Heart Failure–Specific Relationship Between Muscle Sympathetic Nerve Activity and Aortic Wave Reflection

Abstract

Reflected arterial waves contribute to left ventricular (LV) afterload. Heart failure patients with reduced ejection fraction (HFrEF) are afterload sensitive and sympathetically activated. We tested the hypothesis that HFrEF patients exhibit a positive relationship between sympathetic vasoconstrictor discharge and aortic wave reflection. Sixteen treated patients with HFrEF (61 ± 9 years of age, left ventricular ejection fraction 30 ± 7%, 3 women) and 16 similar-aged healthy control subjects (57 ± 7 years of age, 4 women) underwent noninvasive measurements of radial pulse waveforms (applanation tonometry) to calculate central blood pressures and aortic wave reflection characteristics: augmentation pressure (AP), augmentation index (AIx), and AIx corrected to a heart rate of 75 beats/min (AIx@75). Muscle sympathetic nerve activity (MSNA) burst frequency was recorded from the fibular nerve (microneurography). HFrEF patients had higher AIx (26 ± 9 vs 17 ± 15%; P < .05) and MSNA burst frequency (48 ± 7 vs 39 ± 11 bursts/min; P < .05) and lower central diastolic pressure than control subjects (64 ± 8 vs 70 ± 9 mm Hg; P = 0.05). There were no between-group differences in heart rate, other measures of blood pressure (brachial and central; P > .05), AP (11 ± 5 vs 7 ± 8 mm Hg; P = 0.11), or AIx@75 (19 ± 9 vs 13 ± 11%,-P = 0.14). MSNA correlated positively with AP (r = 0.50; P < .05), AIx (r = 0.51; P < .05), and AIx@75 (r = 0.54; P < .05) in HFrEF patients but not in control subjects (r = 0.002-0.18; P > 0.49). In patients with HFrEF, but not similarly aged healthy subjects, indices of aortic wave reflection correlate positively with MSNA. By increasing LV afterload, such neurovascular coupling could impair LV performance and worsen heart failure symptoms. Therapies that attenuate neurogenic vasoconstriction may benefit HFrEF patients by diminishing arterial wave reflection.