Randomized evaluation of the effects of filter-based distal protection on myocardial perfusion and infarct size after primary percutaneous catheter intervention in myocardial infarction with and without ST-segment elevation

Coronary microvascular obstruction and dysfunction in patients with acute myocardial infarction

Despite prompt epicardial recanalization in patients presenting with ST-segment elevation myocardial infarction (STEMI), coronary microvascular obstruction and dysfunction (CMVO) is still fairly common and is associated with poor prognosis. Various pharmacological and mechanical strategies to treat CMVO have been proposed, but the positive results reported in preclinical and small proof-of-concept studies have not translated into benefits in large clinical trials conducted in the modern treatment setting of patients with STEMI. Therefore, the optimal management of these patients remains a topic of debate. In this Review, we appraise the pathophysiological mechanisms of CMVO, explore the evidence and provide future perspectives on strategies to be implemented to reduce the incidence of CMVO and improve prognosis in patients with STEMI.

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.

Complications and failure modes of coronary embolic protection devices: Insights from the MAUDE database

BACKGROUND

There is limited data on complications associated with the use of coronary embolic protection devices (EPDs).

METHODS

We queried the Manufacturer and User Facility Device Experience database between November 2010 and November 2020 for reports on coronary EPDs: Spider FX (Medtronic, Minneapolis, MN) and Filterwire EZ (Boston Scientific, Natick, MA).

RESULTS

We retrieved 119 reports on coronary EPD failure (Spider FX n = 33 and Filterwire EZ n = 86), most of which (78.2%) occurred during saphenous vein graft interventions. The most common failure mode was inability to retrieve the EPD (49.6%), with the filter trapped against stent struts in 76.2% of the cases. Other device complications included filter fracture (28.6%), failure to cross (7.6%), failure to deploy (7.6%), and failure to recapture the filter (3.4%). Filter fracture (54.5 vs. 29.1%) and failure to recapture (9.1 vs. 2.1%) were more commonly reported, while failure to deploy the filter (0 vs. 10.5%) was less commonly reported with the Spider-FX.

CONCLUSIONS

The most common modes of failure of coronary EPDs are the failure of retrieval (49.6%), followed by the filter fracture (28.6%). When using EPDs, careful attention to the technique is essential to avoid failures and subsequent complications.

Thrombus Embolisation: Prevention is Better than Cure

Thrombus embolisation complicating primary percutaneous coronary intervention in ST-elevation myocardial infarction is associated with an increase in adverse outcomes. However, there are currently no proven recommendations for intervention in the setting of large thrombus burden. In this review, we discuss the clinical implications of thrombus embolisation and angiographic predictors of embolisation, and provide an update of current evidence for some preventative strategies, both pharmacological and mechanical, in this setting.

[Management of high thrombus burden in primary PCI]

A large thrombus burden is not uncommon in primary percutaneous coronary intervention, and is associated with more frequent complications. The role of intracoronary thrombolysis and glycoprotein IIb/IIIa inhibitors in the management of a large thrombus burden is discussed. The use of thromboaspiration must follow a particular logic and used with rigorous manipulations; the capacities of the protective filters are often exceeded. Stents dedicated to thrombus management can be used. Interest and limits of these stents are developed. Direct stenting should be encouraged, and delayed stenting probably considered for the most important thrombotic burden despite "negative" results in studies.

A novel guidewire-integrated embolic protection filter device with a handy-folding system: In vitro and in vivo performance assessment

OBJECTIVES

We developed a novel guidewire-integrated filter device with a handy-folding system (IFD: Inoue filter device). In vitro and in vivo studies were conducted to evaluate the feasibilityof the IFD.

BACKGROUND

Although distal atheromatous and thrombotic embolizations remain unresolved critical issues during catheter interventions, distal protection devices are infrequently used partly because of reduced lower maneuverability.

METHODS

In the in vitro experiment, we created an experimental circulation model composed of silicone latex tubes, a reservoir, and a roller pump. After the filter device was deployed in the tube, polystyrene fluorescent microspheres were injected and the capture rate was calculated. Ten trials were performed using the IFD and Spider FX. In the in vivo study, five independent operators deployed, and they retrieved the IFD in swine common iliac and internal carotid arteries. The procedural success rate as well as the delivery and retrieval time was evaluated.

RESULTS

In the in vitro study, the mean capture rate was 94% and 35% in the IFD and Spider groups, respectively. In the in vivo study, all procedures were successful, with no complications. The mean delivery time was 281 ± 87 s and 194 ± 67 s and the mean retrieval time was 24 ± 9 and 13 ±1 s in the left internal carotid and the left common iliac arteries, respectively.

CONCLUSION

Although further studies and improvements are required, the study results indicate that the IFD is feasible.

Mechanical strategies to enhance myocardial salvage during primary percutaneous coronary intervention in patients with STEMI

Primary percutaneous coronary intervention (PPCI) has become the mainstay of reperfusion therapy in patients with ST-segment elevation myocardial infarction (STEMI). Despite timely reperfusion by PPCI and restoration of epicardial blood flow in up to 95% of patients, tissue reperfusion remains suboptimal in a sizeable proportion of patients with STEMI. Over the years mechanical and pharmacological strategies to enhance myocardial salvage during PPCI have been developed and used in patients with STEMI. The most common mechanical strategies used in the setting of PPCI include: coronary stenting, direct stenting, mesh-covered stents, self-expanding stents, deferred stenting, thrombectomy, distal protection devices, intra-aortic balloon pumping, left ventricular assist devices and ischaemic conditioning. These strategies are thought to enhance myocardial salvage via improving acute procedural success, attenuation of distal embolisation, microvascular obstruction and reperfusion injury, and providing haemodynamic support. Coronary (direct) stenting is almost the default approach of reperfusion during PPCI procedures. Evidence on the use of mesh-covered stents, self-expanding stents, deferred stenting or left ventricular assist devices is scant and their use in the setting of PPCI remains limited. Mechanical thrombectomy, distal protection devices or routine intra-aortic balloon counterpulsation seem to offer no clinical benefit when used in the setting of PPCI. Although manual aspiration may improve indices of tissue reperfusion, recent research showed no clinical benefit of routine use of this strategy in patients with STEMI undergoing PPCI. Ischaemic conditioning, although promising, remains at an investigational stage and needs further research.

A review of strategies for infarct size reduction during acute myocardial infarction

Advances in medical and interventional therapy over the last few decades have revolutionized the treatment of acute myocardial infarction. Despite the ability to restore epicardial coronary artery patency promptly through percutaneous coronary intervention, tissue level damage may continue. The reported 30-day mortality after all acute coronary syndromes is 2 to 3%, and around 5% following myocardial infarction. Post-infarct complications such as heart failure continue to be a major contributor to cardiovascular morbidity and mortality. Inadequate microvascular reperfusion leads to worse clinical outcomes and potentially strategies to reduce infarct size during periods of ischemia-reperfusion can improve outcomes. Many strategies have been tested, but no single strategy alone has shown a consistent result or benefit in large scale randomised clinical trials. Herein, we review the historical efforts, current strategies, and potential novel concepts that may improve myocardial protection and reduce infarct size.

Predictors of no- reflow during primary angioplasty for acute myocardial infarction, from Medical College Hospital, Trivandrum

Background

Primary angioplasty (PCI) for acute myocardial infarction is associated with no-reflow phenomenon, in about 5–25% of cases. Here we analysed the factors predicting no reflow .

Methods

This was a case control study of consecutive patients with acute myocardial infarction who underwent Primary PCI from August 2014 to February 2015.

Results

Of 181 patients who underwent primary PCI, 47 (25.9%) showed an angiographic no-reflow phenomenon. The mean age was 59.19 ± 10.25 years and females were 11%.

Univariate predictors of no reflow were age >60 years (OR = 6.146, 95%CI 2.937–12.86, P = 0<0.001), reperfusion time >6 h (OR = 21.94, 95%CI 9.402–51.2, P = < 0.001), low initial TIMI flow (≤1) (OR = 12.12, 95%CI 4.117–35.65, P < 0.001), low initial TMPG flow (≤1) (OR = 36.19, 95%CI 4.847–270.2, P < 0.001) a high thrombus burden (OR = 11.04,95%CI 5.124–23.8, P < 0.001), a long target lesion (OR = 8.54, 95%CI 3.794–19.23, P < 0.001), Killip Class III/IV(OR = 2.937,95%CI 1.112–7.756,P = 0.025) and overlap stenting(OR = 3.733,95%CI 1.186–11.75,P = 0.017).

Multiple stepwise logistic regression analysis predictors were: longer reperfusion time > 6 h (OR = 13.844, 95%CI 3.214–59.636, P = <0.001), age >60 years (OR = 8.886, 95%CI 2.145–36.80, P = 0.003), a long target lesion (OR = 8.637, 95%CI 1.975–37.768, P = 0.004), low initial TIMI flow (≤1) (OR = 20.861, 95%CI 1.739–250.290, P = 0.017).

Conclusions

It is important to minimize trauma to the vessel, avoid repetitive balloon dilatations use direct stenting and use the shortest stent if possible.

Impact of Distal Protection with Filter-Type Device on Long-term Outcome after Percutaneous Coronary Intervention for Acute Myocardial Infarction: Clinical Results with Filtrap®

Aim: Although distal embolization during percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) deteriorates cardiac function, whether distal protection (DP) can improve prognosis is still controversial. We investigated whether a filter-type DP device, Filtrap^®, could improve long-term outcomes after PCI for AMI.

Method: We studied 164 patients (130 men, mean age: 65.7 years) who underwent PCI. Patients were divided into two groups based on the use of Filtrap^®. The occurrence of congestive heart failure (CHF) and major adverse cardiac events (MACE) defined as cardiac death, recurrent AMI, and target vessel revascularization were compared.

Result: Between DP (n = 53, 41 men, mean age: 65.5 years) and non-DP (n = 111, 89 men, mean age: 65.8 years) groups, although there was significantly greater plaque area in the DP group than in the non-DP group, there were no significant differences in coronary reperfusion flow after PCI. Interestingly, patients with CHF in the non-DP group exhibited a higher CK level than those in the DP group. During a 2-year follow-up period, cumulative CHF was significantly lower in the DP group than in the non-DP group (log-rank p = 0.018), and there was no significant difference in the MACE rate (log-rank p = 0.238). The use of DP device could not predict MACE, but could predict CHF by multivariate analysis (odds ratio = 0.099, 95% CI: 0.02–0.42, p = 0.005).

Conclusion: These results demonstrate that favorable clinical outcomes could be achieved by the filter-type DP device in AMI, particularly in patients with CHF.

No-Reflow Phoenomenon by Intracoronary Thrombus in Acute Myocardial Infarction

Recently, percutaneous coronary intervention has been the treatment of choice in most acute myocardial infarction cases. Although the results of percutaneous coronary interventions have ben good, the no-reflow phenomenon and distal embolization of intracoronary thrombus are still major problems even after successful interventions. In this article, we will briefly review the deleterious effects of no-reflow and distal embolization of intracoronary thrombus during percutaneous coronary interventions. The current trials focused on the prevention and treatment of the no-reflow phenomenon and intracoronary thrombus.

Thrombus Aspiration in STEMI

OPINION STATEMENT

ST-segment elevation myocardial infarction (STEMI) remains an important cause of morbidity and mortality. In the USA, the development of an organized STEMI network has allowed STEMI patients greater access to primary PCI. The most important goal in the management of STEMI is timely reperfusion and establishment of normal coronary flow. However, periprocedural thrombus embolization, which can obstruct the distal microvasculature and impair tissue perfusion, is associated with unfavorable outcomes. Over the last years, aspiration thrombectomy has emerged as a novel technique to prevent distal coronary thromboembolism during primary PCI. The initial excitement after the publication of the TAPAS trial changed the practice paradigm among interventional community worldwide. Aspiration thrombectomy was recommended by several society guidelines and became the "standard of care" during primary PCI. However, recent data and publication of two large randomized controlled trials questioned the effectiveness (TASTE trial) and the safety (TOTAL trial) of this technique. Therefore, the recent ACC/AHA/SCAI-focused update document recommended against the routine use of manual thrombectomy during primary PCI. This review will summarize recent data and trials regarding thrombus aspiration in STEMI.

The no-reflow phenomenon: State of the art

Primary percutaneous coronary intervention (PCI) is the best available reperfusion strategy for acute ST-segment elevation myocardial infarction (STEMI), with nearly 95% of occluded coronary vessels being reopened in this setting. Despite re-establishing epicardial coronary vessel patency, primary PCI may fail to restore optimal myocardial reperfusion within the myocardial tissue, a failure at the microvascular level known as no-reflow (NR). NR has been reported to occur in up to 60% of STEMI patients with optimal coronary vessel reperfusion. When it does occur, it significantly attenuates the beneficial effect of reperfusion therapy, leading to poor outcomes. The pathophysiology of NR is complex and incompletely understood. Many phenomena are known to contribute to NR, including leukocyte infiltration, vasoconstriction, activation of inflammatory pathways and cellular oedema. Vascular damage and haemorrhage may also play important roles in the establishment of NR. In this review, we describe the pathophysiological mechanisms of NR and the tools available for diagnosing it. We also describe the microvasculature and the endothelial mechanisms involved in NR, which may provide relevant therapeutic targets for reducing NR and improving the prognosis for patients.

Predictors and outcome of no-reflow post primary percutaneous coronary intervention for ST elevation myocardial infarction

Background

No-reflow (TIMI < 3) during primary PCI (PCI) for STEMI occurs in 11–41% of cases, indicates poor myocardial tissue perfusion, and is associated with a poor outcome. We aimed to determine predictors and 12 month outcomes of patients who developed no-reflow.

Methods

We analysed the PCI database of The Canberra Hospital and identified 781 patients who underwent primary PCI during 2008–2012. Follow-up at 12 months was with letter, phone call and review of hospital records.

Results

No-reflow was observed in 189 patients (25%) at the end of the procedure. Patients with no-reflow were older (64 vs. 61 years, p = 0.03). No-reflow patients were more likely to have initial TIMI flow < 3 (89% vs. 79%, p = 0.001), thrombus score ≥ 4 (83% vs. 69%, p = 0.0001), higher use of glycoprotein IIb/IIIa inhibitors (57% vs. 48%, p = 0.03) and longer median symptom to balloon time (223 min vs. 192 min, p = 0.004). No-reflow was an independent predictor of mortality (HR 1.95, CI 1.04-3.59, p = 0.037) during 12 month follow-up. On multivariate analysis, age > 60 years, thrombus score ≥ 4 and symptom to balloon time > 360 min were independent predictors of no-reflow. In 17% of cases of no reflow, it occurred only after stent insertion.

Conclusions

No-reflow occurred in 25% of STEMI patients undergoing primary PCI and was more likely with older age, high thrombus burden and delayed presentation. No-reflow was associated with a higher risk of death at 12 month follow-up.

Embolization after percutaneous coronary intervention in acute coronary syndrome. Saphenous vein grafts versus native coronary arteries

AIMS

The aim of this study was to assess the occurrence of distal embolization and to quantify the amount of embolic material captured during stent implantation in native coronary arteries, as compared with saphenous vein grafts (SVG) in patients at different time periods after an acute coronary syndrome.

PATIENTS AND METHODS

In all, 104 patients presenting with unstable or stable angina underwent percutaneous coronary intervention (PCI) in 107 vessels and stent implantation in 112 lesions, 53 % of which were in SVG.

RESULTS

Device deployment and retrieval was successful in 111 lesions. Embolic material was detected in 74 % of the protection devices. Early PCI, during a 2-week period after the last ischemic episode, was associated with larger embolic load, especially in the right coronary artery. The length of the lesion was the only preprocedural independent variable that was found to be a significant predictor for the presence of emboli (p = 0.002). The stent diameter and the maximum dilatation pressure were the two procedural variables found to be significant predictors for the presence of emboli (p = 0.025 and p = 0.008, respectively). The irregularity of the lesion and the number of stents deployed were found to have a predictive correlation to the total area of the embolic particles (p = 0.04 and p = 0.005, respectively).

CONCLUSION

Distal embolization of atherosclerotic debris is a frequent phenomenon after PCI not only in SVG but also in native vessels. The amount of embolic material seems to be related to the atherosclerotic burden of the vessel and to the early timing of the procedure as related to acute coronary syndrome.

Development of a novel adenosine-eluting guidewire (Adenowire) for coronary vasodilation during percutaneous coronary intervention

AIMS

Microvascular obstruction (MVO) and "no-reflow phenomenon" (NRP) remain barriers to optimal tissue perfusion after percutaneous coronary intervention (PCI). The purpose of this study was to develop, characterise, and test an adenosine-eluting guidewire (Adenowire) for coronary vasodilation.

METHODS AND RESULTS

Utilising polyurethane chemistry, we developed a non-toxic pentameric form of adenosine (PA) that can be coated onto guidewires (Adenowire) and that allows continuous elution of adenosine into the distal vascular bed during PCI. We characterised PA with Fourier transform infrared spectroscopy, NMR and MALDI time-of-flight mass spectrometry, established its stability by calorimetry, and confirmed its safety by extensive toxicological testing. Adenowires reliably released adenosine in vitro over 60 minutes. In pigs, insertion of an Adenowire into the left circumflex or left anterior descending coronary artery resulted in immediate and sustained (40 minutes) vasodilation. Electron microscopy demonstrated smooth thin coating of the terminal portion of guidewires and showed lack of fibrin or platelet adhesion to the Adenowire after in vivo use.

CONCLUSIONS

Since guidewires are the first devices to cross a culprit lesion, Adenowires would prophylactically medicate vascular beds with adenosine at the target site without the need for additional manipulations by the interventionalist.

Association of target lesion characteristics evaluated by coronary computed tomography angiography and plaque debris distal embolization during percutaneous coronary intervention

BACKGROUND

The slow-flow or no re-flow phenomenon has been associated with distal embolization, especially of plaque debris, and with unfavorable clinical outcomes. Therefore, we examined the association between the coronary computed tomography angiography (CCTA) findings of the target lesion and distal embolization during percutaneous coronary intervention (PCI). METHODS AND RESULTS: Consecutive patients (n=55: 18 unstable angina, 19 stable effort angina, 18 silent ischemia) who underwent PCI with a filter-type distal protection device after evaluation of the target lesion by CCTA were analyzed. CCTA examined low-attenuation plaque (LAP), positive remodeling (PR), and ring-like enhancement of the target lesion. Distal embolization of thrombus and plaque debris was evaluated by pathological examination of material collected in the filter.Any distal embolization and distal embolization of plaque debris were respectively detected in 75% and 0% of patients with LAP or PR alone, in 95% and 17% of patients with both LAP and PR, and in 100% and 27% of patients with all of LAP, PR and ring-like enhancement. The sensitivity and specificity to predict plaque debris embolization by having both findings of LAP and PR was 100% and 46%, respectively.

CONCLUSIONS

The CCTA findings of the target lesion were associated with distal embolization and were very sensitive for predicting plaque debris embolization.

Coronary thrombus in patients undergoing primary PCI for STEMI: Prognostic significance and management

Acute ST-elevation myocardial infarction (STEMI) usually results from coronary atherosclerotic plaque disruption with superimposed thrombus formation. Detection of coronary thrombi is a poor prognostic indicator, which is mostly proportional to their size and composition. Particularly, intracoronary thrombi impair both epicardial blood flow and myocardial perfusion, by occluding major coronary arteries and causing distal embolization, respectively. Thus, although primary percutaneous coronary intervention is the preferred treatement strategy in STEMI setting, the associated use of adjunctive antithrombotic drugs and/or percutaneous thrombectomy is crucial to optimize therapy of STEMI patients, by improving either angiographical and clinical outcomes. This review article will focus on the prognostic significance of intracoronary thrombi and on current antithrombotic pharmacological and interventional strategies used in the setting of STEMI to manage thrombotic lesions.

The randomized physiologic assessment of thrombus aspiration in patients with acute ST-segment elevation myocardial infarction trial (PATA STEMI): study rationale and design

INTRODUCTION

Routine thrombus aspiration is proposed to be superior to conventional primary percutaneous coronary intervention (PCI) in terms of improved myocardial perfusion, in patients with ST-segment elevation acute myocardial infarction (STEMI). However, myocardial perfusion after thrombus aspiration has not been evaluated by a quantitative, invasive method. We intend to determine whether manual thrombus aspiration in the infarct-related coronary artery increases myocardial perfusion assessed by index of microcirculatory resistance (IMR) compared with conventional primary PCI.

STUDY DESIGN

PATA STEMI is a single-center, prospective, randomized trial with a planned inclusion of 128 patients with the first STEMI. Prior to coronary angiography, patients are randomly assigned to thrombus aspiration using the Eliminate aspiration catheter (Terumo Medical Supply, Japan) or to conventional primary PCI. After completion of primary PCI, IMR is determined both in infarct-related artery and in noninfarct-related arteries without critical stenoses. The primary end-point is a group mean value of IMR after thrombus aspiration compared with conventional primary PCI. Secondary end-points are myocardial perfusion grade, resolution of ST-segment elevation, enzymatic estimation of infarct size, left ventricular remodeling assessed by echocardiographic indices, and major adverse cardiac events rate at 1, 6, and 12 months.

CONCLUSION

If manual thrombus aspiration significantly reduces microcirculatory resistance, thereby improving myocardial perfusion, it may become the routine strategy in primary PCI.

Prevention of no-reflow phenomenon in culprit lesions involving a large side branch

No-reflow/slow-flow phenomenon (NF) is a poor prognostic factor in patients undergoing percutaneous coronary intervention. Distal protection devices (DPDs) prevent myocardial injury due to microembolic debris. When the target lesion involves a large side branch, DPDs can only protect the main vessel but not the side branch. In the present report, we describe the use of a two-step deflation in kissing-balloon technique for preventing NF in 4 patients (M/F = 4/0, 65 ± 6 years) in which the culprit lesions with NF risk involved a bifurcation. The procedures were uneventful and the 4 patients were discharged ≤24 h without ECG change and elevation of serum level of creatine kinase. The sequential deflation of kissing-balloon technique may constitute a possible solution for the NF related with the side branch on bifurcation lesions.

Guiding-catheter thrombectomy combined with distal protection during primary percutaneous coronary intervention of a saphenous vein graft

Primary percutaneous intervention of saphenous vein grafts is associated with a high risk of distal embolization and no reflow. We report a case of acute myocardial infarction with a large intragraft thrombus, successfully treated with a technique combining thrombectomy with a 6 Fr guiding catheter and distal protection with the FilterWire EZ.

Treating thrombus in the coronary arteries

Primary percutaneous coronary intervention (PCI) has greatly improved outcomes in patients with ST-elevation myocardial infarction (STEMI) and has, therefore, become the preferred reperfusion strategy for this patient group. The goal of primary PCI is to achieve a thrombolysis in myocardial infarction (TIMI) 3 flow and also to restore adequate perfusion at the myocardial level. Distal thrombus embolization during primary PCI occurs frequently and is also associated with compromised long-term outcomes. In this article, we provide an overview of the treatment of thrombus and the role of thrombectomy in PCI for STEMI.

Pharmacological and physical prevention and treatment of no-reflow after primary percutaneous coronary intervention in ST-segment elevation myocardial infarction

After successful primary percutaneous coronary intervention in ST-segment elevation myocardial infarction, adequate myocardial reperfusion is not achieved in up to 50% of patients. This phenomenon of no-reflow is associated with a poor in-hospital and long-term prognosis. Four main factors are thought to contribute to the occurrence of no-reflow: ischaemic injury; reperfusion injury; distal embolization; susceptibility of the microcirculation to injury. This review evaluates the literature, and in particular the clinical trials, concerned with pharmacological and physical methods for prevention and treatment of no-reflow. A number of drugs may improve no-reflow experimentally and clinically, but some have not yet been associated with conclusive improvements in clinical outcome. The complex interacting factors in no-reflow make it unlikely that any single agent will be effective for all patients. Confirmed methods known to be beneficial in the prevention of no-reflow (such as aspirin therapy, chronic statin therapy, blood glucose control, thrombus aspiration in patients with a high thrombus burden and ischaemic preconditioning) should be offered to patients as often as possible, to prevent and treat no-reflow.

Embolic protection devices in saphenous vein graft and native vessel percutaneous intervention: a review

The clinical benefit of percutaneous intervention (PCI) depends on both angiographic success at the site of intervention as well as the restoration of adequate microvascular perfusion. Saphenous vein graft intervention is commonly associated with evidence of distal plaque embolization, which is correlated with worse clinical outcomes. Despite successful epicardial intervention in the acute MI patient treated with primary PCI, distal tissue perfusion may still be absent in up to 25% of cases [1-3]. Multiple devices and pharmacologic regimens have been developed and refined in an attempt to protect the microvascular circulation during both saphenous vein graft intervention and primary PCI in the acute MI setting. We will review the evidence for various techniques for embolic protection of the distal myocardium during saphenous vein graft PCI and primary PCI in the native vessel.

Distal protection devices in primary percutaneous coronary intervention of native coronary artery lesions: a meta-analysis of randomized controlled trials

OBJECTIVE

The use of embolic protection devices to decrease major adverse cardiac events (MACEs) in patients with saphenous vein graft lesions is considered class I therapy by the recent practice guidelines. However, the benefits of adjunctive protection devices to prevent distal embolization in patients with native coronary artery lesions are still a matter of debate. Therefore, we performed the meta-analysis to determine whether the use of distal protection devices during revascularization can improve myocardial perfusion and reduce the occurrence of MACEs compared with primary percutaneous coronary intervention (PCI) alone.

METHODS AND RESULTS

Studies were identified in English-language articles by search of Medline and Embase database (inception to December 2011). A total of 15 prospective randomized controlled trials involving 2783 patients were included for analysis (1378 patients in the distal protection device group and 1405 cases in the control group). Overall, adjunctive embolic protection was associated with significantly improved postprocedural TIMI 3 (thrombolysis in myocardial infarction 3) flow (OR 1.71; 95% CI 1.13-2.57; P = 0.01) and MBG 3 (myocardial blush grade 3) (OR 1.50; 95% CI 1.09-2.07; P = 0.01), whereas the overall MACEs analysis demonstrated that a nonsignificant trend was observed toward better clinical outcomes associated with adjunctive protection devices at 1 month (OR 0.80; 95% CI 0.55-1.15; P = 0.23) and at 6 months (OR 0.80; 95% CI 0.55-1.17; P = 0.24). When stratified by MACEs, no statistical differences were found among mortality, reinfarction, and target vessel revascularization (TVR), respectively.

CONCLUSIONS

The meta-analysis indicated an improvement of myocardial perfusion in AMI patients treated with adjunctive protection devices. However, a nonsignificant trend was observed toward a lower risk of MACEs in the distal protection device group when compared with the control group.

The management of thrombotic lesions in the cardiac catheterization laboratory

Plaque rupture with superimposed thrombosis is the major mechanism of acute coronary syndromes. Although angiography underestimates the presence of thrombi, their detection is a poor prognostic indicator which is proportional to their size. Although emergent percutaneous coronary intervention (PCI) in the setting of ST elevation myocardial infarction (STEMI) and early PCI in the setting of unstable angina and non-STEMI were shown to be preferred strategies, the presence of angiographic thrombosis by virtue of causing micro and macro embolization can reduce the benefit of the intervention. Antiplatelet therapy especially using glycoprotein IIb/IIIa inhibitors reduces thrombus size, and improves myocardial perfusion and ventricular function. Routine manual aspiration prior to PCI in STEMI also improves myocardial flow and reduces distal embolization and improves survival. Distal embolic protection devices and mechanical thrombectomy do not have the same clinical benefits however, rheolytic thrombectomy may have a role in large vessels with a large thrombi.

Evaluation of the acute effects of distal coronary microembolization using multidetector computed tomography and magnetic resonance imaging

The purpose of this study was to test the potential of clinical imaging modalities, 64-slice multidetector computed tomography (MDCT) and 1.5T magnetic resonance imaging (MRI) for qualitative and quantitative evaluation of acute microinfarcts and to determine the effects of <120 μm microemboli on left ventricular function, perfusion, cardiac injury biomarkers, arrhythmia, and cellular and vascular structures. Under X-ray fluoroscopy, 40-120 μm (16 mm(3) ) microemboli were delivered to embolize the left anterior descending (LAD) coronary artery of nine pigs. MDCT/MRI were performed at 72 h in a single session. Microinfarcts were visible in six of nine animals on delayed contrast-enhanced MDCT/MR images but measurable in all animals using semiautomated threshold methods. Other MDCT and MRI sequences demonstrated decline in left ventricular ejection fraction, regional strain and perfusion in visible and invisible microinfarcted regions. Microemboli caused significant elevation in cardiac injury enzymes and arrhythmias. Various sizes of microinfarcts appeared microscopically as distinct aggregates of macrophages replacing myocardium. Semiautomated threshold methods are necessary to measure and confirm/deny the presence of myocardial microinfarcts. This study offers support for alternative applications of MDCT/MRI in assessing clinical cases in which microemboli <120 μm escape protective devices during percutaneous coronary interventions. Although microembolization resulted in no mortality, it caused left ventricular dysfunction, perfusion deficit, cellular damage increase in cardiac injury enzymes, and arrhythmias.

MRI study on volume effects of coronary emboli on myocardial function, perfusion and viability

BACKGROUND

Coronary filtration devices showed inadequate protection during PCI due to the inability to filter microemboli <120 μm in diameter. The purpose of this study was to determine the impact of two volumes of <120 μm microemboli on LV function, perfusion and viability using magnetic resonance imaging (MRI).

METHODS

Under X-ray guidance, pigs (n = 18) received two different volumes (16 mm(3) or 32 mm(3)) of 40-120 μm microemboli (intracoronary). At 3 days, regional myocardial perfusion and LV function were assessed using first pass perfusion and cine MRI. Viability MRI was performed in beating and non-beating hearts to delineate microinfarcts and compare with histochemical triphenyltetrazolium chloride stain, using semi-automatic threshold method. Histology and cardiac injury enzymes were used to confirm the presence of microinfarcts and characterize cellular and vascular changes.

RESULTS

Microinfarcts were visible as enhanced specks on DE-MRI in all animals that received 32 mm(3), but only two-third of the animals that received 16 mm(3), volume. The decline in ejection fraction and increase in LV volumes and microinfarcts were volume dependent. Regional perfusion and contractility were significantly reduced in the LAD territory compared with remote myocardium. Histology showed apoptosis, edema, inflammation and vascular thrombosis.

CONCLUSIONS

Microemboli of <120 μm have deleterious effects on LV function, perfusion and viability and the effects are dependent on microemboli volume. Microinfarct visualization is crucial to ensure that myocardial dysfunction is related to dislodged microemboli and not only to pre-procedural stunning or hibernation. This noninvasive MRI method may help in evaluating the effectiveness of coronary filtration devices in protecting myocardium from microemboli.

Proximal embolic protection in patients undergoing primary angioplasty for acute myocardial infarction (PREPARE): core lab adjudicated angiographic outcomes of a randomised controlled trial

BACKGROUND

Patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) with the Proxis system (St. Jude Medical, St. Paul, MN, USA) achieved significantly better microvascular flow as measured by ST-segment resolution. However, no differences were observed in left ventricular ejection fraction or infarct size as obtained by cardiovascular magnetic resonance imaging. The goal of the present study was to evaluate the effect of combined proximal embolic protection and thrombus aspiration on core-lab adjudicated angiographic outcomes.

METHODS

In the PRoximal Embolic Protection in Acute myocardial infarction and Resolution of ST-Elevation (PREPARE) study, patients were randomised to primary PCI with the Proxis system (n=141) or primary PCI alone (n=143). An independent core laboratory re-evaluated all angiograms and adjudicated the angiographic outcomes and computerised quantitative blush evaluation (QuBE) value.

RESULTS

There were no significant differences in Thrombolysis In Myocardial Infarction (TIMI) flow grade, myocardial blush grade, or angiographic signs of distal embolisation among the two arms. QuBE values did not significantly differ between the Proxis-treated patients and control patients (15.1±5.4 vs. 15.8±5.5, respectively, p=0.34).

CONCLUSION

Primary PCI with combined proximal embolic protection and thrombus aspiration in STEMI patients more frequently resulted in complete immediate ST resolution compared with control patients. However, there were no significant differences in core laboratory adjudicated angiographic outcomes. (Neth Heart J 2010;18:531-6.).

A multicenter, randomized, controlled study of mechanical left ventricular unloading with counterpulsation to reduce infarct size prepercutaneous coronary intervention for acute myocardial infarction: rationale and design of the Counterpulsation Reduces Infarct Size Acute Myocardial Infarction trial

BACKGROUND

Despite advances in care processes to improve reperfusion in patients with acute myocardial infarction (AMI), the short-term and 1-year mortality remains high, in part, because of reperfusion injury, microvascular obstruction, and infarct expansion. Intraaortic balloon counterpulsation (IABC) is an adjunct to revascularization and has reduced microvascular obstruction and infarct size in animal models of AMI.

METHODS

CRISP AMI is a multicenter randomized trial that aims to determine if IABC initiated before percutaneous coronary intervention (PCI) for reperfusion compared with routine PCI in patients with anterior ST-segment elevation AMI reduces infarct size as measured by cardiac magnetic resonance imaging. Patients are randomly assigned to receive IABC initiated before primary PCI and continued for at least 12 hours or routine PCI with standard-of-care medical therapy in both groups. The primary efficacy end point is infarct size measured by cardiac magnetic resonance imaging at 3 to 5 days post-PCI. The secondary clinical end point is the composite of major adverse clinical events including death, reinfarction, and heart failure at 6 months. According to sample size calculation, 300 patients will be randomized at 50 sites across 10 countries.

CONCLUSION

The CRISP AMI study will determine if IABC before reperfusion in patients with anterior AMI reduces infarct size.

Management of the no-reflow phenomenon

The lack of reperfusion of myocardium after prolonged ischaemia that may occur despite opening of the infarct-related artery is termed "no reflow". No reflow or slow flow occurs in 3-4% of all percutaneous coronary interventions, and is most common after emergency revascularization for acute myocardial infarction. In this setting no reflow is reported to occur in 30% to 40% of interventions when defined by myocardial perfusion techniques such as myocardial contrast echocardiography. No reflow is clinically important as it is independently associated with increased occurrence of malignant arrhythmias, cardiac failure, as well as in-hospital and long-term mortality. Previously the no-reflow phenomenon has been difficult to treat effectively, but recent advances in the understanding of the pathophysiology of no reflow have led to several novel treatment strategies. These include prophylactic use of vasodilator therapies, mechanical devices, ischaemic postconditioning and potent platelet inhibitors. As no reflow is a multifactorial process, a combination of these treatments is more likely to be effective than any of these alone. In this review we discuss the pathophysiology of no reflow and present the numerous recent advances in therapy for this important clinical problem.