Relative effectiveness of the implantable cardioverter-defibrillator and antiarrhythmic drugs in patients with varying degrees of left ventricular dysfunction who have survived malignant ventricular arrhythmias

OBJECTIVES We sought to assess the effect of baseline ejection fraction on survival difference between patients with life-threatening ventricular arrhythmias who were treated with an antiarrhythmic drug (AAD) or implantable cardioverter-defibrillator (ICD). BACKGROUND The Antiarrhythmics Versus Implantable Defibrillators (AVID) study demonstrated improved survival in patients with ventricular fibrillation or ventricular tachycardi with left ventricular ejection fraction (LVEF) ≤0.40 or hemodynamic compromise. METHODS Survival differences between AAD-treated and ICD-treated patients entered into the AVID study (patients presenting with sustained ventricular arrhythmi associated with an LVEF ≤0.40 or hemodynamic compromise) were compared at different levels of ejection fraction. RESULTS In patients with an LVEF ≥0.35, there was no difference in survival between AAD-treated and ICD-treated patients. test for interaction was not significant, but had low power to detect an interaction. For patients with an LVEF 0.20 to 0.34, there was significantly improved survival with ICD as compared with AAD therapy. In the smaller subgroup with an LVEF <0.20, the same magnitude of survival difference was seen as that in the 0.20 to 0.34 LVEF subgroup, but the difference did not reach statistical significance. CONCLUSIONS These dat suggest that patients with relatively well-preserved LVEF (≥0.35) may not have better survival when treated with the ICD as compared with AADs. At lower LVEF, the ICD appears to offer improved survival as compared with AADs. Prospective studies with larger patient numbers are needed to assess the effect of relatively well-preserved ejection fraction (≥0.35) on the relative treatment effect of AADs and the ICDs.