Extensive pectoral muscle necrosis after defibrillation: nonthermal skeletal muscle damage caused by electroporation

A 37-year-old Italian male developed a myocardial infarct with subsequent ventricular fibrillation. He was defibrillated seven times with up to 360 Joules. Thirteen days later the patient died of recurrent myocardial infarct due to thrombotic occlusion of the left circumflex coronary artery. At autopsy, necrosis of the right pectoralis muscle was observed. Electroporation is the pathogenetic mechanism of skeletal muscle damage due to multiple defibrillations with high energy levels. Received: 8 January 1998 Accepted: 15 April 1998     

Frühdefibrillation in Deutschland

Zusammenfassung Die erfolgreiche Anwendung der automatisierten externen Defibrillation in den USA war der Anlass für eine 1989 veröffentliche Pilotstudie in Berlin. Diese führte zur systematischen Einführung der Frühdefibrillation in Berlin und zu vergleichbaren Konzepten in verschiedenen deutschen Städten. Verschiedene erfolgreiche Studien und die technische Weiterentwicklung von leichteren und preiswerteren Geräten führte zur Ausweitung der Konzepte im Sinne einer Defibrillation durch First Responder oder der Public Access Defibrillation. Doch weiterhin bestehen viele ungelöste Probleme: die Frage nach der effektivsten Schockform und der notwendigen Energiemenge ist ebenso ungelöst wie die Frage der Ausbildungsintensität für die Frühdefibrillation außerhalb des Rettungsdienstes. Diese Fragen sollen in z. T. schon laufenden Studien weiter untersucht werden.     

动物实验模型中多极导管心室除颤系统电除颤对心脏功能的影响

评价新型的双极和三极导管自动心室除颤系统电除颤对左心室收缩和舒张功能的影响。动物麻醉后,在X光机指导下,分别在10只犬心脏内装置双极导管自动除颤系统（组Ⅰ）;在10只猪心脏内装置三极导管自动除颤系统（组Ⅱ）;并行电除颤试验。使用食管超声心动图在电除颤前后记录二维、M型和多谱勒超声图像。组I动物接受4次电除颤,电量为64J;组Ⅱ接受平均8次电除颤,电量为210J。结果显示：左室收缩面积分数、左室等容舒张时间和二尖瓣血流E波与A波速度比值以及时间-流速积分比值等反映左室舒缩功能的指标在两组动物除颤后均无显著改变。研究表明：两种经静脉导管自动心室除颤系统中反复低能量心内膜电除颤对左室舒缩功能无明显损伤作用;研究结果为经静脉多极导管自动心室除颤系统在临床的应用和电生理研究提供了可靠的实验数据。     

Impedance-gradient electrode reduces skin irritation induced by transthoracic defibrillation

A new type of disposable external defibrillation electrode has been developed to reduce the skin irritation commonly associated with defibrillation and synchronised cardioversion. This design employs an impedance gradient to reduce the proportion of current delivered to the electrode periphery. The temperature distribution under the new electrode was compared with that of four other types of commercially available electrodes after repeated high-energy biphasic defibrillation discharges to domestic swine. Skin temperature distributions were acquired using non-invasive thermography. Measurements of the maximum temperature rise at each electrode site, taken 3.6s after the fifth defibrillation discharge, demonstrated that the new impedance-gradient electrode produced 50–60% less skin heating than two of the three uniform-impedance electrode designs. Histological examination of erythematous sites excised 24h after defibrillation quantified the associated skin damage using a scoring protocol developed for this study. In contrast to previous studies, histological examinations demonstrated second-degree skin burns following defibrillation. The new electrode design, however, induced 44–46% less skin damage than two of the traditional uniform-impedance electrodes.     

Active response of a one-dimensional cardiac model with gap junctions to extracellular stimulation

To study the response of cardiac tissue to electrical stimulation, a one-dimensional model of cardiac tissue has been developed using linear core-conductor theory and the DiFrancesco-Noble model of Purkinje tissue. The cable lies in a restricted extracellular medium and includes a representation of the junctional resistances known to interconnect cardiac cells. Two electrode geometries are considered: (a) a semi-infinite cable with a monopolar electrode at the end of the cable and (b) a terminated cable with one electrode at each end of the cable. In a series of simulations, stimuli of varying magnitude and polarity are applied at three different times during the plateau of the action potential. The results at the stimulus site show that the action potential duration may either decrease or increase in response to the stimulus, depending on the polarity and application time of the stimulus. The spatial behaviour of the cable in response to the stimulus indicates that sites greater than 200 cells from the stimulating electrode are not affected by the stimulus.