Implantable cardioverter-defibrillators (ICDs) 1989: how close are we to the ideal device?

Major technical advances over the last few years have led to significant improvements in implantable cardioverter-defibrillators. Tachycardias can be detected using a number of criteria which include rate, rate of onset, duration, and stability of tachycardia. A number of target tachyarrhythmias can be distinguished in the same patient and differentiated from sinus or other benign tachycardias. Different tachycardias can then be treated with different electrical therapies. Therapies now incorporated in the latest generation of implantable devices include comprehensive antitachycardia pacing techniques, low-energy cardioversion and high-energy cardioversion-defibrillation. Bradycardia support pacing is also incorporated. Improvements in the electrodes used for sensing tachycardia and delivering therapy have resulted in the first implants of devices without the need for thoracotomy. Improvements in capacitor technology have resulted in a gradual reduction in the size of devices in spite of their increasing sophistication. Further research is needed to evaluate different shock charges and waveforms. Tachycardia prevention by implanted devices is also a field of much current research. Thus, though not yet "ideal," the latest generation of implantable cardioverter-defibrillators represents an important therapeutic option in the treatment of ventricular tachyarrhythmias.