Cardiorenal syndrome and the association with fitness: Data from a telerehabilitation randomized clinical trial

Aims: To investigate the associations of cardiorespiratory fitness with cardiac, vascular, renal and cardiorenal characteristics in chronic heart failure in a telerehabilitation randomized clinical trial. Secondly, to evaluate the associations of cardiorenal syndrome with the effects of exercise.

Methods and results: Sixty-nine heart failure patients attended baseline examination, and 61 patients were randomly assigned 1:1 to 3-month telerehabilitation or control. Data were collected at baseline and 3-month post-intervention, including echocardiography and vascular ultrasound, laboratory tests, exercise test with peak oxygen consumption (VO_2peak ) measurement and 6-min walk test (6MWT). Baseline VO_2peak and 6MWT distance was 0.85 mL*min^-1 *kg^-1 lower and 20 m shorter per 10 mL/min/1.73m² lower estimated glomerular filtration rate (both P < 0.001). Heart failure patients with cardiorenal syndrome had 3.5 (1.1) mL*min^-1 *kg^-1 lower VO_2peak and diastolic dysfunction grade 2-3, and elevated filling pressure was >50% more common compared with those without (all P < 0.05). At the 3-month post-intervention follow-up, only the non-CRS patients in the intervention group increased VO_2peak (0.73 (0.51) mL*min^-1 *kg^-1 ), whereas VO_2peak in the CRS subpopulation of controls decreased (-1.34 (0.43) mL*min^-1 *kg^-1 ). Cardiorenal syndrome was associated with a decrease in VO_2peak in CRS patients compared with non-CRS patients, -0.91 (0.31) vs. 0.39 (0.35) mL*min^-1 *kg^-1 respectively, P = 0.013.

Conclusions: Cardiorenal syndrome was negatively associated with VO_2peak and 6MWT distance in chronic HF, and the associations were stronger than for heart failure phenotypes and other characteristics. The effect of exercise was negatively associated with cardiorenal syndrome. Exercise seems to be as important in heart failure patients with cardiorenal syndrome, and future studies should include CRS patients to reveal the most beneficial type of exercise.