Ventricular Vascular Coupling During Submaximal Exercise In Individuals With And Without Multiple Sclerosis

INTRODUCTION: Multiple sclerosis (MS) is a chronic neuroinflammatory disease of the central nervous system that is associated with low fitness. Low fitness in this population may be due to impaired cardiovascular performance during exercise. Ventricular vascular coupling (VVC) is a key determinant of cardiovascular performance, but has not been evaluated during exercise in individuals with MS. Therefore, we evaluated submaximal VVC in individuals with and without MS and hypothesized that individuals with MS would exhibit impaired VVC. METHODS: Eight individuals with MS (MS: Female: 6, 43 ± 8 yrs, 24.6 ± 4.5 kg·m-2) and 6 without MS (CON: Female: 5, 28 ± 5 yrs, 24.5 ± 3.2 kg·m-2) completed two study visits. During visit one, fitness was measured via maximal incremental cycle test as peak oxygen consumption (VO2peak). Volunteers returned to assess VVC at rest and during submaximal cycle exercise (65% of heart rate reserve). VVC quantified as the ratio of arterial elastance (EA: end-systolic pressure (ESP)/stroke volume (SV)) to ventricular elastance (ELV: ESP/end-systolic volume (ESV)). ESP was determined from central arterial waveforms generated using tonometry while SV and ESV were measured using ultrasound. RESULTS: VO2peak was not different between groups (MS: 30.1 ± 9.0 and CON: 30.7 ± 8.2 ml·min-1·kg-1; p = 0.31). There were no main effects of group (MS vs. CON) nor any group*time interactions for EA, ELV, or VVC. ELV increased from baseline to submaximal exercise (Pooled baseline-immediate post exercise means ± S.D.; ELV: 1.28 ± 0.28 mmHg/ml to 1.55 ± 0.38 mmHg/ml, (p < 0.01)), without a change in EA, resulting in a decrease in VVC from baseline to submaximal exercise (Pooled baseline submaximal exercise means ± S.D.; VVC: 1.01 ± 0.67 to 0.93 ± 0.12, p < 0.01). CONCLUSIONS: Without differences in fitness, individuals with and without MS did not have differences in EA or ELV and both groups exhibited a normal resting VVC that responded appropriately to maximal exercise. Our data suggest that preserved fitness in individuals with MS likely contributes to maintenance of VVC during submaximal exercise. ACSM Foundation Doctoral Student Research Grant