BACKGROUND: Posttraumatic stress disorder (PTSD) develops following exposure to atraumatic event and is characterized by persistent intense reactivity to trauma related cues. Equally important, but less studied, is the failure to restore physiological homeostasis after these excessive reactions. This study investigates psychophysiological markers of sustained cardiac activity after exposure to reminders of traumatic event in PTSD patients. METHODS: Participants passively listened to neutral and personal traumatic event while electrocardiogram was continuously recorded. Heart rate (HR) and heart rate variability (HRV) were analyzed in 19 PTSD patients and 16 trauma-exposed controls. RESULTS: Both PTSD patients and trauma exposed controls exhibited a significant increase in HR to the exposure of their personal trauma. PTSD patients sustained the increase of HR while controls recovered to basal levels. In PTSD patients, sustained HR was positively associated with re-experiencing symptoms. The PTSD group also showed a reduced HRV (a measure of parasympathetic influence on the heart) during personal trauma exposure and lack of recovery. LIMITATIONS: The sample size was small and PTSD patients were under medication. CONCLUSIONS: Our findings provide an experimental account of the failure of PTSD patients to exhibit physiological recovery after exposure to trauma-related stimuli. PTSD patients exhibited a sustained tachycardia with attenuation of HRV that persisted even after cessation of the stressor. Re-experiencing symptoms facilitated engagement in the trauma cues, suggesting that, in their daily-life, patients most likely present repeated episodes of sustained over-reactivity, which may underpin the emotional dysregulation characteristic of PTSD.