Publications

The aim of this prospective, multicenter, single arm study was to assess the safety and feasibility of EXPRESS™ Coronary Stent implantation in native coronary arteries without balloon predilatation. Forty‐two patients with de novo or restenotic lesions were enrolled, of which 38 were eligible for analysis. The coronary lesions were predominantly complex, occurring in arteries with a mean reference diameter of 2.80 ± 0.49 mm. Technical and procedural success were achieved in 89.5% and 84% of the cases respectively. The mean minimal lumen diameter increased from 1.08 ± 0.26 mm to 2.55 ± 0.44 mm and diameter stenosis decreased from 61 ± 7% to 13 ± 8%. The primary endpoint of major adverse cardiac events at 30 days was 2.6% and was limited to only one event (target vessel revascularization, nontarget lesion). No other MACE were observed during the three‐month follow‐up period. Based on the findings of this study, direct stenting with the EXPRESS™ Stent appears feasible and is well tolerated. (J Interven Cardiol 2003;16:491–497)

Once plaques intrude into the lumen, the shear stress they are exposed to alters with hitherto unknown consequences for plaque composition. We investigated the relationship between shear stress and strain, a marker for plaque composition, in human coronary arteries. We imaged 31 plaques in coronary arteries with angiography and intravascular ultrasound. Computational fluid dynamics was used to obtain shear stress. Palpography was applied to measure strain. Each plaque was divided into four regions: upstream, throat, shoulder, and downstream. Average shear stress and strain were determined in each region. Shear stress in the upstream, shoulder, throat, and downstream region was 2.55+/-0.89, 2.07+/-0.98, 2.32+/-1.11, and 0.67+/-0.35 Pa, respectively. Shear stress in the downstream region was significantly lower. Strain in the downstream region was also significantly lower than the values in the other regions (0.23+/-0.08% vs. 0.48+/-0.15%, 0.43+/-0.17%, and 0.47+/-0.12%, for the upstream, shoulder, and throat regions, respectively). Pooling all regions, dividing shear stress per plaque into tertiles, and computing average strain showed a positive correlation; for low, medium, and high shear stress, strain was 0.23+/-0.10%, 0.40+/-0.15%, and 0.60+/-0.18%, respectively. Low strain colocalizes with low shear stress downstream of plaques. Higher strain can be found in all other plaque regions, with the highest strain found in regions exposed to the highest shear stresses. This indicates that high shear stress might destabilize plaques, which could lead to plaque rupture.

The aim of this study was to determine six months restenosis rate measured by off-line quantitative coronary angiography, and to assess the efficacy and safety of newly developed six cells Tsunami stent system for the treatment of symptomatic, de novo, native coronary artery lesions.Between January and August 2001, 100 patients with 120 lesions were included at four clinical sites in this prospective, non-randomized, single arm study. In 35% of the patients two or more stents were implanted, 15% of the lesions were stented with more than one stent and 46% of the lesions were in small vessels (<or= 2.75 mm). The Tsunami stent was available in 10, 15, 20 and 30 mm, length, and 3, 3.5 and 4 mm diameter. Angiographic success rate for stented lesions was 100% (residual diameter stenosis <or= 30%) and procedural success rate was 98%. Mean reference vessel diameter by QCA was 2.83 +/- 0.52, and post-procedural minimal lumen diameter was 2.59+/-0.4. Six months angiographic follow-up was available for 81% of the patients and revealed an in-stent restenosis rate of 13.8% for all lesions and 7.4% for single stented lesions. At 30 days 98% and at 6 months 88% of the patients remained free of major adverse cardiac events.Based on the clinical and angiographic results of the present study we can conclude that the Tsunami stent provides safe and effective percutaneous treatment of obstructive coronary artery disease.

During a 2-year period, 136 self-expanding Wall-stents were implanted in saphenous vein bypass grafts in 69 patients with end-stage coronary artery disease. All patients had severe symptoms and the majority were poor candidates for either repeat surgery or conventional bypass coronary angioplasty because of unfavorable native anatomy, impaired left ventricular function, or a high-risk bypass lesion anatomy for coronary angioplasty. All procedures were technically successful without major complications and a need for emergency bypass surgery. However, during the hospital stay acute thrombotic complications occurred in seven patients (10%) resulting in one death and acute myocardial infarction in five patients and necessitating emergency repeat PTCA in two patients and repeat CABG in four. Twenty-three patients had serious hemorrhagic complications directly related to the rigorous anticoagulation schedule. Two patients died of fatal cerebral bleeding. During follow-up, another five patients died accounting for a total mortality rate of 12%. At late angiographic follow-up (4.9 ± 3.4 months, n = 53), 25 patients (47%) had a restenosis (≥50% DS) within or immediately adjacent to the stent, necessitating reintervention in 19 patients (PTCA, n = 12; repeat CABG, n = 7). In the group without stent-related restenosis (n = 28), 15 patients had progression of disease in either the native or bypass vessels leading to recurrence of major anginal symptoms within 1 to 24 months. Ten of these patients required further intervention (stent, n = 6; PTCA, n = 3; repeat CABG, n = 1). Stenting in saphenous coronary bypass grafts can be performed safely with excellent immediate angiographic and clinical results. Early occlusion, late restenosis, and bleeding complications associated with the aggressive anticoagulant treatment remain significant limitations. Reintervention as a result of restenosis or progression of disease in other lesions is common. Stenting of diseased bypass grafts in symptomatic patients with end-stage coronary artery disease (who are at high risk for conventional angioplasty or surgical reintervention) may be useful as palliative therapy.

Intracoronary thermography is a potential vulnerable plaque detection technique of which the development is ongoing. This review discusses the past and present status of this technique from a more fundamental perspective, in which heat generation, heat transfer and heat detection are considered. Details of the presumed heat source, the macrophage clusters in vulnerable, atherosclerotic plaques, are discussed, including their increased energy consumption and heat production values. Heat transfer by ways of conduction, convection by blood flow and radiation are considered in a quantitative way. Ways to detect heat that are currently used are discussed and suggestions for improvement as well as for utilization of unexplored possibilities are given. This review enables interpretation of previously published results and likely also of results to be published in the future.

Wire arc additive manufacturing (WAAM), a method of directed energy deposition (DED) for metal 3D printing, is capable of producing intricate parts at a relatively high rate and low cost. Despite the great potential of WAAM for applications in construction, knowledge of the performance of WAAM structural elements is still lacking, and the geometric freedom is yet to be fully harnessed. This study is therefore aimed at investigating the local buckling behaviour of carbon steel WAAM elements and exploring the opportunity for improved structural efficiency through optimisation. An optimisation study was initially conducted to derive optimal stiffener layouts for square hollow sections (SHS) under compression. A total of six plain SHS with a broad range of width-to-thickness ratios, along with two SHS strengthened with optimised stiffeners, were manufactured via WAAM and tested. The six benchmark WAAM SHS profiles were examined to allow direct comparisons with conventionally-produced SHS. 3D laser-scanning was carried out to capture the geometric features of the WAAM specimens, and digital image correlation (DIC) was adopted for the full-field measurement of their structural responses during testing. The WAAM SHS stub columns were shown to have comparable load-carrying capacities to conventionally-produced SHS in the stocky range, but exhibited inferior local buckling behaviour in the slender range. Comparisons with the Eurocode 3 (EC3) resistance predictions showed that the existing Class 3 slenderness limit and effective width method specified in EC3 for plated structures may be overly optimistic for WAAM steel elements owing to their typically larger geometric imperfections. Finally, the SHS strengthened with optimised stiffeners were shown to exhibit significantly improved structural efficiency over both the WAAM and conventionally-manufactured plain SHS, bringing disproportionate increases in load-carrying and deformation capacity relative to the increases in mass.

An unstable lesion may rupture and cause an acute thrombotic reaction. These lesions contain a large lipid pool covered by a thin fibrous cap. The stress in the cap increased with decreasing thickness and increasing macrophage infiltration. Intravascular ultrasound (IVUS) elastography might be an ideal technique to assess the presence of lipid pools and identify high stress regions. Elastography assesses the local mechanical properties of tissue using its deformation caused by the intraluminal pressure. The technique was validated in vitro using diseased human coronary and femoral arteries. These experiments demonstrated that the strain in the three plaque types is different (P &lt; 0.001) . Especially between fibrous and fatty tissue, a highly significant difference (P = 0.0012) was found. Additionally, the predictive value for identifying the vulnerable plaque was investigated. A high strain region at the lumen vessel wall boundary has 88% sensitivity and 89% specificity for identifying these plaques. In vivo, the technique is validated in an atherosclerotic Yucatan mini‐pig animal model. This study also revealed higher strain values in fatty than fibrous plaques (P &lt; 0.001) . The presence of a high strain region at the lumen plaque interface has a high predictive value for identifying macrophages. Patient studies revealed high strain values (1–2%) in soft plaques. Calcified material shows low strain values (0–0.2%). With the development of three‐dimensional elastography, identification of weak spots over the full length of a coronary artery becomes possible. In conclusion, intravascular elastography is a unique tool to assess lesion composition and vulnerability. The development of three‐dimensional elastography provides a technique that may develop into a clinical available tool for identifying the rupture‐prone plaque. (J Interven Cardiol 2003;16:253–259)