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An implantable cardioverter-defibrillator (ICD) or automated implantable cardioverter defibrillator (AICD) is a device implantable inside the body, able to perform cardioversion, defibrillation and pacing of the heart. The device is therefore capable of correcting most life-threatening cardiac arrhythmias. The ICD is the first-line treatment and prophylactic therapy for patients at risk for sudden cardiac death due to ventricular fibrillation and ventricular tachycardia. Current devices can be programmed to detect abnormal heart rhythms and deliver therapy via programmable antitachycardia pacing in addition to low-energy and high-energy shocks. "AICD" was trademarked by the Boston Scientific corporation, so the more generic "ICD" is preferred terminology. Current device batteries last about 6–10 years, With advances in the technology (batteries with more capacity or, potentially in the future with rechargeable batteries 〔(WiTriCity being looked at for use in pacemakers )〕〔(Wireless Qi developed for use in pacemakers )〕 it may be possible to increase this well past 10 years. The lead (the electrical cable connecting the device to the heart) has a much longer average longevity but can incur various types of malfunction, specifically insulation failure or fracture of the conductor and require replacement .〔(Replacing of ICD and leads needs to be done every 5 to 10 years )〕 The process of implantation of an ICD system is similar to implantation of a pacemaker. In fact, ICDs are composed of an ICD generator and of wires. The first component or generator, contains a computer chip or circuitry with a RAM memory, programmable software, a capacitor and a battery; this is implanted typically under the skin in the left upper chest. The second part of the system is a electrode wire or wires that, similar to pacemakers, are connected to the generator and passed through a vein to the right chambers of the heart. The lead usually lodges in the apex or septum of the right ventricle. Just like pacemakers, ICDs can have a single wire or lead in the heart (in the right ventricle, single chamber ICD), two leads (in the right atrium and right ventricle, dual chamber ICD) or three leads (biventricular ICD, one in the right atrium, one in the right ventricle and one on the outer wall of the left ventricle). The difference between pacemakers and ICDs is that pacemakers are also available as temporary units and are generally designed to correct slow heart rates, i.e. bradycardia, while ICDs are often permanent safeguards against sudden life-threatening arrhythmias. The most recent development is the subcutaneous ICD (S-ICD). ==Indications== Implantation of ICD is meant to prevent sudden cardiac death and is indicated under various conditions. Two broad but distinct categories are primary and secondary prevention. Primary prevention refers to patients who have not suffered a life-threatening arrhythmia episode. Secondary prevention has the strongest evidence for benefit and it refers to survivors of cardiac arrest secondary to ventricular fibrillation or hemodynamically unstable sustained ventricular tachycardia after reversible causes are excluded. Similarly, ICD use in primary prevention is to prevent cardiac death in patients who are at risk for sustained ventricular tachycardia or ventricular fibrillation. This population accounts for the bulk of all ICD implants. There are a multitude of guideline indications for ICD use in primary preventions with varying degree of supporting evidence. Periodically, both the American College of Cardiology (ACC)/American Heart Association (AHA) and European Society of Cardiology provide an update to this guideline. Some of the Class I indications are as followed:〔 * With LVEF ≤ 35% due to prior Myocardial Infarction (MI) who are at least 40 days post-MI and are in NYHA Functional Class II or III * With LV dysfunction due to prior MI who are at least 40 days post-MI, have an LVEF ≤ 30%, and are in NYHA Functional Class I * With nonischemic DCM who have an LVEF ≤ 35% and who are in NYHA Functional Class II or III * With nonsustained VT due to prior MI, LVEF < 40%, and inducible VF or sustained VT at electrophysiological study * With structural heart disease and spontaneous sustained VT, whether hemodynamically stable or unstable * With syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiological study 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Implantable cardioverter-defibrillator」の詳細全文を読む スポンサード リンク
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