Relationship between depressed baroreflex function and exaggerated sympathetic response to exercise in patients with heart failure

The relationship between impaired baroreflex sensitivity (BS) and the degre e of sympathetic activation during exercise in patients with heart failure (HF) has not been studied in detail. For this purpose, we studied BS and me asured plasma norepinephrine (NE) at rest, and during and after treadmill e xercise in 15 patients and 10 controls. HF patients showed lower BS in comp arison to controls (3.51 +/- 3.62 vs. 9.74 +/- 4.56 ms/mm Hg; p < 0.001), a nd higher levels of plasma NE at rest (449.3 +/- 147.1 vs. 261.1 +/- 82.48 pg/ml; p < 0.001) and during exercise (1,542 +/- 361.2 vs. 524.6 +/- 92.61 pg/ml; p < 0.001). BS was directly related to pVO(2) (r = 0.62; p = 0.0008) and inversely related to NE at peak exercise and to the increase in NE dur ing exercise (r = 0.59, p = 0.005, and r = 0.53; p = 0.0058). Thus, during exercise, a marked sympathetic activation exists in patients with moderate HF. The relationship between increased plasma NE during exercise and decrea sed BS suggests that impaired baroreceptor function may be present in sympa thetic activation in HF patients.