MO605: Exploring the Relationship Between Cardiorespiratory Fitness and Cardiovascular Risk in Kidney Transplant Recipients

BACKGROUND AND AIMS

Cardiovascular disease (CVD) remains a leading cause of mortality for kidney transplant recipients (KTR). Traditional risk factors include smoking, obesity, hypertension and hyperlipidemia. Nontraditional risk factors include creatinine levels, previous transplants and total time on renal replacement therapy. High levels of physical inactivity have long been known to link with poor cardiovascular outcomes. The first United Kingdom Clinical Practice Guidelines for Exercise and Lifestyle in Chronic Kidney Disease recommend that KTRs aim for 150 min of moderate to vigorous physical activity a week (or 75 min vigorous physical activity) plus two strength training sessions in line with current World Health Organisation recommendations for the general population. However, evidence suggests that only 27% of KTRs are sufficiently active for health.

We aimed to explore the relationship between cardiorespiratory fitness and the 7-year risk of major adverse cardiac events (MACE) and 7-year risk of mortality in KTRs.

METHOD

49 KTRs (31 male; mean [±SD]; 59 [±19] eGFR mL/min/1.73 m2; age 49 [±14] years) completed a continuous ramp cardiopulmonary exercise test (1W increase every 4 s) to volitional exhaustion on a cycle ergometer. The cardiovascular risk calculator for renal transplant recipients (CRCRTR-MACE) was used to calculate 7-year risk of MACE and 7-year risk of mortality. Cardiorespiratory fitness categories were defined in accordance with the American College of Sports Medicine guidelines. Data were analyzed using hierarchical multiple regression adjusting for gender.

RESULTS

84% of participants were classified as having ‘poor’ or ‘very poor’ cardiorespiratory fitness (VO2; ml/kg/min). Cardiorespiratory fitness was a significant predictor of 7-year risk of MACE after adjusting for gender (F(2, 40) = 10.64, P < 0.001, adj. R2 = 0.315). Each 1 mL/kg/min increase in VO2 was associated with a 0.5% decrease in 7-year risk of MACE (B = −.523, 95% CI [−0.794, −0.252]). Cardiorespiratory fitness was also a significant predictor of 7-year risk of mortality (F(2, 40) = 8.50, P < 0.001, adj. R2 = 0.263). Each 1 mL/kg/min increase in VO2 was associated with a 1% decrease in 7-year risk of mortality (B = −0.961, 95% CI [−1.483, −0.439]).

CONCLUSION

This exploratory analysis shows that cardiorespiratory fitness explains 31.5% and 26.3% of the variance in the 7-year risk of MACE and the 7-year risk of mortality, respectively. Various interventions have been shown to improve cardiorespiratory fitness in KRTs. Improving levels of physical activity and subsequently cardiovascular fitness provide a low cost strategy to partially attenuate some of widespread impact of CVD-related morbidity and mortality. These results highlight the importance of incorporating physical activity as part of post-transplant care.