[Role of antiarrhythmic drugs in reducing the number of defibrillation shocks]

Abstract

There is a logical basis for the prescription of antiarrhythmic therapy (AAT) in patients with an implanted automatic defibrillator (IAD): the prevention of supraventricular and ventricular arrhythmias, slowing the rate of a ventricular arrhythmia to improve the haemodynamic tolerance and better efficacy of anti-tachycardia stimulation. Adjuvant therapy of this kind is used in 49 to 69% of cases. Forty six per cent of patients in the MADIT I trial had AAT at the last follow-up. In the AVID trial, despite recommendations to avoid the association of AAT and [AD, 18% of patients had this combination because of the large number of shocks in 64% of cases; AAT was associated with both a reduction in the number of shocks (p < 0.05) and in the delay to a recurrence of the arrhythmia (p < 0.0001). In the CASCADE trial, carried out in survivors of cardiac arrest, the prescription of amiodarone in patients with IAD significantly reduced the number of defibrillation shocks. Finally, almost 40% of patients with IAD have an "arrhythmia storm", sometimes during follow-up, usually requiring the association of AAT. Despite the frequent association of AAT and IAD, the results of this combination have rarely been studied systematically. Only one randomised trial has been published comparing D,L-sotalol and placebo in patients with IAD. The treatment reduced the probability of a first defibrillation shock, whether appropriate or not. Amiodarone has often been proposed in association with IAD in isolated cases. The OPTIC trial (Optimal Pharmacological Therapy in Implantable Cardioverter), currently under way, has three sub-groups of IAD (betablocker, amiodarone and betablocker, sotalol), with the aim of determining the preventive value of each AAT with respect to the IAD performance. In addition to the results of combined treatment, the interaction with the threshold of defibrillation is an important factor which is not clearly understood at present. Class I AAT increases the threshold of defibrillation whereas Sotalol reduced it. Amiodarone has a variable effect, neutral or deleterious. The OPTIC trial should provide valuable information via the sub-analysis of the effects of drugs on the threshold of defibrillation in each of the three arms of the trial.