Kaplan-Meier curves showing time to a first occurrence of inappropriate ICD shock according to left atrial (LA) parameters (A–C) and history of atrial fibrillation (AF) prior to ICD implantation (D). The cutoff of LA maximum strain (Smax), pre-atrial contraction strain (SpreA), and absolute value of strain rate in LA contraction (SRa) were ≦20.6% (A), ≦14.6% (B), and ≦1.0 /s (C) for the lower group, respectively.