Heart failure-specific inverse relationship between the muscle sympathetic response to dynamic leg exercise and (V)over dot O2peak

During 1-leg cycling, contralateral muscle sympathetic nerve activity (MSNA) falls in healthy adults but increases in most with reduced ejection fraction heart failure (HFrEF). We hypothesized that their peak oxygen uptake ( (V)over dot O-2peak) relates inversely to their MSNA response to exercise. Twenty-nine patients (6 women; 63 +/- 9 years; left ventricular ejection fraction: 30 +/- 7%; (V)over dot O-2peak: 78 +/- 23 percent age-predicted (%(V)over dot O-2peak); mean 6 SD) and 21 healthy adults (9 women; 58 +/- 7 years; 115 +/- 29%(V)over dot O-2peak) performed 2 min of mild- (loadless) and moderate-intensity (loaded) 1-leg cycling. Heart rate, blood pressure (BP), contralateral leg MSNA and perceived exertion rate (RPE) were recorded. Resting MSNA burst frequency (BF) was higher (p < 0.01) in HFrEF (51 +/- 11 vs 44 +/- 7 bursts.min(-1)). Exercise heart rate, BP and RPE responses at either intensity were similar between groups. In minute 2 of loadless and loaded cycling, group mean BF fell from baseline values in controls (-5 +/- 6 and -7 +/- 7 bursts.min(-1), respectively) but rose in HFrEF (+5 +/- 7 and +5 +/- 10 bursts.min(-1)). However, in 10 of the latter cohort, BF fell, similarly to controls. An inverse relationship between DBF from baseline to loaded cycling and %(V)over dot O-2peak was present in patients (r = -0.43, p < 0.05) but absent in controls (r = 0.07, p = 0.77). In HFrEF, -18% of variance in % (V)over dot O-2peak can be attributed to the change in BF elicited by exercise. Novelty: Unlike healthy individuals, in the majority of heart failure patients with reduced ejection fraction (HFrEF), 1-leg cycling increases muscle sympathetic nerve activity (MSNA). In HFrEF, -18% of age-predicted peak oxygen uptake ((V)over dot O-2peak) can be attributed to changes in MSNA elicited by low-intensity exercise. This relationship is absent in healthy adults.

Automated summary

Unlike healthy individuals, in the majority of heart failure patients with reduced ejection fraction (HFrEF), 1-leg cycling increases muscle sympathetic nerve activity (MSNA). In HFrEF, -18% of age-predicted peak oxygen uptake ((V)over dot O-2peak) can be attributed to changes in MSNA elicited by low-intensity exercise. This relationship is absent in healthy adults.