Sympathetic activation restrains endothelium-mediated muscle vasodilatation in heart failure patients

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Abstract
Although the vasodilatory response during mental stress is blunted in heart failure (HF), the mechanisms underlying this phenomenon are not fully understood. We tested the hypothesis that sympathetic activity limits the endothelium-dependent vasodilatation during mental stress in chronic HF patients. Twenty-one HF patients (age 45 ± 2 yr, functional classes III and IV, New York Heart Asssociation) and 22 age-matched normal controls (NC; age 42 ± 2 yr, P = 0.13) were studied at rest and during 4 min of Stroop color-word test with brachial intra-arterial saline, acetylcholine (endothelium dependent), phentolamine (α-blocker), and phentolamine plus acetylcholine infusion. Forearm blood flow was measured by venous occlusion plethysmography. Baseline forearm vascular conductance (FVC) was significantly lower in HF patients (2.18 ± 0.12 vs. 3.66 ± 0.22 units, P = 0.001). During mental stress with saline, the changes in FVC were significantly blunted in HF patients compared with NC (0.92 ± 0.20 vs. 2.13 ± 0.39 units, P = 0.001). In HF, the vasodilatation with acetylcholine was similar to saline control and significantly lower than in NC. In HF patients, phentolamine significantly increased FVC responses (1.16 ± 0.20 vs. 2.09 ± 0.29 units, P = 0.001), and the difference between HF patients and NC tended to decrease (2.09 ± 0.29 vs. 3.61 ± 0.74 units, P = 0.052). The vasodilatation with phentolamine plus acetylcholine was similar between HF and NC (4.23 ± 0.73 vs. 4.76 ± 1.03 units, P = 0.84). In conclusion, sympathetic activation mediates the blunted muscle endothelium-mediated vasodilatation during mental stress in HF patients.