Implantable Cardioverter–Defibrillators

Abstract

espite advances in emergency medical systems and in techniques of resuscitation, sudden death from cardiac arrest remains a major public health problem. Most persons who have an out-of-hospital cardiac arrest do not survive. 1,2 Those who are resuscitated may have severe, long-term cognitive impairment and motor impairment due to delays before a stable rhythm could be restored. In the 1970s, motivated by the death of a colleague, Drs. Michel Mirowski and Morton Mower, and their colleagues, developed the concept of an implantable device that could automatically monitor and analyze cardiac rhythm and deliver defibrillating shocks when it detected ventricular fibrillation. 3,4 After years of testing, in 1980 the first clinical implantation was performed in a young woman with recurrent ventricular fibrillation. 5 Subsequently, the implantable cardioverter-defibrillator evolved from a therapy of last resort for patients with recurrent cardiac arrest to a management standard for use in primary prevention (the prevention of a first life-threatening event) and secondary prevention (prevention of a recurrence of a potentially fatal arrhythmia or cardiac arrest) in patients with coronary heart disease. An implantable cardioverter-defibrillator system comprises a pulse generator and one or more leads for pacing and defibrillation electrodes (Fig. 1). The pulse generator has a number of components (Table 1). 6 A sealed titanium can encloses a lithium-silver vanadium oxide battery, voltage converters and resistors, capacitors to store charges, microprocessors and integrated circuits to control the analysis of the rhythm and the delivery of the therapy, memory chips to store electrographic and other data, and a telemetry module. Technological advances have made possible a gradual reduction in the size of the pulse generator, permitting subcutaneous implantation of the defibrillator on the anterior chest wall in most patients. The top of the pulse generator contains an epoxy resin header for connecting the pacing and defibrillation leads. The defibrillation leads must be capable of delivering high-energy shocks to the heart without damaging the myocardium. In the earliest defibrillators, epicardial patches were used, but transvenous leads are now standard. Each defibrillation lead contains one or two coils that dissipate heat during high-voltage discharges. In most systems, the pulse generator can serve as a part of the defibrillation pathway. The defibrillation lead also contains bipolar electrodes, which are used for ventricular pacing and sensing. If both pacing electrodes are independent of the defibrillation coils, they form what is called a dedicated bipole. If a defibrillation coil is linked to the ring electrode for sensing, it forms what is called an integrated bipole. Both systems are effective in most patients. Active-fixation (screw-in) and passive-fixation lead systems are in clinical use. Dual-chamber and biventricular devices also have ports for atrial or left ventricular electrodes, which are used for pacing and...

Role of Antiarrhythmic Drugs: Frequent Implantable Cardioverter-Defibrillator Shocks, Risk of Proarrhythmia, and New Drug Therapy

“…1,2 The primitive ICD introduced in the 1980s by Mirowski and colleagues has become much more sophisticated with programming capabilities, atrial and left ventricular leads, antitachycardia pacing (ATP) algorithms, bi-ventricular pacing and cardioverting and defibrillating shocks. 1,3 Similarly, indications for ICD implantation are expanding as well. 4 Assessment for eligibility of an ICD implantation is considered one of the integral parts of management of cardiomyopathy patients due to mortality benefits.…”

“…4 Assessment for eligibility of an ICD implantation is considered one of the integral parts of management of cardiomyopathy patients due to mortality benefits. 1,2 Consequently, the number of ICD implantations has increased significantly in the last decade with a concurrent decrease in the use of stand-alone antiarrhythmic drugs for ventricular arrhythmia indications. [5][6][7] The ICD prevents sudden cardiac death (SCD) by terminating the episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), delivering ATP therapy or ICD shock.…”

Infection after ICD implantation: operating room versus cardiac catheterisation laboratory

“…An ICD system comprises a pulse generator and one or more leads for pacing and defibrillation electrodes (ICD with single, dual, or triple chamber pacing). 1 The first-generation devices required an abdominal pocket for the pulse generator and insertion of an epicardial lead system by means of thoracotomy. 1 The epicardial lead system was later replaced by a transvenous non-thoracotomy lead system in the subclavian or cephalic veins while preserving abdominal pulse generators.…”

“…1 The first-generation devices required an abdominal pocket for the pulse generator and insertion of an epicardial lead system by means of thoracotomy. 1 The epicardial lead system was later replaced by a transvenous non-thoracotomy lead system in the subclavian or cephalic veins while preserving abdominal pulse generators. Technological advances have made a gradual reduction in the size of the pulse generator possible, thereby permitting superficial implantation of the pulse generator in the anterior chest wall.…”

“…Technological advances have made a gradual reduction in the size of the pulse generator possible, thereby permitting superficial implantation of the pulse generator in the anterior chest wall. 1 This technique resembles pacemaker (PM) implantation.…”