Heart rate assessment for posttraumatic stress disorder symptoms among military veterans: A narrative literature review

Post-Traumatic Stress Disorder (PTSD) is a psychiatric condition affecting as much as 20% of the returning veterans from the current wars in Afghanistan and Iraq (Ramchand et al., 2010). Due to its prevalence, assessment and intervention methods for PTSD symptoms among veterans are timely to ensure veterans’ faster recovery and their reintegration into society. A narrative review of literature was conducted to examine the literature on techniques and methods for detection and measurement of PTSD symptoms. Relevant reviews and seminal papers associated with psychophysiological measurements with emphasis on heart rate, the prevalence of PTSD in military veterans, and detection of PTSD were included. Psychophysiology involves the non-invasive recording of biological processes simultaneously (Pole, 2007). The measures that were found to be reliably related to PTSD are: (1) higher resting heart rate; (2) larger heart rate responses to standardized trauma cues; and (3) for idiographic cues facial muscle electromyography (EMG) and heart rate responses (Pole, 2007). Studies based on heart rate found that there were five beats per minute (bpm) increase in resting heart rates for combat veterans who suffer from PTSD compared to those who were not diagnosed (Beckham et al., 2000, Woodward et al., 2009). Buckley et al. (2004) found that for a mixed population (veterans and civilians) PTSD patients had a resting heart rate increase of 6.6 bpm compared to non-PTSD patients while adjusting for covariates. The exact mechanisms of how stress affects heart rate are not well-known; however, it is possible to observe stressful events and relate these to physiological changes in heart rate that can be measured using modern sensors (Andreoli et al., 2010). In the literature, heart rate is analyzed using statistical, geometric, frequency domain, time-frequency and non-linear feature analysis (Acharya et al., 2006). Non-linear features have been developed to quantify the dynamics of heart rate fluctuations. These include approximate entropy, Detrended Fluctuation Analysis (DFA), Lyapunov exponent, Recurrence Plots (RPs) and Correlation Dimension (CD) (Pincus, 1991; Huikuri et al., 2000; Acharya et al., 2004; Acharya et al., 2006). Our synthesis resulted in identification of three research gaps. Heart rate analysis has shown promise to link PTSD symptoms to differences in PTSD and non-PTSD subjects (Pole, 2007) but a characterization of PTSD symptoms from heart rate data seems to remain a research gap. While continuous monitoring of physiological parameters is gaining momentum, this particular method has not been studied to infer key characteristics associated with PTSD among military veterans. Continuous monitoring might be able to highlight muted response to startle or treatment. There is also a research gap in the assessment of heart rate accelerations and decelerations in response to specific PTSD symptoms (Khanade et al., 2017). The investigation into accelerations/decelerations associated with PTSD hyper-arousal triggers might have a potential to detect hyper-arousal instantaneously and would shed light on trigger-specific interventions to reduce harmful effects of PTSD triggers in a timely manner. In addition, most studies were conducted to observe differences among PTSD and non-PTSD populations. More work is warranted to focus on PTSD patients in isolation to explain variety of triggers and their specific physiological reactions.