Jurrissen Thomas J, Luchkanych Adam M S, Boyes Natasha G, Marshall Rory A, Khan M Rafique, Zhai Alexander, Haddad Haissam, Marciniuk Darcy D, Tomczak Corey R, Olver T Dylan
Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
J Appl Physiol (1985). 2025 Apr 1;138(4):891-898. doi: 10.1152/japplphysiol.00834.2024. Epub 2025 Mar 4.
Impaired cerebrovascular control in patients with heart failure with reduced ejection fraction (HFrEF) has been attributed to cardiac impairment and exaggerated sympathetic-mediated cerebral vasoconstriction. The goal of this study was to examine the effect of muscle metaboreflex activation (MMA) on cerebrovascular hemodynamics in patients with HFrEF under conditions of preserved cardiac output. It was hypothesized that reductions in the index of cerebral blood flow and cerebrovascular conductance (CVCi) during MMA would be exaggerated in HFrEF and independent of reduced cardiac output. Middle cerebral blood velocity (MCA; transcranial Doppler), blood pressure, cardiac output (Finometer), and end-tidal CO were examined at rest, during isometric handgrip, and during muscle MMA (postexercise circulatory occlusion) in 18 patients with HFrEF and 21 healthy, sex-, and age-matched controls. To minimize differences in β-adrenergic control, patients with HFrEF withdrew from β-blockade medications before the study. Cardiac index and blood pressure were not significantly different between groups under any condition. The MCA was lower at rest and during exercise in HFrEF. The CVCi (MCA/mean arterial pressure) and MCA decreased during MMA in the control group. In contrast, the CVCi remained unchanged and MCA increased during MMA in the HFrEF group. Despite similar systemic hemodynamics, patients with HFrEF display lower MCA at rest and an increase in MCA during MMA. These novel findings implicate aspects other than reduced cardiac output or exaggerated sympathetic constriction as underlying causes of altered cerebrovascular regulation in HFrEF. Compared with controls, patients with heart failure with reduced ejection fraction (HFrEF) displayed reduced indices of cerebral perfusion at rest and increases in perfusion in response to postexercise circulatory occlusion (PECO, method to isolate muscle metaboreflex activation). This occurred despite similar cardiac output and blood pressure values between groups. Thus, lower resting indices of cerebral perfusion and increased perfusion during sympathoexcitation in HFrEF may occur independently from differences in systemic hemodynamics.
射血分数降低的心力衰竭（HFrEF）患者脑血管控制受损被认为与心脏功能损害以及交感神经介导的脑血管过度收缩有关。本研究的目的是在心脏输出量保持的情况下，研究肌肉代谢反射激活（MMA）对HFrEF患者脑血管血流动力学的影响。研究假设，在MMA期间，HFrEF患者脑血流量和脑血管传导率（CVCi）指标的降低会更加明显，且与心输出量降低无关。在静息状态、等长握力运动期间以及肌肉MMA（运动后循环阻断）期间，对18例HFrEF患者和21例年龄、性别匹配的健康对照者进行了大脑中动脉血流速度（MCA；经颅多普勒）、血压、心输出量（Finometer）和呼气末二氧化碳检测。为尽量减少β-肾上腺素能控制方面的差异，HFrEF患者在研究前停用β受体阻滞剂药物。在任何情况下，两组之间的心指数和血压均无显著差异。HFrEF患者在静息和运动时MCA较低。对照组在MMA期间CVCi（MCA/平均动脉压）和MCA降低。相比之下，HFrEF组在MMA期间CVCi保持不变而MCA增加。尽管全身血流动力学相似，但HFrEF患者在静息时MCA较低，在MMA期间MCA增加。这些新发现表明，除心输出量降低或交感神经过度收缩外，其他因素也是HFrEF患者脑血管调节改变的潜在原因。与对照组相比，射血分数降低的心力衰竭（HFrEF）患者静息时脑灌注指标降低，运动后循环阻断（PECO，一种分离肌肉代谢反射激活的方法）后灌注增加。尽管两组之间的心输出量和血压值相似，但仍出现这种情况。因此，HFrEF患者静息时较低的脑灌注指标和交感神经兴奋时灌注增加可能独立于全身血流动力学差异而发生。
