Endothelial Dysfunction Predicts Systolic Blood Pressure Slope During Whole Body Maximal Exercise in Patients with Chronic Kidney Disease
Downey RM, et al
Exercise is good for almost anything that ails someone. Patients with chronic kidney disease (CKD) often find it difficult to exercise, even before their disease advances to requiring intervention. Little is known about the vascular response of CKD patients to exercise.
This study looked at the vascular effects of high intensity exercise in patients with stage 3 CKD compared to age-matched control subjects. CKD3 patients are often asymptomatic, diagnosed only through an abnormal lab test. CKD3 is the level of kidney dysfunction that gets flagged as abnormal by most labs. CKD3 has a wide range of function, from 20 mL/min/1.73m^2 to 59 mL/min/1.73m^2. Patients above 40 mL/min/1.73m^2 are much less likely to have secondary complications of CKD than those in the lower half of the range.
They then subjected these participants to maximal treadmill exercise while monitoring blood pressure, heart rate, and peak oxygen uptake. Brachial artery flow-mediated dilation (FMD) was measured to assess endothelial dysfunction. This study occurred just before and 1 hour after the treadmill test.
CKD patients had similar maximal blood pressure to controls; however, the rate of rise to maximal blood pressure was much greater in CKD patients. Maximum heart rate was lower in CKD patients, but the rate of rise was higher than the age-matched controls. Finally, peak oxygen uptake was significantly lower in CKD patients than in control subjects. FMD did not change pre- and post-exercise in either group, but they were significantly lower in the CKD patients. Basal levels of FMD predicted the slope of rise of blood pressure with exercise in CKD patients. Those with lower FMD had accelerated blood pressure and heart rate response during exercise.
CKD encompasses a relatively wide range of estimated glomerular filtration rate. Some nephrologists have suggest splitting it into CKD3a (40-59 mL/min/1.73m^2) and CKD3b because of the different risk profiles for these groups. Did dividing the study patients this way predict lower FMD for CKD3b? Apparently not.
So what follows this translational study? The next step will be exercise training for CKD3 patients to see if their endothelial dysfunction can be improved, resulting in better exercise tolerance. After all, exercise is good for almost everything.