Biomedical subjects

David I Levy

Publications and source records attributed to David I Levy.

4 recordsLinked to original sources

PubMed2006

Recent steps toward a reconstructive endovascular solution for the orphaned, complex-neck aneurysm.

OBJECTIVE: The purposes of this article are to summarize recent developments and concerns in endovascular aneurysm therapy leading to the adjunctive use of endoluminal devices, to review the published literature on stent-supported coil embolization of cerebral aneurysms, and to describe our experience with this technique in a limited subgroup of problematic complex aneurysms over a medium-term follow-up period. METHODS: Between January 2003 and June 2004, 28 individuals among 157 patients with cerebral aneurysms we evaluated were identified as harboring aneurysms with exceptionally broad necks. Out of these 28 patients, 16 were treated with a combination of stents and detachable coils, preserving the parent artery. Recorded data included patient demographics, the clinical presentation, aneurysm location and characteristics, procedural details, and clinical and angiographic outcome. RESULTS: Over an 18-month period, 16 patients with large cerebral aneurysms additionally characterized by neck sizes between 7 and 14 mm were treated, using combined coil embolization of the aneurysm with stent reconstruction of the aneurysm neck. Thirteen out of the 16 aneurysms were occluded at angiographic reevaluation between 11 and 24 months (mean angiographic follow-up, 17.5 mo). There were no treatment-related deaths or clinically evident neurological complications. Thirteen patients experienced excellent clinical outcomes, with good outcomes in two patients and a poor visual outcome in one patient (mean clinical follow-up, 29 mo). A single technical complication occurred, involving transient nonocclusive stent-associated thrombus, which was treated uneventfully with abciximab. CONCLUSION: Stent-supported coil embolization of large, complex-neck cerebral aneurysms seems to provide superior medium-term anatomic reconstruction of the parent artery compared with historic series of aneurysms treated exclusively with endosaccular coils. In the near future, increasingly sophisticated endoluminal devices offering higher coverage of the neck defect will likely enable more definitive endovascular treatment of complex cerebral aneurysms and further expand our ability to manipulate the vascular biology of the parent artery.

Blood Vessel Prosthesis↗

PubMed2005

Hemodynamic changes due to stent placement in bifurcating intracranial aneurysms.

OBJECT: The aim of this study was to measure changes in intraaneurysm flow dynamics and mechanical stresses resulting from the placement of Neuroform stents in bifurcating intracranial aneurysm models. METHODS: A digital particle image velocimetry (DPIV) system was used to measure the pulsatile velocity and shear stress fields within the aneurysm and at the aneurysm neck-parent artery interface. The DPIV system provides an instantaneous two-dimensional measurement of the temporal and spatial variations of the velocity vector field of the flow inside the aneurysm pouch and the parent vessel, providing information on both the temporal and spatial variations of the velocity field during the entire cardiac cycle. The corresponding shear stress field was then computed from the velocity field data. A flexible silicone model of bifurcating intracranial aneurysms was used. Two Neuroform stents with a 60- to 65-microm strut thickness and an 11% metal/artery ratio were placed in a Y-configuration, and measurements were obtained after placing the stents. CONCLUSIONS: Two three-dimensional vortices of different strengths persisted within the aneurysm during the entire cardiac cycle. The peak velocity and strength of these vortices were reduced after placing the two bifurcating stents. The effect of placing the Neuroform stent across the neck of a bifurcating intracranial aneurysm was shown to reduce the magnitude of the velocity of the jet entering the sac by as much as 11%. Nevertheless, the effect of the stents was particularly noticeable at the end of the cardiac cycle, when the residual vorticity and shear stresses inside the sac were decreased by more than 40%.

Blood Flow Velocity↗

PubMed2005

Flow changes caused by the sequential placement of stents across the neck of sidewall cerebral aneurysms.

OBJECT: The goal of this study was to quantify the reduction in velocity, vorticity, and shear stresses resulting from the sequential placement of stents across the neck of sidewall cerebral aneurysms. METHODS: A digital particle image velocimetry (DPIV) system was used to measure the pulsatile velocity field within a flexible silicone sidewall intracranial aneurysm model and at the aneurysm neck-parent artery interface in this model. The DPIV system is capable of providing an instantaneous, quantitative two-dimensional measurement of the velocity vector field of "blood" flow inside the aneurysm pouch and the parent vessel, and its changes at varying stages of the cardiac cycle. The corresponding vorticity and shear stress fields are then computed from the velocity field data. Three Neuroform stents (Boston Scientific/Target), each with a strut thickness between 60 and 65 microm, were subsequently placed across the neck of the aneurysm model and measurements were obtained after each stent had been placed. The authors measured a consistent decrease in the values of the maximal averaged velocity, vorticity, and shear stress after placing one, two, and three stents. Measurements of the circulation inside the sac demonstrated a systematic reduction in the strength of the vortex due to the stent placement. The decrease in the magnitude of the aforementioned quantities after the first stent was placed was remarkable. Placement of two or three stents led to a less significant reduction than placement of the first stent. CONCLUSIONS: The use of multiple flexible intravascular stents effectively reduces the strength of the vortex forming in an aneurysm sac and results in a decrease in the magnitude of stresses acting on the aneurysm wall.

Cerebrovascular Circulation↗

PubMed2005

Changes in the intraaneurysmal pressure due to HydroCoil embolization.

BACKGROUND AND PURPOSE: The purpose of this study was to measure the changes in the intraaneurysmal fluid pressure and parent vessel flow characteristics resulting from packing the aneurysmal sac with hydrogel-coated coils. METHODS: Platinum coils coated with an expansible hydrogel were used to embolize a silicone model of the basilar tip aneurysm. The intraaneurysmal fluid pressure was measured with a NeuroCare Camino Pressure Micro-Probe at various packing ratios. A programmable pulsatile pump was used to input a physiologically relevant pulsatile flow in the parent artery. RESULTS: The intraaneurysmal fluid pressure did not increase when packing the aneurysm with hydrogel-coated platinum coils, even with a coil density up to 93%. CONCLUSION: Packing the aneurysm with hydrogel-coated coils at a density up to 93% did not increase the intraaneurysmal fluid pressure.

Blood Pressure↗