Reversal of adaptive left ventricular atrophy following electrically-stimulated exercise training in human tetraplegics

Abstract

Left ventricular (LV) myocardial atrophy and diminished cardiac function have been shown to accompany chronic human tetraplegia. These changes are attributable both to physical immobilisation and abnormal autonomic circulatory regulation imposed by a spinal cord injury (SCI). To test whether exercise training increases LV mass following chronic SCI, 8 neurologically complete quadriplegic males at 2 SCI rehabilitation and research centres underwent one month of electrically-stimulated quadriceps strengthening followed by 6 months of electrically-stimulated cycling exercise. Resting M-mode and 2-D echocardiograms were measured before and after exercise training to quantify the interventricular septal and posterior wall thicknesses at end-diastole (IVSTED and PWTED, respectively), and the LV internal dimension at end-diastole (LVIDED). LV mass was computed from these measurements using standard cube function geometry. Results showed a 6.5% increase in LVIDED following exercise training (p less than 0.02), with increases in IVSTED and PWTED of 17.8 (p less than 0.002) and 20.3% (p less than 0.01), respectively. Computed LV mass increased by 35% following exercise training (p = 0.002). These data indicate that myocardial atrophy is reversed in tetraplegics following electrically-stimulated exercise training, and that the changes in cardiac architecture are likely to be the result of both pressure and volume challenge to the heart imposed by exercise.