Determinants of Oxygen Uptake (VO2) among Patients with CF-LVADs

Abstract

Characterize individual components of VO2 (cardiac output [Qc] and (A-V)O2 difference) at rest and during submaximal and peak exercise among CF-LVAD patients. Thirteen CF-LVAD participants (56±12 yrs, 12 male) and 9 healthy controls 42±12 yrs, 7 male) completed invasive cardiopulmonary exercise testing on a stationary upright cycle ergometer. Hemodynamic data and gas-exchange parameters were collected at rest, two submaximal levels of exercise below the ventilatory threshold, and peak workload. Swan-Ganz catheterization was performed to determine baseline hemodynamics. A conductance catheter was then used to calculate Qc at each stage of exercise. VO2was recorded on a breath-by-breath basis by indirect calorimetry. Blood pressure was continuously monitored by arterial line. Musculoskeletal performance was assessed by calculating the (A-V)O2 difference at each stage of exercise. Cohort characteristics and baseline demographics are demonstrated in table 1. Peak VO2 among CF-LVAD participants was severely reduced compared to healthy controls. When CF-LVAD participants were matched to healthy controls by workload according to VO2 quartiles, the CF-LVAD participants had a hypotensive response to exercise, as well as a blunted rise in Qc, with modest increases only from rest to submaximal exercise (figure 1). As a result, (A-V)O2 difference was higher for CF-LVAD participants than healthy controls at each VO2 quartile. Due to impairments in contractile reserve, CF-LVAD participants exhibit a greater (A-V)O2 difference than healthy individuals when exercising at similar workloads.