Publications by authors named "Alan Rappe"

2 Publications

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Hemodynamic versus hydrodynamic effects of Guglielmi detachable coils on intra-aneurysmal pressure and flow at varying pulse rate and systemic pressure.

AJNR Am J Neuroradiol 2004 Jun-Jul;25(6):1049-57

Department of Radiology, University of Wisconsin Health Sciences Center, Madison, USA.

Background And Purpose: Alterations in intra-aneurysmal pressure and flow have been observed after treatment with Guglielmi detachable coils (GDCs). We wished to determine whether these changes could be assigned to a hydrodynamic effect of the coils themselves or a compound effect of coils plus thrombus formation.

Methods: Intra-aneurysmal pressure and flow were measured with a 0.014-inch guidewire- mounted transducer in a canine aneurysm in vivo and in vitro before and after treatment with GDCs. Flow was evaluated by using the thermodilution technique. Pressure and flow were also recorded in a bifurcational silicone aneurysm mounted onto a flow phantom during variations in systemic pressure and pulse rate before and following the insertion of GDCs.

Results: The insertion of GDCs induced a reduction in flow that was qualitatively similar when the aneurysm was perfused either by blood (in vivo) or with normal saline (in vitro). Quantitatively, however, flow was reduced less distinctly during perfusion with saline. In the silicone aneurysm, pressure was inversely related to pulse rate and increased with augmenting systemic pressure, whereas flow remained constant regardless of variations in pressure and pulse rate. After GDC placement, reduced flow was dependent on pulse rate but independent of systemic pressure.

Conclusion: GDCs significantly reduced flow even in the absence of thrombus, indicating that they have a purely hydrodynamic effect. In the silicone model, the decrease in intra-aneurysmal flow after coiling relied upon the pulse rate in a manner suggesting the presence of resonance phenomena.
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October 2004

Effect of Guglielmi detachable coils on intraaneurysmal flow: experimental study in canines.

AJNR Am J Neuroradiol 2002 Feb;23(2):288-94

Department of Neurosurgery, Rikshospitalet, National Hospital, Oslo, Norway.

Background And Purpose: Guglielmi detachable coils (GDCs) are effective in preventing rebleeding of ruptured aneurysms. To better understand the mechanism underlying this protective effect, we evaluated blood flow in aneurysms and their parent arteries before and after GDC coil placement.

Methods: An 0.14-inch guidewire containing a combined pressure and thermistor sensor was inserted through a microcatheter into both the parent artery and the dome of surgically created canine aneurysms. Before and after GDC coil placement, intravascular pressures and thermodilution responses where recorded in the parent artery and aneurysmal dome during injections of room-temperature isotonic sodium chloride solution over 4 seconds (5 mL/s) and 2 seconds (20 mL/s) in the parent artery.

Results: Before GDC coil placement, similar U-shaped thermodilution curves were present in the parent artery and in the dome of the aneurysm. GDC coil placement reduced intraaneurysmal flow by 61-99.6% (P <.05), prolonged aneurysmal filling and washout (dilution interval increased from 5.16 seconds before coil placement to 26.79 seconds after coil placement, P < 0.05), and caused a dissociation of pressure and flow (shift epsilon was 0.45 seconds before coil placement versus 0.56 seconds after coil placement, P <.05). Flow in the parent artery was not significantly affected by GDC coil placement in the aneurysm.

Conclusion: In this model, intraaneurysmal blood flow can be evaluated with thermodilution. GDC coil placement significantly reduces blood flow in aneurysms.
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February 2002