In addition to medical treatment for ventricular tachyarrhythmias which has not proven to be sufficient, nonmedical modes of treatment are available such as electrophysiologically-guided surgical measures and catheter ablation, both of which are restricted to only a relatively small patient population and require further technical refinement. In 1980, Mirowski introduced the automatic implantable defibrillator and, to date, world-wide, this device has been implanted in 8000 patients. CHARACTERISTICS AND IMPLANTATION OF THE AUTOMATIC IMPLANTABLE CARDIOVERTER/DEFIBRILLATOR (AICD): The AICD continuously monitors the electrical activity of the heart, recognizes the onset of threatening ventricular tachycardias and terminates these according to the respectively programmed mode by delivering direct current shocks or stimuli. The currently used defibrillators consist of an impulse generator with lithium batteries and an electrode system. The batteries can charge a capacitor with about 700 volts in five to eight seconds which produces a current with an energy up to 30 Joules on discharge. The current is delivered either by two plate electrodes on the right and left ventricles or a plate electrode on the left ventricle and a spiral electrode inserted in the superior vena cava. The electrodes also serve the purpose of tachycardia detection by means of an electrical signal, the probability density function (PDF), that is, a significant decrease in the potentials to isoelectric. With this, it is only possible to terminate ventricular fibrillation. Additional electrical detection criteria are obtained and analyzed by two adjacently positioned epicardial screw electrodes or a bipolar endocardial electrode, enable identification of ventricular tachycardia as well. If the tachycardia detection criteria are fulfilled, the capacitor is discharged according to its programmed shock energy. In 1988, programmable defibrillators were introduced. Current defibrillator treatment also incorporates the possibility for antitachycardia stimulation. Attempts to use, instead of the monophase, square-wave impulse, a biphasic defibrillation impulse, to achieve a sequential impulse and to make use of the bidirectional impulse extension have rendered improved reliability for tachycardia termination and energy savings. After median sternotomy, the plate electrodes are usually sutured to the epicardium and the spiral electrode for the bipolar ECG is positioned at the anterior aspect of the right ventricle. The generator is implanted on the left side para-umbilically in subcutaneous or subfascial tissue. With the subxyphoid approach to avoid sternotomy, the plate electrode is sutured extrapericardially over the left ventricle and the spiral electrode is positioned at the epicardium. Alternatively, for those in whom prior cardiac surgery has been carried out, a lateral thoracotomy can be used. The defibrillation threshold, that is the lowest possible energy for defibrillation of ventricular fibrillation or ventricular tachycardia, should be determined intraoperatively after stimulation of the arrhythmia. The energy required for termination of a stable ventricular tachycardia is usually less than that for termination of ventricular fibrillation and can be determined postoperatively. A margin of security should be taken into consideration which, for defibrillation thresholds of up to 10 Joules, is about twice the amount of the defibrillation threshold itself.(ABSTRACT TRUNCATED AT 400 WORDS)

Improved internal defibrillation efficacy with a biphasic waveform. Clinically available automatic implantable defibrillators use a monophasic truncated exponential waveform shock; after delivery the charge remaining on the device's capacitors is "dumped" internally and wasted. The efficacy of a monophasic and biphasic truncated exponential defibrillation waveform produced by a single capacitor discharge was compared in seven closed-chest, pentobarbital-anesthetized dogs. Defibrillation leads consisted of a new deployable intrapericardial electrode system. The monophasic waveform was positive and 6 msec in duration. The biphasic waveform had a positive phase identical to that of the monophasic waveform and a negative phase of equal duration with its initial voltage equal to 50% of the final voltage of the positive phase. Defibrillation shocks of varying initial voltage were delivered to construct curves of the percentage of successful defibrillation versus initial voltage and delivered energy, and the voltage and energy required for 50% (V50 and E50, respectively) and 80% (V80 and E80, respectively) success were compared.

Capacitors come in many sizes. They can be as small as an ant or as large as a dustbin. A few capacitors are adjustable. All capacitors have two connections, or leads. Most kinds of capacitors can be replaced easily by someone who has basic skills in electronics. However, one of the more powerful types - the electrolytic capacitor - must be used the correct way, or they can explode violently. While capacitors can store energy, as batteries do, capacitors can release all their stored energy very quickly, even faster than a second. A defibrillator or a photoflash capacitor uses this ability. It gradually charges, until it cannot be filled any more, and then quickly discharges its stored power to a device that needs to have it quickly. Supercapacitor Supercapacitors hold a bigger charge than regular capacitors. They are used to store electricity for motors and other purposes when batteries won't discharge quickly enough. [2] Polystyrene film capacitors This type of capacitor is not for use in high frequency circuits, being made with a coil inside. They can charge and discharge even more quickly than other capacitors.

Design of an ultrahigh-energy hydrogen thyratron/SCR research defibrillator. The design features of an ultrahigh-energy research defibrillator are described. Three voltage sources are used. The first is a 60-Hz supply of adjustable amplitude and duration for inducing fibrillation. The second source uses an 18.000-joule capacitor bank which can be charged to 800, 1600, or 2400 volts. SCRs in series with the chest are used to initiate the discharge, and SCRs shunting the capacitor bank terminate the discharge. The third source employs another 18,000-joule capacitor bank which can be charged to 5000, 10,000 or 15,000 volts. In this source, large ceramic-enveloped hydrogen thyratrons are used for both initiating and terminating the discharge. In the second and third sources, which can deliver rectangular, trapezoidal, truncated exponential, or untruncated exponential waveforms, capacitor charge time is 10 sec and the duration of the delivered shock is continuously adjustable from 100 musec through 1 sec. Published in Medical instrumentation

small capacitors considerably reduced the size and weight of external defibrillators, which could now be easily brought to victims in a wide range of environments The history of cardiopulmonary resuscitation (CPR) can be traced as far back as the literary works of ancient Egypt (c. 2686 – c. 2181 BC). However, it was not until the 18th century that credible reports of cardiopulmonary resuscitation began to appear in the medical literature. Mouth-to-mouth ventilation has been used for centuries as an element of CPR, but it fell out of favor in the late 19th As early as the 1930s, it was known that small electric shocks…