.1%) and 10 mg (59.5%) combined versus placebo (34.1%); OR=2.47 (95% CI 1.16 to 5.22, p=0.018) interaction p=0.005) and higher incidence of myocardial haemorrhage (alteplase 20 mg (53.1%) and 10 mg (57.9%) combined vs placebo (27.5%); OR=3.26 (95% CI 1.44 to 7.36, p=0.004) interaction p=0.001). These effects were not observed in participants with TIMI 3 flow pre-drug. There were no interactions between TIMI flow pre-drug, alteplase and 3-month CMR findings.

CONCLUSION

In patients with impaired culprit artery flow (

TRIAL REGISTRATION NUMBER

NCT02257294.

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Key Words

• acute myocardial infarction

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MESH Headings Collapse

Grants

• FS/16/74/32573 British Heart Foundation
• MC_PC_12037 Medical Research Council
• MC_PC_15113 Medical Research Council

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Affiliation(s)

Annette Marie Maznyczka Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK British Heart Foundation Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
Peter McCartney Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK
Patrycja Duklas Robertson Centre for Biostatistics, Institute of Health and Wellbeing, University of Glasgow, Glasgow, UK
Margaret McEntegart Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK
Keith G Oldroyd Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK British Heart Foundation Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
John P Greenwood Department of Cardiology, Leeds General Infirmary, Leeds, UK Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
Douglas Muir James Cook University Hospital, Middlesbrough, UK
Saqib Chowdhary Manchester University NHS Foundation Trust, Manchester, UK
Anthony H Gershlick Division of Cardiology, University of Leicester, Leicester, UK
Clare Appleby Liverpool Heart and Chest Hospital NHS Foundation Trust, Liverpool, UK
Hany Eteiba Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK
James Cotton Department of Cardiology, Royal Wolverhampton Hospitals NHS Trust, Wolverhampton, Wolverhampton, UK
Andrew Wragg Barts and The London Hospital, London, UK
Nick Curzen Wessex Cardiac Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK
R Campbell Tait Department of Haematology, Glasgow Royal Infirmary, Glasgow, UK
Peter MacFarlane Electrocardiology Group, Royal Infirmary, Glasgow, UK
Paul Welsh British Heart Foundation Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
Naveed Sattar British Heart Foundation Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
Mark C Petrie British Heart Foundation Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
Ian Ford Robertson Centre for Biostatistics, Institute of Health and Wellbeing, University of Glasgow, Glasgow, UK
Keith A A Fox Department of Cardiology, University of Edinburgh and Royal Infirmary of Edinburgh, Edinburgh, UK
Alex McConnachie Robertson Centre for Biostatistics, Institute of Health and Wellbeing, University of Glasgow, Glasgow, UK
Colin Berry Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK British Heart Foundation Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK

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Low-Dose Alteplase During Primary Percutaneous Coronary Intervention According to Ischemic Time

BACKGROUND

Microvascular obstruction affects one-half of patients with ST-segment elevation myocardial infarction and confers an adverse prognosis.

OBJECTIVES

This study aimed to determine whether the efficacy and safety of a therapeutic strategy involving low-dose intracoronary alteplase infused early after coronary reperfusion associates with ischemic time.

METHODS

This study was conducted in a prospective, multicenter, parallel group, 1:1:1 randomized, dose-ranging trial in patients undergoing primary percutaneous coronary intervention. Ischemic time, defined as the time from symptom onset to coronary reperfusion, was a pre-specified subgroup of interest. Between March 17, 2016, and December 21, 2017, 440 patients, presenting with ST-segment elevation myocardial infarction within 6 h of symptom onset (<2 h, n = 107; ≥2 h but <4 h, n = 235; ≥4 h to 6 h, n = 98), were enrolled at 11 U.K. hospitals. Participants were randomly assigned to treatment with placebo (n = 151), alteplase 10 mg (n = 144), or alteplase 20 mg (n = 145). The primary outcome was the amount of microvascular obstruction (MVO) (percentage of left ventricular mass) quantified by cardiac magnetic resonance imaging at 2 to 7 days (available for 396 of 440).

RESULTS

Overall, there was no association between alteplase dose and the extent of MVO (p for trend = 0.128). However, in patients with an ischemic time ≥4 to 6 h, alteplase increased the mean extent of MVO compared with placebo: 1.14% (placebo) versus 3.11% (10 mg) versus 5.20% (20 mg); p = 0.009 for the trend. The interaction between ischemic time and alteplase dose was statistically significant (p = 0.018).

CONCLUSION

In patients presenting with ST-segment elevation myocardial infarction and an ischemic time ≥4 to 6 h, adjunctive treatment with low-dose intracoronary alteplase during primary percutaneous coronary intervention was associated with increased MVO. Intracoronary alteplase may be harmful for this subgroup. (A Trial of Low-Dose Adjunctive Alteplase During Primary PCI [T-TIME]; NCT02257294).

Polyhedral erythrocytes in intracoronary thrombus and their association with reperfusion in myocardial infarction

OBJECTIVE

The tightly packed arrays of polyhedral erythrocytes, polyhedrocytes, formed during thrombus contraction, have been detected in some intracoronary thrombi (ICT) obtained from patients with ST-segment elevation myocardial infarction (STEMI). We sought to investigate determinants of polyhedrocyte content in ICT and its association with reperfusion in STEMI.

METHODS

We assessed the composition of ICT obtained during thrombectomy within 12 h since the symptom onset in 110 STEMI patients, following 300 mg of aspirin (n = 110) and 600 mg of clopidogrel (n = 75). The predominance of fibrin, erythrocytes, polyhedrocytes or platelets was evaluated using scanning electron microscopy.

RESULTS

Polyhedrocytes were found in 34 (30.9%) ICT, in which they covered 20-50% (median 38.8%) fields of view. Patients with polyhedrocytes in ICT had lower median minimal reference infarct-related artery (IRA) diameter by 20% (p < 0.0001) and area by 31% (p < 0.0001) versus those without polyhedrocytes. Time of ischemia showed association with the polyhedrocyte content (r = 0.26, p = 0.007). By multivariate analysis, minimal IRA diameter (β = - 0.50, p < 0.0001) and ischemia time (β = 0.20, p = 0.035) independently affected polyhedrocyte content in ICT (R² = 0.45, p < 0.0001). Patients with ischemia time of > 3 h and polyhedrocytes present in ICT had more frequently TIMI-2/3 flow after thrombus aspiration (96% vs. 67%, p = 0.02) and final TIMI-2/3 myocardial perfusion grade (92% vs. 57%, p = 0.044) versus those without polyhedrocytes.

CONCLUSIONS

Our findings indicate that the presence of polyhedrocytes in ICT, observed in one-third of STEMI patients, is associated with smaller minimal IRA diameter, prolonged ischemia and their formation in late presenters is associated with more effective thrombus aspiration and better myocardial reperfusion.

Effect of Low-Dose Intracoronary Alteplase During Primary Percutaneous Coronary Intervention on Microvascular Obstruction in Patients With Acute Myocardial Infarction: A Randomized Clinical Trial

IMPORTANCE

Microvascular obstruction commonly affects patients with acute ST-segment elevation myocardial infarction (STEMI) and is associated with adverse outcomes.

OBJECTIVE

To determine whether a therapeutic strategy involving low-dose intracoronary fibrinolytic therapy with alteplase infused early after coronary reperfusion will reduce microvascular obstruction.

DESIGN, SETTING, AND PARTICIPANTS

Between March 17, 2016, and December 21, 2017, 440 patients presenting at 11 hospitals in the United Kingdom within 6 hours of STEMI due to a proximal-mid-vessel occlusion of a major coronary artery were randomized in a 1:1:1 dose-ranging trial design. Patient follow-up to 3 months was completed on April 12, 2018.

INTERVENTIONS

Participants were randomly assigned to treatment with placebo (n = 151), alteplase 10 mg (n = 144), or alteplase 20 mg (n = 145) by manual infusion over 5 to 10 minutes. The intervention was scheduled to occur early during the primary PCI procedure, after reperfusion of the infarct-related coronary artery and before stent implant.

MAIN OUTCOMES AND MEASURES

The primary outcome was the amount of microvascular obstruction (% left ventricular mass) demonstrated by contrast-enhanced cardiac magnetic resonance imaging (MRI) conducted from days 2 through 7 after enrollment. The primary comparison was the alteplase 20-mg group vs the placebo group; if not significant, the alteplase 10-mg group vs the placebo group was considered a secondary analysis.

RESULTS

Recruitment stopped on December 21, 2017, because conditional power for the primary outcome based on a prespecified analysis of the first 267 randomized participants was less than 30% in both treatment groups (futility criterion). Among the 440 patients randomized (mean age, 60.5 years; 15% women), the primary end point was achieved in 396 patients (90%), 17 (3.9%) withdrew, and all others were followed up to 3 months. In the primary analysis, the mean microvascular obstruction did not differ between the 20-mg alteplase and placebo groups (3.5% vs 2.3%; estimated difference, 1.16%; 95% CI, -0.08% to 2.41%; P = .32) nor in the analysis of 10-mg alteplase vs placebo groups (2.6% vs 2.3%; estimated difference, 0.29%; 95% CI, -0.76% to 1.35%; P = .74). Major adverse cardiac events (cardiac death, nonfatal MI, unplanned hospitalization for heart failure) occurred in 15 patients (10.1%) in the placebo group, 18 (12.9%) in the 10-mg alteplase group, and 12 (8.2%) in the 20-mg alteplase group.

CONCLUSIONS AND RELEVANCE

Among patients with acute STEMI presenting within 6 hours of symptoms, adjunctive low-dose intracoronary alteplase given during the primary percutaneous intervention did not reduce microvascular obstruction. The study findings do not support this treatment.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02257294.

Advances in Coronary No-Reflow Phenomenon-a Contemporary Review

PURPOSE OF REVIEW

Coronary artery no-reflow phenomenon is an incidental outcome of percutaneous coronary intervention in patients presenting with acute myocardial infarction. Despite advances in pharmacologic and non-pharmacologic therapies, coronary no-reflow phenomenon occurs more commonly than desired. It often results in poor clinical outcomes and remains as a relevant consideration in the cardiac catheterization laboratory. In this systematic review, we have sought to discuss the topic in detail, and to relay the most recent discoveries and data on management of this condition.

RECENT FINDINGS

We discuss several pharmacologic and non-pharmacologic treatments used in the prevention and management of coronary no-reflow and microvascular obstruction. Covered topics include the understanding of pharmacologic mechanisms of current and future agents, and recent discoveries that may result in the development of future treatment options. We conclude that the pathophysiology of coronary no-reflow phenomenon and microvascular obstruction still remains incompletely understood, although several plausible theories have led to the current standard of care for its management. We also conclude that coronary no-reflow phenomenon and microvascular obstruction must be recognized as a multifactorial condition that has certain predispositions and characteristics, therefore its prevention and treatment must begin pre-procedurally and be multi-faceted including certain medications and operator techniques in the cardiac catheterization laboratory.

Importance of Endogenous Fibrinolysis in Platelet Thrombus Formation

The processes of thrombosis and coagulation are finely regulated by endogenous fibrinolysis maintaining healthy equilibrium. When the balance is altered in favour of platelet activation and/or coagulation, or if endogenous fibrinolysis becomes less efficient, pathological thrombosis can occur. Arterial thrombosis remains a major cause of morbidity and mortality in the world despite advances in medical therapies. The role endogenous fibrinolysis in the pathogenesis of arterial thrombosis has gained increasing attention in recent years as it presents novel ways to prevent and treat existing diseases. In this review article, we discuss the role of endogenous fibrinolysis in platelet thrombus formation, methods of measurement of fibrinolytic activity, its role in predicting cardiovascular diseases and clinical outcomes and future directions.

Increased von Willebrand factor, P-selectin and fibrin content in occlusive thrombus resistant to lytic therapy

Therapeutic fibrinolysis is ineffective in 40 % of ST-segment elevation acute myocardial infarction (STEMI) patients, but understanding of the mechanisms is incomplete. It was our aim to compare the composition of coronary thrombus in lysis-resistant STEMI patients with that of lysis-sensitive patients. Intracoronary thrombi (n=64) were obtained by aspiration in consecutive STEMI patients. Of them, 20 had received fibrinolysis and underwent rescue percutaneous coronary intervention (r-PCI, lysis-resistant patients) and 44 underwent primary PCI (p-PCI). Lysis-sensitivity was determined in vitro by clot permeability measurements and turbidimetric lysis in plasma of 44 patients undergoing p-PCI and 20 healthy donors. Clot-lysis sensitivity was defined as a clot-lysis time not greater than 1 SD over the mean of healthy donors. Coronary thrombus composition in 20 lysis-resistant and in 20 lysis-sensitive patients was analysed by immunofluorescence with confocal microscopy. Plasma biomarkers (P-selectin, VWF, PAI-1, t-PA, D-dimer, TF pathway markers, plasmin and CD34+) were measured simultaneously on peripheral blood. Lysis-resistant clots had higher levels of fibrin (p=0.02), P-selectin (p=0.03) and VWF (p=0.01) than lysis-sensitive clots. Among thrombi obtained ≤ 6 hours after onset of symptoms, those from lysis-resistant patients showed a higher content in fibrin than those from p-PCI patients (p=0.01). Plasma PAI-1 (p=0.02) and D-dimer levels were significantly higher (p=0.003) in lysis-resistant patients, whereas plasmin levels were lower (p=0.03). Multivariate analysis showed the content of fibrin and VWF within thrombus as predictors of thrombolysis resistance. In conclusion, coronary thrombi in STEMI patients resistant to fibrinolysis are characterised by higher fibrin, P-selectin and VWF content than lysis-sensitive thrombi.

Evolution of Coronary Flow in an Experimental Slow Flow Model in Swines: Angiographic and Pathological Insights

Objective. Pathomechanism of coronary slow flow phenomenon remains largely unclear now. Present study observed the pathological and angiographic evolution in a pig model of coronary slow flow. Methods. Coronary slow flow was induced by repeat coronary injection of small doses of 40 µm microspheres in 18 male domestic pigs and angiographic and pathological changes were determined at 3 hours, 7 days, and 28 days after microspheres injection. Results. Compared to control group treated with coronary saline injection (n = 6) and baseline level, coronary flow was significantly reduced at 3 hours and 7 days but completely recovered at 28 days after coronary microsphere injection in slow flow group. Despite normal coronary flow at 28 days after microsphere injection, enhanced myocardial cytokine expression, left ventricular dysfunction, adverse remodelling, and ischemia/microembolism related pathological changes still persisted or even progressed from 3 hours to 28 days after coronary microsphere injection. Conclusions. Our results show that this large animal slow flow model could partly reflect the chronic angiographic, hemodynamic, and pathological changes of coronary slow flow and could be used to test new therapy strategies against the slow flow phenomenon.

Coronary microvascular obstruction in acute myocardial infarction

The success of a primary percutaneous intervention (PCI) in the setting of ST elevation myocardial infarction depends on the functional and structural integrity of coronary microcirculation. Coronary microvascular dysfunction and obstruction (CMVO) occurs in up to half of patients submitted to apparently successful primary PCI and is associated to a much worse outcome. The current review summarizes the complex mechanisms responsible for CMVO, including pre-existing coronary microvascular dysfunction, and highlights the current limitations in the assessment of microvascular function. More importantly, at the light of the substantial failure of trials hitherto published on the treatment of CMVO, this review proposes a novel integrated therapeutic approach, which should overcome the limitations of previous studies.

Simple clinical risk score for no-reflow prediction in patients undergoing primary Percutaneous Coronary Intervention with acute STEMI

Objectives:

To identify the STEMI patients at high risk in terms of no-reflow during percutaneous coronary intervention (PCI) with a simple risk score system that can be used before reperfusion.

Methods:

Total 173 patients who had undergone primary or rescue percutaneous coronary intervention following the diagnosis of STEMI, were classified as “no-reflow” developers and “no-reflow” non-developers, during the procedure. The pre-procedural ECGs, laboratory parameters, demographic data, time for the treatment, and the treatment methods were evaluated with univariate analysis. The independent predictors were identified by multivariate logistic regression analysis among the no-reflow risk factors. Using the independent predictors, we developed a simple risk score system proportional to area under the ROC (AUROC) curves.

Results:

The independent predictors of “no-reflow” phenomenon were identified as follows: high values of blood glucose at reference; long symptom-onset-to-balloon-time; and low lymphocyte count. The incidence rates of “no-reflow” in patients with low (0-1), moderate (2-3) and high (4-6) risk factors were 13.3%, 40.0%, and 46.7%, respectively. The risk score system demonstrated a good risk prediction between patients with various risk levels of the development of “no-reflow” with a c-statistics of 0.734 (95% CI 0.654-0.814).

Conclusion:

The development of “no-reflow” which is an adverse event in STEMI treatment can be predicted efficiently by simple clinical risk scoring method.

Evaluation of the Clinical and Procedural Predictive Factors of no-Reflow Phenomenon Following Primary Percutaneous Coronary Intervention

BACKGROUND

The no-reflow phenomenon is an uncommon and critical occurrence which myocardial reperfusion does not restore to its optimal level. Several predisposing factors of the no-reflow phenomenon have been identified. However, at present we know little about clinical predictors of no-reflow after percutaneous coronary intervention (PCI).

OBJECTIVES

In this study, we evaluated clinical predictors of no-reflow phenomenon after PCI in patients with acute STEMI, to plan a better treatment of these patients.

PATIENTS AND METHODS

During an 18-month period, from 2013 to 2014, 438 patients with acute myocardial infarction (AMI) presenting within the first 24 hours from symptoms onset were treated with primary PCI in the Rajaie Cardiovascular Medical and Research Center. Thrombolysis in myocardial infarction (TIMI) flow was measured in all patients on the first angiography, following stenting. A total of 49 patients were allocated to the case group, based on the no-reflow phenomenon occurred during primary PCI (TIMI grade 0 and 1) and 50 patients without the no-reflow phenomenon (TIMI grade ≥ 3) were randomly selected, as the control group. They were evaluated from the point of demographic variables and also infarction territory, pain duration, maximal ST-change, left ventricle (LV) function, laboratory data, coronary anatomy, culprit vessel, location of lesion, target vessel diameter, lesion length, eccentricity, thrombus grade, tortuosity, lesion angulation, bifurcation, predilation, postdilation, thrombus aspiration, number of stent, in stent thrombosis. Data were then analyzed with the SPSS statistical software.

RESULTS

Mean age of patients was 59.47 (SD = 12.48) years, of which 75 (75.8%) were male and 24 (24.2%) were female. Based on univariable analysis, white blood cell (WBC) count, pain duration, LV function, maximal ST-change, thrombus grade and eccentricity were identified as predictors of the no-reflow phenomenon. After multivariable logistic regression: WBC count and thrombus grade remained the significant independent predictors of the no-reflow phenomenon (P < 0.05). In case group, slow-flow was seen in 42 (9.5%), while no-reflow was seen in seven (1.6%) patients.

CONCLUSIONS

The WBC count and thrombus grade are strong, independent predictive factors of developing the no-reflow phenomenon, in AMI patients undergoing primary PCI. There is also an association between the no-reflow phenomenon and pain duration, maximal ST-change, LV function, high sensitivity C-reactive protein (hs-CRP), bifurcation, eccentricity and coronary anatomy.

Plasma fibrin clot phenotype independently affects intracoronary thrombus ultrastructure in patients with acute myocardial infarction

Determinants of intracoronary thrombus (ICT) composition in patients with ST-elevation myocardial infarction (STEMI) are largely unknown. We sought to investigate whether plasma fibrin phenotype and platelet reactivity affect ICT ultrastructure. We assessed the content of fibrin, platelets and erythrocytes including polyhedrocytes by scanning electron microscopy on the surface and inside ICT aspirated from 80 STEMI patients within 12 hours since chest pain onset. Plasma fibrin clot permeability (Ks), which indicates the average pore size, lysis time (t50 %), platelet reactivity index (PRI) and ADP-induced platelet aggregation (ADP5, 20µM) were evaluated on admission. All patients received aspirin and 45 (56.3 %) 600 mg of clopidogrel, 80 (60-120) min prior to aspiration. Higher content of fibrin (61.6 vs 34.3 %, P< 0.0001) and platelets (8.2 vs 4.8 %, P=0.018) and lower erythrocyte content (15.8 vs 42.9 %, P< 0.0001) were found on ICT surface compared with its inner part. After adjustment for fibrinogen, in both ICT parts fibrin content was correlated with Ks (r≤-0.55, P< 0.0001) and t50 % (r≥ 0.29, P≤ 0.02) but not with PRI and ADP5,20µM. Polyhedrocytes were observed in 16 (20 %) patients and their large amount expressed as ≥ 50 % fields of view covered by polyhedrocytes was associated with the lower PRI values (40 vs 69 %, P=0.015), but not Ks or t50 %. By multivariate regression, Ks (β=-0.62, P< 0.0001), clopidogrel pretreatment (β=-0.36, P< 0.001), ischemia time (β=0.19, P=0.044) and family history (β=0.18, P=0.049) independently predicted fibrin content in the whole ICT (R²=0.65, P< 0.0001). Formation of denser plasma fibrin clots is independently associated with high fibrin content within the ICT in STEMI.

Concordance of angiographic and electrocardiographic indexes of microvascular obstruction: myocardial haemorrhage role

BACKGROUND

Angiographic and electrocardiographic (ECG) indexes of microvascular obstruction (MVO) have been described. We aimed at assessing by cardiac magnetic resonance (CMR) anatomical features underlying concordance between them.

METHODS

Forty-one patients were enrolled. Patients presented with neither angiographic nor ECG indexes of MVO (without MVO) (44%), with either angiographic or ECG indexes of MVO (discordant with MVO) (22%) or with both angiographic and ECG indexes of MVO (concordant with MVO) (34%). All patients underwent in-hospital CMR. Echocardiographic data obtained after 6 months were compared with those obtained in hospital.

RESULTS

Concordant patients with MVO had larger infarct size, lower myocardial salvage index and higher rate of myocardial haemorrhage (all assessed by CMR) [33% (25-41%), 15% (10-29%) and 88%, respectively] as compared with patients without MVO [12% (9-16%), 66% (52-79%) and 0%; Bonferroni-adjusted P < 0.001, Bonferroni-adjusted P < 0.001 and P < 0.001, respectively], or with discordant ones [25% (21-39%), 35% (20-48%) and 7%; Bonferroni-adjusted P = 0.03, Bonferroni-adjusted P = 0.002 and P = 0.04, respectively]. After 6 months, ejection fraction significantly decreased in concordant patients with MVO (P < 0.001) without significant changes in the other groups.

CONCLUSIONS

Concordance of angiographic and ECG indexes of MVO reflects more severe myocardial damage translating into unfavourable left ventricular remodelling.

Pathophysiology of coronary thrombus formation and adverse consequences of thrombus during PCI

Atherosclerosis is a systemic vascular pathology that is preceded by endothelial dysfunction. Vascular inflammation "fuels" atherosclerosis and creates the milieu for episodes of intravascular thromboses. Thrombotic events in the coronary vasculature may lead to asymptomatic progression of atherosclerosis or could manifest as acute coronary syndromes or even sudden cardiac death. Thrombus encountered in the setting of acute coronary syndromes has been correlated with acute complications during percutaneous coronary interventions such as no-reflow, acute coronary occlusion and long term complications such as stent thrombus. This article reviews the pathophysiology of coronary thrombogenesis and explores the complications associated with thrombus during coronary interventions.

Sonography characteristics of the intra-graft thrombus: association with procedure success and procedure time of percutaneous transluminal angioplasty for thrombosed prosthetic dialysis graft

Percutaneous transluminal angioplasty (PTA) for thrombosed dialysis graft is both difficult and time-consuming that may increase radiation exposure. A predictor of PTA success and procedure time has not been identified yet. Sonography data and the PTA results of 88 grafts were reviewed retrospectively. The echogenicity of the majority of the intra-graft thrombus and the presence/absence of thrombus free space in the grafts were examined. The association between the sonography findings and PTA procedure success and procedure time was analyzed. The echogenicity of the intra-graft thrombus and presence/absence of thrombus free space were the major determinants of procedure success and procedure time. Higher intra-graft echogenicity and lack of thrombus free space were associated with more procedure failures (p < 0.01 vs. p = 0.04) and longer procedure times (p = 0.03 vs. p < 0.01). Thrombi from occluded dialysis grafts may differ in resistance to mechanical/pharmacological thrombolysis. Sonography characteristics of the intra-graft thrombus may help to differentiate them.

No-reflow phenomenon and endothelial glycocalyx of microcirculation

The progress in reperfusion therapy dictated the necessity for developing new tools and procedures for adjacent/additional therapy of acute cardiovascular disorders. The adjacent therapy is targeted on the damage of the microcirculation, leading to the unfavorable prognosis for the patients. The no-reflow phenomenon holds special place in the multifactorial etiology of the microcirculation disorders, offering a new challenge in treating the patients associated with ST-segment elevation on ECG at myocardial infarction. One of the numerous causes of no-reflow, the influence of the endothelial glycocalyx of the microcirculation, is analyzed. The results obtained in the studies of the endothelial glycocalyx ultrastructure are generalized, the effect that the fragments of the glycocalyx glycosaminoglycans have on the function of the vascular wall is demonstrated. The trends in searching for correlations between the thickness of the capillary glycocalyx and the cardiovascular disease risk are noted.

Fibrin clot structure and function: a role in the pathophysiology of arterial and venous thromboembolic diseases

The formation of fibrin clots that are relatively resistant to lysis represents the final step in blood coagulation. We discuss the genetic and environmental regulators of fibrin structure in relation to thrombotic disease. In addition, we discuss the implications of fibrin structure for treatment of thrombosis. Fibrin clots composed of compact, highly branched networks with thin fibers are resistant to lysis. Altered fibrin structure has consistently been reported in patients with several diseases complicated by thromboembolic events, including patients with acute or prior myocardial infarction, ischemic stroke, and venous thromboembolism. Relatives of patients with myocardial infarction or venous thromboembolism display similar fibrin abnormalities. Low-dose aspirin, statins, lowering of homocysteine, better diabetes control, smoking cessation, and suppression of inflammatory response increase clot permeability and susceptibility to lysis. Growing evidence indicates that abnormal fibrin properties represent a novel risk factor for arterial and venous thrombotic events, particularly of unknown etiology in young and middle-aged patients.

Reduced thrombin formation and altered fibrin clot properties induced by polyunsaturated omega-3 fatty acids on top of dual antiplatelet therapy in patients undergoing percutaneous coronary intervention (OMEGA-PCI clot)

OBJECTIVE

The goal of this study was to investigate whether omega-3 polyunsaturated fatty acids (n-3 PUFA) are able to alter plasma fibrin clot properties and reduce thrombin formation in stable coronary artery disease patients undergoing percutaneous coronary intervention (PCI).

METHODS AND RESULTS

In an investigator-initiated, prospective, double-blind, placebo-controlled, randomized study, patients undergoing PCI who received standard pharmacotherapy were assigned to the treatment with 1 g/day n-3 PUFA (n = 30) or placebo (n = 24) for 1 month. Plasma fibrin clot permeability (K(s)); lysis time (t(50%)); prothrombin fragment 1.2; and peak thrombin generation from automated thrombogram, 8-isoprostaglandin F(2α) (8-iso-PGF(2α), an oxidative stress marker), and C-reactive protein were determined at baseline, 3 to 5 days after randomization, and 30 days after randomization. At baseline, both treatment groups did not differ significantly. A 1-month treatment with n-3 PUFA compared with placebo was associated with 15.3% higher K(s), indicating larger pores in the fibrin network (P = 0.0005); 14.3% shorter t(50%), indicating increased susceptibility to fibrinolysis (P<0.0001); 33.8% lower prothrombin fragment 1.2 (P = 0.0013); 13.4% lower peak thrombin generation (P = 0.04); and 13.1% lower 8-iso-PGF(2α) (P = 0.009). Treatment with n-3 PUFA had no effect on fibrinogen and C-reactive protein. After 1 month of treatment, fibrinogen (r = -0.53, P<0.0001), treatment assignment (r = 0.29, P = 0.006) and 8-iso-PGF(2α) (r = -0.27, P = 0.015) were independently associated with clot permeability (P<0.0001, R(2) = 0.66).

CONCLUSIONS

Adding n-3 PUFA to standard therapy in stable patients undergoing PCI significantly decreases thrombin formation and oxidative stress and favorably alters fibrin clot properties. These findings indicate novel antithrombotic effects induced by n-3 PUFA in humans.

Predicting the no-reflow phenomenon following successful percutaneous coronary intervention

In the setting of acute myocardial infarction, early and adequate reopening of an infarct-related artery is not necessarily followed by a complete restoration of myocardial perfusion. This condition is usually defined as ‘no-reflow’. The pathophysiology of no-reflow is multifactorial since extravascular compression, microvascular vasoconstriction, embolization during percutaneous coronary intervention, and platelet and neutrophil aggregates are involved. In the clinical arena, angiographic findings and easily available clinical parameters can predict the risk of no-reflow. More recently, several studies have demonstrated that biomarkers, especially those related to the pathogenetic components of no-reflow, could also have a prognostic role in the prediction and in the full understanding of the multiple mechanisms of this phenomenon. Thus, in this article, we investigate the role of several biomarkers on admission in predicting the occurrence of no-reflow following successful percutaneous coronary intervention.

Myocardial no-reflow in humans

In a variable proportion of patients presenting with ST-segment elevation myocardial infarction, ranging from 5% to 50%, primary percutaneous coronary intervention achieves epicardial coronary artery reperfusion but not myocardial reperfusion, a condition known as no-reflow. Of note, no-reflow is associated with a worse prognosis at follow-up. The phenomenon has a multifactorial pathogenesis including: distal embolization, ischemia-reperfusion injury, and individual predisposition of coronary microcirculation to injury. Moreover, it is spontaneously reversible in some patients, thus suggesting that it might be amenable to treatment also when we fail to prevent it. Several recent studies have shown that biomarkers and other easily available clinical parameters can predict the risk of no-reflow and can help in the assessment of the multiple mechanisms of the phenomenon. Several therapeutic strategies have been tested for the prevention and treatment of no-reflow. In particular, thrombus aspiration before stent implantation prevents distal embolization and has been recently shown to improve myocardial perfusion and clinical outcome as compared with the standard procedure. However, it is conceivable that the relevance of each pathogenetic component of no-reflow is different in different patients, thus explaining the occurrence of no-reflow despite the use of mechanical thrombus aspiration. Thus, in this review article, for the first time, we propose a personalized management of no-reflow on the basis of the assessment of the prevailing mechanisms of no-reflow operating in each patient.

Evolution of myocardial perfusion during primary angioplasty in spontaneously reperfused infarct-related artery: impact on long-term clinical outcomes and left ventricular function recovery

BACKGROUND

TIMI myocardial perfusion grade (TMPG) reflects the integrity of microvasculature in ST-elevation myocardial infarction (STEMI). We sought to investigate whether TMPG evolution during primary angioplasty (pPCI) in spontaneously reperfused STEMI patients might predict long-term outcomes.

METHODS

392 patients with TIMI-3 flow before pPCI were analyzed. According to pre- and post-pPCI TMPG four reperfusion patterns were created: A. TMPG deterioration from grade 2/3 to 0/1 after pPCI (n = 55, 14.0%), B. TMPG-0/1 before and after pPCI (n = 111, 28.3%), C. TMPG improvement from grade 0/1 to 2/3 (n = 52, 13.3%), D. TMPG-2/3 before and after pPCI (n = 174, 44.4%). 30-day and 1-year mortality and heart failure requiring hospitalization (HF-hosp) were recorded. Left ventricular ejection fraction (LVEF) was measured at first day (1D) and after 6 months (6M).

RESULTS

1D-LVEF was similar in A-D groups. After 6M, LVEF improved in pattern D (7.5 ± 5.4%, p<0.01) and C (3.7 ± 3.4%, p < 0.05), deteriorated in pattern A (5.2 ± 3.9%, p<0.01) and did not change in pattern B. 6M-LVEF increased (p < 0.001) and frequency of 1-year HF-hosp decreased (p < 0.001) in stepwise fashion among A-D patterns. A 30-day mortality rate for A-D patterns was 9.1%, 2.7%, 1.9% and 0%, respectively (p < 0.001). 1-year mortality was 16.3%, 7.2%, 5.8% and 0.6%, respectively (p < 0.001). By multivariate analysis (c-index = 0.79), TMPG evolution was independent predictor of 1-year mortality (HR = 2.5, 95%CI 1.3-4.0, p = 0.006).

CONCLUSIONS

Maintaining TMPG-2/3 or improving TMPG-0/1 through pPCI in STEMI implies LV function recovery and good long-term survival. In contrast, substantial deterioration of TMPG is associated with lack of LV function recovery, and the highest mortality rate.