Hypokinetic circulation in persons with paraplegia.
BACKGROUND
It is well established that hemodynamic dysfunction, resulting in diminished upper-extremity work capacity, occurs in persons with spinal cord injury (SCI) as compared with those who are nondisabled (ND). Although it has been shown that persons with paraplegia display higher values of heart rate (HR) with lower values of stroke volume (SV) during exercise, it is not resolved whether there is adequate compensation to produce similar values of cardiac output (.Q) as in ND.


OBJECTIVE
This study examined central cardiovascular responses (HR, SV, and .Q) of 20 subjects with complete thoracic level SCI (T(4)-T(11)) and 20 sedentary ND subjects during matched levels of arm-crank (AC) exercise.


METHODS
All subjects performed an incremental peak AC test to volitional exhaustion with continuous metabolic analysis and HR measurement via open circuit spirometry and 12-lead electrocardiography, respectively. Stroke volume was assessed using transthoracic impedance.


RESULTS
Heart rate was higher for SCI (P< 0.05) with significantly lower values for SV and .Q at rest (approximately 25%). Peak responses were significantly higher for ND in all factors except HR. Although subpeak HRs at matched absolute workloads were significantly higher for SCI (12-20 beats.min (-1) ), SV and .Q were significantly lower (P< 0.05).


CONCLUSIONS
The results of this study indicate that .Q is significantly lower in SCI than in ND during AC, despite significantly greater values of HR. These findings also suggest that the disparity in exercise values of .Q is related to differences exhibited at rest.
Jacobs
Patrick L
PL
Department of Neurological Surgery, University of Miami School of Medicine, Miami, FL 33101, USA. pjacobs@miamiproject.med.miami.edu
Mahoney
Edward T
ET
Robbins
Allison
A
Nash
Mark
M
D000328:Adult; D000704:Analysis of Variance; D001132:Arm / Q000502:physiology; D001775:Blood Circulation; D002302:Cardiac Output; D002319:Cardiovascular System / Q000503:physiopathology*; D017097:Electric Impedance; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010264:Paraplegia / Q000503:physiopathology*; D005082:Physical Exertion; D013147:Spirometry; D013318:Stroke Volume