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Left‐Ventricular Pressure and Volume Responses to Active‐ and Passive‐Exercise Training Following Experimental Spinal Cord Injury
Author(s) -
West Christopher R.,
DeVeau Kathryn M.,
Harman Kathryn A.,
Squair Jordan,
Magnuson David S. K.,
Krassioukov Andrei V.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1239.6
Subject(s) - medicine , spinal cord injury , stroke volume , cardiology , cardiac output , venous return curve , ventricle , cardiac function curve , blood pressure , anesthesia , spinal cord , heart rate , hemodynamics , heart failure , psychiatry
Exercise is commonly prescribed post‐spinal cord injury (SCI) to reduce cardiovascular disease risk. From a cardiac perspective, there is general agreement that upper extremity exercise does little to improve function; hence, there is a growing interest in exercising the lower‐limbs post‐SCI to facilitate venous return and subsequently improve cardiac function. The objective of the present study was to directly compare the potential cardio‐therapeutic effect of active‐upper vs. passive‐lower body exercise in rodents with high‐thoracic SCI. Contusion SCI was induced at the T2 spinal cord level (400kdyn, 5s dwell, Infinite Horizon Impactor). Seven days post‐SCI, rodents were randomly assigned to receive 4 weeks of either swim exercise (SWIM, 5d/wk, 30 min/d, n=5), passive hind‐limb cycling exercise (PHLC, 5d/wk, 30min/d, n=5), or remained as non‐exercise control (SCI; n=5). At the end of the experimental period (5wk), the left‐ventricle (LV) was cannulated with a pressure‐volume conductance catheter (Millar, SPR‐869) via a right carotid approach under pressure guidance. Results were compared to a non‐SCI control group (CON; n=5). Mean arterial pressure was lower in all SCI groups relative to CON (all p<0.001). SCI and SWIM exhibited reduced flow‐ (stroke volume (SV), cardiac output (CO), ejection fraction, stroke work (SW)) and pressure‐derived (end‐systolic pressure, LV developed pressure, rates of pressure generation) cardiac indices relative to CON (all p<0.001). Conversely, PHLC improved SV, CO, and SW such that values exceeded those in both T2 and SWIM (all p<0.01), but there was no effect on pressure‐derived indices. Systemic vascular resistance (SVR) was lower in SHAM and PHLC compared to SCI and SWIM (all p<0.054). Passively engaging the lower‐limbs in exercise post‐SCI improves flow‐derived cardiac indices whereas actively engaging the upper‐limbs exerts no effect. That SVR was reduced in PHLC relative to SWIM and SCI suggests that PHLC may exert a beneficial effect via alterations in peripheral hemodynamics. Support or Funding Information Heart and Stroke FoundationRepresentative left‐ventricular pressure‐volume loops from all experimental groups. T2 spinal cord injury (SCI) exhibited reduced pressure‐and flow‐derived indices relative to uninjured control (CON). Note that 4 weeks of swim training (SWIM) post‐SCI exerted no effect on cardiac function; whereas 4 weeks of passive hind‐limb cycling exercise (PHLC) post‐SCI increased stroke volume and cardiac output to values similar to that in CON.