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Abstract  The piezoelectric, microstructural and electrical characteristics of thick PZT films on relatively inert alumina substrates and on two LTCC tapes, i.e., Du Pont 951 and Electro Science Labs 41020 were studied. A thick-film paste was prepared from the pre-reacted PZT powder (PbZr0.53Ti0.47O3) and printed and fired on LTCC tapes and on alumina substrates, respectively. Dielectric permittivities, dielectric losses, remnant polarizations and coercive fields were measured. The dielectric constants (100–150) of thick films fired on LTCC substrates are low. The piezoelectric coefficients d 33 were measured by different methods, i.e. Berlincourt piezometer, interferometry and piezoresponse force microscope (PFM). The d 33 values on LTCC substrates are low (30–70 pm/V) as compared with values obtained on alumina substrates (around 120 pm/V). Lower dielectric constants and piezoelectric coefficients d 33 of films on LTCC substrates are attributed to the formation of phases with a low permittivity due to the diffusion of silica from LTCC substrates into PZT films. The d 33 constants of samples with different thicknesses of PZT layers (from 20 to 160 μm) at first increase with the increasing thickness of PZT layers and then decrease for thicker films. As the cracks in the structure were not observed the reason for the decreasing d 33 values for thicker films is still unclear. [ABSTRACT FROM AUTHOR]

Mesenteric inflammatory veno-occlusive disease (MIVOD) is a rare but increasingly recognized cause of intestinal ischemia. It can be defined as phlebitis or venulitis affecting either the bowel or mesentery, without any evidence of coexisting arterial inflammatory involvement or an obvious predisposing cause. We report the clinicopathological characteristics of five patients who, after presenting with an acute abdomen, underwent exploratory laparotomy and resection of ischemic bowel. The distinctive histopathological characteristics of MIVOD were identified in all five patients. We review the literature on this under-reported condition. [ABSTRACT FROM AUTHOR]

Introduction: Pulmonary vein (PV) isolation for the curative treatment of atrial fibrillation using conventional radiofrequency ablation (RF) catheters with the point by point technique is time consuming and carries a remaining risk for thrombembolic complications.Aims of the Study: Aim of the present in vivo study was to evaluate feasibility and safety of a novel multipolar irrigated ablation catheter designed to create contiguous lesions encircling the PV ostium in a single ablation position.Methods: The entire ablation section (tripolar, length of each electrode 22 mm, interelectrode distance 2 mm, helix radius: 9 and 10 mm) of the 7F RF catheter (Encirclr, Medtronic, MN, USA) was covered by a porous membrane (pore size 30 micron) providing continuous irrigation. The helical formed catheter was used in two different experimental settings. Initially, a thigh muscle preparation has been performed in 7 anesthetized sheep in order to evaluate the development of lesions at different power level (40–80 W) and RF duration (30–90 sec). The ablation catheter was placed at the surface of the thigh muscle in a perpendicular position (0.1 N contact pressure) and perfused with heparinized blood (250 ml/min, 37C°). Irrigation was provided with a flow rate of 10 ml/min. The resulted lesion morphology was evaluated with regard to coagulum or crater formation and lesion depth and diameter. Subsequently in 9 anesthetized sheep intracardiac ablation has been achieved with 50 W and an irrigation flow of 10 ml/min. Transseptal puncture and RF ablations were guided using fluoroscopy and intracardiac echocardiography (ICE, Acuson, USA). Endpoint of the intracardiac RF applications was the reduction of local electrogram amplitude >50%. RF applications were achieved at both atrial appendages and in the orifices of the coronary sinus (CS), the vena cava inferior (VCI) and PV. Following RF ablation all animals were sacrificed and following in vivo staining (2% TTC) macroscopically and histologically investigations of the lesions were performed.Results: At the thigh muscle preparation 57 RF applications have been performed. The lesion depth was homogeneous without gaps between the ablation electrodes. There was a significant increase comparing 30 with 90 sec of RF duration for 40, 50 and 60 W applications respectively: 40 W: 1.1 ± 0.4 vs. 3.6 ± 0.5; 50 W: 1.2 ± 0.3 vs. 4.6 ± 0.4 mm and 60 W: 2.6 ± 0.6 vs. 4.8 ± 0.5 mm. All applications with 80 W (n = 3) had to be terminated due to immediate increase of impedance >150 ω . Late impedance rises (>60 sec) without occurrence of coagulum formation have been observed in 1 out of 4 RF applications with 60 W.A total of 85 RF applications could be achieved intracardiacally in the right atrium (right atrial appendage n = 18, ostium of the coronary sinus n = 12, ostium of the inferior caval vein: n = 12) and in the left atrium (left atrial appendage: n = 15, ostium of the PV: n = 28). ICE guided positioning of the catheter and showed during all applications no coagulum formation at the electrode or impedance rise (>150 Ω). Reduction of local electrograms (>50%) were observed following 48 out 85 (56%) RF applications. The lesions showed a homogeneous depth of 4 ± 2 mm and a width 5 ± 2 mm at the surface. No charring or crater formation could be observed in any of the lesions.Conclusions: In the present in vivo studies it could be demonstrated that long irrigated ablation electrodes induce continuous lesions without the risk of thrombus formation at the electrode. Increase of RF duration from 30 to 90 seconds with power setting of 40–60 W, respectively, created deeper lesions without the risk of thrombus formation. Thus, the helical formed irrigated ablation catheter appears to be appropriate for simplified PV isolation. [ABSTRACT FROM AUTHOR]