Heart failure-specific inverse relationship between the muscle sympathetic response to dynamic leg exercise and V̇O2peak

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-nin...

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Published in:	Applied physiology, nutrition, and metabolism nutrition, and metabolism, 2021, Vol.46 (9), p.1119-1125
Main Authors:	Keir, Daniel A, Notarius, Catherine F, Badrov, Mark B, Millar, Philip J, Floras, John S
Format:	Article
Language:	eng
Subjects:	activité nerveuse sympathique musculaire Bicycling cardiopulmonary exercise test Cardiovascular system consommation maximale d’oxygène cycling Ejection fraction Exercise Exercise physiology Heart failure Heart rate Legs Maximum oxygen consumption microneurographie microneurography muscle sympathetic nerve activity peak oxygen uptake pédalage sympathetic nervous system système nerveux sympathique test d’effort cardiopulmonaire
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Summary:	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.
ISSN:	1715-5312 1715-5320