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Implantable cardioverter-defibrillators
Last reviewed: 06.07.2025
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Implantable cardioverter-defibrillators perform cardioversion and defibrillation of the heart in response to VT or VF. Modern ICDs with an emergency therapy function involve connecting the pacemaker function in the development of bradycardia and tachycardia (in order to stop sensitive supraventricular or ventricular tachycardia) and recording an intracardiac electrocardiogram. Implantable cardioverter-defibrillators are sutured subcutaneously or retrosternally, the electrodes are implanted transvenously or (less often) during thoracotomy.
Implantable cardioverter defibrillators (ICDs) are the treatment of choice for patients who have had an episode of VF or hemodynamically significant VT that is not due to a reversible or transient cause (eg, electrolyte imbalance, proarrhythmia due to antiarrhythmic drugs, acute MI). ICDs may also be indicated for patients with VT or VF induced during an electrophysiologic study and for patients with idiopathic or ischemic cardiomyopathy, LVEF < 35%, and a high risk of VF or VT. Other indications are less well established. Because ICDs primarily terminate VT and VF rather than prevent them, patients prone to these arrhythmias may require both ICDs and antiarrhythmic drugs to reduce the number of episodes and the need for uncomfortable ICD shocks; This approach also increases the service life of the ICD.
The lifespan of ICD generators is approximately 5 years. ICDs may fail and therefore deliver inappropriate pacing or shocks in response to sinus rhythm or SVT, or fail to deliver an appropriate shock. Possible ICD failures include lead or generator migration, inadequate sensitivity and threshold increase due to epicardial fibrosis from previous defibrillations, and battery depletion. If a patient reports that an ICD is not functioning properly, the device may be tested to determine the cause.
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