Key result
Unlike healthy adults, 1-leg cycling increased muscle sympathetic nerve activity in HFrEF patients, with the change in burst frequency inversely correlating with peak oxygen uptake (r = -0.43, p<0.05).
Why the study?
During 1-leg cycling, contralateral muscle sympathetic nerve activity falls in healthy adults but increases in most with HFrEF, prompting the hypothesis that peak oxygen uptake relates inversely to the MSNA response to exercise.
Does the muscle sympathetic nerve activity response to dynamic leg exercise inversely correlate with VO2peak in patients with HFrEF?
Observational (n=50)
Does the muscle sympathetic nerve activity response to dynamic leg exercise inversely correlate with VO2peak in patients with HFrEF?
Effect estimate: r = -0.43
p-value: p=< 0.05
In patients with HFrEF, the increase in muscle sympathetic nerve activity during low-intensity exercise is inversely related to peak oxygen uptake, explaining ~18% of the variance in VO2peak.
Sympathetic activation during low-intensity exercise was associated with lower VO2peak in HFrEF; hypothesis-generating for targeted neural modulation.
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 (V̇O 2peak ) relates inversely to their MSNA response to exercise. Twenty-nine patients (6 women; 63 ± 9 years; left ventricular ejection fraction: 30 ± 7%; V̇O 2peak : 78 ± 23 percent age-predicted (%V̇O 2peak ); mean ± SD) and 21 healthy adults (9 women; 58 ± 7 years; 115 ± 29%V̇O 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 ΔBF from baseline to “loaded” cycling and %V̇O 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 %V̇O 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 (V̇O 2peak ) can be attributed to changes in MSNA elicited by low-intensity exercise. This relationship is absent in healthy adults.
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Keir et al. (2021) conducted an observational in Heart failure with reduced ejection fraction (HFrEF) (n=50). 1-leg cycling vs. Healthy adults was evaluated on Correlation between change in MSNA burst frequency from baseline to loaded cycling and %VO2peak (r = -0.43, p=< 0.05). Unlike healthy adults, 1-leg cycling increased muscle sympathetic nerve activity in HFrEF patients, with the change in burst frequency inversely correlating with peak oxygen uptake (r = -0.43, p<0.05).
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