Local Vessel Wall Research Articles

Local calcification as a determinant of the outcome of excimer laser coronary angioplasty

Calcification influences the outcome of various angioplasty techniques in the treatment of coronary artery disease. During angioscopic in vitro studies, we observed that dissections and perforations not caused by vessel bending frequently occurred at the boundary areas of plaque and adjacent vessel wall. This study investigated whether this is related to the distribution of calcific deposits. Postmortem excimer laser coronary angioplasty (308-nm XeCl) was performed in 51 stenotic coronary arteries. Twenty-three segments were further examined; these consisted of 11 perforations, six dissections, three segments with no ablative effect after the application of 20,000 laser impulses, and three successfully passed stenoses without complications. X-ray diffraction analysis and scanning electron microscopy were performed to detect calcium deposits and their spatial relationship to perforations and dissections. X-ray diffractions analysis detected calcifications in 21 of 23 specimens. Postmortem angiography revealed calcifications only on 11 of 23 segments. Three of 11 perforations were located at the plaque border, as were three of six dissections. In all six complications at the plaque border, x-ray diffraction analysis revealed that the plaque border was identical with a border of calcium deposits. Eight of 11 perforations and three of six dissections could be explained by axis divergence between the laser catheter and the vessel orientation. Contributing factors for perforations and dissections during excimer laser coronary angioplasty are axis divergence and the distribution of plaque calcification. More sensitive methods are needed to detect local vessel wall calcium in vivo.

Numerical analysis of intramural stresses and blood flow in arterial bifurcation models

The study deals with the calculation of the stresses in elastic arterial walls and with the analysis of the interaction of local blood flow and vessel wall motion. While the stress study is primarily carried out in a basic end-to-side bypass anastomosis model incorporating different material properties of the graft and the artery, the flow study is performed in a compliant carotid artery bifurcation model. The displacement and stress analysis uses geometrically non-linear shell theory. The flow analysis applies the time-dependent, three-dimensional, incompressible, Navier-Stokes equations for non-Newtonian inelastic fluids In an iteratively coupled approach the equations of the fluid motion and the transient shell equations are numerically solved using the finite element method.

Transbrachial approach for aortic and selective supraaortic vessel catheterization using a safe and easy technique to reform the Simmons II catheter tip

A total of 286 patients (158 outpatients) were examined by intra-arterial DSA in the evaluation of cerebrovascular disease using a transbrachial approach. In all cases a 5F introducer sheath, a 5F pigtail catheter for aortic arch injection and a 5F Simmons II catheter for selective catheterization were used. Excellent demonstration of aortic arch and supraaortic arteries (including intracranial circulation) was obtained (92.2–100%). The complication rate was favorable, with only one major complication (thrombosis of an axillary artery). The use of an introducer sheath minimizes local complications and vessel wall damage during catheter exchange. Aortic arch injection must always be performed prior to selective catheterization. The results of selective catheterization prove the suitability of the Simmons II catheter, whose typical shape was easily and safely obtained using the configuration of the pigtail catheter and a 180 cm long guide wire for catheter exchange. Using the technique as described, the transbrachial approach is a safe and easy way for optimal vascular evaluation in cerebrovascular disease, especially useful in outpatients.

Effects of limiters on reversed-field pinch confinement

This paper documents the effects on confinement of introducing discrete limiters into the edge plasma of the ZT-40M reversed-field pinch (RFP) [Fusion Technol. 8, 1571 (1985)]. RFP confinement is not significantly degraded by appropriately designed single limiters inserted to a sufficient depth for effective local vacuum vessel wall protection. Inserting limiters too deeply into the plasma results in excess limiter heating, and a consequent increase in the impurity content of the plasma. Under these conditions the plasma loop voltage increases. The heating of the limiters is observed to be asymmetric, with the majority of the heat flux in ZT-40M being attributable to suprathermal electrons [Tsupra∼2–3×Te(0)] reaching the edge moving almost unidirectionally along magnetic-field lines.

Arterial Responses to Compromised Blood Flow*

Chronic decreases in arterial blood flow rates elicit arterial constriction followed by remodeling of the artery wall that entrenches a reduced internal diameter. This adaptive response may provide an important compensatory adaptation to physiological reductions in blood flow, but it may also exacerbate pathologic disorders that compromise tissue perfusion. A capacity to manipulate this response requires a knowledge of the mechanisms that control it. Our studies have shown that the response is endothelium-dependent, and that it is probably initiated by release of a vasoconstrictor. This finding suggests that endothelium-derived agonist(s) are involved. We assessed the potential role of prostanoids, endothelin, and a local vessel wall renin-angiotensin system. All of these assessments yielded negative results. It appears, therefore, that a novel vasoactive substance initiates the adaptive response of arteries to reduced blood flow.