Cardiac Pacing and Defibrillation in Children and Young Adults

The population of children and young adults requiring a cardiac pacing device has been consistently increasing. The current generation of devices are small with a longer battery life, programming capabilities that can cater to the demands of the young patients and ability to treat brady and tachyarrhythmias as well as heart failure. This has increased the scope and clinical indications of using these devices. As patients with congenital heart disease (CHD) comprise majority of these patients requiring devices, the knowledge of indications, pacing leads and devices, anatomical variations and the technical skills required are different than that required in the adult population. In this review we attempt to discuss these specific points in detail to improve the understanding of cardiac pacing in children and young adults.     

肌浆网钙ATP酶过表达对心房颤动兔心房及L型钙通道alc蛋白表达的影响

目的探讨心肌肌浆网钙ATP酶2a（SERCA2a）基因过表达,对兔急性心房颤动（AF）的心房肌L型电压依赖钙通道蛋白alc亚单位（LVDCCalc）表达的影响。方法48只成年新西兰兔,随机分成为房颤组（AF组,n=12）、9一型腺相关病毒＋增强型绿色荧光蛋白组＋房颤组（rAAV9＋EGFP＋AF组,n=12）、9一型腺相关病毒＋肌浆网钙ATP酶2a＋增强型绿色荧光蛋白组＋房颤组（rAAV9＋SERCA2a＋EGFP＋AF组,n=12）,并设假手术组作为对照（Control组,,l=12）。rAAV9＋EGFP＋AF组和rAAV9＋SERCA2a4-EGFP4-AF组起搏前30d开胸心包腔内注射包含报告基因的rAAV9一EGFP和包含靶基因的rAAV9-SERCA2a—EGFP各500肛L（1×10”v．g／ptL）。转染30d后,AF组、rAAV9＋EGFP＋AF组和rAAV9＋SERCA2a＋EGFP＋AF组,以600BPM刺激频率,持续起搏兔右心房24h制作AF模型。处死各组动物,倒置荧光显微镜下观察右心房肌组织EGFP表达情况,行HE染色对右心房组织形态检查,应用免疫组化技述检测SERCA2a蛋白及LVDCCalc蛋白在心房肌中的表达情况。结果rAAV9＋EGFP＋SERCA2a4-AF组SERCA2a蛋白及LVDCCalc蛋白表达量显著高于AF组和rAAV9＋EGFP＋AF组（P〈0．05）,但与对照组比较差异无显著性。结论心房肌转SERCA2a基因,显著减少了急性房颤心房肌的LVDCCalc蛋白表达的降低,有逆转急性AF电重构的作用。     

Electrical stimulation of cardiomyocytes activates mitochondrial matrix metalloproteinase causing electrical remodeling

Cardiac arrhythmias, instigated by mechanical and electrical remodeling, are associated with activation of extracellular matrix metalloproteinases (MMPs). However, the connection between intracellular MMPs activation and arrhythmogenesis is not well established. Previously, we determined localization of MMP in the mitochondria using confocal microscopy. We tested the hypothesis that electrical pacing induces the activation of mitochondrial MMP (mtMMP) and is associated with myocyte mechanical dysfunction. Myocytes were isolated and field stimulated at 1 and 4 Hz. Myocyte mechanics and calcium transient was studied using Ion-Optix system. Mitochondrial MMP-9 activation was evaluated using zymography. There was a 25% increase in 1 Hz and 40% increase in 4 Hz stimulation. We observed an increase in mtMMP activation with increase in electrical pacing compared to 0 Hz with a significant increase (p < 0.05, n = 3). Field stimulation at 4 Hz decreased cell re-lengthening. The levels of calcium transient were reduced with increase in contraction frequency. We conclude that electrical stimulation activates mtMMP-9 that is associated with myocyte mechanical dysfunction.     

复方苦参注射液联合TACE对中晚期肝癌患者预后、生存质量和血清AFP、AFP-L3水平的影响

摘要 目的：观察肝动脉化疗栓塞术（TACE）联合复方苦参注射液对中晚期肝癌患者预后、生存质量和血清甲胎蛋白（AFP）、甲胎蛋白异质体（AFP-L3）水平的影响。方法：选择我院于2016年3月~2019年10月期间收治的98例中晚期肝癌患者,经随机数字表法分为对照组（49例,TACE治疗）和研究组（49例,复方苦参注射液联合TACE治疗）。对比两组疗效、生存率、生存质量改善率、血清AFP、AFP-L3水平及不良反应发生率。结果：与对照组比较,研究组的临床总有效率明显升高（P<0.05）。研究组的1年生存率高于对照组（P<0.05）。与对照组比较,研究组的生存质量改善率明显升高（P<0.05）。两组治疗后血清AFP、AFP-L3水平较治疗前下降,且研究组低于对照组（P<0.05）。两组不良反应总发生率组间对比无统计学差异（P>0.05）。结论：TACE基础上联合复方苦参注射液治疗中晚期肝癌患者,可改善其短期预后及生存质量,降低其血清AFP、AFP-L3水平。     

肝动脉栓塞化疗术对原发性肝癌伴 有不同类型肝炎后肝硬化患者预后的影响

目的:探讨肝动脉栓塞化疗(TACE)对原发性肝癌伴有不同肝炎后肝硬化类型患者术后肝功能、凝血功能及其对远期预后的影响。方法:2007年8月至2009年8月,131例曾行TACE的伴有不同肝炎后肝硬化原发性肝癌患者,以肝炎后肝硬化类别(乙肝、丙肝)分类,乙肝后肝硬化组为组1,丙肝后肝硬化组为组2,随访观察术后一年肝功能、凝血功能、血小板等的变化以及预后。两组研究因素采用SPSS17.0进行卡方检验,随访预后采用Kaplan-Meier方法计算生存率,Log-rank法检验生存差异。以P<0.05为差异有统计学意义。结果:随访统计结果显示术后半年和一年AST、ALT、ALP、GGT、PT、PLT在两组间均无统计学差异,(P>0.05);组一半年、一年远处转移率同组二差异间无统计学意义;组一半年、一年生存率分别为70.1%,48.1%;组二半年、一年生存率分别为68.5%,58.9%,两组间同期生存率差异无统计学意义。(X2=0.039,P=0.884;X2=0.183,P=0.669)。结论:TACE治疗PHC安全可靠,对于伴有乙肝或丙肝后肝硬化患者术后肝功能、凝血功能、疗效及预后效果相当。     

The downside of right ventricular apical pacing

The right ventricular (RV) apex has been the standard pacing site since the development of implantable pacemaker technology. Although RV pacing was initially only utilized for the treatment of severe bradyarrhythmias usually due to complete heart block, today the indications for and implantation of RV pacing devices is dramatically larger. Recently, the adverse effects of chronic RV apical pacing have been described including an increased risk of heart failure and death. This review details the detrimental effects of RV apical pacing and their shared hemodynamic pathophysiology. In particular, the role of RV apical pacing induced ventricular dyssynchrony is highlighted with a specific focus on differential outcome based upon QRS morphology at implant.     

Speed, pacing strategy and aerodynamic drafting in Thoroughbred horse racing

Choice of pacing strategy and the benefit of aerodynamic drafting are thought to be key determinants of racing performance. These effects have largely been analysed without reference to final outcome, in small datasets with low temporal resolution, and a focus on human swimming, cycling and running. Here, we determined the position and speed of 44,803 racehorses, once per second, in 3,357 races ranging in length from 1006 to 4225 m (50.9-292.9 seconds duration) using a validated radio tracking system. We find that aerodynamic drafting has a marked effect on horse performance, and hence racing outcome. Furthermore, we demonstrate that race length-dependent pacing strategies are correlated with the fastest racing times, with some horses reaching a maximum speed in excess of 19 m s(-1). The higher speeds seen with certain pacing strategies may arise due to the nature of pack racing itself, or may be a reflection of individual capabilities, that is, corresponding to horses that perform well in roles suited to their 'front-running' or 'chaser' personality traits.     

High resolution three-dimensional strain mapping of bioprosthetic heart valves using digital image correlation

Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment option for patients deemed at high and intermediate risk for surgical aortic valve replacement. Similar to surgical aortic valves (SAVs), transcatheter aortic valves (TAVs) undergo calcification and mechanical wear over time. However, to date, there have been limited publications on the long-term durability of TAV devices. To assess longevity and mechanical strength of TAVs in comparison to surgical bioprosthetic valves, three-dimensional deformation analysis and strain measurement of the leaflets become an inevitable part of the evaluation. The goal of this study was to measure and compare leaflet displacement and strain of two commonly used TAVs in a side-by-side comparison with a commonly used SAV using a high-resolution digital image correlation (DIC) system. 26-mm Edwards SAPIEN 3, 26-mm Medtronic CoreValve, and 25-mm Carpentier-Edwards PERIMOUNT Magna surgical bioprosthesis were examined in a custom-made valve testing apparatus. A time-varying, spatially uniform pressure was applied to the leaflets at different loading rates. GOM ARAMIS® software was used to map leaflet displacement and strain fields during loading and unloading. High displacement regions were found to be at the leaflet belly region of the three bioprosthetic valves. In addition, the frame of the surgical bioprosthesis was found to be remarkably flexible, in contrary to CoreValve and SAPIEN 3 in which the stent was nearly rigid under a similar loading condition. The experimental DIC measurements can be used to characterize the anisotropic materiel behavior of the bioprosthetic heart valve leaflets and validate heart valve computational simulations.     

Environmental influences on stereotypy and the activity budget of Indian leopards (Panthera pardus) in four zoos in Southern India

To eliminate abnormal behaviors in leopards (Panthera pardus), such as stereotypic pacing, by utilizing environmental enrichment techniques, a proper understanding of their behavior in captive environments is required. Hence there is a need for animal welfare studies in Indian zoos. The activity budgets of 16 leopards were recorded across four southern Indian zoos: Thiruvananthapuram Zoo, Arignar Anna Zoological Park, Shri Chamarajendra Zoological Gardens, and the Guindy Children's Park. Of the 16 study animals, 14 were studied on‐exhibit on zoo holidays as well as on days with visitors present, and all 16 individuals were studied off‐exhibit on other days with visitors present. The 11 behaviors recorded were categorized into active, resting, and stereotypic behaviors. Leopards exhibited higher levels of activity in the on‐exhibit enclosures on days with no visitors. Feeding time influenced the behavioral repertoire of all 14 leopards studied on‐exhibit. Lower proportions of resting were exhibited during the hours before feeding. The proportion of active behaviors differed significantly across zoos. Stereotypic pacing levels were not influenced by the presence of visitors or by feeding time, but was significantly influenced by enclosure features. Higher levels of stereotypic pacing were exhibited in off‐exhibit than on‐exhibit enclosures. Our study shows that the behavior of captive leopards is influenced by enclosure type, feeding regime, and the presence of visitors. Zoo Biol 21:585–595, 2002. © 2002 Wiley‐Liss, Inc.     

Supra-annular Valve-in-Valve implantation reduces blood stasis on the transcatheter aortic valve leaflets

Leaflet thrombosis following transcatheter aortic valve replacement (TAVR) and Valve-in-Valve (ViV) procedures has been increasingly recognized. This study aimed to investigate the effect of positioning of the transcatheter aortic valve (TAV) in ViV setting on the flow dynamics aspect of post-ViV thrombosis by quantifying the blood stasis in the intra-annular and supra-annular settings. To that end, two idealized computational models, representing ViV intra-annular and supra-annular positioning of a TAV were developed in a patient-specific geometry. Three-dimensional flow fields were then obtained via fluid-solid interaction modeling to study the difference in blood residence time (BRT) on the TAV leaflets in the two settings. At the end of diastole, a strip of high BRT ($⩾1.2s$) region was observed on the TAV leaflets in the ViV intra-annular positioning at the fixed boundary where the leaflets are attached to the frame. Such a high BRT region was absent on the TAV leaflets in the supra-annular positioning. The maximum value of BRT on the surface of non-, right, and left coronary leaflets of the TAV in the supra-annular positioning were 53%, 11%, and 27% smaller compared to the intra-annular positioning, respectively. It was concluded that the geometric confinement of TAV by the leaflets of the failed bioprosthetic valve in ViV intra-annular positioning increases the BRT on the leaflets and may act as a permissive factor in valvular thrombosis. The absence of such a geometric confinement in the ViV supra-annular positioning leads to smaller BRT and subsequently less likelihood of leaflet thrombosis.