Distal Protection in Peripheral Vascular Interventions

Embolic debris during interventional procedures is practically universal. External Doppler monitoring has shown embolic “hits” occur during atherectomy and with wire crossing, balloon crossing, balloon inflation, balloon deflation, stent placement, and stent expansion. Embolic debris can be thrombus, cholesterol particles, slivers of shaved atheroma, and various combinations of these. The vast majority of embolic particles result in no immediate adverse clinical events or obvious angiographic findings. These “minor” emboli have been historically regarded as benign. Whether or not undetected embolic events are totally benign remains to be established. Major embolic events, however, can result in vascular occlusion, slow flow, and no reflow, which may result in easily recognized adverse clinical events. The clinical sequelae of these emboli depend upon the affected vascular bed, the perfused organ, and whether or not flow can be reestablished in a timely manner. 

All interventionists strive to avoid major embolic debris during intervention. Meticulous technique is imperative in all interventions but particularly with atherectomy. Thrombus removal prior to intervention via aspiration or thrombolysis can clearly lessen the risk of thrombotic debris. A balloon that can dilate then create a partial vacuum while being inverted for removal (Proteus; Angioslide) has been shown to capture and remove debris. Embolic protection devices are routinely utilized in carotid interventions and are often utilized in peripheral interventions although none of these devices were originally designed for peripheral interventions. The devices typically utilized in peripheral interventions are distal protection devices with pore sizes large enough to allow blood to flow through but small enough to capture particles of 100 microns or greater. These devices have limited basket size, have poor shaft support, and can fail secondary to migration or failure to adequately appose the distal vessel. 

Distal protection devices are presently recommended routinely in the instructions for use of certain atherectomy devices but there remains great debate among interventionists about routine use in peripheral interventions. Although all agree that the desired outcome is to avoid major embolic events, vascular specialists have to consider the extra cost per procedure and potential complications from attempting to prevent emboli such as bleeding with thrombolysis and potential for vascular injury with the other devices. We also need to better understand whether or not emboli that we consider to be minor have long-term adverse clinical outcomes. Clearly there is a need for devices designed specifically for peripheral interventions, particularly in high-risk cases. Lower cost devices would allow more routine utilization.