Embolic protection devices in saphenous vein graft interventions

Saphenous vein grafts (SVGs) are widely used as aortocoronary conduits during coronary artery bypass surgery and are critical in the high early success of coronary bypass revascularization. Saphenous vein grafts tend to be more prone than native coronary arteries to accelerated atherosclerosis and intimal fibrosis and thus frequently lead to recurrent symptoms and require further revascularization. Percutaneous coronary interventions (PCI) have become the prime means of SVG mechanical revascularization but are plagued by higher complication rates than PCI on native coronaries, largely due to embolic debris mobilized from around the target lesion in the SVG. Several mechanical devices and techniques have been developed to capture this friable material during the PCI before it can embolize; these devices have shown great promise in reducing the morbidity and mortality of these interventions and should be employed routinely.     

Embolic protection devices for carotid artery stenting: better results than stenting without protection?

AIMS: Carotid artery stenting (CAS) for carotid artery stenoses has become an alternative to carotid endarterectomy. However, CAS itself can cause cerebral ischaemic events. Embolic protection devices (PD) promise to reduce the incidence of these events. METHODS AND RESULTS: From July 1996 to March 2003, 1483 patients from 26 hospitals were included in the prospective CAS Registry of the ALKK study group. A PD was used in 668 of 1483 patients (45%). The use of a PD has grown rapidly over the years and reached 100% in 2003. Patients treated with a PD had prior carotid artery dilatation more often (3.5% versus 1%, p < 0.001), a prior myocardial infarction (34% versus 27.4%, p = 0.007) and a history of arterial hypertension (89.9% versus 78.6%, p = 0.007) compared to patients treated without a PD. A thrombus was more often visible in patients treated under distal protection (16.5% versus 8%, p < 0.001). The use of a PD led to a 10-min longer intervention (45 min versus 35 min median, p < 0.001). Patients treated with a PD had a lower rate of ipsilateral stroke (1.7% versus 4.1%, p = 0.007) and a lower rate of all non-fatal strokes and all deaths (2.1% versus 4.9%, p = 0.004) during the hospital stay. This was confirmed by multiple logistic regression analysis (adjusted OR = 0.45, 95% CI: 0.23-0.91, p = 0.026). A similar reduction could be found for symptomatic as well as asymptomatic carotid artery stenoses. CONCLUSION: Since 1996 there has been a steady increase in the use of PDs for CAS, with a 100% use in 2003. The use of a PD may lower the rate of ipsilateral strokes during CAS.     

Embolic protection: Limitations of current technology and novel concepts

Distal embolic event is one of the major limitations of coronary and non‐coronary vascular interventions. Balloon and filter‐based Embolic Protection Devices (EPDs) are a new class of interventional devices, used to prevent consequential morbidity and mortality of the distal embolic events. Data from first generation EPD supply proof of concept and show approximately 40% reduction in mortality and morbidity, when EPDs are used during saphenous vein grafts (SVGs) interventions. Current limitations of all first generation EPD technology taper their penetration. With breakthroughs in embolic protection technology, it is estimated that, in the near future, EPDs will be used with stenting in all high‐risk lesions (SVGs, carotid arteries and acute coronary syndromes), become the standard of care and even be used in low risk cases.     

Thrombectomy and distal protection devices

Visible distal embolization is a relatively rare complication during percutaneous coronary interventions but it may occur in 15-20% of angioplasties in saphenous vein grafts (SVG) and in thrombus containing lesions of native coronary arteries, especially in the setting of acute myocardial infarction (AMI). Mechanical thrombectomy devices and distal protection devices have been introduced to reduce the incidence of distal embolisation. Angiojet thrombectomy has shown positive outcomes in thrombus containing lesions when compared with intracoronary thrombolysis but a randomised trial failed to show benefit in the context of AMI. The X-Sizer, Excimer LASER and various simple aspiration thrombectomy catheters show promise in treatment of AMI with improvement shown in surrogate end-points such as resolution of ST-elevation but there have been no randomised trials large enough to demonstrate changes in hard clinical end-points. Distal protection devices have come to be routinely used during SVG treatment and, after the results of the SAFER and FIRE trials; they became a treatment recommendation in the recently issued European Society of Cardiology (ESC) guidelines. For AMI, these devices showed great promise in early single-centre studies which have been offset by the lack of clinical benefit in the multi-centre EMERALD trial. Proximal occlusion devices may further decrease the incidence of distal embolisation, especially in the treatment of totally occluded SVGs or native arteries, by reversing the blood flow and offering protection at a very early stage of the procedure before wire passage. Despite continuous technical improvement and a growing number of miniaturised thrombectomy devices and filters, because of the paucity of controlled large studies, it remains unclear whether these devices will remain limited to niche' applications or will become a regular companion to balloons and stents in mainstream angioplasty procedures.     

Coronary interventional devices: balloon, atherectomy, thrombectomy and distal protection devices

With increased operator experience and improved device technology, there has been a constant growth in the number of complex lesions (ie, thrombotic lesions, diffuse lesions,calcified lesions, nondilatable rigid lesions, ostial lesions, bifurcations, and chronic total occlusions) attempted by interventionalists with the use of drug-eluting stents. Although coronary stent implantation remains the mainstay and ultimate step for the treatment of most coronary lesions, adjunctive devices may be essential for lesion preparation in some cases (5%-10%) to allow stent deployment and expansion and prevent distal embolization.Thrombectomy and distal protection devices have shown to be effective in the interventions of saphenous vein graft lesions, although their use remains unproven in acute myocardial infarctions.     

Cerebral protection devices during transcatheter aortic valve implantation

Transcatheter aortic valve implantation (TAVI) in patients with aortic valve stenosis is associated with an improvement of clinical outcomes, quality of life, and self-sufficiency. The most feared TAVI-related complication is the occurrence of stroke. In order to reduce peri-procedural cerebral embolizations, diverse cerebral protection devices have been developed. These devices work though deflection or filtering of emboli, and are in different stages of testing. Silent cerebral infarctions identified by diffusion-weighted magnetic resonance imaging (DW-MRI) are used as surrogate primary outcomes, but the clinical significance is still unclear. This review provides a synopsis of the diverse cerebral protection devices and summarizes the current evidence on their efficacy during TAVI.     

Embolic protection filters for carotid stenting: differences in flow obstruction depending on filter construction.

PURPOSE: To investigate the pressure gradient and degree of flow reduction associated with embolus protection filters for carotid stenting in an in vitro experiment. METHODS: Three filter devices with a perforated membrane design and one wire mesh type filter were tested. At a pressure of 70 mmHg, the flow reduction and pressure gradient were measured in a 5-mm tube using blood-mimicking fluid. RESULTS: The pressure gradient in the wire mesh filter was 1.65+/-0.49 mmHg (95% CI 1.32 to 1.86). The mean pressure gradient in the perforated membrane filters was 6.88+/-2.62 mmHg (95% CI 6.22 to 7.55, p<0.0001). There was also a significant correlation between pressure gradient and flow reduction (r=-0.77, p<0.01). CONCLUSION: Embolic protection filters cause a pressure gradient and obstruct blood flow. This effect is marked in perforated membrane filters and almost absent in the wire mesh filter.     

Carotid artery stenting: utility of cerebral protection devices

Neurologic deficits secondary to embolic events have been the most significant concern regarding carotid bifurcation stenting. Experimental studies utilizing human carotid plaques have shown that embolic particles were released from all specimens. In addition, transcranial Doppler studies have confirmed the fact that multiple emboli are released during each case. Preliminary experiences with the use of cerebral protection devices for carotid stenting have shown encouraging results with embolic particles recovered from each case, although these experiences have also revealed some of the down sides of its use. The present article provides the rationale for routine use of these protection devices and also reviews various protection devices, some of which are currently undergoing clinical trials.     

滤网保护装置在颈动脉和椎动脉狭窄支架置入术中的应用

目的 探讨滤网保护装置在血管内支架治疗颈动脉和椎动脉狭窄中的应用。方法 配合应用滤网保护装置，对颈动脉和椎动脉狭窄患者进行经皮血管内支架成形术36例次(其中颈动脉33例次，椎动脉起始部3例次)，对手术过程、治疗效果和病理学检查结果进行分析。结果全部病例成功应用滤网保护装置进行了支架置入术，手术相关并发症的发生率为O。血管狭窄率由支架前的81．4％下降至支架后的14．1％；病理学检查显示，27例患者保护装置的滤网内有斑块成分，占75％；保护装置捕捉到的有形成分包括纤维蛋白、斑块碎片(坏死组织、胆同醇碎片、钙化成分等)。结论 滤网保护装置可以捕捉到颈动脉和椎动脉狭窄支架成形术中碎解的斑块成分，降低术中栓塞性并发症的发生概率；目前临床治疗中应用的滤网保护装置可以选择性地应用于椎动脉起始部狭窄的支架成形术中；滤网保护装置应进一步向微型化发展，以适应更多部位的血管内支架成形术。