#5045 CARDIORESPIRATORY FITNESS IN KIDNEY TRANSPLANT RECIPIENTS: A CASE-CONTROL STUDY AND INITIAL REVIEW OF THE EFFECTS OF A HOME-BASED EXERCISE PROGRAMME
Authors: Billany Roseanne E , Mubaarak Zahra , Burns Stephanie , Vadaszy Noemi , Bishop Nicolette , Smith Alice , Mccann Gerry , Graham-Brown Matthew 
Published: June 2023

Abstract

Background and Aims
Kidney transplant recipients (KTRs) have an increased burden of cardiovascular disease (CVD) due to clustering of traditional and non-traditional risk factors. Poor cardiorespiratory fitness (CRF) is linked to higher levels of morbidity and mortality. Cardiorespiratory fitness is a significant predictor of 7-year risk of mortality, with each 1 ml/kg/min increase in VO2 associated with a 1% decrease in risk of mortality.[1] Although KTRs have higher CRF than patients with kidney failure, performance compared to the general population has not been quantified. Neither has the link between CRF and physical function. We assessed differences in CRF between KTRs and healthy volunteers in a case-control study. We then explored relationships between CRF and physical function and possible effects of a 12-week structured home-based exercise programme in KTRs.

Method
Case-control: 20 KTRs (10 male; age 61.2 ±8.1 years; body mass 84.1 ±19.9 kg) and 20 healthy volunteers (10 male; age 61.9 ±7.7 years; body mass 76.7 ±18.1 kg) completed a continuous ramp cardiopulmonary exercise test (CPET) to volitional exhaustion on a cycle ergometer. CPET variables were compared between groups using independent samples t-tests.
Thirteen KTRs (6 male; age 47.8 ±15.9 years; eGFR 64.6 ±19.1 ml/min/1.73 m2), to date, have completed a 12-week structured, combined aerobic and resistance, home-based exercise programme as part of a pilot randomised controlled trial.[2] Bivariate correlations were used to explore the association between cardiorespiratory fitness and physical function measures (sit-to-stand 60 [STS60], timed up and go [TUAG], gait speed [GS] and handgrip strength [HGS]). Paired samples t-tests were used to compare pre- and post-intervention variables.

Results
Case-control: Cardiorespiratory fitness (VO2 peak) was lower in KTRs (18.4±5.2 mL/kg/min) than in healthy volunteers (24.3 ±5.9 mL/kg/min), a difference of 5.9 mL/kg/min (95% CI, 2.4-9.5), t(38) = 3.35, p &lt;.001. Peak heart rate achieved was higher in healthy volunteers than in KTRs (154 v 136 bpm; p = .009). Maximum power achieved was higher in healthy volunteers but did not reach significance (147 v 116 W; p = .052). There was a positive correlation between STS60 and VO2 peak (r = .652, p = .016) and between GS and VO2 peak (r = .583, p = .037). There was a negative correlation between TUAG and VO2 peak (r = .-.664, p = .013) and no association between HGS and VO2 peak. There was an increase in VO2 peak after the 12-week exercise programme (19.4±4.5 mL/kg/min to 20.4±5.0 mL/kg/min, p = .018). Maximum power achieved did not change post-intervention (118 v 121 W; p = .423). STS60 was the only physical function test to improve post-intervention (24 v 27; p = .010).

Conclusion
Cardiorespiratory fitness in KTRs is significantly impaired compared to healthy control subjects. In KTRs, aerobic fitness assessed with VO2 peak correlated with field tests assessing physical function. Initial findings suggest that CRF may improve following a structured, home-based programme of exercise, but these data need confirming in larger studies and will be assessed in the final analysis of this pilot randomised trial.