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 < 0.002), whereas Type D (P = 0.001), social support (P = 0.02), and ICD shock (P < 0.001) determined trajectory membership for device-related concerns. The course of general anxiety in ICD patients was stable the first year post implantation, whereas device-related concerns fluctuated more. Type D personality and social support were determinants of trajectory membership for all outcomes, whereas ICD shock was related to device-related concerns only. A simple pre-implant screening may help identify patients at risk for high-distress trajectory membership.