Microscopic Assessment of Healing and Effectiveness of a Foam-Based Peripheral Occlusion Device

Abstract

The IMPEDE Embolization Plug is a catheter-delivered vascular occlusion device that utilizes a porous shape memory polymer foam as a scaffold for thrombus formation and distal coils to anchor the device within the vessel. In this study, we investigated the biological response of porcine arteries to the IMPEDE device by assessing the extent of healing and overall effectiveness in occluding the vessel at 30, 60, and 90 days. Compared to control devices (Amplatzer Vascular Plug and Nester Embolization Coils), the host response to IMPEDE showed increased cellular infiltration (accommodated by the foam scaffold), which led to advanced healing of the initial thrombus to mature collagenous connective tissue (confirmed by transmission electron microscopy (TEM)). Over time, the host response to the IMPEDE device included degradation of the foam by multinucleated giant cells, which promoted fibrin and polymer degradation and advanced the healing response. Device effectiveness, in terms of vessel occlusion, was evaluated histologically by assessing the degree of recanalization. Although instances of recanalization were often observed at all time points for both control and test articles, the mature connective tissue within the foam scaffold of the IMPEDE devices improved percent vessel occlusion; when recanalization was observed in IMPEDE-treated vessels, channels were exclusively peri-device rather than intradevice, as often observed in the controls, and the vessels mostly remained >75% occluded. Although total vessel occlusion provides the optimal ischemic effect, in cardiovascular pathology, there is a progressive ischemic effect on the downstream vasculature as a vessel narrows. As such, we expect a sustained ischemic therapeutic effect to be observed in vessels greater than 75% occluded. Overall, the current study suggests the IMPEDE device presents advantages over controls by promoting an enhanced degree of healing within the foam scaffold, which decreases the likelihood of intradevice recanalization and ultimately may lead to a sustained ischemic therapeutic effect.

Clinical experience with a shape memory polymer peripheral vascular embolisation plug: a case series

“…Near complete degradation was observed in vivo in rat subcutaneous and rabbit intramuscular implants at 180 days." Longer-term follow-up will show longer-term clinical results, however preclinical work demonstrated the conversion of thrombus to mature collagenous connective tissue as the polymeric scaffold degrades (Jessen et al 2020).…”

“…The polymer fabrication and physical properties have previously been described (Landsman et al 2016 ). Preclinical work characterised cellular infiltration into the shape memory polymer scaffold and conversion of thrombus to mature collagenous connective tissue over time (Jessen et al 2020 ). Furthermore, preclinical work suggests shape memory polymer-based devices support an advanced state of healing, within a designated timeframe, compared to other commonly used vessel embolisation devices (Jessen et al 2020 ).…”

“…Preclinical work characterised cellular infiltration into the shape memory polymer scaffold and conversion of thrombus to mature collagenous connective tissue over time (Jessen et al 2020 ). Furthermore, preclinical work suggests shape memory polymer-based devices support an advanced state of healing, within a designated timeframe, compared to other commonly used vessel embolisation devices (Jessen et al 2020 ). Following CE marking of the devices, the manufacturer established a post market study to collect data on their routine clinical use.…”

Shape memory polymer ovarian vein embolisation in a patient with nickel allergy

“…When the device is deployed into the warm and aqueous environment of a blood vessel, the polymer recovers, or remembers, its original shape and self-expands. The porous nature of the expanded vascular plug supports the acute formation of thrombus throughout its structure and preclinical work has demonstrated that increased cellular infiltration leads to advanced healing of the initial thrombus to mature collagenous connective tissue when compared to other common embolic devices (Jessen et al 2020).…”

Clinical Experience With a Shape Memory Polymer Peripheral Vascular Embolisation Plug: A Case Series

“…Preclinical work characterised cellular in ltration into the shape memory polymer scaffold and conversion of thrombus to mature collagenous connective tissue over time (Jessen et al, 2020). Furthermore, preclinical work suggests shape memory polymerbased devices support an advanced state of healing, within a designated timeframe, compared to other commonly used vessel embolisation devices (Jessen et al, 2020). Following CE marking of the devices, the manufacturer established a post market study to collect data on their routine clinical use.…”