Abnormal Cardiovascular Functional Responses After the Long Interdialytic Interval: A Quasi-Experimental Crossover Study

ctional response patterns, as assessed by cardiopulmonary exercise testing (CPET), following the short- and long- interdialytic intervals. Methods: We conducted an exploratory single center, quasi-experimental two-arm study involving crossover of treatment sequences in patients on conventional thrice-weekly maintenance HD. All patients underwent CPET, bioelectrical impedance spectroscopy, and physical function testing on three study visits: Post-HD, and Pre-HD at the end of a two-day and the three-day interdialytic intervals. Results: Thirty-one patients (N=19 men, mean [SD] age 55 (12) years, median [IQR] dialysis vintage 56 [24, 96] months) completed all study visits. Interdialytic weight gain and total body fluid were greater following three-day compared with two-day (P <0.001). Ventilation/carbon dioxide production (VE/VCO2) slope, a non-invasive index of exercise pulmonary vascular resistance and right ventricular (RV) dysfunction, was significantly elevated at three-day (31.2 (4.8) L VE/L VCO2; P=0.002) compared with two-day (29.5 (3.9) L VE/L VCO2). No significant differences between interdialytic intervals were observed for peak oxygen uptake (VO2Peak) or VO2 at the anaerobic threshold. Change (Δ) in VE/VCO2 slope (ΔVE/VCO2) from two-day to three-day was correlated with Δbody weight (r=0.36, P=0.04) and left ventricular mass index (r=0.44, P=0.02). Conclusions: The long interdialytic interval is associated with abnormal exercise-derived ventilatory and hemodynamic responses, including ventilation-perfusion mismatch and potentially RV dysfunction and RV–pulmonary artery uncoupling during exercise as suggested by elevated VE/VCO2 slope. Copyright © 2025 by the American Society of Nephrology...