Background: The need for treatment of posttraumatic stress disorder (PTSD) among combat veterans returning from Afghanistan and Iraq is a growing concern. PTSD has been associated with reduced cardiac coherence (an indicator of heart rate variability [HRV]) and deficits in early stage information processing (attention and immediate memory) in different studies. However, the co-occurrence of reduced coherence and cognition in combat veterans with PTSD has not been studied before.

Primary study objective: A pilot study was undertaken to assess the covariance of coherence and information processing in combat veterans. An additional study goal was assessment of effects of HRV biofeedback (HRVB) on coherence and information processing in these veterans.

Methods/design: A two-group (combat veterans with and without PTSD), pre-post study of coherence and information processing was employed with baseline psychometric covariates.

Setting: The study was conducted at a VA Medical Center outpatient mental health clinic.

Participants: Five combat veterans from Iraq or Afghanistan with PTSD and five active-duty soldiers with comparable combat exposure who were without PTSD.

Intervention: Participants met with an HRVB professional once weekly for 4 weeks and received visual feedback in HRV patterns while receiving training in resonance frequency breathing and positive emotion induction.

Primary outcome measures: Cardiac coherence, word list learning, commissions (false alarms) in go-no go reaction time, digits backward.

Results: Cardiac coherence was achieved in all participants, and the increase in coherence ratio was significant post-HRVB training. Significant improvements in the information processing indicators were achieved. Degree of increase in coherence was the likely mediator of cognitive improvement.

Conclusion: Cardiac coherence is an index of strength of control of parasympathetic cardiac deceleration in an individual that has cardinal importance for the individual's attention and affect regulation.