Kallmes, David F.

Shape memory polymers can be programmed into a secondary geometry and recovered to their primary geometry with the application of a controlled stimulus. Porous shape memory polymer foam scaffolds that respond to body temperature show particular promise for embolic medical applications. A limitation for the minimally invasive delivery of these materials is an inherent lack of X-ray contrast. In this work, a triiodobenzene containing a monomer was incorporated into a shape memory polymer foam material system to chemically impart X-ray visibility and increase material toughness. Composition and process changes enabled further control over material density and thermomechanical properties. The proposed material system demonstrates a wide range of tailorable functional properties for the design of embolic medical devices, including X-ray visibility, expansion rate, and porosity. Enhanced visualization of these materials can improve the acute performance of medical devices used to treat vascular malformations, and the material porosity provides a healing scaffold for durable occlusion.

Abstract BACKGROUND The safety of Pipeline TM Embolization Device (PED; Medtronic Inc, Dublin, Ireland) in posterior circulation aneurysms is still controversial. OBJECTIVE To study complications associated with the treatment of posterior circulation aneurysms by conducting a subgroup analysis from the International Retrospective Study of PED registry. METHODS Data from 91 consecutive patients with 95 posterior circulation aneurysms at 17 centers between July 2008 to February 2013 were analyzed. The primary endpoint was defined as any complication leading to neurological morbidity or death. The outcome predictors were calculated using Kaplan–Meier and Cox regression methods. RESULTS The mean aneurysm size was 13.8 mm. Aneurysm types were saccular (36.8%), fusiform (29.5%), dissecting (28.4%), and others (5.3%). The median follow-up was 21.1 mo. Twelve (13.2%) patients encountered a primary endpoint event. In multivariate analysis for the primary endpoint, use of ≥3 PEDs and fusiform shape compared with other shapes had hazard ratios (HRs) of 7.77 (95% confidence interval [CI], 2.48-25.86; P = .0007) and 3.48 (95% CI, 1.06-13.39; P = .0488), respectively. The multivariate HR of aneurysm size for neurological morbidity after PED implantation was 1.11 (95% CI, 1.04-1.18; P = .0015), and HRs of ruptured aneurysm and age for neurological mortality were 8.1 (95% CI, 1.31-41.26; P = .0197) and 1.07 (95% CI, 1.02-1.15; P = .0262), respectively. Basilar artery aneurysm had an HR of 3.54 (95% CI, 1.12-14.18, P = .0529) in the univariate analysis for major outcomes. CONCLUSION PED implantation may be considered for the treatment of posterior circulation aneurysms, especially of saccular or dissecting type. Our major complications appear to be comparable to those reported previously after clipping and coiling in the literature. Neurointerventionists should consider the shape, size, rupture, and location of complex posterior circulation aneurysms as well as age and PED number before the PED placement.

Intracranial aneurysms are heterogeneous in histopathology and imaging appearance. The biological behavior of different types of aneurysms is now known to depend on the structure and physiology of the aneurysm wall itself in addition to intraluminal flow and other luminal features. Aneurysm wall structure and imaging markers of physiology such as aneurysm wall enhancement have been assessed in many prior investigations using conventional-resolution MRI. Recently, high-resolution vessel wall imaging (HR-VWI) techniques with MRI have been introduced. Reports of findings on high-resolution imaging have already emerged for many types of aneurysms demonstrating detailed characterization of wall enhancement, thickness, and components, but many questions remain unexplored. This review discusses the key HR-VWI literature to date. Aneurysm wall findings on conventional-resolution MRI are also discussed as these may help one understand the potential utility and findings on HR-VWI for various aneurysm types. The authors have illustrated these points with several examples demonstrating both features already described in the literature and novel cases demonstrating the potential for future clinical and research applications.

Background and Purpose— Because of the perceived risk of contrast-induced acute kidney injury (AKI), many centers require pre-imaging serum creatinine levels, potentially delaying care. We performed a systematic review and meta-analysis evaluating AKI rates in patients with acute ischemic stroke receiving computed tomographic angiography (CTA) and computed tomographic perfusion (CTP). Methods— We searched MEDLINE, EMBASE, and the Web of Science through December 2016 for studies reporting on AKI in patients with acute ischemic stroke receiving CTA/CTP. Using a random-effects model, estimates were pooled across studies. Outcomes of interest were (1) the odds of AKI in patients receiving CTA/CTP versus noncontrast computed tomography, (2) overall rate of AKI and hemodialysis in patients with acute ischemic stroke undergoing CTA/CTP, and (3) the odds of CTA/CTP-associated AKI among patients with and without chronic kidney disease. Results— Fourteen studies were included (6 case–control studies and 8 single-arm studies) with 5727 CTA/CTP and 981 noncontrast computed tomography patients. In case–control studies, AKI was significantly lower among CTA/CTP patients compared with noncontrast computed tomography patients (odds ratio=0.47; 95% confidence interval=0.33–0.68; P <0.01). Adjusting for baseline creatinine, there was no difference in AKI rates between groups (odds ratio=0.34; 95% confidence interval=0.10–1.21). The overall rate of AKI in CTA/CTP patients was 3% (95% confidence interval=2%–4%). The overall rate of hemodialysis in the CTA/CTP group was 0.07% (3 of 4373). There was no difference in AKI among CTA/CTP patients with and without chronic kidney disease (odds ratio=0.63; 95% confidence interval=0.34–1.12). Conclusions— Nonrandomized evidence suggests that CTA/CTP are not associated with statistically significant increase in risk of AKI in patients with stroke, even those with known chronic kidney disease.

Limited data exist on clot composition and detailed characteristics of arterial thrombi associated with large vessel occlusion in acute ischemic stroke. Advances in endovascular thrombectomy and related imaging modalities have created a unique opportunity to analyze thrombi removed from cerebral arteries. Insights into thrombus composition, etiology, physical properties and neurovascular interactions may lead to future advancements in acute ischemic stroke treatment and improved clinical outcomes. Advances in imaging techniques may enhance clot characterization and inform therapeutic decision-making prior to treatment and reveal stroke etiology to guide secondary prevention. Current imaging techniques can provide some information about thrombi, but there remains much to evaluate about relationships that may exist among thrombus composition, occlusion characteristics and treatment outcomes. Improved pathophysiological characterization of clot types, their properties and how these properties change over time, together with clinical correlates from ongoing studies, may facilitate revascularization with thrombolysis and thrombectomy. Interdisciplinary approaches covering clinical, engineering and scientific aspects of thrombus research will be key to advancing the understanding of thrombi and improving acute ischemic stroke therapy. This consensus statement integrates recent research on clots and thrombi retrieved from cerebral arteries and provides a rationale for further analyses, including current opportunities and limitations.