Plasma adenosine concentration during and after dynamic exercise in patients with chronic heart failure

The purpose of this study was to evaluate the changes of plasma adenosine concentration by dynamic exercise in patients with chronic heart failure. We studied six patients with chronic heart failure (heart failure group) and six normal subjects (normal group). A symptom-limited ramp exercise test was performed with subjects sitting upright on a bicycle ergometer. The first exercise test was performed to determine the anaerobic threshold. The second exercise test was performed 2 days thereafter, and blood samples for assay of adenosine, lactate, and norepinephrine were taken from the antecubital vein at rest, during, and after exercise. In the heart failure group, VO2 at anaerobic threshold and peak exercise was significantly lower than that in the normal group, whereas there was no difference in respiratory quotient at peak exercise between the two groups. There was a significant increase in the plasma adenosine level from the point before anaerobic threshold to 10 minute after exercise in the normal group, whereas a mild increase in plasma adenosine level was observed only 15 minute after exercise in the heart failure group. The change of plasma adenosine was significantly smaller in the heart failure group (p<0.05). There was a significant relationship between plasma adenosine and lactate levels (r=0.42, n=48,p<0.01). These findings indicate that production of adenosine is decreased in patients with chronic heart failure, and vasodilation of exercising muscle induced by adenosine might be impaired during exercise.