Implantable cardioverter defibrillators (ICDs) are well accepted by most patients, but 25-33% of patients are anxious and report device-related concerns. Previous studies focused on prevalence rates and mean scores, whereas the course of anxiety over time is unknown in individual patients. We examined the trajectory of anxiety in ICD patients during a 1-year period and determinants of these trajectories. Consecutive patients (N = 348) implanted with an ICD completed standardized measures of general anxiety and device-related concerns at five assessment occasions and the Type D Scale at baseline. Type D personality is defined by increased negative emotions and the inhibition of these emotions in social interactions. Seven trajectories were identified for state and trait anxiety and eight for device-related concerns. The course of the trajectories for general anxiety was stable over time, whereas device-related concerns showed more fluctuation, with a decrease in concerns generally spread out during the 1 year. Type D personality and social support were determinants of trajectory membership for general anxiety (all P