In Vitro Study of Transcatheter Delivery of a Shape Memory Polymer Foam Embolic Device for Treating Cerebral Aneurysms

摘要

We are developing shape memory polymer (SMP) foam devices for embolizing and treating cerebrovascular aneurysms. Cerebral aneurysm rupture occurs in approximately 30,000 people per year in the United States, with devastating consequences [1]. Further, three-fourths of patients will either die or become neurologically debilitated [1]. The SMP foam device is designed to rapidly and efficiently promote acute blood clotting with one device treating an aneurysm [2]. Some key features in the foams that enable the clotting efficacy are biocompatibility [3], open cell architecture with tortuous flow and high surface area to volume ratios [3], and large (50x-100x) volume expansions that permit compact delivery through a catheter with actuation and deployment in the aneurysm. This paper describes additional challenges and engineered solutions for transcatheter delivery of a SMP foam embolic device. The primary challenge addressed here which is the engineering tradeoff between self-deploying foams, which actuate at body temperature, versus foams that actuate above body temperature. If body temperature is used to actuate the foams, then they must be physically constrained or sheathed as they are delivered through the catheter. Deployment in the aneurysm then involves unsheathing the foam after it has been placed in the aneurysm. Retractable sheathing systems or other mechanical constraints on the foam become more challenging for devices that are to be delivered through small catheters (3 Fr, ～1000 μm ID) and microcatheters (～500 μm ID). Given that the SMP foams can be designed to actuate at temperatures above body temperature [4], we elected to use foams that stay crimped at body temperature and use a resistive heating delivery device to deploy the foams once they are located in the aneurysm.