Implantable cardioverter-defibrillators.

udden cardiac death is a common problem, and increasing numbers of patients are surviving a first episode of a life threatening ventricular arrhythmia. In the absence of an acute myocardial infarction, patients who survive either ventricular fibrilla-tion or sustained ventricular tachycardia have a high risk of further episodes, which may be fatal. 1 Until recently, class I and class III antiarrhythmic drugs have been the standard treatment for patients with malignant ventricu-lar arrhythmias. Amiodarone 2 and sotalol 3 have been shown to be superior to class I drugs, but despite using the best appropriate medical treatment, arrhythmia recurrence rates are still 40–50% at five years. There is now growing evidence to support the wider use of implantable cardioverter-defibrillators (ICDs) as primary treatment in certain patients with serious ventricular ar-rhythmias. These devices were developed in the 1970s, with the first human implant in 1980. 4 Original devices had a single therapy option of defibrillation only; the generator was implanted in the abdomen, and thoracotomy was required for electrode placement. With advances in technology the units have become smaller (current ICDs are little bigger than a pacemaker) and can be implanted pectorally. With improvements in sensing, the latest devices oVer graded therapeutic responses to a sensed ventricular arrhythmia. Antitachycardia pacing , low energy synchronised cardioversion, and high energy defibrillation shocks can be given via a single transvenous lead. Implant procedure Implantation of an ICD is now technically very straightforward, and only a little more complicated than pacemaker implantation. As with pacemaker implantation, strict attention to asepsis is necessary, and prophylactic antibiotics are generally used. In the past, ICD implants were performed under general anaesthesia ; however, many centres now implant these devices using a combination of local anaesthesia and intravenous sedation. Usually an incision 5–8 cm in length is made in the left infraclavicular region, and a pocket is fashioned for the generator either subcutaneously or deep to the pectoralis major muscle. A ven-tricular lead (for sensing, pacing, and defibril-lation) is inserted via the cephalic or subclavian vein, and if appropriate an atrial lead is also inserted. Standard tests of pacing and sensing are performed, as for pacemaker implantation. It is then important to induce ventricular fibrillation, in order to test that the device can detect the arrhythmia and defibrillate eVec-tively with an adequate safety margin. Ventricu-lar fibrillation is usually induced either by delivering a small shock (via the device) synchronous with …