Patients with an implantable cardioverter defibrillator (ICD) show clinically relevant depression and anxiety, but little is known about their levels of posttraumatic stress. We assessed chronic posttraumatic stress attributable to a traumatic cardiac event and its predictors in patients at two time points after ICD placement. METHODS: We investigated 107 consecutively enrolled patients (57±14years, 62% men) on average 24±21months after ICD placement (baseline) and again 41±18months later (follow-up). All patients completed the Impact of Event Scale-Revised (IES-R) to self-rate the severity of posttraumatic stress (range 0-110). The 30% of patients with the highest IES-R scores (≥25) at baseline were defined as PTSD cases; the same threshold was applied to define PTSD caseness at follow-up. RESULTS: Posttraumatic stress increased from baseline to follow-up (19±22 vs. 25±19, p<0.001); 19% of patients had PTSD at both assessments, 12% at baseline only, and 18% at follow-up only. Female gender as well as greater peritraumatic dissociation and depression predicted greater posttraumatic stress at baseline (p-values≤0.041). Greater baseline posttraumatic stress, helplessness, alexithymia, and ≥5 shocks during follow-up all predicted greater posttraumatic stress at follow-up (p-values≤0.029). Female gender, helplessness, and depression predicted PTSD at baseline (p-values≤0.022); low education and posttraumatic stress at baseline predicted PTSD at follow-up (p-values≤0.003). CONCLUSIONS: Between 2 and 5.5years post-ICD placement chronic posttraumatic stress slightly increased and nearly one-fifth of patients had newly developed PTSD. The identified psychological predictors of long-term chronicity of posttraumatic stress might particularly inform behavioral interventions for ICD recipients.