Background: Aerobic capacity is impaired in end-stage renal disease (ESRD), reducing quality of life and longevity. Whilst determinants of maximal exercise intolerance are well defined, little is known of limitation during submaximal exercise. By comparing ESRD and healthy controls, the aim of this study was to characterise mechanisms of exercise intolerance in ESRD by assessing cardiopulmonary physiology at rest and during exercise.
Methods: Resting spirometry and echocardiography were performed in 20 ESRD participants and 20 healthy age and gender matched controls. Exercise tolerance was assessed with ventilatory gas exchange and central hemodynamics during a maximal cardiopulmonary exercise test (CPEX) and 30 minutes of submaximal constant load exercise (CLEX).
Results: Left ventricular mass (292 ± 102 vs. 185 ± 83 g; p = 0.01) and filling pressure (E/e': 6.48 ± 3.57 vs. 12.09 ± 6.50 m/s; p = 0.02) were higher in ESRD; forced vital capacity (3.44 ± 1 vs. 4.29 ± 0.95 L/min; p = 0.03) and peak VO2 (13.3 ± 2.7 vs. 24.6 ± 7.3 ml.kg-1.min-1; p < 0.001) were lower. During CLEX, the relative increase in (a-v) O2 difference (13 ± 18 vs. 74 ± 18%) and heart rate (32 ± 18 vs. 75 ± 29%) were less in ESRD despite exercise being performed at a higher percentage of maximum VE (48 ± 3 vs 39 ± 3%) and HR (82 ± 2 vs. 64 ± 2%).
Conclusion: Ventilatory and chronotropic incompetence contribute to exercise intolerance in ESRD. Both are potential targets for medical and lifestyle interventions.
