Electrical storm presages nonsudden death - The antiarrhythmics versus implantable defibrillators (AVID) trial

Background-Electrical storm, multiple temporally related episodes of ventri cular tachycardia (VT) or ventricular fibrillation (VF), is a frequent prob lem among recipients of implantable cardioverter defibrillators (ICDs). How ever, insufficient data exist regarding its prognostic significance. Methods and Results-This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31+/-13 months. Electrical storm was defined as great er than or equal to3 separate episodes of VT/VF within 24 hours. Characteri stics and survival of patients surviving electrical storm (n=90) those with VT/VF unrelated to electrical storm (n=184), and the remaining patients (n =183) were compared. The 3 groups differed in terms of ejection fraction, i ndex arrhythmia, revascularization status, and baseline medication use. Sur vival was evaluated using time-dependent Cox modeling, Electrical storm occ urred 9.2+/-11.5 months after ICD implantation, and most episodes (86%) wer e due to VT. Electrical storm was a. significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (re lative risk [RR], 2.4; 95% confidence interval [CI], 1.3 to 4.2; P=0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 8.6 to 1. 7; P=0.9). The risk of death was greatest 3 months after electrical storm ( RR, 1.9; 95% CI, 1.0 to 12.3; P=0.0001) and diminished beyond this time (RR , 1.9; 95% CI, 1.0 to 3.6; P=0.04), Conclusions-Electrical storm is an important, independent marker for subseq uent death among ICD recipients particularly in the first 3 months after it s occurrence, However the development of VT/VF unrelated to electrical stor m does not seem to be associated with an increased risk of subsequent death .