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Solinsky R, Taylor JA. Commentary: Spinal Cord Stimulation to Improve Autonomic Regulation After Spinal Cord Injury: Can Reflex Control Be Restored. Top Spinal Cord Inj Rehabil 2023; 29:31-33. [PMID: 37235193 PMCID: PMC10208254 DOI: 10.46292/sci22-00048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Affiliation(s)
- Ryan Solinsky
- Cardiovascular Research Lab, Spaulding Rehabilitation Hospital, Cambridge, Massachusetts
- Spaulding Research Institute, Boston, Massachusetts
- Department of Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - J. Andrew Taylor
- Cardiovascular Research Lab, Spaulding Rehabilitation Hospital, Cambridge, Massachusetts
- Spaulding Research Institute, Boston, Massachusetts
- Department of Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
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El-Kotob R, Craven BC, Mathur S, Ditor DS, Oh P, Miyatani M, Verrier MC. Assessing Heart Rate Variability As a Surrogate Measure of Cardiac Autonomic Function in Chronic Traumatic Spinal Cord Injury. Top Spinal Cord Inj Rehabil 2018; 24:28-36. [PMID: 29434458 DOI: 10.1310/sci17-00002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Background: Although cardiac autonomic dysfunction is a contributing factor for cardiovascular disease development in individuals with a spinal cord injury (SCI), it remains poorly understood. Heart rate variability (HRV) analysis has the potential to non-invasively assess the cardiac autonomic nervous system. The study objectives are (a) to determine if there are differences in HRV measures across neurological level of impairment (NLI) and American Spinal Cord Injury Association Impairment Scale (AIS) subgroups, and (b) to determine if there is a relationship between HRV frequency measures (low frequency [LF] and high frequency [HF]) at rest. Methods: We conducted a secondary data analysis of a primary data set from a published cross-sectional study of electrocardiogram recordings of 56 subjects (44 men and 12 women, mean age ± SD = 46.75 ± 12.44 years) with a chronic traumatic SCI (C1-T12, AIS A-D, ≥2 years post injury). HRV was analyzed using time and frequency domain measures. Results: There were no significant HRV differences across NLI and AIS subgroups. The LF and HF indices were positively correlated in the entire sample (r = 0.708, p < .0001) and among impairment subgroups. Conclusion: No differences were observed in the HRV time and frequency measures when compared across NLI and AIS subgroups. The results were considered inconclusive, since possible explanations include inadequate sample size as well as other physiological considerations. A positive correlation was found between LF and HF when assessed at rest. The relationship between LF and HF may not necessarily represent a rebalanced autonomic nervous system, but it does question the utility of solely measuring LF:HF at rest in persons with chronic SCI.
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Affiliation(s)
- Rasha El-Kotob
- University Health Network, Toronto Rehabilitation Institute, Lyndhurst Centre, Toronto, Ontario, Canada.,Graduate Department of Rehabilitation Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - B Catharine Craven
- University Health Network, Toronto Rehabilitation Institute, Lyndhurst Centre, Toronto, Ontario, Canada.,Department of Medicine, Division of Physical Medicine & Rehabilitation, University of Toronto, Toronto, Ontario, Canada
| | - Sunita Mathur
- University Health Network, Toronto Rehabilitation Institute, University Centre, Toronto, Ontario, Canada.,Department of Physical Therapy, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - David S Ditor
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada
| | - Paul Oh
- University Health Network, Toronto Rehabilitation Institute, Rumsey Centre, Toronto, Ontario, Canada.,Department of Medicine, Clinical Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - Masae Miyatani
- University Health Network, Toronto Rehabilitation Institute, Lyndhurst Centre, Toronto, Ontario, Canada
| | - Mary C Verrier
- University Health Network, Toronto Rehabilitation Institute, Lyndhurst Centre, Toronto, Ontario, Canada.,Department of Physical Therapy, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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Habazettl H, Stahn A, Nitsche A, Nordine M, Pries AR, Gunga HC, Opatz O. Microvascular responses to (hyper-)gravitational stress by short-arm human centrifuge: arteriolar vasoconstriction and venous pooling. Eur J Appl Physiol 2015; 116:57-65. [PMID: 26280651 DOI: 10.1007/s00421-015-3241-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 08/08/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE We hypothesized that lower body microvessels are particularly challenged during exposure to gravity and hypergravity leading to failure of resistance vessels to withstand excessive transmural pressure during hypergravitation and gravitation-dependent microvascular blood pooling. METHODS Using a short-arm human centrifuge (SAHC), 12 subjects were exposed to +1Gz, +2Gz and +1Gz, all at foot level, for 4 min each. Laser Doppler imaging and near-infrared spectroscopy were used to measure skin perfusion and tissue haemoglobin concentrations, respectively. RESULTS Pretibial skin perfusion decreased by 19% during +1Gz and remained at this level during +2Gz. In the dilated area, skin perfusion increased by 24 and 35% during +1Gz and +2Gz, respectively. In the upper arm, oxygenated haemoglobin (Hb) decreased, while deoxy Hb increased with little change in total Hb. In the calf muscle, O2Hb and deoxy Hb increased, resulting in total Hb increase by 7.5 ± 1.4 and 26.6 ± 2.6 µmol/L at +1Gz and +2Gz, respectively. The dynamics of Hb increase suggests a fast and a slow component. CONCLUSION Despite transmural pressures well beyond the upper myogenic control limit, intact lower body resistance vessels withstand these pressures up to +2Gz, suggesting that myogenic control may contribute only little to increased vascular resistance. The fast component of increasing total Hb indicates microvascular blood pooling contributing to soft tissue capacitance. Future research will have to address possible alterations of these acute adaptations to gravity after deconditioning by exposure to micro-g.
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Affiliation(s)
- H Habazettl
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany. .,German Heart Institute Berlin, Berlin, Germany. .,Center for Space Medicine Berlin, Berlin, Germany.
| | - Alexander Stahn
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
| | - Andrea Nitsche
- Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany
| | - Michael Nordine
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
| | - A R Pries
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Cardiovascular Research, Charité-University Medicine Berlin, Berlin, Germany
| | - H-C Gunga
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
| | - O Opatz
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
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West CR, Gee CM, Voss C, Hubli M, Currie KD, Schmid J, Krassioukov AV. Cardiovascular control, autonomic function, and elite endurance performance in spinal cord injury. Scand J Med Sci Sports 2014; 25:476-85. [DOI: 10.1111/sms.12308] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2014] [Indexed: 12/17/2022]
Affiliation(s)
- C. R. West
- International Collaboration on Repair Discoveries (ICORD); Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
| | - C. M. Gee
- International Collaboration on Repair Discoveries (ICORD); Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
| | - C. Voss
- Centre for Hip Health and Mobility; Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
| | - M. Hubli
- International Collaboration on Repair Discoveries (ICORD); Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
| | - K. D. Currie
- International Collaboration on Repair Discoveries (ICORD); Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
| | - J. Schmid
- Paracycling Classification; International Cycling Union; Aigle Switzerland
| | - A. V. Krassioukov
- International Collaboration on Repair Discoveries (ICORD); Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
- Division of Physical Medicine and Rehabilitation; Faculty of Medicine; University of British Columbia; Vancouver British Columbia Canada
- GF Strong Rehabilitation Centre; Vancouver Health Authority; Vancouver British Columbia Canada
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Protheroe CL, Ravensbergen HRJC, Inskip JA, Claydon VE. Tilt testing with combined lower body negative pressure: a "gold standard" for measuring orthostatic tolerance. J Vis Exp 2013:e4315. [PMID: 23542558 DOI: 10.3791/4315] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Orthostatic tolerance (OT) refers to the ability to maintain cardiovascular stability when upright, against the hydrostatic effects of gravity, and hence to maintain cerebral perfusion and prevent syncope (fainting). Various techniques are available to assess OT and the effects of gravitational stress upon the circulation, typically by reproducing a presyncopal event (near-fainting episode) in a controlled laboratory environment. The time and/or degree of stress required to provoke this response provides the measure of OT. Any technique used to determine OT should: enable distinction between patients with orthostatic intolerance (of various causes) and asymptomatic control subjects; be highly reproducible, enabling evaluation of therapeutic interventions; avoid invasive procedures, which are known to impair OT(1). In the late 1980s head-upright tilt testing was first utilized for diagnosing syncope(2). Since then it has been used to assess OT in patients with syncope of unknown cause, as well as in healthy subjects to study postural cardiovascular reflexes(2-6). Tilting protocols comprise three categories: passive tilt; passive tilt accompanied by pharmacological provocation; and passive tilt with combined lower body negative pressure (LBNP). However, the effects of tilt testing (and other orthostatic stress testing modalities) are often poorly reproducible, with low sensitivity and specificity to diagnose orthostatic intolerance(7). Typically, a passive tilt includes 20-60 min of orthostatic stress continued until the onset of presyncope in patients(2-6). However, the main drawback of this procedure is its inability to invoke presyncope in all individuals undergoing the test, and corresponding low sensitivity(8,9). Thus, different methods were explored to increase the orthostatic stress and improve sensitivity. Pharmacological provocation has been used to increase the orthostatic challenge, for example using isoprenaline(4,7,10,11) or sublingual nitrate(12,13). However, the main drawback of these approaches are increases in sensitivity at the cost of unacceptable decreases in specificity(10,14), with a high positive response rate immediately after administration(15). Furthermore, invasive procedures associated with some pharmacological provocations greatly increase the false positive rate(1). Another approach is to combine passive tilt testing with LBNP, providing a stronger orthostatic stress without invasive procedures or drug side-effects, using the technique pioneered by Professor Roger Hainsworth in the 1990s(16-18). This approach provokes presyncope in almost all subjects (allowing for symptom recognition in patients with syncope), while discriminating between patients with syncope and healthy controls, with a specificity of 92%, sensitivity of 85%, and repeatability of 1.1±0.6 min(16,17). This allows not only diagnosis and pathophysiological assessment(19-22), but also the evaluation of treatments for orthostatic intolerance due to its high repeatability(23-30). For these reasons, we argue this should be the "gold standard" for orthostatic stress testing, and accordingly this will be the method described in this paper.
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Affiliation(s)
- Clare L Protheroe
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University
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