Heart Rate Variability: A Novel Modality for Diagnosing Neuropathic Pain after Spinal Cord Injury.

Jay Karri,Shengai Li,Larry Zhang,Argyrios Stampas,Sheng Li,Yen-Ting Chen

doi:10.3389/fphys.2017.00495

Abstract

Background: Heart rate variability (HRV), the physiological variance in the heart's R-R interval length, can be analyzed to produce various parameters reflective of one's autonomic balance. HRV analysis may be used to capture those autonomic aberrations associated with chronic neuropathic pain (NP) in spinal cord injury (SCI). This study assesses the capacity of HRV parameters to diagnose NP in an SCI cohort.Methods: An electrocardiogram (ECG) was collected at rest from able bodied participants (AB, n = 15), participants with SCI only (SCI-NP, n = 11), and those with SCI and NP (SCI+NP, n = 20). HRV parameters were analyzed using conventional time and frequency analysis.Results: At rest, there were no heart rate differences amongst groups. However, SCI+NP participants demonstrated lower overall HRV, as determined by the SDNN time domain parameter, compared to either AB (p < 0.01) or SCI-NP (p < 0.05) groups. Moreover, AB and SCI-NP participants were statistically comparable for all HRV time and frequency domain parameters. Additional analyses demonstrated no differences in HRV parameters between T4, above vs. T5, below SCI groups (for all parameters: p > 0.15) or between C8, above vs. T1, below SCI groups (p > 0.30).Conclusions: Participants with SCI and NP exhibit a lower overall HRV, which can be determined by HRV time domain parameter SDNN. HRV analysis is an innovative modality with the capacity for objective quantification of chronic NP in participants with SCI.

Highlights

Heart rate variability (HRV), the physiological variance in the heart’s R-R interval length, can be analyzed to produce various parameters reflective of one’s autonomic balance
Criteria for able-bodied participants (AB) were persons (1) between 18 and 75 years of age, (2) capable of providing consent, (3) without clinically significant or unstable medical, neuropsychiatric, or chronic pain disorders, (4) without a history of substance abuse or dependence, (5) without a history of brain surgery, intracranial metal implantation, or tumor, and (6) without a history of cardiac pathology, implanted pacemakers, or current use of rhythm altering medication like beta-blockers. In addition to those criteria used for AB, participants with Spinal cord injury (SCI) were recruited into either the SCI without neuropathic pain (NP) study group (SCI-NP) or SCI with NP study group (SCI+NP) if they were diagnosed with an SCI at least 6 months prior
Our study cohort included participants stratified into AB (n = 15), SCI and without neuropathic pain (SCI-NP) (n = 11), or SCI and chronic neuropathic pain (SCI+NP) (n = 20) study groups

Summary

Introduction

Heart rate variability (HRV), the physiological variance in the heart’s R-R interval length, can be analyzed to produce various parameters reflective of one’s autonomic balance. HRV analysis may be used to capture those autonomic aberrations associated with chronic neuropathic pain (NP) in spinal cord injury (SCI). Managing pain in persons with SCI is clinically challenging, in part due to existing numerous presentations, often concomitantly (O’Connor and Dworkin, 2009; Bryce et al, 2012). Above chronic pain conditions contribute greatly to patient suffering, neuropathic pain after SCI has been reported to be especially distressing (Jensen et al, 2007b; O’Connor and Dworkin, 2009; Bryce et al, 2012). Prevalent in up to 85% of patients with SCI, neuropathic pain (NP) is a chronic pain presentation that is challenging to treat, partially related to the fact that mechanisms of NP pathophysiology are poorly understood (Urch, 2011; Margolis et al, 2014). Many patients even report their pain to persist or worsen over time even with pharmacological intervention (O’Connor and Dworkin, 2009; Urch, 2011; Margolis et al, 2014)

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