A Novel Filter-Based Distal Embolic Protection Device for Percutaneous Intervention of Saphenous Vein Graft Lesions

A fresh look at coronary microembolization

Mechanical stress from haemodynamic perturbations or interventional manipulation of epicardial coronary atherosclerotic plaques with inflammatory destabilization can release particulate debris, thrombotic material and soluble substances into the coronary circulation. The physical material obstructs the coronary microcirculation, whereas the soluble substances induce endothelial dysfunction and facilitate vasoconstriction. Coronary microvascular obstruction and dysfunction result in patchy microinfarcts accompanied by an inflammatory reaction, both of which contribute to progressive myocardial contractile dysfunction. In clinical studies, the benefit of protection devices to retrieve atherothrombotic debris during percutaneous coronary interventions has been modest, and the treatment of microembolization has mostly relied on antiplatelet and vasodilator agents. The past 25 years have witnessed a relative proportional increase in non-ST-segment elevation myocardial infarction in the presentation of acute coronary syndromes. An associated increase in the incidence of plaque erosion rather than rupture has also been recognized as a key mechanism in the past decade. We propose that coronary microembolization is a decisive link between plaque erosion at the culprit lesion and the manifestation of non-ST-segment elevation myocardial infarction. In this Review, we characterize the features and mechanisms of coronary microembolization and discuss the clinical trials of drugs and devices for prevention and treatment.

Current State of the Art in Approaches to Saphenous Vein Graft Interventions

Saphenous vein grafts (SVGs), used during coronary artery bypass graft surgery for severe coronary artery disease, are prone to degeneration and occlusion, leading to poor long-term patency compared with arterial grafts. Interventions used to treat SVG disease are susceptible to high rates of periprocedural MI and no-reflow. To minimise complications seen with these interventions, proper stents, embolic protection devices (EPDs) and pharmacological selection are crucial. Regarding stent selection, evidence has demonstrated superiority of drug-eluting stents over bare-metal stents in SVG intervention. The ACCF/AHA/SCA American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Society for Cardiovascular Angiography and Interventions guidelines recommend the use of EPDs during SVG intervention to decrease the risk of periprocedural MI, distal embolisation and no-reflow. The optimal pharmacological treatment for slow or no-reflow remains unclear, but various vasodilators show promise.

Orbital atherectomy system in treating calcified coronary lesions: 3-Year follow-up in first human use study (ORBIT I trial)

BACKGROUND/PURPOSE

The ORBIT I trial evaluated the safety and performance of an orbital atherectomy system (OAS) in treating de novo calcified coronary lesions. Severely calcified coronary arteries pose ongoing treatment challenges. Stent placement in calcified lesions can result in stent under expansion, malapposition and procedural complications. OAS treatment may be recommended to facilitate coronary stent implantation in these difficult lesions.

MATERIALS/METHODS

Fifty patients with de novo calcified coronary lesions were enrolled in the ORBIT I trial. Patients were treated with the OAS followed by stent placement. Our institution treated 33/50 patients and continued follow-up for 3 years.

RESULTS

Average age was 54.4 years and 90.9% were males. Mean lesion length was 15.9mm. The average number of OAS devices used per patient was 1.3. Procedural success was achieved in 97% of patients. Angiographic complications were observed in five patients (two minor dissections, one major dissection and two perforations). The cumulative major adverse cardiac event (MACE) rate was 6.1% in-hospital, 9.1% at 30 days, 12.1% at 6 months, 15.2% at 2 years, and 18.2% at 3years. The MACE rate included two in-hospital non Q-wave myocardial infarctions (MI), one additional non Q-wave MI at 30 days leading to target lesion revascularization (TLR), and three cardiac deaths.

CONCLUSIONS

The ORBIT I trial suggests that OAS treatment may offer an effective method to modify calcified coronary lesion compliance to facilitate optimal stent placement in these difficult-to-treat patients with acceptable levels of safety up to 3 years post-index procedure.

Cardioprotective effect of high-dose intragraft adenosine infusion on microvascular function and prevention of no-reflow during saphenous vein grafts intervention

BACKGROUND

Despite the use of embolic protection devices, no-reflow can still occur during saphenous vein grafts (SVGs) intervention. High-dose intracoronary adenosine infusion preconditions the myocardium, improves coronary flow, and prevents no-reflow. The role of high-dose intragraft adenosine infusion on protection of microvascular function and prevention of no-reflow has not been investigated

OBJECTIVES

We investigated the cardioprotective effect of high-dose intragraft adenosine infusion, compared with placebo, on microvascular function and prevention of no-reflow during SVGs intervention.

METHODS

We randomized 22 patients with SVGs stenoses to receive either a 10-min intragraft adenosine infusion (200 μg/min; total dose = 2,000 μg) or normal saline prior to stenting. Average peak velocity (APV), coronary flow velocity reserve (CVR), thrombolysis in myocardial infarction (TIMI) frame count (TFC), TIMI myocardial perfusion grade (TMPG), and the rate of no-reflow were compared between the two groups before adenosine or saline infusions and after stenting

RESULTS

After stenting, hyperemic APV, CVR, and TMPG were significantly higher in the adenosine-treated group than in the control group (60 ± 18 vs. 35 ± 10 cm/sec; 2.6 ± 0.54 vs. 1.8 ± 0.47; and 2.8 ± 0.90 vs. 2.1 ± 0.80, respectively; P < 0.05. TFC was significantly lower in the adenosine-treated group than in the control group (14 ± 3.0 vs. 26 ± 13; P < 0.05). In the control group, four patients (36%) developed no-reflow compared to none in the adenosine-treated patient; P < 0.05 CONCLUSIONS: This study provides the first evidence that high-dose intragraft adenosine infusion compared with placebo protects microvascular function and prevents no-reflow during SVGs intervention.

Embolic Protection Devices for Saphenous Vein Graft Percutaneous Coronary Interventions

Saphenous vein graft (SVG) percutaneous coronary interventions (PCIs) are associated with adverse clinical events caused by distal embolization in 10% to 20% of cases. Various embolic protection devices (EPDs) have been developed to lower the risk of distal embolization during SVG PCI: distal balloon occlusive devices, distal embolic filters, and proximal balloon occlusive devices. Despite evidence for improved outcomes and cost-effectiveness, rates of national EPD use remain low, the main cause of underutilization being operator preference. With increasing familiarity of operators with EPDs, their use should continue to increase in SVG PCI and lead to better outcomes.

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.

Secondary revascularization after CABG surgery

CABG surgery is an effective way to improve symptoms and prognosis in patients with advanced coronary atherosclerotic disease. Despite multiple improvements in surgical technique and patient treatment, graft failure after CABG surgery occurs in a time-dependent fashion, particularly in the second decade after the intervention, in a substantial number of patients because of atherosclerotic progression and saphenous-vein graft (SVG) disease. Until 2010, repeat revascularization by either percutaneous coronary intervention (PCI) or surgical techniques was performed in these high-risk patients in the absence of specific recommendations in clinical practice guidelines, and within a culture of inadequate communication between cardiac surgeons and interventional cardiologists. Indeed, some of the specific technologies developed to reduce procedural risk, such as embolic protection devices for SVG interventions, are largely underused. Additionally, the implementation of secondary prevention, which reduces the need for reintervention in these patients, is still suboptimal. In this Review, graft failure after CABG surgery is examined as a clinical problem from the perspective of holistic patient management. Issues such as the substrate and epidemiology of graft failure, the choice of revascularization modality, the specific problems inherent in repeat CABG surgery and PCI, and the importance of secondary prevention are discussed.

Proximal protection in recanalization of totally occluded saphenous vein grafts in acute coronary syndrome

Percutaneous treatment of old, degenerated saphenous vein grafts (SVG) is associated with a high likelihood of major adverse cardiac events. When an acute coronary syndrome (ACS) develops in a patient with old SVG, fresh thrombus may superimpose on an old, degenerative atheroma: a sudden increase in the athero-thrombotic burden ensues with consequent, frequent total occlusion of the lumen. In this scenario, transluminal recanalization of the graft is usually associated with the highest chance of distal embolization and no-reflow and positioning of an embolic protection device (EPD) is almost mandatory. However, distal EPD are difficult to place when the vessel is totally occluded and do not completely avoid distal embolization. We report two cases of totally occluded SVG in patients admitted for ACS that were recanalized with the aid of a proximal EPD system with angiographic and clinical success.

Contemporary incidence and predictors of major adverse cardiac events after saphenous vein graft intervention with embolic protection (an AMEthyst trial substudy)

The incidence and predictors of major adverse cardiac events after percutaneous coronary intervention of saphenous vein grafts have not been evaluated in the era of routine embolic protection device (EPD) use and the current standards of antiplatelet therapy. The Assessment of the Medtronic AVE Interceptor Saphenous Vein Graft Filter System (AMEthyst) is the largest randomized trial of vein graft intervention comparing the Interceptor EPD and either the GuardWire or FilterWire EPD as the control. The baseline demographic, procedural, and clinical characteristics and the 30-day major adverse cardiac events ([MACE] death, myocardial infarction, and repeat revascularization [either surgery or percutaneous coronary intervention] of the target vessel) were recorded for 748 patients who had undergone vein graft intervention with distal embolic protection. At 30 days, MACE had occurred in 58 patients (7.8%). The univariate predictors of MACE at 30 days included plaque volume (odds ratio 1.005/mm(3), p <0.0001), target lesion length (odds ratio 1.046/mm, p <0.001), vein graft degeneration score (odds ratio 1.631, p = 0.001), coronary narrowing classification (odds ratio 1.697, p = 0.004), reference vessel diameter (odds ratio 1.689, p = 0.004), and male gender (odds ratio 2.406, p = 0.046) and was independent of device type (p = 0.74). The plaque volume was the most important and only multivariate predictor of MACE. The highest quartile of plaque volume defined a subset at particular risk, despite EPD use (MACE 15.8% vs 5.0%, p <0.001). In conclusion, in a patient population in which EPD and preprocedure thienopyridine therapy were uniformly implemented, MACE occurred with an incidence of 7.8% at 30 days. An increasing plaque volume was the most important determinant of MACE and defined a population at particular risk.

Coronary microembolization: from bedside to bench and back to bedside

Coronary microembolization from the erosion or rupture of a vulnerable atherosclerotic plaque occurs spontaneously in acute coronary syndromes and iatrogenically during percutaneous coronary interventions. Typical consequences of coronary microembolization are microinfarcts with an inflammatory response, contractile dysfunction, and reduced coronary reserve. Apart from transient elevations of creatine kinase and troponin, microemboli can be visualized by intracoronary Doppler and the resulting microinfarcts by late-enhancement nuclear magnetic resonance. Statins, antiplatelet agents, and coronary vasodilators protect against microembolization and microinfarction when started before percutaneous coronary interventions. Distal protection devices can retrieve atherothrombotic debris and prevent its embolization into the microcirculation, but their effect on clinical outcome has been disappointing so far, except for saphenous vein bypass grafts. Devices for aspiration of thrombi and thrombus-derived vasoconstrictor, thrombogenic, and inflammatory substances, however, reduce thrombus burden, improve perfusion, and provide protection in patients with acute myocardial infarction.

Current status of distal embolization in percutaneous coronary intervention: mechanical and pharmacological strategies

Distal embolization during percutaneous coronary intervention for acute myocardial infarction or saphenous vein graft disease may result in microvascular obstruction and the 'no-reflow' phenomenon. The incidence of distal embolization ranges from 2 to 42% in saphenous vein graft intervention and from 6 to 15% in primary percutaneous coronary intervention and is associated with impaired myocardial perfusion and poor outcome. Several mechanical and pharmacological strategies have been proposed to prevent or to treat embolization in percutaneous coronary intervention and have been tested in clinical trials. The pivotal role of distal embolization in the pathophysiology of microvascular obstruction will lead to the further development of preventive and therapeutic strategies. Strategies to counteract distal embolization and future directions are discussed in this review.