Stanley E . Rittgers

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The observation of intimal hyperplasia at bypass graft anastomoses has suggested a potential interaction between local hemodynamics and vascular wall response. Wall shear has been particularly implicated because of its known effects upon the endothelium of normal vessels and, thus, was examined as to its possible role in the development of intimal(More)
Doppler ultrasound was used to detect experimental and clinical renal artery stenosis (RAS) and increased renovascular resistance (RVR). Parameters assessing RAS included elevated systolic frequency and spectral broadening, while diastolic/systolic frequency ratios predicted elevated RVR. In canine models these parameters detected graded RAS before(More)
Flow in distal end-to-side anastomoses of iliofemoral artery bypass grafts was simulated using a steady flow, three-dimensional numerical model. With the proximal artery occluded, anastomotic angles were varied over 20, 30, 40, 45, 50, 60 and 70 deg while the inlet Reynolds numbers were 100 and 205. Fully developed flow in the graft became somewhat skewed(More)
Pioneers in the field of small diameter graft development sought to promote graft endothelialization and, thereby, increase patency by transplanting a varying degree of autologous endothelial cells onto vascular grafts prior to implantation. This process has become known as endothelial cell seeding. The underlying hypothesis is quite simple; that is, by(More)
Doppler ultrasonography sound-spectrum analysis (SSA) was used to evaluate blood flow in the transplanted kidney and its renal artery. Seven patients with posttransplant hypertension and a bruit over the transplanted kidney were screened for renal artery stenosis (RAS). In five patients, RAS was diagnosed by SSA, and in two it was not. These findings were(More)
OBJECTIVE The purpose of this study was to simultaneously monitor the transcriptional levels of 12 endothelial growth factor genes in response to alterations in wall shear stress (WSS) under conditions relevant to the development of intimal hyperplasia, a major cause of arterial bypass graft failure. METHODS Human umbilical vein endothelial cells were(More)
A steady flow, in vitro model of distal arterial bypass graft junctions was used to examine the effects of junction angle and flow rate on the local velocity field. Three test sections were fabricated from Plexiglas tubing having anastomotic junction angles of either 30, 45, or 60 deg. Flow visualization revealed velocity profiles skewed toward the outer(More)
Asymmetric 75% and 95% area reduction, transparent Sylgard stenotic models were operated under internal carotid artery (ICA) (Womersley parameter, α=5.36, Remean=213 and 180, respectively, and Repeak=734 and 410, respectively) and left anterior descending coronary artery (LAD) flow wave forms (α=2.65,Remean=59 and 57, respectively, and Repeak=137 and 94,(More)
A pulsatile flow in vitro model of the distal end-to-side anastomosis of an arterial bypass graft was used to examine the effects that different flow ratios between the proximal outlet segment (POS) and the distal outlet segment (DOS) have on the flow patterns and the distributions of hemodynamic factors in the anastomosis. Amberlite particles were tracked(More)
Mass screening of hypertensive patients by a noninvasive method could uncover the 10% of those cases where renal artery stenosis is the primary etiology. Treatment by transluminal angioplasty or surgery could replace a long-term medical regimen. To investigate an ultrasonic technique, normal velocity waveforms were obtained from the abdominal aorta, celiac(More)